Team 12: Iron Man
Modified Running Cart
Final Design Report
Allen Bosscher
Andrew Vriesema
Lukas Woltjer
ENGR 339/340 Senior Design Project
Calvin College
15 May 2014
COPYRIGHT
© 2014 Team 12 and Calvin College. All Rights Reserved
Executive Summary
This report outlines and describes the research, design decisions, final design, and constructed prototype
that team 12, Iron Man, has worked on over the past year through the Calvin College senior design
project. Team 12 has designed and built an off-road capable running cart that can be easily collapsed and
transported. For this design, the team has made the vehicle as light as possible while maintaining the
necessary strength to carry the designated carrying load. The team has specifically designed the running
cart with a handicapped or mentally disabled passenger in mind. This was accomplished through working
closely with several caretakers and care centers with intimate knowledge of what features would be
required in such a project. The important aspects for this design that needed significant engineering focus
were the collapsibility, quick-wheel change, overall passenger comfort, and maneuverability of the
running cart. The team also designed the prototype and final design to be as inexpensive as possible for
future manufacturing and business possibilities. Through the research, analyses, and created prototype
presented in this report, Team 12 has concluded that the objectives of this project were met, as a
lightweight, collapsible, and handicapped capable running cart was created.
Table of Contents
1. Introduction ............................................................................................................1
1.1 Team Members ...................................................................................................................... 1
1.2 Description of Calvin College and Senior Design Course .................................................... 2
1.3 Project Definition .................................................................................................................. 2
2. Project Management ..............................................................................................3
2.1 Team Organization ................................................................................................................ 3
2.1.1 Team Member Roles ...................................................................................................... 3
2.1.2 Organization Chart ......................................................................................................... 4
2.1.3 Team Meetings ............................................................................................................... 5
2.1.4 Team Documents ............................................................................................................ 5
2.2 Schedule Management .......................................................................................................... 5
2.3 Budget ................................................................................................................................... 6
2.4 Method of Approach ............................................................................................................. 6
3. Requirements .........................................................................................................8
3.1 Functional Requirements....................................................................................................... 8
3.1.1 Strength Requirement ..................................................................................................... 8
3.1.2 Mobility Requirement..................................................................................................... 8
3.2 Performance Requirements ................................................................................................... 9
3.2.1 Transportable Requirement ............................................................................................ 9
3.2.2 Multiple Surface Requirement...................................................................................... 10
3.2.3 Easy Entry and Exit Requirement ................................................................................ 10
3.2.4 Passenger Comfort Requirement .................................................................................. 11
3.3 Interface Requirements ....................................................................................................... 11
3.3.1 Customer Interaction Requirements ............................................................................. 11
3.3.2 Cost Requirements ........................................................................................................ 12
3.4 Team Deliverables............................................................................................................... 12
4. Task Specifications ..............................................................................................14
4.1 Schedule .............................................................................................................................. 14
5. Research ...............................................................................................................16
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5.1 Material Options .................................................................................................................. 16
5.2 Similar Projects ................................................................................................................... 16
5.2.1 Overview ...................................................................................................................... 16
5.2.1 Analyses........................................................................................................................ 17
5.3 Resources ............................................................................................................................ 20
5.4 Safety Requirements ........................................................................................................... 20
6. Design ..................................................................................................................22
6.1 Design Criteria .................................................................................................................... 22
6.2 Primary Application ............................................................................................................ 22
6.2.1 Primary Application Design Criteria ............................................................................ 22
6.2.2 Primary Application Alternatives ................................................................................. 22
6.2.3 Primary Application Design Decision .......................................................................... 23
6.3 Frame Material .................................................................................................................... 23
6.3.1 Frame Material Design Criteria .................................................................................... 23
6.3.2 Frame Material Alternatives ......................................................................................... 24
6.3.3 Frame Material Design Decision .................................................................................. 25
6.4 Quick Change Wheel Design .............................................................................................. 26
6.4.1 Quick Change Wheel Design Criteria .......................................................................... 26
6.4.2 Quick Change Wheel Design Alternatives ................................................................... 27
6.4.3 Quick Change Wheel Design Decision ........................................................................ 29
6.5 Collapsible Design .............................................................................................................. 31
6.5.1 Collapsible Design Criteria .......................................................................................... 31
6.5.2 Collapsible Design Alternatives ................................................................................... 32
6.5.3 Collapsible Design Decision ........................................................................................ 33
6.6 Fabric Material Design ........................................................................................................ 34
6.6.1 Fabric Material Design Criteria .................................................................................... 34
6.6.2 Fabric Material Design Alternatives............................................................................. 34
6.6.3 Fabric Material Design Decision .................................................................................. 35
6.7 Easy Entry and Exit Design ................................................................................................ 36
6.7.1 Easy Entry and Exit Design Criteria............................................................................. 36
6.7.2 Easy Entry and Exit Alternatives.................................................................................. 37
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6.7.3 Easy Entry and Exit Design Decision........................................................................... 37
6.8 Block Diagram .................................................................................................................... 38
6.9 Preliminary Design .............................................................................................................. 38
6.9.1 Initial Sketch ................................................................................................................. 38
6.9.2 Initial Computer Model ................................................................................................ 39
6.9.3 Finite Element Modeling .............................................................................................. 40
6.10 Final Design ...................................................................................................................... 42
6.11 Applicable Design Norms ................................................................................................. 42
6.11.1 Transparency .............................................................................................................. 43
6.11.2 Stewardship ................................................................................................................ 43
6.11.3 Caring ......................................................................................................................... 44
6.11.4 Trust ............................................................................................................................ 44
6.12 Calculations ....................................................................................................................... 44
6.12.1 Frame Stress Calculations .......................................................................................... 44
6.12.2 Frame Deflection Calculations ................................................................................... 47
6.12.3 Weight Estimations..................................................................................................... 48
6.12.4 Center of Gravity Calculations ................................................................................... 50
7. Prototype Construction ........................................................................................51
7.1 Materials Acquisition .......................................................................................................... 51
7.2 Frame Construction ............................................................................................................. 52
7.3 Addition of Key Features .................................................................................................... 52
7.3.1 Collapsing Mechanism ................................................................................................. 52
7.3.2 Quick-change Wheels ................................................................................................... 53
7.3.3 Sliding Seat Mechanism ............................................................................................... 55
7.4 Modifications and Revisions ............................................................................................... 55
7.5 Final Touches ...................................................................................................................... 56
7.6 Prototype Budgeting............................................................................................................ 57
8. Prototype Testing .................................................................................................59
8.1 Transportability ................................................................................................................... 59
8.2 Deflection Test .................................................................................................................... 62
8.3 Flutter Test .......................................................................................................................... 63
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9. Business Analysis ................................................................................................65
9.1 Marketing Study .................................................................................................................. 65
9.1.1 Competitive Analysis ................................................................................................... 65
9.1.2 Target Markets .............................................................................................................. 65
9.2 Cost Estimate....................................................................................................................... 66
9.2.1 Development ................................................................................................................. 66
9.2.2 Production ..................................................................................................................... 67
10. Suggested Modifications ....................................................................................70
10.1 Brake System Changes ...................................................................................................... 70
10.2 Caster Flutter ..................................................................................................................... 70
10.3 Sliding Seat ....................................................................................................................... 70
10.4 Seat Cushion...................................................................................................................... 70
10.5 Quick-change Rear Axle ................................................................................................... 70
11. Conclusion .........................................................................................................72
12. Acknowledgements ............................................................................................73
13. References ..........................................................................................................74
Appendix A. Pro-forma Financial Statements .........................................................78
Appendix B. User Manual .......................................................................................81
Appendix C. Work Breakdown Structure ................................................................85
1st Semester Tasks ..................................................................................................................... 85
2nd Semester Tasks .................................................................................................................... 87
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Table of Figures
Figure 1: Team 12 – Iron Man ........................................................................................................ 1
Figure 2: Organization Chart .......................................................................................................... 4
Figure 3: Gantt Chart Example Section ........................................................................................ 14
Figure 4: Carrying Weight vs. Selling Price ................................................................................. 17
Figure 5: Vehicle Weight vs. Selling Price ................................................................................... 18
Figure 6: Product Weight vs. Carrying Weight ............................................................................ 19
Figure 7: Quick Release Skewer Examples .................................................................................. 28
Figure 8: Quick Release Hitch Pin................................................................................................ 28
Figure 9: Hitch Pin and Clip ......................................................................................................... 29
Figure 10: Quick Connect Hitch Pin Example ............................................................................. 29
Figure 11 : Jointed Design Examples ........................................................................................... 33
Figure 12: System Block Diagram ................................................................................................ 38
Figure 13: Initial Hand Sketch ...................................................................................................... 39
Figure 14: Initial Computer Model ............................................................................................... 39
Figure 15: Initial Frame Design .................................................................................................... 40
Figure 16: Forces Acting on the Frame of the Cart ...................................................................... 40
Figure 17: Simulation Results....................................................................................................... 41
Figure 18: Final Designed Computer Model ................................................................................ 42
Figure 19: Beam Loading Diagram .............................................................................................. 45
Figure 20: Final Finite Element Loading ...................................................................................... 46
Figure 21: Final Finite Element Stress Results ............................................................................. 46
Figure 22: Sample Beam Calculations Worksheet ....................................................................... 47
Figure 23: Sample EES Calculations ............................................................................................ 48
Figure 24: Sample EES Results .................................................................................................... 49
Figure 25: Method of Determining Frame Weight ....................................................................... 49
Figure 26: Final Cart Weight Determination ................................................................................ 50
Figure 27: Final Prototype ............................................................................................................ 51
Figure 28: Completed Collapsing Mechanism ............................................................................. 53
Figure 29: Demonstration of Rear Quick-Release Mechanism .................................................... 54
Figure 30: Demonstration of Front Quick-Release Mechanism ................................................... 54
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Figure 31: Front Wheel Mount Used for Testing and Modification ............................................. 56
Figure 32: Sewing Process for Assembly of the Seat Back .......................................................... 57
Figure 33: Cart in Honda Civic Trunk .......................................................................................... 61
Figure 34: Deflection Test Setup .................................................................................................. 62
Figure 35: Deflection Test Results ............................................................................................... 63
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Table Of Tables
Table 1: Frame Material Design Criteria ...................................................................................... 23
Table 2: Frame Material Alternative Properties ........................................................................... 25
Table 3: Frame Material Decision Matrix .................................................................................... 26
Table 4: Quick Wheel Change Design Criteria ............................................................................ 26
Table 5: Front Wheel Quick Change Decision Matrix ................................................................. 30
Table 6: Rear Wheel Quick Change Decision Marix ................................................................... 30
Table 7: Collapsibility Design Criteria ......................................................................................... 31
Table 8: Collapsible Method Decision Matrix.............................................................................. 33
Table 9: Fabric Material Design Criteria ...................................................................................... 34
Table 10: Fabric Material Decision Matrix .................................................................................. 35
Table 11: Easy Entry and Exit Design Criteria ............................................................................. 36
Table 12: Easy Entry and Exit Decision Matrix ........................................................................... 37
Table 13 : Final Team Prototype Budget ...................................................................................... 58
Table 14: Timed Transportability Test ......................................................................................... 60
Table 15: Cart Dimensions ........................................................................................................... 60
Table 16: Trunk Dimensions for Chrysler Town and Country ..................................................... 61
Table 17: Trunk Loading Tests ..................................................................................................... 61
Table 18: Flutter Test Speed Results ............................................................................................ 64
Table 19: Team Budget ................................................................................................................. 67
Table 20: Estimated Fixed Costs .................................................................................................. 67
Table 21: Estimated Variable Costs .............................................................................................. 68
Table 22: Pro-forma Statement of Income.................................................................................... 78
Table 23: Pro-forma Statement of Cash Flows ............................................................................. 78
Table 24: Break-Even Analysis .................................................................................................... 79
Table 25: Break-Even Analysis (continued) ................................................................................. 80
Table 26: Iron Man Corporation Budget ...................................................................................... 80
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1. Introduction
Team 12 (Iron Man) is composed of three senior engineering students, all pursuing a degree in
engineering with a mechanical concentration at Calvin College in Grand Rapids. Each member provides a
variety of experiences, skills, and background to this project. The team consists of (from left to right in
Figure 1): Lukas Woltjer, Andrew Vriesema, and Allen Bosscher.
1.1 Team Members
Figure 1: Team 12 – Iron Man
Allen Bosscher
Allen was born and raised in Grand Rapids, Michigan. He is a senior engineering student at Calvin
College and expects to graduate in May 2014 with a Bachelor of Science in Engineering degree with a
mechanical concentration. Allen has interned at Rapid-Line, a metal fabrication company, for the past
three years. Through this internship he has learned valuable insight into production and design
engineering. Allen will continue working at Rapid-Line full time as a Design and Manufacturing
Engineer upon graduating.
Lukas Woltjer
Lukas was born in Nashville, Tennessee and has lived in Washington State and Portland, Oregon. He is a
senior engineering student at Calvin College and expects to graduate in May 2014 with a Bachelor of
Science in Engineering degree with a mechanical concentration. Lukas has interned at Calvin College as a
student researcher, Cascade Engineering as a renewable energy intern, and Oregon State University as a
technical lab assistant. Lukas has accepted a position at K-Line Industries as a Mechanical Design
Engineer.
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Andrew Vriesema
Andrew was born and raised in North Haledon, New Jersey. He is a senior engineering student at Calvin
College and expects to graduate in May 2014 with a Bachelor of Science in Engineering degree with a
mechanical concentration. Andrew has interned at Rapid-Line for the past six months. He has accepted a
position at LG Chem as a Production Engineer.
1.2 Description of Calvin College and Senior Design Course
Calvin College is a Christian liberal arts college located in Grand Rapids, Michigan with an enrollment of
approximately 4,000 undergraduate students.1 Calvin offers an ABET-accredited Bachelor of Science in
Engineering degree (BSE), with concentrations in Chemical, Civil & Environmental, Electrical &
Computer, and Mechanical Engineering. In conjunction with this project, the team has taken part in a
design course required for all senior engineering students at Calvin College. This course is taught by four
professors, one from each engineering concentration offered at Calvin. This course lasts over both
semesters and has five outcomes upon completion of the course: to be able to define, plan and implement
a major project; to participate effectively as a team member; to understand business and finance; to launch
a successful career; and to integrate the Calvin education.2
1.3 Project Definition
The project the design team has worked on includes researching, designing, constructing, and testing of a
running cart, usable by a person with moderate physical disabilities. The project definition was to design
and construct an improved running cart specifically for disabled passengers. In order to accomplish this
project, several features were outlined that needed to be met in order to achieve the project definition: the
design must be light-weight, easy and comfortable to use by both the runner and the passenger, able to
travel well on various surfaces, easy to transport, and low cost.
To achieve these objectives, the team worked closely with caretakers and care institutions who have
significant experience in assisting disabled people. The team also employed best practices in machine
design and structural analysis to ensure the safety of the passenger and runner, and to ensure reliable
performance of the cart.
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2. Project Management
2.1 Team Organization
2.1.1 Team Member Roles
Many of the larger tasks associated with the design project were completed as a team, with a specific
team member designated in charge of particular responsibilities within these tasks.
Allen Bosscher was in charge of the research, team management, decision making, and creating and
updating the necessary larger assignments required for this project. He coordinated with the rest of the
team about which areas of the project needed to be researched more in depth as the project proceeded and
was in charge of compiling all collected research. He was also in charge of maintaining the team’s
schedule, which included setting up most of the team meetings and keeping track of the various
assignments that were required as part of the course. Allen was also in charge of the decision making
process for this project, which included deciding upon the best course to pursue for each team member, as
well as what needed to be accomplished by when. Finally, Allen was the primary person in charge of
creating and updating the larger papers and presentations that were required as part of the course. This
included being the lead on the Project Proposal and Feasibility Study (PPFS), the Final Design Report,
the CEAC presentation, faculty review, and in-class presentations.
Lukas Woltjer was the webmaster and was responsible for updating and maintaining the team’s website.
This included updating the website as required through the course, as well as adding various other
sections as he saw fit in order to provide a good overview of the project. He was also the primary contact
between the team and the resources gained through this project, which meant he was the primary face of
this project to outside resources. He also was the primary person in charge of ordering the materials
required for this project. Lukas was also the primary lead on refining the designed computer models for
the project. He was in charge of how the design options were modeled and analyzed through a variety of
methods such as finite element analysis (FEA). Lukas was also in charge of most of the initial prototype
construction, which included welding and assembling the frame.
Andrew Vriesema was in charge of testing the constructed prototype, which included outlining the
necessary tests and assigning which team members would do which tests. He was also the lead on the
initial computer model, which provided a great baseline for the project. Besides these primary roles,
Andrew greatly assisted Allen and Lukas in their roles, providing his assistance whenever necessary.
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2.1.2 Organization Chart
Figure 2: Organization Chart
The team’s organizational chart is displayed in the above figure. This chart outlines the organization of groups and individuals related to this
project. The team recognized three distinct divisions within this project: project resources, design resources, and the administrative resources. Each
of these groups had distinct influences on the project as a whole.
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2.1.3 Team Meetings
Formal team meetings were held approximately twice a week for roughly thirty minutes each, which
varied according to the amount of work that needed to be discussed. During these meetings the team
reported on what work was accomplished and planned out what tasks needed to be completed next.
Meetings with outside resources were scheduled as necessary in order to have all team members present.
Meetings with the team’s advisor, Professor Ned Nielsen, were conducted when it was necessary to seek
out his assistance throughout the duration of the project.
2.1.4 Team Documents
All electronic documents are saved on Calvin College’s “Shared Drive” through the file path
S:\Engineering\Teams\Team12. Additionally, hard copies of research documents and important
correspondence are compiled by Allen Bosscher and are available upon request. The design team also has
a team website located at the following URL: http://www.calvin.edu/academic/engineering/2013-14team12/index.html. This is maintained by Lukas Woltjer and contains important documents and general
team information, links to outside resource web pages, and updates on the project.
2.2 Schedule Management
The team decided to dedicate as much time as was needed at the beginning of the first meeting of each
week on reviewing the schedule of tasks. The team updated the schedule as needed when new issues and
other project necessities arose. Allen Bosscher was the primary schedule coordinator, and updated the rest
of the team on what tasks needed to be completed first and the deadlines associated with them. Allen was
also in charge of submitting the necessary assignments as part of the senior design course in which the
team was enrolled. Priority was assigned to tasks which require immediate response, which include
unforeseen issues and customer relations. The design team will strive to minimize the amount of
unforeseen issues, allowing the team to focus on important yet non-urgent tasks. This was suggested by
Professor David Wunder, as urgent and important tasks are typically large time sinks, forcing the team to
deviate from the predicted schedule. In this way, the schedule was used as a management tool, as it
clearly outlined what aspects of the project needed to be accomplished when. The team was able to very
easily see what needed to be accomplished by maintaining the schedule through keeping it up to date with
the actual project’s progress. This enabled Allen, the lead for the team’s management, to quickly delegate
and assign tasks to all of the team’s members. When scheduling issues arose the team worked through
them as a team, making sure to work out meeting times which fit all of the team member’s individual
schedules. The largest sources of these scheduling conflicts consisted of scheduling around practice times
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for those members on sports teams, as well as the work schedules of all members. The number of hours
worked on the project per week per team member was varied quite largely, with a range between five and
fifty hours, depending on the tasks outlined through the team’s meetings and the necessary course
assignments.
2.3 Budget
Lukas Woltjer was the primary budget coordinator, and was in charge of maintaining the budget and
adjusting it as the design progressed. All team members had access to the budget, and were able to
purchase necessary materials already listed on it without conferring with other team members.
Adjustments which added to the budget were made with team consensus, and were only suggested if an
important and necessary need arose which required the reallocation of funds. Increase of the budget,
especially in costs which only emerged once the project progressed beyond the initial design stage, were
avoided when possible, but the team made sure there was a contingency which allowed for these
unforeseen costs to be covered within the initial budget approved by Calvin College. This budgeting
method was suggested by Professor Matthew Heun, and has been successfully implemented in many
critical projects. Because the budget is indicative of the overall cost of the running cart, great care was
taken to ensure it was accurate and that costs were kept low. The detailed project budget appears in the
prototype construction section of the report. The budget was used to great lengths as a management tool,
as it provided a good idea of the overall stage of the prototype construction. The extended budget
forecasting the costs in the event of full-scale production appears in the business analysis section. The
budget also clearly displayed all of the necessary objectives identified with this project through the
allocation of funds toward their respective sections.
2.4 Method of Approach
The team's approach was to break the project down into four stages, which involved iteration and overlap
at some stages. The first stage was to research currently available and similar projects, to see how the
team could differentiate the final design product and provide a unique service or experience to the end
user. This stage also included interacting with those who would potentially use such a product, which
helped guide the overall objectives of the project and outline necessary features. The second stage of the
project was to design, model, and analyze the prototype primarily through the use of computer software
such as SolidWorks, Mathcad, Engineering Equation Solver (EES), and Excel. Hand calculations and
sketches were also created, mostly during the initial stages of the design process. The third stage of the
project was to construct the modeled prototype, using the purchased materials and making use of the
resources available to the team, including the metal shop on Calvin College’s campus and Rapid-Line, a
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metal fabrication company which graciously allowed the team to use their facilities as needed. The fourth
and final stage was to test and analyze the completed prototype. This included making modifications
during the construction stage, performing technical tests and human trial runs using the product, as well as
creating a business analysis which detailed all of the team’s suggested changes to the prototype, in order
to create the best possible model for the end user.
Team communication was primarily achieved through the biweekly face-to-face meetings previously
mentioned. However, if issues or questions arose outside of these meeting times which required other
team member input, communication was then primarily achieved through email. For the quicker questions
or ideas which required a shorter response time table, or where easily answered by only one team
member, communication was achieved through text messages or phone calls. Team communication with
outside resources was also accomplished primarily through email and phone calls, as the team realized
that face-to-face meetings with these resources would take even more time away from their
responsibilities.
There were several key Christian principles that guided the teamwork, behavior, and relationships present
throughout this project. Showing respect toward each team member, through listening and considering all
ideas and treating one another equally, was crucial to the project’s success. The team also recognized the
strengths and weaknesses of each team member, and allocated responsibilities according to the God-given
talents present in each member. Whenever disagreements emerged within the project the team attempted
to remain as level headed as possible. However, the team acknowledges that sin is present in the world, so
heated arguments did occur. These arguments were quickly solved through the intervention of the
remaining team member, at which time a decision was reached.
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3. Requirements
The overall project definition for the running cart was to design and construct an improved running cart
specifically for disabled passengers. The product needed to be designed in such a way as to allow a
teenage handicapped child to be able to get outdoors and experience nature in a way that they would not
normally be able to. This meant that the running cart design would need to have several key requirement
groups: functional, performance, and interface. The team formulated requirements and goals according to
the S.M.A.R.T. goal guidelines identified through research. This guideline seeks to create goals that are:
specific, measurable, attainable, realistic, and time bound.3
3.1 Functional Requirements
Functional requirements for this project were requirements, identified by either the team’s resources or
through the team’s research to be necessary in order to deliver a completed project, that involve physical
properties on the designed prototype. These functional requirements defer from performance requirements
in that performance requirements by definition have some ability to be directly measured and quantified,
allowing performance requirements to achieve various levels of success. In comparison, functional
requirements are those which need to be met in order to have a functional prototype, and are more basic in
nature.
3.1.1 Strength Requirement
The first functional requirement identified for this project was strength. The designed prototype needed to
be strong enough to support a teenage child over potentially tough terrain. This meant that the frame of
the design must be able to be strong enough to survive repeated drops of more than two feet, as this was
the predicted displacement of the product in unloading and loading. The frame must be strong enough to
survive repeated use on various surfaces, particularly bike trails, where the surface is often not smooth.
The strength of the cart is an important aspect of the design. The design team initially designed the
product to be able to support a 150 pound carrying capacity, but as the project progressed and additional
testing and calculations were performed, the team was able to update the supported carrying capacity to
support 200 pounds, while still maintaining adequate safety factors. The frame must also be rigid enough
to handle the various terrains with ease.
3.1.2 Mobility Requirement
The next functional requirement identified with this project was that the running cart must be mobile, i.e.
able to be moved easily by a caretaker. This requirement is the basic form of the performance requirement
of multiple surface capability, as the prototype must be able to function first on the most widely used
surface, which the team identified as cemented streets or sidewalk. This mobility requirement means that
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the cart must be able to easily move through the caretaker exerting force on the product in the direction of
desired motion. This requirement is purposefully very broad, as all this requirement entails is that the
prototype is able to move through a caretaker’s actions.
3.2 Performance Requirements
Performance requirements for this project were requirements, identified by either the team’s resources or
through the team’s research to be necessary in order to deliver a completed project, that involve features
present on the designed prototype. These performance requirements are able to be directly measured and
quantified, allowing various levels of success to be achieved.
3.2.1 Transportable Requirement
The first performance requirement identified through caretaker surveying for the design is that it needed
to be transportable. This meant that the cart would need to be able to fold up or easily come apart so that a
caretaker could lift it up and place it in the back of a van or bike rack, enabling the product to be
transported to the necessary destination while not in use. There are two sub requirements the team
identified to go along with this main requirement: the size and weight of the product.
3.2.1.1 Size Requirement
The size of the cart needed to be big enough so that the strength requirement was met, while also
maintaining the comfort of the passenger. However, the product also needed to be designed so that it
would be small enough to be easily maneuverable while in use and small enough to fit within the trunk of
a standard van or on a mounted bike rack. The team identified this size requirement such that a standard
sized human could easily maneuver the product while in use and lift a height of two feet off the ground,
so that it could be placed onto a bike rack or van trunk. The size of the product was still variable within
these requirement, as the product could be designed with a collapsible nature or a sectioned design. If the
cart were designed to be able to break apart into sections, the product could be larger than if it were just
collapsible, as the sections would be required to meet this specification individually. The length of the
cart was chosen such that an average height teenager would be able to comfortably ride in it. The width of
the cart was chosen such that the shoulders of the passenger would comfortably fit within the frame
design, with additional room on either side. This additional free space on each side of the passenger was
deemed necessary through communication with the caretakers, as they explained that handicapped or
mentally disabled passengers do not like to feel trapped or contained within a product, as this negatively
affects their mood and greatly increases the probability that they will not enjoy the product while riding in
it. The height of the cart was constrained such that an average size adult could easily maneuver the
product without discomfort.
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3.2.1.2 Weight Requirement
The other requirement detailing the transportable aspect of the product was the overall weight of the
design. The product should be light enough for the caretaker to be able to maneuver without issue on a
variety of surfaces. Additionally, the product must be light enough so that the caretaker could easily lift
the product to place it in the back of a van trunk or onto a mounted bike rack, which the team specified to
mean that the product must be able to be lifted a vertical distance of two feet. Through communication
with the outside resources acquired through this project, such as the caretakers and hospital staff
interviewed, the design team reached a weight goal for the product to not weigh more than eighty pounds.
This was selected as the design weight as it enabled the carrying capacity load to be achievable, while still
achieving the transportable requirement.
3.2.2 Multiple Surface Requirement
The next performance requirement that needed to be achieved for this product to be successful was that
the product would need to be able to handle various terrains. This concept was brought up through the
caretaker survey, as nearly all caretakers surveyed expressed this feature as being necessary in the final
product. The team defined this requirement in two ways: first, that the default tires selected for the
product must be able to handle a large amount of terrains, and second, that there be a quick and easy way
to switch out all three of the tires on the product, allowing tires made for specific terrain to be used as
needed. The team outlined the following terrains as needing to be traversable options in order for the
project to be a success: cement, asphalt, bike trail (packed dirt), and grass. The final design, which
includes all suggested changes to the prototype, would also need to be able to handle beach terrain,
through the use of specialized beach tires with wider tire thicknesses.
3.2.3 Easy Entry and Exit Requirement
An additional performance requirement identified through the team’s research was that the product must
be designed such that it is easy for the passenger to enter and exit the cart. The team realized that for a
large portion of the product’s designed user base it is often the caretaker’s responsibility to greatly assist
the passenger enter and exit the vehicle, as they often do not have the necessary motor functions to
perform these actions themselves. Communicating with the caretakers made this issue very apparent, as
all of the surveyed caretakers expressed their dissatisfaction with the seating systems present in similar
models on the market. These products often have a bucket seat, which results in the passenger resting
deep with the product’s seat. It is extremely difficult for the caretaker to then reach into this bucket seat in
order to lift the passenger out, as this requires additional actions in order to slide the passenger toward the
front of the bucket seat before the passenger is able to be rotated and exit the vehicle. These actions put
significant strain on the caretaker’s backs and arms, resulting in the caretakers experiencing issues with
Page 10
their backs and not being able to operate at full strength for the rest of the day or week. The team
therefore realized that the designed product must include a system such that the passenger could easily be
assisted when entering and exiting the product.
3.2.4 Passenger Comfort Requirement
The final performance requirement was not as quantifiable as the previously mentioned requirements.
None the less, it was still a vital requirement for the product to be successful, as not designing the product
to include this feature would inevitably result in the product not being used. This requirement was that the
passenger needed to feel comfortable while riding in the product. This requirement needed to be clearly
visible in the seat design, as this is where the passenger would have the most contact with the product.
However, designing a seat which made the passenger feel comfortable was not the only concept that
needed to be achieved in order to satisfy this requirement. In addition to the comfort of the seat, the
overall product must be pleasing and safe in the passenger’s view. Since the product was designed with
handicapped or mentally disabled people in mind, this requirement is even more important. This is
because, as the caretakers explained, passengers of these natures focus on minor annoyances much more
than the rest of the population. This meant that the comfort of the design did not just extend to the feel of
the product, but also to a more mental level. The team strived to design the product in such a way as to
alleviate as much of these problems as could be predicted, but acknowledged that this was an inexact
process, as everyone has different minor annoyance triggers. The team ended up summarizing this
requirement by designing the product such that passengers would not express so much displeasure while
riding in the product that they would rather not ride in it.
3.3 Interface Requirements
Interface requirements for this project were requirements that involve features more applicable to the
caretaker’s needs and desires when not using the product in its primary role. These interface requirements
were therefore an extension of the product during times in which the caretaker was not pushing the
passenger, applicable to the more administrative features that needed to be present in the design.
3.3.1 Customer Interaction Requirements
The customer interaction requirements were chosen by the team through listening to the caretaker’s ideas
on a broader level, meaning these requirements were not necessarily features that needed to be present in
the design, but rather were requirements that should be present such that the caretaker could spend as little
effort as possible in order to feel comfortable with the product. The team outlined these requirements into
two main categories: first, the product must be designed in such a way so that its purpose and function is
almost inherent within the product, and second, that there would be some type of documentation readily
Page 11
available to the caretaker or entity using this product which would detail the necessary features and proper
use of the product.
3.3.2 Cost Requirements
An additional interface requirement that the team identified was in the cost aspect of the product. Due to
medical costs related to disabilities, many families with physically disabled members do not have the
opportunity to purchase expensive equipment. This is the primary reason for why a crucial aspect of this
project was to aim to keep the total product cost as low as possible, while still achieving all other
requirements. The growing trend toward deinstitutionalizing mentally disabled or handicapped children
has resulted in families being the most important source of long-term assistance.4 This trend has resulted
in families bearing more of the financial burden than was previously required. This concept is evident in a
survey of families with a child with special needs, where a full forty percent experienced a large financial
burden related to their child’s condition.5
3.3.2.1 Material Costs
The design team recognized that designing the product in a method that minimized material costs was
necessary in order to keep the selling price as low as possible. To do this, material options were limited to
commonly available metals and polymers, despite having to make weight sacrifices to maintain necessary
strength. The design team also realized that this meant that the design should be required to make use of
commonly available materials whenever possible, as custom fabricated parts would drastically increase
the cost of the product.
3.3.2.2 Manufacturing Costs
Manufacturing costs for the budget given to Calvin College were set at $0, as the team did all the required
welding, machining, and assembly in-house. However, the team realized that this design project needed to
be extended beyond the prototype stage. This meant that minimizing manufacturing costs whenever
possible was also a requirement of this project. This requirement greatly guided the design process as a
whole, in particular the joining and fabrication processes necessary in creating the final design. Through
courses taken as part of Calvin College’s engineering curriculum, the design team was informed of the
general principle present in many products; that eighty percent of the cost of the project is determined in
the design phase, often before a prototype is even created.6
3.4 Team Deliverables
The deliverables for this project were diverse in nature, in order to accommodate the requirements of the
course and those selected by the team specific to this project. The Project Proposal and Feasibility Study
(PPFS), was the first large deliverable for this project, and was submitted in December, 2013. This
Page 12
document outlined all of the work accomplished to that point, and described what work would be
accomplished and whether the project was feasible. Other deliverables required by the course that the
team submitted were the Final Design Report (which is the document you are currently reading), a
working prototype of the team’s design, a team website, and design notebooks. The Final Design Report
summarizes all the work that was accomplished through this project. Design notebooks were turned into
the team’s advisor, which included important documents created throughout the project in order to show
what each team member worked on. These design notebooks included meeting notes, tasks lists,
resources, contact information, team communications, and sketches of the design throughout the various
stages. The team website was created so that anyone at any time would be able to see the project worked
on by the team. This website also includes links to all important documents and information related to the
project. The team’s website is found by going to the following link in the web browser of your choice:
http://www.calvin.edu/academic/engineering/2013-14-team12/. The team also identified an additional
deliverable that was not directly required through the course but was recognized to be necessary in order
to deliver the best product possible. This deliverable is a user manual for the prototype, which describes
all of the important features in the design, how to use the product safely, and contact information. The
user manual is available on the team website, as well as in Appendix B of this report.
Page 13
4. Task Specifications
4.1 Schedule
The design team realized that detailed task specifications were a key part of the project’s success.
Therefore, a work breakdown structure (WBS) was created during the initial stages of the design, and
then modified as the project progressed. This work breakdown structure featured only broad tasks, as the
team developed a detailed Gantt chart in order to carefully schedule the project. The work breakdown
structure appears in Appendix C of this report. This schedule included an approximate time budget for the
various tasks, which factored in some slack, as the team acknowledges that even the best laid plans are
often ruined in their execution.
The design team also created a more detailed schedule using the Microsoft Project software. This enabled
the team to create a Gantt chart, which clearly showed dependencies present within the various tasks, time
allocated, team members responsible, and due date. This Gantt chart was modified as the need arose, and
was incorporated into the team’s shared Google calendar, which showed important milestones. A
screenshot of a section of the team’s Gantt chart is shown in the figure below.
Figure 3: Gantt Chart Example Section
By using the work breakdown structure, Gantt chart, and shared Google calendar the design team was
able to clearly see what needed to be completed by what time. This enabled each member to know their
Page 14
responsibilities, and allowed the team to stay on task. The team acknowledges that significant changes
were made to the initial schedule as the project progressed, as much more design time needed to be
allocated than initially estimated.
Page 15
5. Research
5.1 Material Options
Following the constraints imposed in the requirements section, the design team found four material
options for the frame. These options are detailed in the frame material design section of the report. Seat
and cushion material options were also researched. These options are detailed in the seat design section of
the report. The design team made sure to choose materials that would withstand mold and mildew due to
sweat and water and which would maintain integrity when exposed to sunlight repeatedly. Other desirable
characteristics included comfort and durability (tear resistance).
5.2 Similar Projects
5.2.1 Overview
While the team desired to design and deliver a novel idea, the team did not want to ignore the work done
on similar projects. Researching these projects enabled the team to observe areas of improvement and
issues that should be avoided through the entire design process. Through research, the team was able to
find several similar projects that provided a baseline for which to build the project upon.
The first similar idea researched was the project known as “Team Hoyt.” This is a father and son duo who
participate in various marathons and triathlons. The son, Rick Hoyt, has cerebral palsy and is limited to
riding in a special boat during the swimming portion, the front of a special bicycle during the bike
portion, and a special wheelchair during the running portion of the triathlons. This idea is quite similar to
the team’s design, as the primary goal of both designs are to enable a parent or family member to more
easily involve a disabled or motion-limited child in outdoor endeavors.7 The physical differences the team
plans on incorporating are the collapsible design and the quick-change wheels. The design team also
desires to make the running cart more affordable than the “running chair” that Team Hoyt uses.
The second similar idea comes from the entity known as His Wheels International. This is a non-profit
Christian organization which focuses on providing people with lower-body disabilities hand-pedaled
“trikes” for transportation.8 Their focus is mainly overseas, where the effects of polio are still common,
and where many have no means of transportation or assistance, and must pull themselves around with
their hands. His Wheels, although producing a somewhat similar product, are focusing on a much
different need.
The third similar idea is known as myTEAM TRIUMPH (mTT). This is an organization that provides
resources and equipment for disabled “Captains” to participate in long-distance events with the assistance
of their “Angels.”9 However, mTT does not manufacture equipment and is therefore not a competitor to
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the designed product detailed within this report. This organization greatly assisted the design team in the
initial design stages, particularly the CEO, Ronald Robb.
The final similar project that the team looked into while working through this project was a past Calvin
College senior design team. This 2008-2009 design team, called TRIumph, worked with myTEAM
TRIUMPH on designing and manufacturing a cart that could function both as a pulled bicycle trailer and
a pushed running chair.11 This project was primarily used by Iron Man during the initial stages of the
team’s design, mostly by showing a clear market the team’s product should enter. The design team began
the project by identifying two markets for the product: competitive and recreational. The competitive
market actually explains where the team’s name of “Iron Man” came from, as it is named after the series
of long-distance triathlon races, termed Ironman Triathlons. Since the previous design team modeled their
product for a competitive application, Iron Man ultimately decided to not tread back over this idea, and
instead designed the product to be marketed toward the recreational market.
5.2.1 Analyses
The design team collected data from approximately fifty similar products, ranging from baby strollers to
high end adult running carts. The team was interested in determining the relationships between three
variables; carrying weight, selling price, and weight of the vehicle. These relationships are displayed in
the following three figures.
3000
Selling Price ($)
2500
2000
1500
1000
500
0
0
50
100
150
200
250
300
Carrying Weight (lb)
Figure 4: Carrying Weight vs. Selling Price
The above figure displays the vendor designated carrying weight against the selling price of the
researched products. There is a direct relationship between these two variables, albeit it a slightly weak
Page 17
relationship. This idea complemented the design team’s initial assumptions, as it makes logical sense that
increasing the carrying capacity of the product would increase the cost of materials, thereby increasing the
selling price of the product. What was interesting about this research was how little of a relationship there
was between these two variables, as the linear fit to this data had very poor residual values, especially
when the carrying capacity went closer to its upper researched limit of 250 pounds.
3000
Selling Price ($)
2500
2000
1500
1000
500
0
0
5
10
15
20
25
30
35
40
45
Weight of Vehicle (lb)
Figure 5: Vehicle Weight vs. Selling Price
This figure displays the product’s listed weight against the selling price of the product. This was an
interesting and valuable graph in that it seems to display that there is not a visible relationship between
these two variables. This led the team to conclude that there were more important variables in this market
than the weight of the vehicle, which is very interesting in that the team had initially assumed that these
variables would be directly related, meaning that as the weight of the vehicle increased so would the
selling price. However, this is not the case, which caused the design team to do some additional research
and thought into the potential reasons as to why this is the case. The design team ultimately was able to
reason this relationship out, which provided valuable information which was incorporated into the
designed product. The design team reasoned that these variables did not have a visible relationship as the
weight of the product is ultimately desired to be as light as possible, while still maintaining all other
requirements. This means that while heavier products, which usually indicate more material used, are
typically associated with higher selling prices, since the weight of the vehicle is a key selling feature these
heavier products are sold at a lower markup due to the market’s demand to have lighter products. Put
another way, even though heavier products may use more material, the vendors cannot price them higher,
Page 18
as the market desires light products and will not want to purchase an expensive and heavy product. The
team also reasoned that there are many different materials employed to create the various products,
resulting in the weight being much more based on the material selected than on the size of the product.
While the design team was not able to see a relationship in this figure, the team was still able to glean
valuable insight into this market which was incorporated into the team’s design. The most important
information gained from this figure is that the material used for the product is a much better indicator of
the selling price of the product than the weight of the product. This placed a larger emphasis on the
material selection aspect of this design, and lessened the focus on the weight of the prototype. The team
reasoned that the material of the prototype would almost assuredly be different than the material
ultimately selected in the proposed final design. The large amount of plastics made available in a larger
scale production design would assuredly lower the weight of the product, while still significantly
influencing the selling price of the product.
300
Carrying Weight (lb)
250
200
150
100
50
0
0
5
10
15
20
25
30
35
40
45
Weight of Vehicle (lb)
Figure 6: Product Weight vs. Carrying Weight
The above figure displays the product’s weight against the carrying capacity of the product. This figure
aligned much more closely with the team’s initial assumptions regarding these two variables, as logically
a heavier vehicle would have a higher chance of being able to support a heavier load. However, the linear
relationship between these variables was once again very weak, signifying that there are many underlying
factors not accounted for in this research. The team reasoned that a significant underlying factor was the
company name associated with each product. In specialized markets, where the products can be incredibly
Page 19
varied, the concept of brand recognition is very important.10 If several companies have emerged within
this market and are associated with higher quality they could afford to raise the selling price of their
product.
5.3 Resources
The team established several contacts as resources through the duration of this project. The primary
knowledge the team gleaned from resources were the specific needs and requirements of a disabled
person that pertain to the running cart design. The ideas expressed by the resources were able to be
transformed into requirements, necessary features, and design options.
The first contact identified was His Wheels International. The team’s communications with this
organization mostly pertained to the ergonomics of the design. His Wheels was able to assist the team due
to their extensive experience with people with physical disabilities, and was a vital resource for all
specific needs corresponding to that. The primary contact with His Wheels was Alice Teisan, the founder
and executive director. Communication with Alice was primarily achieved through email exchanges.
The second contact identified was Becky Van Zanen. She was a part-time caretaker for a disabled client,
and has extensive experience using a running cart. She provided the team with extremely valuable
information regarding the importance of various features of a running cart, and represented her client’s
needs thoroughly. Her input was able to tailor the design to meet the needs of many disabled people.
Unfortunately for the design team, Becky left this part-time job during the second semester, effectively
eliminating physical testing with her and her patients. The team was able to overcome this through the use
of other resources.
The third contact identified was myTEAM TRIUMPH (mTT). This was a contact highly recommended
by Becky Van Zanen. This organization provides equipment and resources for disabled participants of
long-distance events. The team primarily was in contact with the CEO of mTT, Ronald Robb, and gained
valuable information from him regarding ergonomics, competitors, and other design considerations.
The final contact identified for this project were the various other caretakers surveyed through several
care facilities. These contacts were used solely for the survey, which proved to be valuable during the
initial design stage of this project.
5.4 Safety Requirements
To ensure the safety of the passenger and runner, the design team considered methods which would
prevent any possible form of injury. The possible injury scenarios considered included: roll-over,
passenger ejection, collision with stationary objects, collision with vehicles or pedestrians, abrasion from
asphalt contact, injury by moving components, skin irritation/damage from unsuitable materials, cuts or
Page 20
skin tears from cart entry/exit, neck or head injury from excessive vibration and/or shock, and bruises and
cuts to the runner due to insufficient leg clearance. The design team cannot foresee all potential hazards,
but it was necessary to thoroughly test the cart and minimize the likelihood and severity of injuries
sustained from use of the cart. Through communicating with the team’s resources the team learned that
round tubing would be preferred on any surface that the passenger would possible come into contact with.
The resources expressed this is of greater importance with handicapped passengers, as they are more
likely to injure themselves. Additionally, through the resources the team discovered that rounded edges
were better than square, as someone who does not have sensitivity in the feeling of their skin could tear
skin off on a sharp edge without knowing or feeling it. The team accomplished this design requirement by
thoroughly de-burring all sharp edges and by applying a protective paint layer on the prototype. The
fabric material was selected in accordance with the previously mentioned safety requirements in mind.
The design team also designed the product such that there was a safety harness for the passenger, as the
safety of the passenger was of the upmost importance.
Page 21
6. Design
6.1 Design Criteria
The team followed several criteria when designing the running cart. The first was that the team strived to
make the designed product as simple as possible. This enabled easy and inexpensive product assembly
and repair work. Creating a simple design was important in order to maintain the team’s selling price goal
of this project. Another design criteria for the running cart was to design the cart to be as light as possible,
while still maintaining the necessary strength needed to support a carrying capacity of approximately 150
pounds. The product needed to be light enough so that a caretaker could easily pick it up and place on
their transportation method of choice. Also, the team designed the product in such a way that it could be
easily collapsed, which furthered the ease of transporting the product. The product also was designed in
such a way as to be strong and reliable enough that customers would feel comfortable using the product
without worrying about a catastrophic failure. The product also was designed to have interchanging
wheels, which allowed the caretaker to easily switch out all three wheels as needed, according to the
terrain present during their excursions. The following sections will describe each major design decision
made during this project and designed into the prototype, with sections on the feature’s design criteria,
alternative options considered, and final design decision.
6.2 Primary Application
6.2.1 Primary Application Design Criteria
The first major design decision that the team analyzed was what the primary application for the product
should be. This meant identifying which market the product should be designed toward. The design team
desired to create and deliver a novel idea which would benefit those in need. The product’s objective was
to enable mentally handicapped or disabled passengers to experience the beauty of God’s creation.
However, this objective could be achieved by designing a product which could be applicable to several
markets, so the design team needed to select a particular market to design the product toward.
6.2.2 Primary Application Alternatives
The design team identified two potential markets for this product to be geared toward: competitive and
recreational markets. The competitive market would require the product to be designed for triathlons or
other events in which the caretaker would need to continuously push the product for distances over one
mile. This would mean the product would have a much more limited use, as long distance designs would
focus primarily on weight, and place the other design features off to the side unless absolutely necessary.
Page 22
The second identified market, the recreational market, would be geared more toward home or caretaker
needs. This market would require the product to be used over much shorter distances, but over a wider
range of terrains. The most important design features would be much more focused on the comfort of the
passenger, as the excursions would not be timed or required to traverse a set distance. This would allow
the product to be designed towards a much more general use.
6.2.3 Primary Application Design Decision
In order to decide which market the product should be designed for, the design team spoke with the
team’s resources and looked into similar projects, which were outlined in previous sections of this report.
From this research, the team found a past senior design project, TRIumph, which designed a similar
product to be used in the competitive market. This design team did not desire to go back over this design,
instead desiring to focus on a more novel design. This led the team to lean towards designing the product
to fit within the recreational market. The design team also spoke with the various resources in order to see
whether there was a strong demand toward either market. From these communications, it was very clear
that caretakers and the other resources desired the product to be designed for the recreational market. This
is quite understandable, as many of the team’s resources would be able to use a product designed for the
recreational market much more than a competitive design. Therefore, the design team decided to design
the product to enter the recreational market.
6.3 Frame Material
6.3.1 Frame Material Design Criteria
The second major design decision the team analyzed was the material which would be used for the frame.
The criteria the team used to decide upon the final material appears in the table below.
Table 1: Frame Material Design Criteria
Criteria
Weight
Cost
25
Strength
25
Manufacturability
20
Durability
15
Stewardship
5
Trust
5
Integrity
5
Page 23
As shown in the table above, the cost and strength of the frame material were designated to be the most
important design criteria. This was due to these criteria directly affecting the design requirements. One of
the primary goals the team designed towards was to maintain a low cost product, while still maintaining
the necessary strength requirements. The manufacturability of the frame material was also designated to
be an important design criteria. This took into consideration the ease of purchasing the material, the ease
of machining the material using the tools provided in Calvin College’s metal shop, as well as the ease of
welding. The durability of the product took into consideration the long term material properties, as well as
relative ease of fixing issues that could occur several years into the product’s lifespan. Finally, the team
identified three design norms that were directly applicable to the frame material design. As Christians, the
team sought to design in such a way as to carefully use the earth’s resources. In this way, the team strived
to be good stewards of the earth. Therefore, the team included the design norm stewardship as a design
criteria, as the frame material chosen must consider the availability of earth’s resources. Economic and
environmental concerns of the material chosen were also included in this criteria. The next design norm
integrated into this design decision was trust. This criteria was rather straightforward in the designed
product. The team had to choose a frame material that would be credible, dependable, and reliable.
Potential users of the product should not be concerned with the frame’s design at first glance. Integrity
was the final design norm that directly applied to the frame design. The frame needed to be designed so
that it is pleasing and intuitive to use. The material chosen needed to accomplish these goals, so that the
passenger and runner would not be uncomfortable with the product.
These design criteria proved to exist in tension during the design of this product. Maintaining the low cost
of the frame while still reaching the necessary strength and integrity requirements proved challenging,
and required significant time in order to weigh all the options and carefully choose the best course.
6.3.2 Frame Material Alternatives
The design team researched potential frame material options and narrowed the list down to four: 4130
alloy steel, 6061 aluminum alloy, 3AL-2.5V titanium alloy, and carbon fiber. The other material options
that were researched were ultimately eliminated due to the availability of the material as well as the
amount of information available. These material options were not commonly used on similar projects and
would have added a large amount of difficulty in procuring and using said materials.
The team selected 4130 alloy steel as a potential frame material as it is a very common material in frame
constructions. This alloy of steel is also easy to machine and weld, which was important to the design
team due to the limited welding experience of the team. Steel was also found to be the easiest material to
purchase due to its large presence in the manufacturing realm.21
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The team selected 6061 aluminum alloy as a potential frame material primarily due to its current
application in similar products. This alloy is commonly used in bicycle frames, which perform a similar
function to the team’s designed frame. Aluminum has a better strength-to-weight ratio than steel, which
would result in a stiffer frame than steel. Aluminum is also a very common material in the manufacturing
realm, so procuring the material would not prove to be difficult.22
The team selected 3AL-2.5V titanium alloy as a potential frame material due to its high strength-toweight ratio and excellent resistance to corrosion. This titanium alloy is 3.5% aluminum and 2.5%
vanadium by weight, which are added to the material in heat treatment processes to result in a higher
strength product. This higher strength would result in a frame ideal for off road and rugged use. In
addition, a titanium frame would be more durable than most of the other options. However, titanium is
more expensive than steel and aluminum and would provide manufacturing issues.23, 24
Carbon fiber was the final potential frame material considered by the team. Carbon fiber is gaining
popularity in bicycle frames, mostly due to its light-weight yet corrosion-resistant and high strength
properties. Carbon fiber was the most expensive material option, but was found to have the largest
strength-to-weight ratio. Beyond this monetary issue, carbon fiber is also more difficult to repair than the
other options, as fatigue failure occurs more readily in carbon fiber. Repairing cracks and other fatigue in
the frame would require more time and effort than the other options.25
The table below summarizes the material properties for all four material options.
Table 2: Frame Material Alternative Properties26
Material
Yield Strength
Specific Strength
Density
Tensile Modulus
(MPa)
(kNm/kg)
(g/cm3)
(GPa)
4130 Steel
910
254
7.84
200
6061 Aluminum
270
214
2.71
69
3AL-2.5V Titanium
930
288
4.63
110
Carbon Fiber
4000
2457
1.75
250
The material properties displayed above clearly show the differences between each material. As
mentioned, carbon fiber is clearly the strongest yet lightest, whereas aluminum yields at a much smaller
force.
6.3.3 Frame Material Design Decision
In order for the team to decide which material was the best option for this design project, a decision
matrix was created. This decision matrix listed the design criteria mentioned earlier and assigned a 1-10
Page 25
value for each material, with 1 being the lowest and least preferred. This decision matrix appears in the
table below.
Options
Table 3: Frame Material Decision Matrix
Design Criteria
Weight
4130 Steel
6061 Aluminum
3AL-2.5V Titanium
Carbon Fiber
Cost
25
10
8
5
1
Strength
25
8
6
6
10
Manufacturability
20
10
8
5
3
Durability
15
10
7
5
3
Stewardship
5
8
8
5
3
Trust
5
8
7
6
8
Integrity
5
10
10
7
4
The above decision matrix clearly shows that 4130 steel was the best frame material option for this
project. Therefore, the team chose 4130 steel as the frame material for the prototype. However, this
decision does not necessarily apply to the final designed product. The design team has catalogued an
extensive list of suggested changes to the prototype in order to modify the design into a full-scale
production run. These suggested changes appear in section ten of this report. The outcome of using 4130
steel as the frame material is shown in the prototype construction and testing sections of this report.
6.4 Quick Change Wheel Design
6.4.1 Quick Change Wheel Design Criteria
The next design feature the team analyzed for this project was the multiple surface capability requirement.
The team designed the product in a manner in which the wheels could be quickly and easily removed, so
that different wheel options could be used. This allowed the product to easily traverse the applicable
terrain options. The constructed prototype was able to travel on the following terrains: road asphalt,
sidewalk concrete, compacted dirt bicycle path, and grass. The criteria the team used to decide upon the
final quick wheel change method appears in the table below.
Table 4: Quick Wheel Change Design Criteria
Criteria
Weight
Cost
25
Ease of change
25
Change-over time
20
Durability
15
Trust
5
Transparency
5
Integrity
5
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Total
930
740
540
455
As shown in the table above, the cost and relative ease of changing the wheels were designated to be the
most important design criteria. This was due to these criteria directly affecting the design requirements.
One of the primary goals the team designed towards was to maintain a low cost product, while still
enabling the end users to quickly and easily change tire options. The durability criteria took into
consideration the long term potential for the designed feature, as well as the relative ease of fixing issues
that could occur several years into the product’s lifespan. The team also identified three design norms that
were directly applicable to this component. Similar to the frame material, trust was a design norm for the
quick wheel change method. The team needed to design this feature in such a way that it was readily
apparent to the end users how to operate and change. The final design for the quick wheel change method
had to be reliable and easily repeatable. This concept was directly applicable to the next design norm,
transparency. The quick wheel change design had to be understandable to someone without extensive
technical knowledge. This feature also had to be consistent. The design team strived to eliminate all
possible sources of confusion to the end users concerning this feature, as these issues would effectively
eliminate the use of the feature. Integrity was the final design norm that the design team determined
applied to this component. The design team recognized that this feature in particular needed to be
pleasing and intuitive to use. If the end users did not feel comfortable with the quick wheel change design,
they would most likely not use it. This would inevitably result in a product that would not perform to
adequate levels on the various terrains, leading to an increased potential for damage or even personal
injury to occur.
These design criteria did oppose each other once the design team began the decision making process.
Maintaining the low cost of the quick wheel change method while still reaching the necessary time and
ease of assembly requirement proved challenging.
6.4.2 Quick Change Wheel Design Alternatives
The team researched potential quick wheel change designs, and were able to determine two main options
for the product. The first quick wheel change option has been used on bicycles ever since its creation in
1927 by Tullio Campagnolo, and is commonly referred to as a quick release skewer.27 This design is
shown in the following figure.
Page 27
Figure 7: Quick Release Skewer Examples 8
The quick release lever is tightened while in use, which secures the wheel and axle to the bicycle’s fork.
To remove a wheel equipped with a quick release skewer, the user must simply loosen the quick release
lever. This quick wheel change method has both positives and negatives. It is very common in the bicycle
realm, so procuring the components would be relatively simple. Additionally, the installation and use of
said design is straightforward, minimizing the potential for the end user to become frustrated with the
design. However, this method leaves the wheels to be susceptible to theft, as the release mechanism is
quite quick and easy. The potential for the wheel to become disengaged while the product is in use is also
larger than in other designs, so care would need to be taken to ensure that it is properly tightened.
The second quick wheel change option that the team researched was quite similar to the quick release
skewer idea, but even less complex. This design option is simply referred to as a quick release hitch pin
system. The design option is displayed in the figure below.
Figure 8: Quick Release Hitch Pin29
This design option is very inexpensive and quite common, so purchasing this would be straightforward.
However, the potential for the end user to incorrectly use this design alternative is larger than with the
quick release skewer. This design would also take longer to remove than the skewer and would not be as
reliable or understandable to the end user.
The next design option operates in much the same way as the quick release hitch pin, yet was different
enough to warrant its own section. This option is simple called a hitch pin and clip, and is displayed in the
following figure.
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Figure 9: Hitch Pin and Clip12, 13
This option requires the customer to remove the clip from the pin before changing out the wheel, and is
composed of two distinct pieces.
The final quick wheel change option that the team identified as a possibility was a more complex version
of the hitch pin, referred to as a quick connect hitch pin. This design option would only require one hand
to remove, whereas both hands are needed for the other design options. An example of the quick connect
hitch pin is displayed in the figure below.
Figure 10: Quick Connect Hitch Pin Example14,15
This product is very intuitive to use, does not separate into multiple sections, and would not require the
customer to bend down as much to remove as the other options.
6.4.3 Quick Change Wheel Design Decision
In order to determine which quick wheel change method was the best option for this design project, a
decision matrix was created. This decision matrix listed the design criteria mentioned earlier and assigned
a 1-10 value for each option, with 1 being the lowest and therefore least preferred. The team realized that
the quick wheel change capability for the designed product could use different methods for the front and
rear wheels. Therefore, the team analyzed these two sections with separate decision matrices. The
decision matrix for the front wheel quick change method appears below.
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Table 5: Front Wheel Quick Change Decision Matrix
Ease of
Change
Changeover Time
Durability
Trust
Transparency
Integrity
25
25
20
15
5
5
5
Total
QR Skewer
6
7
8
5
9
9
7
685
QR Hitch Pin
9
10
7
6
5
8
7
5
10
6
3
5
5
3
7
5
5
6
4
4
8
675
580
755
Design Criteria Cost
Options
Weight
Pin and Clip
QC Hitch Pin
The above decision matrix showed the design team that the quick connect hitch pin method was most
likely the preferred option for the front wheel quick wheel change capability. The design team therefore
designed the initial product with this product. However, as the design progressed, the team determined
that using such a system for the front wheel did not work well with how the front wheel was attached to
the frame. Since the front wheel was designed to be rigidly attached to an axle, using the quick connect
hitch pins were not reasonable. Therefore, the design team looked again at the decision matrix, in order to
determine the best possible option that was suitable for the designed front wheel and frame assembly. The
only viable option for this assembly was found to be the quick release skewer, which was the second best
option in the decision matrix. Therefore, the design team chose the quick release skewer as the final
option for the front wheel quick wheel change method.
The design team next had to analyze the rear wheel quick wheel change method. The created decision
matrix for this option appears below.
Table 6: Rear Wheel Quick Change Decision Marix
Design Criteria
Options
Weight
QR Skewer
QR Hitch Pin
Pin and Clip
QC Hitch Pin
Cost
Ease of
Change
Change-over
Time
Durability
Trust
Transparency
Integrity
25
25
20
15
5
5
5
9
10
4
6
4
8
7
5
10
6
3
6
7
3
7
6
5
6
5
4
6
The design team realized that the quick release skewer method would not be a feasible design option for
the rear wheels, unless the rear wheel and frame assembly was significantly redesigned. These extensive
modifications were estimated to be much more involved than the potential benefit from using quick
Page 30
Total
695
555
685
release skewer pins on the rear wheels. The design team therefore selected quick release hitch pins as the
final option for the rear wheel quick wheel change method.
6.5 Collapsible Design
6.5.1 Collapsible Design Criteria
The next major design decision the team analyzed was the collapsible aspect of the design. One of the
requirements specified through the research conducted by the team was that the designed product needed
to be easily transportable from the care facility to location of interest. The design team determined in
order to accomplish this objective the product needed to be designed in such a manner which would allow
the product to be easily collapsed, enabling the user to easily transport the product in the trunk of a
standard car or on a bike rack. This would allow the product to be used more often and for more varied
purposes. The criteria the team used to decide upon the collapsible nature of the product appears in the
table below.
Table 7: Collapsibility Design Criteria
Criteria
Weight
Ease of use
30
Cost
20
Risk to user
20
Durability
15
Trust
5
Transparency
5
Integrity
5
As shown in the table above, the ease of use for the collapsible design was designated as the most
important design criteria. This design feature was interesting, as cost was not the most important design
criteria. The design team concluded that designing a low cost collapsible design was not as important as
creating a design which would be easy to use and understandable to the end user. The potential risk to the
end user was also one of the most important design criteria, as this feature needed to be designed in such a
way as to eliminate or minimize all potential personal injury possibilities. The design team did not want
the collapsible aspect of the product to present additional risk to the end user, as this would greatly
increase the possibility of lawsuits and negative public image. Additionally, if the end user considered the
collapsible feature to be potentially dangerous, they would most likely end up not using it, effectively
nullifying all of the design team’s work on this feature. Once again, durability was a criteria that the
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design team took into consideration in this feature’s design. This criteria considered the life span of the
design, as well as the cost to repair. Finally, the team identified three design norms that were directly
applicable to this feature. Trust was once again a design norm. The team needed to design the collapsible
nature of the product in such a way that it was readily apparent to the end users how to use. The final
design needed to be reliable and safe. The collapsible feature of this product also needed to be transparent
to the end users. It was necessary to minimize the injury potential, as well as be readily understood. The
design team did not want the collapsibility of the product to confuse the end users, as that would
effectively eliminate the use of the feature, as well as increase the injury potential. Integrity was the final
design norm that the design team determined applied to this feature. Similar to the quick wheel change, if
the end users do not feel comfortable collapsing the product, they will most likely not use it. This would
result in a product that would not be as easily transported. Additionally, the potential for the end user to
be injured would increase if the collapsible feature was not used, as handling the final design otherwise
would be too burdensome.
These design criteria were in tension within this feature’s design. While most of the design criteria
focused on making the product easier to use and understand, the cost criteria forced the design team to
consider the cost of potential safety concerns. The design team made sure to not sacrifice the safety of the
design in order to minimize the cost, which was reflected in the relative weight of the design criteria.
6.5.2 Collapsible Design Alternatives
The design team identified two distinct collapsible method options through research and communicating
with the team’s resources. These collapsible options were: detaching the product into distinct parts, or
creating a jointed assembly, which would allow the product to be folded up to occupy a smaller area.
The detaching collapsible option would consist of designing the prototype in such a way as to allow it to
be taken apart into separate parts. This would be achieved through a design which would use clips and
fasteners to attach the distinct parts together. This option would allow the highest transportability of the
design, as the three separate parts would be able to be loaded and unloaded from a vehicle separately.
The second collapsible option would involve jointed features, allowing the design to fold up. This would
minimize the space required to transport the design, and minimize the size of the product, enabling it to be
more easily maneuvered and picked up. This design is comparable to jointed systems present in most
strollers, folding tables, or jointed ladders. The general concept of this option is displayed in the figure
below.
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Figure 11 : Jointed Design Examples16,17,18
6.5.3 Collapsible Design Decision
In order to determine which collapsible method was the best option for this project, a decision matrix was
created. This decision matrix listed the design criteria mentioned earlier and assigned a 1-10 value for
each option, with 1 being the lowest and therefore least preferred. The decision matrix for the collapsible
method of the final product appears below.
Table 8: Collapsible Method Decision Matrix
Options
Design Criteria
Weight
Detachable
Jointed
Ease of Use
Cost
Risk to User
Durability
Trust
Transparency
Integrity
30
20
20
15
5
5
5
8
6
5
7
6
6
4
6
7
5
5
7
5
7
As you can see, the jointed collapsible design was determined to be the preferred option for this design.
Both design options had positives and negatives associated with them, but the design team reasoned that
the detachable system would be overly complex to the customers, resulting in a significant amount of
time to disassemble and reassemble the product every time it was used. The cost associated with a
detachable design was also established to be more than a jointed assembly, due to the necessary clip and
fastener strength requirements. However, considering all aspects of both designs, the design team
reasoned that the detachable system would be more readily understood to customers. The jointed
assembly, on the other hand, was reasoned to be lower cost and more durable. According to the above
decision matrix and team research, the jointed design option was selected as the collapsible method for
the final design. This design uses a folding linkage to support the handlebars, and cast railing connectors
to provide a hinged axis with the lower frame.
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Total
605
625
6.6 Fabric Material Design
6.6.1 Fabric Material Design Criteria
The next major design decision the team analyzed for this project was the fabric material of the design,
which would be used for the backrest and cover for the seat design. The team designed the product in a
manner which placed great importance on the comfort of the passenger. This would enable the product to
be used more often and increase the overall enjoyment of the product. The criteria the team used to decide
upon the fabric material which would be used in the product appears in the table below.
Table 9: Fabric Material Design Criteria
Criteria
Weight
Comfort
40
Cost
20
Durability/Strength
20
Outdoor Capability
15
Trust
5
As shown in the table above, the comfort of the selected fabric material was designated as the most
important design criteria. This feature was interesting, as cost was once again not the most important
criteria, as the design team concluded that using a low cost fabric was not as important as creating a
design which would be comfortable and reliable to the passenger. The durability of the fabric was a
criteria that the design team took into consideration in its design. This criteria considered the life span of
the fabric, as well its strength. Finally, the team also identified a design norm that was directly applicable
to this feature, trust. The team needed to select a fabric which would be reliable and safe.
Once again, these design criteria were in tension when designing the product. As reflected in the relative
weight of the design criteria, the design team made sure to not sacrifice the comfort of the design in order
to minimize the cost, as the fabric material was a very visible feature which would be directly interfaced
with the passenger. The outdoor capability and cost criteria were also in tension, as most of the fabric
options were available in non-coated options at a much lower cost. However, the design team strived to
design the product in such a way as to have a long life cycle, so fabric options which would not perform
well in outdoor settings were not selected.
6.6.2 Fabric Material Design Alternatives
As the design team did not have much experience in the outdoor fabric realm, significant research was
required to determine available fabric options. The design team also traveled to the local outdoor supply
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store Gander Mountain, where the researched fabrics could be physically observed and felt. Through this
research and hands-on experience, the design team narrowed down the list of possible fabric materials to
three possible options. These options were: coated nylon, polyester, and acrylic canvas.
Coated nylon is a common outdoor material used in hammocks, tents, or parachutes. It is stronger and
more durable than polyester, but stretches more from extended use.19 From the team’s hands-on
experience, nylon was the softest fabric to touch. Nylon is often coated with a urethane ultraviolet
protective spray, which protects the fabric from mold and mildew accumulation present in outdoor use.
Polyester is the most common outdoor fabric material for seats, covers, and canopies.20 It is the most
commonly used base outdoor material due to its well-rounded properties, as it is strong, durable, and low
cost. However, polyester does not protect against mold and mildew as well as nylon does, nor did it feel
comfortable in the team’s hands-on experience.
Acrylic canvas was the final fabric material option recognized for this project. This fabric is commonly
used for patio cushions. Acrylic is generally regarded as the most comfortable fabric option for outdoor
use, and is also durable and easily cleaned. Similar to nylon, acrylic is resistant to mold and mildew
buildup. However, acrylic does not support loads very well and is one of the more expensive outdoor
fabric materials available.
6.6.3 Fabric Material Design Decision
In order to determine which fabric material was the best option for this project, a decision matrix was
created. This decision matrix listed the design criteria mentioned earlier and assigned a 1-10 value for
each option, with 1 being the lowest and therefore least preferred. This decision matrix appears below.
Table 10: Fabric Material Decision Matrix
Options
Design Criteria Comfort
Weight
Nylon
Polyester
Acrylic
40
9
7
10
Cost
Durability/ Outdoor
Strength Capability
20
8
6
5
20
9
7
5
15
9
7
9
Trust
5
9
8
6
Total
880
685
765
Based upon this decision matrix and the team’s hands-on experience, the team concluded that coated
nylon was the fabric material for this project. To be specific, the design team used 1.9 ounce, 70 denier
urethane coated ultraviolet nylon as the fabric material for the prototype. This type of nylon is comparable
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to the fabric used in hammocks or tents, so the outdoor durability of the material was not a concern. This
material was also selected due to its high comfort while still remaining cost effective.
6.7 Easy Entry and Exit Design
6.7.1 Easy Entry and Exit Design Criteria
The final major design decision the team analyzed for this project was the easy entry and exit mechanism,
which would enable the caretaker to assist the passenger when entering and exiting the product. Through
the team’s interactions with the resources, this feature was stressed as a necessity, as current bucket
seating present in existing competitor products make it very difficult for the caretaker to assist the
passenger when entering and exiting. The criteria the team used to decide upon the final entry and exit
mechanism used in the product appears in the table below.
Table 11: Easy Entry and Exit Design Criteria
Criteria
Weight
Ease of Use
30
Adjustability
20
Durability
15
Cost
15
Transparency
10
Trust
5
Caring
5
The most important criteria of this design were that the feature had to be easy to use and adjustable. This
would allow the product to be modified as needed on an individual customer base without extensive
modifications to the designed prototype. The durability of the design was also an important consideration,
as designing a seat that would potentially fail during the designed lifetime of the product would not be
desired. The design norm transparency had a larger weight than in previous design decisions as it was
crucial that the easy entry and exit design be as clear as possible to both the caretaker and passenger.
Trust and caring were the remaining design norms, and were needed in this feature so that it would
consider due care for all individuals involved in this feature, particularly the caretaker.
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6.7.2 Easy Entry and Exit Alternatives
The design team identified three design options for the easy entry and exit design of the prototype. They
were to design the product with: open seating, adjustable translational seating, and adjustable translational
and rotational combination seating.
The open seating design would effectively eliminate the need for an adjustable system, as the passenger
would be able to very easily enter and exit the product, with minimal help required from the caretaker.
This design would closely resemble standard chairs, where the seat does not have support or restraining
bars running along the side of the passenger.
The adjustable translational seating is the option that is present in many car seats, where there is a system
under the seat which enables the user to lift up on a handle and slide the seat forwards or backwards.
The final design option was a combined translational and rotational seating option, where the previously
mentioned option was combined with the system commonly used in “Lazy Susan” designs. This would
enable the seating mechanism to slide forward and then rotate, allowing the passenger to very easily exit.
However, this would be costly to implement.
6.7.3 Easy Entry and Exit Design Decision
In order to determine which easy entry and exit design was the best option for this project, a decision
matrix was created. This decision matrix listed the design criteria mentioned earlier and assigned a 1-10
value for each option, with 1 being the lowest and therefore least preferred. This decision matrix appears
below.
Table 12: Easy Entry and Exit Decision Matrix
Design Criteria
Options
Weight
Open Seat
Translational
Combined
System
Ease of
Use
Adjustability Durability
Cost
Transparency Trust Caring
30
10
8
20
3
8
15
9
7
15
8
7
10
9
10
5
9
9
5
5
9
Total
775
800
6
8
5
5
7
8
9
645
As you can see from the decision matrix, the adjustable translational system was the preferred design
option for this product. This is because it is a very transparent design, easily understood by the customer,
and relatively cheap to implement. Therefore, the design time selected this option in order to accomplish
the entry and exit design feature.
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6.8 Block Diagram
The block diagram shown below will be used to ensure all necessary considerations will be taken into
account in the design process. It will serve as a “map” for the design team as they work on designing and
assembling individual components of the cart together, so that all needs are addressed and all
requirements are met.
Due to the nature of this design, the block diagram is relatively minimal. However, it did clearly outline
the importance of certain features that may not have been obvious. For example, realizing that the seat,
harness, and back rest are the primary means of interaction with the passenger highlights the importance
of these features in building a successful prototype. Without such guidance, the team could have easily
given less attention to such aspects, instead focusing on the more technically interesting challenges
associated with the design of this cart.
Figure 12: System Block Diagram
6.9 Preliminary Design
6.9.1 Initial Sketch
The team began the design phase with a rough sketch of what the running cart would look like, which can
be seen below. This sketch was developed with the help of Becky and Robert Van Zanen, whose
Page 38
extensive experience with disabled people provided valuable insights into the desired qualities of this cart.
It illustrates a reclined seating position, a swiveling front wheel, and a collapsing mechanism. These
suggestions were taken very seriously by the team, and our final design and prototype reflect these
features.
Figure 13: Initial Hand Sketch
Figure 14: Initial Computer Model
6.9.2 Initial Computer Model
This sketch was then drawn on AutoCAD software to get a sense of the necessary scale of the project.
The result of this is shown above in Figure 14. The general appearance of the design shown above is the
approximate idea of what the team then began to design and model in SolidWorks. Once the team had
come up with the initial sketch, it looked for ways to improve the design of the cart. To do this the team
conducted research and talked to the contacts that it had made. The initial frame that the team has come
up with was drawn using the 3D modeling program SolidWorks, and can be seen below in Figure 15.
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Figure 15: Initial Frame Design
This frame design was modeled using 4130 steel as the material, which was the material that the design
team concluded was the best option for this project. This frame is still basic in nature, but does display the
overall idea of the frame that the design team is considering.
6.9.3 Finite Element Modeling
Once the cart had been drawn in SolidWorks, the team modeled the effects of the forces that would occur
from a person sitting on it using the program Autodesk Simulation Multiphysics 2012. The initial results
were disappointing, and the team decided to further model and simulate the frame. The figure below
shows the distribution of the forces on the second iteration of the cart’s frame.
Figure 16: Forces Acting on the Frame of the Cart
Page 40
The team modeled the cart assuming a downward force of 300 pounds. This downward force of the
passenger is represented by the arrows pointing down in the figure above, and is distributed over the area
in which the seat is planned to be and ultimately where the passenger will be sitting. The red circles
represent the supports of the frame, which in reality are the connections to the wheels. After placing these
forces onto the frame design the team then ran the simulation program, which displayed the stress values
on the frame. The results of this simulation are shown in the figure below.
Figure 17: Simulation Results
The simulation determined that the highest stress applied to the cart is 3300 psi. The team compared this
to the yield strength of 4130 Steel, which was found to be 60,000 psi. The yield strength of the cart is
much greater than the applied stress on the cart due to a 300 pound load. However, this result was not
congruent with the results calculated using the beam equations. The beam equations calculated a
maximum stress of around 35,000 psi. After double-checking the beam calculations, the team suspected
that because of the magnitude of the difference between these results, the FEA model was inaccurate
because of inadequate mesh granularity. When using brick elements, it is necessary to maintain at least
two elements across the thickness of any material. This requirement was not met in the FEA model above,
and as such, the model was revised.
To assess the various options for frame and overall cart design, the team evaluated how readily the
necessary features could be incorporated into the design. Using this method iteratively, the team
approached a final design that met the goals of the project. This guided the team’s approach aside from
the strength considerations. The frame was appropriately sized using average human dimensions, and
space was allowed in the design to accommodate the other desired features. The iterative design approach
proved to be invaluable in achieving a final design the team was confident would meet all of the project
goals.
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6.10 Final Design
The figure below displays the design team’s final frame design. The collapsible, quick wheel change, and
adjustable seat mechanics are factored into this design. Figure 18 shows a render of the final design’s
SolidWorks model, and Figure 27 shows the constructed prototype.
The final design includes all of the features needed to achieve the project goals. The swiveling front
wheel allows for the cart to be easily steered when in use, the quick wheel change designs on all four
wheels allow for multiple wheel types to be easily interchanged, and the adjustable sliding seat allows for
a greater ease of entry and exit.
While the model below shows connectors being used for the frame, the real-life prototype uses welds for
increased strength. The use of the connectors allowed for much more flexible modeling than welds would
have provided, and were prohibitively expensive to use according to our budget. Corresponding with
Calvin’s shop manager, the team decided upon tack-welding the frame components for initial fit testing,
and once the function of the design was confirmed, the frame was finish-welded. Details regarding the
production process are found in section 7.
Figure 18: Final Designed Computer Model
The final design’s frame was also simulated using finite element methods to ensure adequate strength.
Details regarding the methods and results of this analysis can be found in the calculations section.
6.11 Applicable Design Norms
Team 12, Iron Man, integrated design norms throughout the design process, as shown in the decision
matrices for each major design decision. While all of the design norms discussed throughout the team’s
Page 42
education at Calvin College were factored into this design, the team placed a larger emphasis on four
design norms in particular. These emphasized design norms for the project as a whole were: transparency,
stewardship, caring, and trust.
6.11.1 Transparency
Transparency was critical to the team’s design as the design needed to be readily understood to all parties
involved. This means that there must be a very clear and open communication about the designed features
and functions of the design to the end users. The product also must be reliable and consistent in
application, as transport vehicles in particular face intense scrutiny in the current culture. In order to
ensure that the team’s design was as transparent as possible to the clients, the team plans to create a user
manual to guide the users through all of the cart’s features and operation requirements. This user manual
will include a step by step initial assembly process, which will guide the client through assembling the
product from when it is removed from its packaging to when it is fully operational. Additionally, the user
manual will include step by step processes describing how to make use of the design’s important features,
including how to operate the quick-wheel change mechanism, how to collapse the design into its
transportation stage, and how to make use of the sliding seat when unloading and loading the passenger.
The transparency of the design goes beyond the user manual, as the team acknowledges that these
documents are often ignored or misplaced by the clients. Integrated into the business strategy, if the team
were to begin full scale production on this product and bring it to the marketplace, there are
accommodations and funds set aside for a member of the staff to be primarily focused on interacting with
the customer to ensure their satisfaction. Part order forms will also be included in the final product,
enabling the clients to easily order any replacement parts as needed.
6.11.2 Stewardship
Stewardship was another crucial design norm throughout this project, as the team strived to carefully
consider the environmental impact of the design. This meant that the team had to balance economic,
environmental, and human resources against the overall profit of the product. While the team could have
used much more exotic materials, such as a carbon fiber frame, the team realized that this would not use
environmental and economic resources efficiently. Using more expensive materials not only affects the
selling point of the product, it also has the potential to negatively affect the overall experience of the
client, as ordering replacement parts could prove more expensive than they were expecting, resulting in
the product being tossed aside and not used.
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6.11.3 Caring
The design norm of caring was also emphasized throughout the design process. This design norm is
displayed in the team’s communications with caretakers, who would potentially end up using this product
on a daily basis. As the team did not have much experience in providing care for mentally disabled or
handicapped people, it was essential to the product’s success that people with this background and
knowledge were integrated into the design process. This was accomplished through distributing surveys
to caretakers throughout Grand Rapids, as well as direct communication with several caretakers who
graciously volunteered their time and expertise to this project. The design norm caring means that the
design must show due care for all people involved or affected by the product. While the comfort and other
physical and psychological effects experienced by the passenger of the design were of the utmost
importance, the team made sure to also include the needs and desires of the caretaker as well. Since the
caretaker would be doing all of the manual labor in assembling, collapsing, lifting, and pushing the
design, it was very important to factor in what physical and psychological effects the design would have
on them as well.
6.11.4 Trust
The final design norm the team focused on throughout this year long project was that of trust. This idea is
closely related to that of transparency and integrity, as in order to achieve a design that is trustworthy it is
necessary to have an understandable and reliable design, as well as one that is pleasing and intuitive to
use. Designing a trustworthy product means that it must be dependable, reliable, and honest to the end
client. The design must be credible, meaning that someone without an engineering or technical
background be able to view the product and not express concern about its appearance or perceived
reliability. Products that are centered on providing care to mentally disabled or handicapped clients in
particular need to be trustworthy, as the team discovered in communicating with several caretakers. If the
passenger does not view the product in a positive light, it is very difficult to convince them to use it.
6.12 Calculations
6.12.1 Frame Stress Calculations
Regarding strength, the team was primarily concerned with ensuring that the frame would not fail as this
would result in the most severe mode of failure. The frame also represented a significant amount of the
total material used in the cart, and therefore the frame material selection would strongly influence the
overall weight of the cart. To minimize weight, thorough calculations were performed to select the best
material for this application.
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To begin, the team modeled the frame as a pair of simply supported beams, each carrying half of the total
load as a concentrated load at a specified distance of 12 inches (the approximate location of the seat) from
the end of the beam. Figure 19 shows the basic beam model used. The maximum stress resulting load was
calculated to compare to other models.
Figure 19: Beam Loading Diagram53
Additionally, frame was analyzed using Autodesk Simulation Multiphysics as a finite element analysis
tool through several iterations. The maximum stress in the long bars was compared to that calculated to
the maximum stress calculated using the beam equations as shown in Figure 22. This was used as a check
to ensure no errors were done in the FEA model. The stresses calculated in FEA were initially very low
compared to those calculated by hand, and this was probably a result of inadequate meshing. Because the
model was exported from SolidWorks, the only meshing option was to use brick elements, and this
together with the geometry of the frame made a very fine mesh necessary to achieve realistic stresses
across the wall thickness of the tube. The final FEA model provided stress results that were relatively
close to those found by the beam calculations, and this suggested that the design had been correctly
modeled and analyzed. Figures 20 and 21 show the final loading and stress results on the designed frame.
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Figure 20: Final Finite Element Loading
Figure 21: Final Finite Element Stress Results
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Figure 22: Sample Beam Calculations Worksheet
6.12.2 Frame Deflection Calculations
Because stress cannot be effectively measured in testing, additional calculations were performed to
calculate the expected deflections of the frame at the point of loading and stiffness of the frame at the
point of load application. These were performed in the same Mathcad worksheet as the stress calculations
to ensure the results were being calculated for the same load case. After testing was completed, the
stiffness results were compared to test values. This comparison was used as a measure of how effective
the calculations were in determining the mechanical behavior of the frame. Potential factors of deviation
include the presence of the collapsing mechanism that may act as a truss to stiffen the frame, and
weaknesses in the frame caused by the presence of welds connecting the seat support bars.
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6.12.3 Weight Estimations
In order to estimate the effects of the use of various materials, the team used Engineering Equations
Solver to solve for the total weight of the cart. The dimensions of the tubing were input along with the
known material properties. The total frame weight and the total cart weight were estimated using simple
mass and density methods along with approximations for the weight of other cart components. Figures 23
and 24 below show a sample of this worksheet, and figures 25 and 26 show the actual cart being weighed
with the load cell.
Figure 23: Sample EES Calculations
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Figure 24: Sample EES Results
These calculations were input so that the design team could easily see the ramifications present when
altering the chosen materials or when modifying the prototype design.
Figure 25: Method of Determining Frame Weight
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Figure 26: Final Cart Weight Determination
6.12.4 Center of Gravity Calculations
Based on the suggestion of the CEAC review panel, the team calculated the center of gravity of the cart to
ensure that the cart would remain stable in use. To do this, the team estimated the portion of the total
cart’s weight that would be supported by the front wheel and the portion that would be supported by the
rear wheel. These estimates, along with the dimensions of the cart, allowed for force and moment
summations to be performed, which resulted in a center of mass along the length of the cart. The cart’s
design is symmetrical, therefore the center of mass is halfway between the rear wheels along the width of
the cart. These calculations and the assumptions they are dependent on were also verified and modified as
necessary through the testing process as described in section 7.
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7. Prototype Construction
Figure 27: Final Prototype
7.1 Materials Acquisition
Due to the diversity of the parts included in the prototype, the team had to look to various sources to find
the necessary parts. Whenever possible, parts and materials were ordered through Bob DeKraker from
local or online sources with reliable shipping. All metal stock was ordered from Central Iron and Steel in
Grand Rapids. Many components such as the brakes, rear wheels, brake levers and cables were found
online at ebay.com and amazon.com at lower costs than were found locally.
When researching options for the front wheel and fork, which was designed to be smaller than most
bicycle wheels, online and local options proved to be prohibitively expensive. An alternative was
discovered in the form of a used children’s bicycle on sale locally. This bicycle was purchased at a cost
lower than either the wheel or fork could be sourced. As a bonus, it included the head tube, which allowed
the team more time to focus on the more unique features of the cart instead of fabricating a custom head
tube and bearing races.
The most challenging acquisition of the project was finding and receiving a sliding seat mechanism. This
was ordered well in advance as to provide time for shipping. However, due to delays in shipment, the part
arrived on the second-to-last day of prototype construction. This, among other delays, put our final
construction schedule far behind the initially planned construction schedule.
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7.2 Frame Construction
The frame, composed of welded-seam steel tubing one inch in outer diameter, was built using three
primary operations. First, the models was consulted for dimensions, and the metal was cut to the proper
length on a horizontal band saw. Next, to increase the strength of the welds, covets were cut into the ends
at the necessary angle. Once de-burred, the metal pieces were fitted together by hand, measured to ensure
a proper fit, and then tack-welded together. All of these manufacturing processes took place in the Calvin
machine shop.
After the basic frame was completed tacked together, the wheels were fitted, and the dynamic
performance was subjectively evaluated. Any deviations from desired behavior were noted, researched,
and the necessary modifications were made before the final welds were made.
Once the entire frame was tacked together and checked for proper fit and behavior, finish welds were
done to permanently join the frame components. The use of welds ensured that the frame will have longlasting strength and will resist repeated stress well.
7.3 Addition of Key Features
Upon completion of the basic frame, the team focused on the integration of the key features into the
prototype.
7.3.1 Collapsing Mechanism
The first of these key features is the collapsible handlebar mechanism. This mechanism functions
similarly to the collapsing mechanism present in a folding table, and allows for the overall dimensions to
be reduced significantly for easy transportation and storage. This design was first tested with a wooden
mock-up, and once the design was evaluated, modified, and confirmed to work properly, the links to
complete the mechanism were laser-cut from aluminum plate at Rapid-Line and installed on the cart. The
steel connectors were also laser-cut at Rapid-Line and welded to the frame in the designated places. Once
complete, the mechanism was evaluated a final time and modified slightly by hand as necessary to
achieve a smooth collapsing motion. Locking links were also laser-cut out of aluminum plate and fitted
on the cart. Figure 28 shows the final linkage installed on the cart, not including the locking links. The
mechanism was designed with ease of use in mind. Testing to quantify the performance is documented in
section 8.
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Figure 28: Completed Collapsing Mechanism
7.3.2 Quick-change Wheels
An essential component of the project, the quick-change wheel mechanism is divided into two areas, front
and rear wheel. The rear wheel design is based on a pinned axle and sleeve concept. To prototype this
design, a steel axle was selected for strength and ease of manufacture, and a PVC sleeve within the steel
rear tube was selected for its light weight and low friction surface. The PVC sleeve was first machined on
the outside to fit into the steel tubing. It was then reamed on the inside to provide a close clearance fit
with the steel axle. Finally, a clearance hole for the selected locking pin was drilled through all
components. Figure 29 shows the final mechanism being used to remove the rear wheel.
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Figure 29: Demonstration of Rear Quick-Release Mechanism
The front wheel design was based on existing components to reduce prototyping time and cost. Because
wheel and fork connection is very common in bicycles, an existing bicycle quick-release skewer was
used. It uses a locking cam to apply pressure to the fork, clamping the wheel on and providing a relatively
easy tool-free wheel removal and replacement. Figure 30 shows the quick-release skewer as used on our
final prototype.
Figure 30: Demonstration of Front Quick-Release Mechanism
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7.3.3 Sliding Seat Mechanism
The final key feature for this cart was the sliding seat mechanism which allows for easy entry and exit of
the passenger. This mechanism was selected to be based on a car seat mechanism. As mentioned in
section 6.7, the car seat mechanism was identified as a robust solution which enabled significant
translation of the seat without compromising stability. This was found to be true in the construction of the
prototype. While not completely ideal for production use, the seat mechanism ordered and received by the
team is adequate for prototype purposes. In addition, the late arrival of the mechanism left too little time
to explore alternative solutions.
Upon arrival of the seat mechanism, aluminum supports were machined to fit snugly on the support bars,
and the seat mechanism was fastened through the supports to the rear support and to the deck forwards of
the front support bar. The team took great care to ensure the individual sliding tracks were parallel to each
other, as any skew from a parallel alignment would cause significant difficulty in using the mechanism.
Finally, the plywood and pine seat top was attached to the sliding mechanism via robust wood screws.
The seat was then upholstered with foam and fabric for comfort visual congruity. The entire seat
mechanism was thoroughly tested through the range of its motion to ensure smooth operation. While the
seat mechanism performed adequately in these tests, it was more difficult to operate than the team had
expected. For the next iteration, the team would look to several different suppliers, test the various
models, and select a best option from these.
7.4 Modifications and Revisions
The first modification was made to reduce the flutter found in the front wheel at higher speeds. A
negative caster angle had been previously used in an effort to maintain a forward direction of travel when
pushing the cart. However, this had the negative unforeseen consequence of causing the front wheel to
easily enter a state of resonance and shake the cart violently. Some research on caster flutter was
performed54, and as a result, a slight positive caster angle55 was decided upon and implemented. Figure 31
shows the temporary implementation of this modification. Once the solution was verified to be effective,
it was made permanent by finish welding.
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Figure 31: Front Wheel Mount Used for Testing and Modification
The second modification necessary was reduction of the rear quick-change axle diameter. The clearance
between the steel axle and the PVC insert was too close for the interaction to be classified as “quickchange”. This was likely a result of the local heat generated by welding the nearby steel. Any time
welding was performed, the team found problems with the quick-change wheel mechanism. The PVC was
repeatedly machined with the use of a ream, but the fit of the axle remained too tight. Therefore, the axle
was brought back to the shop and machined to a slightly smaller diameter. After several iterations of
machining, sanding, and fitting, the axle was found to fit as the team desired.
7.5 Final Touches
To make the cart presentable on senior design night, the team decided to have the steel and aluminum
parts powder-coated at Rapid-Line. In addition to being very visually attractive, this coating will serve as
a barrier to corrosion throughout the life of the cart. The seat back fabric was then sewn between the top
fabric support and the rear seat support. This process was very time intensive and will be modified upon
the creation of a second prototype. Figure 32 shows some of this process. To fasten the cushion for the
seat back, the team decided to utilize a sewing machine to stitch a fabric pocket for the cushion, and stitch
the pocket to the seat back in a few select places. This method greatly reduced the time required to attach
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the cushion. Other finishing touches to the cart involved the addition of a brake, safety harness, and
rubber footrests.
Figure 32: Sewing Process for Assembly of the Seat Back
7.6 Prototype Budgeting
The budget approved for the project was $665. Of this, $80 is a contingency in the case of unexpected
expenses. The table below shows the predicted budget break-down and the actual amounts spent. The
team found no issue remaining under budget, thanks to thorough cost estimation performed at the
beginning of the project. In addition, several parts and materials were donated at no cost. The team sought
to minimize costs in prototype construction in order to have the necessary funds to recover from an
unexpected failure or additional need. However, there were few unexpected costs, and the project was
completed under budget without use of the contingency.
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Table 13 : Final Team Prototype Budget
Item
Estimated Cost (USD)
Metal for frame
150
Bolts and joint fasteners
25
Wheels (all)
100
Brake components
50
Seat materials and padding
40
Sheet metal for passenger deck
20
Bearings
20
Forks/wheel mounts (bike unit)
50
Handles
15
Brake hardware (lever, cable, etc.)
10
Paint
30
Suspension
75
Seat Mechanism
Safety Harness
Prototype Total
585
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Actual Cost (USD)
68
48.52
47.27
31.81
47.6
4.22
30
65.11
44.52
110.23
38
545.87
8. Prototype Testing
The design team completed construction of the prototype on May 8, 2014. Once this construction was
completed, the team began testing and optimizing the prototype as needed. The design team tested the
prototype in five primary aspects: the rigidity, transportability, ease of assembly, maneuverability, and
ability to travel on a variety of terrains. Each testing area was completed in a week. These tests were
performed in coordination with the design team’s resources, which allowed these resources to have direct
input into which areas of the prototype needed further work. The rigidity of the prototype was tested
through stress and strain calculations through the use of strain gauges when loading the prototype with
varying loads. This enabled the design team to determine the upper limit of the transportable weight. The
transportability of the prototype was tested using a team member’s car, in order to determine whether or
not the design can fit within the designed size constraints. The ease of assembly of the prototype was also
tested during this time, as the difficulty of disassembling and assembling the prototype under real life
conditions with test subjects was determined. The weight of the design was also tested and optimized at
this point, which assisted the design team in determining whether the design is simple and light-weight
for the end user to understand and easily handle. Finally, the maneuverability and all-terrain versatility of
the prototype was tested in the field through several methods. The prototype was tested on the following
surfaces: road asphalt, sidewalk concrete, compacted dirt bicycle path, and grass. The force needed to
start, stop, and maintain a set speed was recorded on each terrain, which enabled the team to determine
which tires were best for which surface and which terrains the design team should be focused on.
8.1 Transportability
The goal for testing the transportability of the cart is to determine if the cart can fit in the back of a car or
van, and to see how quickly the cart can be loaded and unloaded. To do this the team performed several
timed test with the cart. The first test that the team performed was done to determine the time that it takes
to take the wheels off of the cart. This test involved one team member taking off the wheels while being
timed by another team member. This was done five times to determine an average time for taking the
wheels off. The results of this test are shown in the table below.
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Table 14: Timed Transportability Test
Wheels Off
(s)
Wheels On
(s)
Collapse
(s)
Stand Up
(s)
1.
2.
3.
4.
5.
98
56
54
42
43
144
73
69
76
56
16
18
23
15
14
34
23
23
18
17
Avg.
59
84
17
23
Trial
The test shows that on average it takes close to 1 minute to take the wheels off of the cart. The opposite
timed test was also performed in the same way. One team member put the wheels on while being timed
by another teammate. The results of this test can also be seen in the above tables, which shows that it took
on average 1:24 to put the wheels on. This gives a total time of approximately 2:24 to take the wheels off
and put them back on. The team deemed that this was a good time as the team believes that it is only a
small fraction of the time that the team believes the caretaker will be using the cart. A similar test was
also performed on the handlebar frame with a team member timing the other on how long it takes for the
handlebar frame to be collapsed and put back up. The results of showed that the handlebar frame can be
taken down and put back up in approximately 40 seconds.
Once this test was completed the team determined if the cart would fit in the back of a car or van. The
team used two different steps to show this. The first step that the team took was to measure the overall
dimensions of the cart. The dimensions can be seen in the table below.
Table 15: Cart Dimensions
Height
Width
Length
(in)
(in)
(in)
16.5
36.25
51.25
These dimensions were then compared to the trunk dimensions of other vehicles. One such vehicle is the
Chrysler Town and Country. The dimensions for the town and country are shown in the table below.
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Table 16: Trunk Dimensions for Chrysler Town and Country56
Height
Width
Length
(in)
(in)
(in)
46.2
49
24.4
While the length of the cart exceeds both the height and width of the Town and Country the team
determined that the cart would fit in the trunk if the cart was placed sideways in the trunk and angled
along the height of the trunk. After measuring the dimensions of the cart the team then used a Honda
Civic to see if the cart could be transported in a small sedan. To do this the team removed the wheels and
collapsed the handlebar frame, and placed the cart in the back of the Civic. Figure 33 shows the cart in
the back of the Honda Civic.
Figure 33: Cart in Honda Civic Trunk
The team believes that it is reasonable to assume that because the cart can fit in the back of the small two
door Civic that the cart should be able to fit in most vehicles. Once it was determined that the cart was
able to fit in the trunk the team measured the time that it took to put the cart in and take the cart out of the
trunk. The table below shows both the time it takes to place the cart in and take the cart out of the trunk.
Table 17: Trunk Loading Tests
Take Out
277
s
Place In
210
s
The test shows that it takes 3:30 to put the cart into the car and 4:37 to take the cart out of the trunk. The
time for putting the cart into the trunk involved taking the wheels of the cart and folding down the
handlebar frame. When compared to the times that were recorded for just taking off the wheels and
folding down the handlebar frame it can be seen that most of the time putting the cart into the trunk of the
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civic was spent in placing the cart in the trunk. The test for taking the cart out of the trunk was performed
by physically taking the car out of the trunk, putting on the wheels, and setting up the handlebar frame.
During this test it was observed by the team that the majority of the time getting the cart ready to be used
was spent putting the front wheel on.
8.2 Deflection Test
Aside from determining how transportable the cart is the team also wanted to determine how strong the
cart is, and how much force it would take to push it. To determine the strength of the cart the team
measured the deflection of the frame under a measured load. This test was implemented by taking off the
wheels of the cart and mounting it on risers. A load was then added to the cart, and a digital calipers was
used to measure how much the cart deflected under the load. Figure 34 shows the setup that was used to
take the data.
Figure 34: Deflection Test Setup
Once the data was taken, the deflection of the frame was plotted against the applied load to determine the
stress in the frame. The figure below shows the plot of the deflection against load.
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Measured deflection of cart under load
0.080
0.070
Deflection (in)
0.060
0.050
0.040
0.030
0.020
0.010
0.000
0.0
50.0
100.0
150.0
200.0
250.0
Load (lbf)
Figure 35: Deflection Test Results
This graph shows a relatively linear stiffness of the cart. This is expected for steel at small deflections. As
the material approaches the yield strength, it would be expected that the data assumes some curvature.
Compared to the calculated stiffness of the frame at the same load point, the tested data varied by about
15%. This test confirms the strength of the steel and its use as the frame material.
8.3 Flutter Test
Over the course of general testing the team noticed that if the cart reached a certain speed the front wheel
would begin to wobble back and forth, or flutter. The team then set out to determine at what speed the
flutter would begin. To do this the team planned to load the cart and push it until it reached the flutter
speed and record it. This would be done several times to find an average speed at which the front wheel of
the cart begins to flutter. Due to lack of a speedometer on the cart the team decided to measure out a
certain distance, bring the loaded cart up to the speed of the flutter, and then measure the time that it took
to cross that distance. The team used the width of the foyer of the Engineering Building as the distance
that the speed would be recorded over. The width of the foyer is 236 in, and the team measured the time
to cross it in seconds. The speed was then calculated in in/s and converted to mph. The table below
shows the times recorded for crossing the foyer, and the speed that was calculated from that time.
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Table 18: Flutter Test Speed Results
Trial
1
2
3
Time to
Cross (s)
Speed
(in/s)
Speed
(mi/hr)
1.48
1.44
1.35
159.78
163.89
174.94
9.08
9.31
9.94
Avg.
9.44
The data shows that the average speed at which the front wheel of the cart flutters is 9 mph. At this speed
a person would be jogging at a fast pace, and because the cart is for recreational use the team believes that
most users will not achieve this speed and experience the flutter phenomena.
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9. Business Analysis
9.1 Marketing Study
9.1.1 Competitive Analysis
9.1.1.1 Existing Competitors
Companies that could be considered competitors to Iron Man include wheelchair manufacturers, custom
running cart makers, high-end running cart makers, and other athletic wheelchair manufacturers. Very
few companies with an online presence make a product similar to what the Iron Man team will be
producing. These competitors are generally well focused in their respective market, and make a decent
product; their products are both comfortable and reliable. Their biggest strength over Iron Man is their
name recognition. However, these competitors also have weaknesses. Iron Man has found very few
competitors that are effectively targeting the normal family with a disabled child/adult. Such existing
products have some design flaws that make it difficult for the caretaker, and hard on the passenger.
Products that do not include these design flaws are prohibitively expensive to the normal family, or
perform well in some areas while being impractical for storage or poor in comfort.
9.1.1.2 Potential Competitors
Companies that could be considered competitors to Iron Man are mostly start-up companies that see the
team’s product and want to make it cheaper, or believe they can provide a superior product or the same
design at a better profit margin. Large companies that produce wheelchairs or similar products may desire
to enter the market, and would present significant competition with their extensive capital for marketing
and production. As long as Iron Man’s business continues to build name recognition and maintains a good
brand name, competition will likely not be able to take the team’s market share. There appears to be a
significantly larger market than the team’s planned capacity, so some competition would most likely not
directly affect the customer base Iron Man has built up. Iron Man has to stay competitive in design, cost,
and customer support to avoid being put out of business if a large company were to enter the market.
9.1.2 Target Markets
An estimated 3.3 million American citizens are bound to a wheelchair.30 Not all of them are limited to the
extent that they would benefit from our running chair, but if even 1% was, that gives us a market of
33,000. In addition, it is reported that about 11,000 new spinal cord injuries occur each year, resulting in
paraplegia (loss of lower body function), and quadriplegia (loss of function in arms and legs) 31, 32. Based
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upon this research, the design team has identified physically handicapped clients, caretakers, and health
organizations as the primary potential target markets.
9.1.2.1 Handicapped Clients
The product designed and produced by Iron Man would allow handicapped clients to experience nature in
a way that they would not otherwise be able to. Making this product affordable is extremely important to
handicapped clients, because they generally have more expenses to cover with a comparably smaller
income than others in their age demographic. These clients will be looking for comfort as a primary
product feature, as well as features that are targeted towards caretakers.
9.1.2.2 Caretakers
Caretakers will be able to better care for their clients by being able to take them out more often and with
greater ease. Dependability, light weight, ease of maneuverability, ease of client transfer, and
transportability are features that were identified which would be important to caretakers. These features
would also benefit the handicapped clients, because it would make it easier for their caretakers to take
them outside for a run.
9.1.2.3 Health Organizations
Health organizations would be looking for a product with low cost and high dependability. Using this
product, they could offer a wider variety of activities to their clients, increasing their reputation and client
base.
The design team surveyed each of these three demographics in order to gauge what features were most
desirable and what price they would be expecting to pay for the product. Through these conversations it
was clear to the design team that the overall cost of the product was the primary concern in all three target
markets. Following this, the dependability and passenger comfort were emphasized. The need for this
product was shown in each of the three target markets, as all of the potential clients that were surveyed
expressed the desire to purchase the product. The price of the product varied between the clients,
according to what features they mentioned were necessary. The average price from all three surveyed
markets came out to roughly be $1,500. This correlates nicely with the design team’s estimated
production cost.
9.2 Cost Estimate
9.2.1 Development
The development budget for Iron Man is limited to the funds provided through the senior design course at
Calvin College as well as any external grants that the team was able to secure. The design team is not
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currently seeking out donors for the project, as the budget submitted by the team to Calvin College was
approved. This budget is listed in the table below, which details the estimated cost of all necessary items
to produce the design.
Table 19: Team Budget
Item
Estimated Cost [$]
Metal for frame
150
Bolts and joint fasteners
25
Wheels (all)
100
Brake component
50
Seat materials and padding
40
Sheet metal for passenger deck
20
Bearings
20
Forks/wheel mounts
50
Handles
15
Brake hardware (lever, cable, etc.)
10
Paint
30
Suspension
75
Total
585
The budget approved by Calvin College was $665, which enables the group a fifteen percent leeway in
the overall cost of the design. This will hopefully solve any as of now unforeseen budgetary issues that
will emerge as the design progresses.
9.2.2 Production
9.2.2.1 Fixed Costs
The estimated complete development costs appear in the table below. Overhead costs are also included.
Table 20: Estimated Fixed Costs
Item
Cost ($)
Total Development Budget
Design Time ($100/hr)
Prototype
Tooling and Manufacturing
30,585
30,000
585
36,400
CNC Band Saw
25,000(33)
MIG Welder
2,400(34)
Knee Mill
9,000(35)
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Other Capital Expenditures
480,000(36)
Manufacturing Plant
400,000
Offices
80,000
20,600
Overhead
Advertising
5,000
Legal Fees
5,000(37)
Interest Fees
Electricity
10,000
4,600(38)
567,585
Total
9.2.2.2 Variable Costs
The variable costs for the product sold by Iron Man are based upon the estimated market and annual sales.
These estimations are described in the financial summary section of the report, and are detailed in the proforma financial statements in Appendix C. The estimated complete variable costs, on a per-unit basis,
appear in the table below.
Table 21: Estimated Variable Costs
Item
Cost ($/unit)
245
Machined Components
Frame
150(39)
Passenger Deck
20(40)
Suspension System
75
340
Purchased Components
Brake System
60 (41, 42, 43)
Bolts and joint fasteners
25(44)
Wheels (three per unit)
100(45)
Bearings
20(46)
Seat Cushion
40(47)
Paint
30(48)
Forks/wheel mounts
50(49)
Handles
15(50)
17
Packaging
Cardboard
10(51)
Poly-foam
4(52)
Instruction Manual
3
200
Labor
Saw operator
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40
Mill operator
40
Welder
80
Assembly
40
0
Distribution
802
Total
9.2.2.3 Financial Summary
The estimated retail price of the running cart produced by Iron Man is roughly $1,000. This retail price is
based off of market data collected by the team, which surveyed the three main target markets,
handicapped clients, caretakers, and health organizations. These markets are described in the target
markets section of the report. The price anticipated by these clients for such a product averaged around
$1,500. The full product cost that the design team expects is roughly $800. The difference between the
full product cost and the estimated retail price is the expected profitability per unit for Iron Man. This
profitability is therefore $200 per unit. Based upon the pro-forma financial statements prepared by the
team this product is therefore expected to be profitable. These statements appear in Appendix C. The
break-even point computed by the team will occur in the first year with the 644th unit sold. The expected
annual units sold is estimated to be 1,000 units. The design team based these break-even results according
to the expectation that Iron Man will have a first year sales revenue of roughly $1,000,000. This is
reasonable, as at the expected retail price of $1,000 only 1000 units would have to be sold. As mentioned
earlier, roughly 3.3 million American citizens are bound to a wheelchair. Selling 1000 units to this market
would correspond to only a 0.03% target market acceptance. Targeting individual American citizens
would most likely be the most time consuming and challenging, especially with a start-up company. The
design team would therefore achieve these desired annual sales by aggressively targeted the wealthiest
target market first, the health organizations. Advertising to this target market would allow name
recognition to grow quicker than pursuing the other target markets. There are ten open hospitals in Kent
County, Michigan. These would be the first health organizations targeted by the design team due to their
close proximity to Calvin College. There are 5,724 hospitals in the United States. The design team
estimates that an average of two running carts will be purchased by all interested hospitals, which means
to achieve the anticipated annual units sold, 417 hospitals would need to purchase Iron Man’s product.
The team anticipates achieving the annual sales volume by selling to each target market.
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10. Suggested Modifications
10.1 Brake System Changes
The braking system currently installed on the prototype has not been found to be ideal. Long lengths of
cable housing and custom-made cable connections increase the friction with the brake cable and result in
a greater than desired force applied to the brake lever necessary to stop the cart.
A parking brake mechanism would be very useful for this cart. It was found that when sliding the seat, the
cart would tend to move. This requires the caretaker to use one foot to keep the cart steady, and this is not
good for day-to-day use. The team desired for the caretakers to be concerned with as few tasks as possible
when using the cart, and the need to hold the cart conflicts with this desire. A simple pin or clamp that
could be put in place on the existing brake lever should suffice as a parking brake mechanism.
If a taller person happened to be riding in the cart there is a potential for said person to hit their head on
the brake lever. This could cause an injury, and possibly break the brake lever. To fix this the team would
move the handle farther out along the handlebar, and rotate it so that the brake lever was parallel with the
bar that attaches to the lower frame.
10.2 Caster Flutter
Another improvement that the team would like to make for the next model is to reduce the flutter in the
front wheel to allow the user to run at a faster pace. To do this the team would adjust the angle of the front
wheel as well as possibly using a smaller wheel.
10.3 Sliding Seat
The team also noticed that the sliding mechanism for the seat can be difficult to use. To fix this the team
would replace the current sliding mechanism with one that is not as difficult to slide in and out.
10.4 Seat Cushion
Another area that the team would like to improve is the seat. Currently the foam padding used to make the
seat has a lot of give and lacks support. To fix this the team would add a stiffer foam at the bottom of the
seat to add support, and have the spongier foam on top for comfort.
10.5 Quick-change Rear Axle
Finally the team identified an area that is not currently a problem but could be in the future. Currently the
rear wheels are only supported on one side of the wheel. To improve the life of the wheel axle, and the
Page 70
stability of the cart the team would add a bracket from the frame to the outer part of the wheel. This
would give support to both sides of the wheel and prevent the wheel axle from bending which would
improve the life of the wheel.
Page 71
11. Conclusion
The team has designed and constructed a running cart according to the initial goals and objectives of the
project. The constructed running cart is just a prototype, so the previously mentioned suggested changes
should be considered before releasing the product to full-scale production. However, through the team’s
design, analyses, simulations, and tests the team has concluded that the overall objectives of the project
were met, and are glad to see that the prototype is put to good use, assisting handicapped and mentally
disabled passengers to better experience the wonder of God’s creation.
Page 72
12. Acknowledgements
The design team would like to thank the entire Calvin College engineering department, in particular
Professor Nielsen, who served as the team’s advisor for the duration of the project. The team would also
like to thank Alice Teisan, the primary contact from the organization His Wheels for her support and
advice on design options. Thanks to Curtis Kortman for his initial involvement in the project and for
initiating contact with the potential customer. Thanks to Ronald Robb of myTEAM TRIUMPH for
meeting with us and providing valuable insight. Thanks to Becky and Robert Van Zanen for providing
many design considerations and initial design ideas. Thanks to Rapid-Line for allowing the use of their
facility at various points throughout the project. Finally, the team would like to thank Phil Jasperse for his
support in the metal shop and throughout the construction of the design.
Page 73
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22. Brown, Sheldon. "Frame Materials for the Touring Cyclist." Frame Materials for the Touring Cyclist.
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25. Johnson, Todd. "Carbon Fiber Basics." About.com Composites / Plastics. N.p., n.d. Web. 08 Dec.
2013.
26. Riley, William F., Leroy D. Sturges, and Don H. Morris. "Average Properties of Selected
Engineering Materials." Mechanics of Materials. 6th ed. Hoboken, NJ: John Wiley, 2007. N. pag.
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27. Frank Berto (2009). The Dancing Chain (3rd ed.). Van der Plas Publications. pp. 140–141.
28. "Bicycle Tutor." The Bicycle Tutor RSS. N.p., n.d. Web. 08 Dec. 2013.
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Dec. 2013.
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Tetraplegia and Types of Paralysis. N.p., n.d. Web. 08 Dec. 2013.
33. "W.F. Wells W-9-14A CNC Automatic Bandsaw FREE Shipping." EBay. N.p., n.d. Web. 08 Dec.
2013.
34. "Lincoln Power MIG 256 (208/230) - (K3068-1)." Lincoln Power MIG 256 (208/230). N.p., n.d.
Web. 08 Dec. 2013.
35. "Metalworking Tools, Lathes, Drill Presses, Saw Blades, Drill Bits, Reamers, Threading, End Mills."
Global Industrial. N.p., n.d. Web. 08 Dec. 2013.
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Dollar-per-square-foot Construction Costs for Four Industrial-type Buildings. N.p., n.d. Web. 08
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37. "How Much Are Legal Fees to Launch a Startup Company?" Startup Lawyer. N.p., n.d. Web. 08 Dec.
2013.
38. "Household Electricity Bills Skyrocket." USATODAY.COM. N.p., n.d. Web. 07 Dec. 2013.
39. "1015 Steel Square Structural Tubing." Zoro Tools Industrial Supplies. N.p., n.d. Web. 08 Dec. 2013.
40. "Metals Depot - America's Metal Superstore!" MetalsDepot®. N.p., n.d. Web. 08 Dec. 2013.
41. "Novara Brake Cable Kit." REI. N.p., n.d. Web. 08 Dec. 2013.
42. "Shimano R451 Long Reach Caliper Bicycle Brake- BR-R451." Www.bikesomewhere.com. N.p., n.d.
Web. 08 Dec. 2013.
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43. "Avid FR-5 Brake Levers." Jensonusa.com/. N.p., n.d. Web. 08 Dec. 2013.
44. “Hex Nut Assortment, Standard, Steel, Zinc, Number of Pieces 216." EBay. N.p., n.d. Web. 08 Dec.
2013.
45. "Northern Industrial Tools Tire/Wheel - 26in., Spoked." Amazon.com. N.p., n.d. Web. 08 Dec. 2013.
46. "Zipp 950 Disc Wheel Rear Wheel Bearing Set Bicycle Ball Bearings." VBX Ball Bearings. N.p., n.d.
Web. 08 Dec. 2013.
47. "Carex Memory Foam Seat Cushion." Walmart.com. N.p., n.d. Web. 08 Dec. 2013.
48. “Dupli-Color BSP304 Paint Shop Finishing System Candy Apple Green Paint." Auto Body Tool
Mart. N.p., n.d. Web. 08 Dec. 2013.
49. "700 Steel Fork 1 1/8" Threadless Black Thread Less BIKE ROAD CRUISER FIXIE." EBay. N.p.,
n.d. Web. 08 Dec. 2013.
50. “2012 RITCHEY WCS TRUE GRIPS BLACK MTB BIKE." EBay. N.p., n.d. Web. 08 Dec. 2013.
51. “Staples® Corrugated Shipping Boxes." Staples.com. N.p., n.d. Web. 08 Dec. 2013.
52. “Charcoal Pick & Pluck Foam." OnlineFabricStore.net. N.p., n.d. Web. 08 Dec. 2013.
53. Beam Design Formulas with Shear and Moment Diagrams. Rep. Washington, DC: American Forest
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54. "Causes and Corrections of Caster Flutter." Caster Concepts, 2014. Web. 15 May 2014.
55. "Nissan Patrol Forum." Patrol 4x4 Nissan Patrol Forum. N.p., n.d. Web. 15 May 2014.
56. "New 2013 Chrysler Town & Country Interior Specs." New 2013 Chrysler Town & Country Interior
Specs. N.p., n.d. Web. 15 May 2014.
Page 77
Appendix A. Pro-forma Financial Statements
Table 22: Pro-forma Statement of Income
The Iron Man Corporation
Pro-forma Statement of Income
Year 1
Year 2
Year 3
Sales revenue
1,000,000
1,100,000
1,210,000
Variable Cost of Goods Sold
553,080
608,180
668,790
Fixed Cost of Goods Sold
190,000
190,000
190,000
Depreciation
7,202
12,772
9,978
Gross Margin
249,718
289,048
341,232
Variable Operating Costs
70,000
77,000
84,700
Fixed Operating Costs
37,600
37,600
37,600
Operating Income
142,118
174,448
218,932
Interest Expense
7,966
14,182
10,682
Income Before Tax
134,152
160,266
208,250
Income tax (40%)
53,661
64,107
83,300
Net Income After Tax
80,491
96,160
124,950
Table 23: Pro-forma Statement of Cash Flows
The Iron Man Corporation
Pro-Forma Statement of Cash Flows
Year 1
Year 2
Year 3
-
800,293
1,391,625
Net Income After Tax
80,491
96,160
124,950
Depreciation expense
7,202
12,772
9,978
Invested Capital (Equity)
535,400
535,400
535,400
Increase (decrease) in borrowed funds
227,600
(50,000)
(50,000)
Equipment Purchases
(50,400)
(3,000)
(3,000)
Ending Cash Balance
800,293
1,391,625
2,008,953
Beginning Cash Balance
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Table 24: Break-Even Analysis
Year 1
Sales revenue
Year 2
1,000,000
Year 3
1,100,000
1,210,000
Less: Variable Costs:
Variable Cost of Goods Sold
Variable Operating Costs
553,080
608,180
668,790
70,000
77,000
84,700
Total Variable Costs
623,080
685,180
753,490
Contribution Margin
376,920
414,820
456,510
Less: Fixed Costs
Fixed Cost of Goods Sold
190,000
190,000
190,000
Fixed Operating Costs
37,600
37,600
37,600
Depreciation
7,202
12,772
9,978
Interest Expense
7,966
14,182
10,682
Total Fixed Costs
242,768
254,554
248,260
Income Before Tax
134,152
160,266
208,250
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Table 25: Break-Even Analysis (continued)
Year 1
Total Fixed Costs
242,768
Contribution Margin %
Break Even Sales Volume
Year 2
254,554
38%
248,260
38%
644,084
Break Even Unit Volume
Year 3
38%
675,013
644
658,025
675
658
Table 26: Iron Man Corporation Budget
Equipment
Depreciation
Purchases
Year 1
Equipment Purchases Year 1
50,400
7,202
Equipment Purchases Year 2
3,000
Equipment Purchases Year 3
3,000
0.1429
12,343
8,815
429
735
0.2449
12,772
0.1749
Interest Expense:
Annual interest rate on debt
Average debt balance
Interest expense
7%
Year 1
Year 2
Year 3
113,800
202,600
152,600
7,966
14,182
10,682
Page 80
Year 3
429
7,202
MACRS Rates (7-year recovery period)
Year 2
9,978
Appendix B. User Manual
Contact Us
This product is the result of a year-long senior design project worked on
by three members of the senior design engineering course, taught as a
section of the Calvin College Engineering Curriculum. To contact the
department, please see the information below. Team 12, Iron Man, hopes
that this project can help bring joy and fulfillment to your life and the lives
of your loved ones. God Bless!
1734 Knollcrest Circle SE
Grand Rapids, MI 49546
User Manual
Phone: (616) 526-6500
Email: engineering@calvin.edu
Web: www.calvin.edu/academic/engineering/
Direct Contact for Team 12 (Allen Bosscher)
Phone: (616) 581-6453
Email: bosschera@gmail.com
Web: www.calvin.edu/academic/engineering/2013-14-team12/
TEAM 12: IRON MAN
Calvin College Engineering Department
Team 12: Iron man
1734 Knollcrest Circle SE
Grand Rapids, MI 49546
Page 81
Team Members
Table of Contents
Key Features .................................................................................................................... 1
Allen Bosscher
Thank You! ....................................................................................................................... 2
Allen Bosscher is a senior engineering
student at Calvin College with a
mechanical concentration. He has
worked for the past three years as an
intern for Rapid-Line, a metal
fabrication company. He expects to
enter the workforce at Rapid-Line
following graduation in May.
Our Mission ................................................................................................................. 2
Values and Principles ............................................................................................. 2
Cart Assembly ................................................................................................................. 3
Using the Cart .................................................................................................................. 4
Safety.............................................................................................................................. 4
Andrew Vriesema
Suggested Care .......................................................................................................... 4
Andrew Vriesema is a senior
engineering student at Calvin College
with a mechanical concentration. After
graduation he is planning on finding a
full-time engineering position. He enjoys
watching and playing sports, and being
outdoors.
Team Members ............................................................................................................... 5
Lukas Woltjer
Lukas Woltjer is also studying
engineering at Calvin College, specifically
the mechanical concentration. He will be
moving to Holland, MI after graduation.
He is an avid biker and enjoys
woodworking, and spending time with
his wife Daniella.
5
Page 82
Using the Cart
Key Features
We designed this cart to be as flexible as possible. If you would
like to use it on a trail with your 5-year-old son, you may! If you
would like to use it on the beach with your 15-year-old daughter,
you may!
Collapsing Mechanism
The unique collapsing handlebar
allows the user to easily store or
transport the cart. With the wheels
removed, the cart will even fit in the
back seat of a car!
With that said, there are some important points to remember for
the safety of you and your passenger. In addition, we would like
to highlight some use suggestions resulting from our own inhouse testing.
Safety
Sliding Seat
Ensure that your passenger is always securely buckled in the
cart.
To improve the quality of life of our
customers, we have included a
sliding seat which will make the cart
easier to enter and exit, reduce back
strain and injury for caretakers, and
allow the disabled passenger to be
taken out more frequently.
The passenger weight limit is 200 pounds. The cart has been
tested with higher loads, however, we do not sanction overloading the cart.
Maintain controllable speeds. While the cart performs very well
at moderate jogging/running speeds, there exists the potential
for front wheel flutter at high speeds. If flutter occurs, gentle use
of the brake will quickly bring the cart back to stable travel.
Quick-Change Wheels
With quick-change front and back
wheels, you will be able to use the
Iron Man cart on practically any
surface in a matter of seconds. See
the Cart Assembly section for
operating instructions.
When using the cart with tall passengers, be aware that the
brake lever is in close proximity to their head. This is a flaw that
will be corrected upon request.
Suggested Care
While the cart is weather-resistant, please avoid exposure of the
wheel hubs to sand and dirt. If you must tip the cart on its side,
please do so on a clean surface.
To clean the cart, simply wipe down the fabric and frame with a
moist cloth.
4
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1
Thank You!
Cart Assembly
Our Mission
From the box to the trail – in minutes!
Attach the front wheel
We aim to be the leader in providing high quality and affordable
running carts to our customers. Thank you for participating with
us in this goal by purchasing a running cart! We hope that it will
serve you well for many years.
Loosen the quick-release skewer,
disconnect the brake cable, slide the front
wheel in place, and re-tighten the skewer
and brake cable.
Goal - To design and construct an
improved running cart specifically
for disabled passengers
Attach the rear wheels
Remove the quick pin from the axle. Slide
the axle into its sleeve, making sure the pin
hole is aligned with the hole on the cart
frame. Replace the pin, and fasten the
security clip.
Values and Principles
Raise the handlebars
Team 12: “Iron Man” desires to show its high regard for all who
use our product by creating a quality product that can be
depended upon and which shows an effort of care that other
products on the market have not.
Lift the handlebars until the side linkages
are straight. Lift the locking links, and slide
them onto the bolt. Tighten the wing-nut to
secure the links.
The design norms used to design and create your cart are:
Transparency
Stewardship
Enjoy yourself!
Caring
Enjoy the outdoors, wherever you are.
Enables your disabled friend or family
member to also enjoy themselves!
Trust
We hope that through the use of this product you will see the
results of these guiding principles on the design.
Page 84
2
3
Appendix C. Work Breakdown Structure
1st Semester Tasks
 Customer Interface: The design team will have to meet with the customer to better understand
objectives (10 hours)
o Contact customer
o Travel to customer’s home
o Establish a direct line of communication
o Learn about customer’s overall goals and desires for deliverable
o Present design iterations and receive feedback
o Design and deliver
 Research: The design team will have to research extensively for this project (30 hours)
o Meet with Greg Remelts
o Research existing models of tentative design
o Research potential construction materials
o Research strength and rigidity of possible designs
o Research wheel design and easy-change tire methods
o Research water-accessible tires
 Verbal Presentation 1: The design team will present the objective of the project to the senior design
class (10 hours)
o Prepare for presentation
o Introduce and describe project
o Identify problem team hopes to solve
o Identify customer
o Identify influence of Christian faith on project
 Project Website Posted: The design team will have to design a website which succinctly describes the
project while still remaining technical (5 hours)
o Team member brief descriptions
o Home page
o PPFS link
o Final report and deliverable information
o Overall appearance and functionality
 Industrial Consultant Review: The design team will have to sit down with an industrial consultant to
have a review of the overall project (3 hours)
o Prepare for review
o Meet with consultant
o Take notes
o Review suggestions
 Updated Project Poster (2 hours)
o Update and upload project poster
o Post new copy on team board
 Preliminary Cost Estimate: The design team will have to create and estimate an overall cost for the
design project (5 hours)
o Fill out rough budget in Excel
o Meet with Phil Jaspers to discuss material availability
Page 85
o
o



Team operational budget request
Production and construction cost estimate
 Material
 Design time
 Fixed costs
 Distribution
 Marketing
 Sales
Draft PPFS: An outline of what the final design report will include (20 hours)
o Title Page
o Copyright Page
o Executive Summary
o Table of Contents
o Table of Figures
o Introduction
o References
o Project Management
o Requirements
o Research
o Task Specifications and Schedule
o System Architecture
o Design
o Testing
o Conclusion
o Acknowledgements
Verbal Presentation 2 (10 hours)
o Prepare for presentation
o Introduce team
o Introduce project
o Clearly state May deliverables
o Feasibility of project
o Create helpful visuals
Final PPFS (40 hours)
o Update draft PPFS
o Extensively look over and refine grammar and sentence structure
o Verify data and results
Page 86
2nd Semester Tasks














Update Frame Model (10 day duration)
o Jointed system
o Size and system constraints
o FEA model update
o Verify FEA results with hand calculations
Market Research (4 day duration)
o Reach out to resources
 Confirm general features
 Share current status
 Ask for suggestions
o Research existing competitors
 Carrying capacity
 Weight
 Selling Price
Define Tangible and Measurable Goals (2 day duration)
o Interface Requirements
o Performance Requirements
o Functional Requirements
Update Website (3 hours)
Order Frame Material (1 day duration)
o Confirm pricing with vendor
o Give order form to Bob
Contemporary Issue Paper (2 day duration)
o Research ideas
o Compile
o Write and refine paper
Cut Frame Material (5 day duration)
Weld Frame Together (5 day duration)
o Tack first to see fit and function
o Test and refine
o Finish welds
Verbal Presentation (3 day duration)
o Prepare presentation
o Rehearse
Industrial Consultant Project Brief (1 day duration)
Fridays at Calvin Visitors
o Update poster
o Clean up area
o Rehearse general ideas
Attach Wheels (2 day duration)
o Construct rear wheel custom design
o Put on quick release skewer on front wheel
Design Banquet Invitation (3 hour duration)
Order Remaining Materials (7 day duration)
Page 87







o Fabric material
o Seat mechanism
o Cushion
o Brake system
o Handlebar tape
Complete Assembly (14 day duration)
Test and Refine Prototype (5 day duration)
CEAC Project Review (2 day duration)
o Create presentation
o Rehearse
Project Night Preparation (10 day duration)
o Create final posters
o Create user manual
o Modify prototype appearance
o Create presentation
o Rehearse
o Clean up area
Final Assignments (2 day duration)
o Website finalized
o Notebooks turned in
o Project site cleaned up
Final Design Report (5 day duration)
o Modify rough draft
o Proofread
o Turn in report
Faculty Review (1 day duration)
o Create presentation
o Rehearse
Page 88