Calvin College Engineering
THERATRYKE
Final Report
ENGR 340: Senior Design
May 13, 2015
Team 5
David Evenhouse
Jack Kregel
Nick Memmelaar
Connor VanDongen
Advisor
David Wunder
Calvin College Engineering
Calvin College Engineering
TheraTryke
David Evenhouse, Jack Kregel, Nick Memmelaar, Connor VanDongen
Executive Summary
Project Brief:
The goal of team TheraTryke was to create a tricycle that would provide a unique mix of
recreational and therapeutic benefits for persons of low or limited mobility. The resulting trike is
primarily hand pedaled, but was designed with an original gear train that incorporates foot
pedals as well. This design boasts two significant advantages over traditional hand powered
tricycles. For persons living with paraplegia, the tricycle passively moves their legs through a full
range of motion by transferring some power from the hand pedals to the foot pedals. This
realizes significant therapeutic benefits while allowing the user to be active outside. For persons
with limited mobility in all limbs, this design allows them to power the trike using both their arms,
and their legs. This is not only therapeutic, but also provides people with a viable outdoor
recreation alternative.
Problem Overview:
Physical disabilities, and the costs or limitations associated with such conditions, effect a wide
variety of people across the globe. The treatment of many of these conditions requires
therapeutic exercise, even while the condition acts to limit the individual’s ability to move. Due to
the relatively small market demographic and high product development costs, there are few
recreational and therapeutic options available to people living with disability.
Historically, there has been limited interaction between those living with disability, and the
manufacturers developing products for use by persons with limited mobility. This divide between
the designer and the end-user has led to the creation of somewhat inferior products, while
simultaneously encouraging a “helping hand” mentality in regards to designing for disability. In
order to mitigate stereotyping and dismissal of the disabled community, and encourage free
access and independent living for disabled persons, a tradition of collaborative design needs to
be established within the therapeutic products industry.
Problem Setting:
Senior Design 2014-2015 Team 5 entered into the class with two main goals. First, they wanted
to work on a project that would directly benefit the Calvin community in some way. Second, they
wanted to have fun doing it. To accomplish this, the team members conducted extensive
research in the Calvin College community in order to encounter problems or needs that could be
addressed. It was through this process that the team was put in contact with members of the
disability community. It was through one of these conversations that the team was made aware
of the need for economical recreation alternatives that incorporate therapeutic benefits.
Calvin College Engineering
Problem Solution:
Team TheraTryke worked to develop a trike that may be used by persons living with low mobility
for recreational and therapeutic purposes. The goal was to be able to accommodate a variety of
users including spinal-cord injury patients, persons living with low mobility conditions, and
persons with paraplegia. To accomplish this, TheraTryke kept in frequent conversation with
disabled persons, medical professionals, local manufacturers, and bike shops, in order to
acquire the information and skills necessary to produce a quality and useful product. The team
also worked with Nancy Remelts, a member of the Calvin Community living with Multiple
Sclerosis (MS). Acting as their main client, Nancy gave recommendations and insights
concerning the trike’s design, and will be the principal user of the product after the end of the
2014-2015 school year.
Design Specifications:
The trike designed to be recumbent and incorporates crank-sets for both the hands and feet.
The frame is in the tadpole style, and is manufactured almost entirely from 1/8’’ thick Al-6061-T6
tubing. Components of the trike include parts that were purchased, hand-manufactured, or
scavenged from existing bicycles. These include but are not limited to: independent linkage
steering mechanism, simultaneously actuated disc brakes, adjustable reclining seat, adjustable
4-point harness, integrated leg supports, internal hub gear shifter, and removable push-bar.
Further specifications may be seen in the table below.
TheraTryke Specifications
Trait Name
Weight
Wheelbase
Wheeltrack
Seat Height
Overall Length
Overall Height
Turning Circle
Hand-to-Foot
Revolution Ratio
Speeds
Load Limit
Value
67 lbs
55.375 in
31.75 in
14 in
89 in
41 in
21 ft
2:1
7
250 lbs
A full cost breakdown may be found at the end of each design section, or compiled in section
6.2.1. Of particular note is the final Bill of Materials (BOM), which may be found in Table 38. An
abbreviated table of values has been included below for the sake of convenience.
Abbreviated Cost Summary
Trait Name
Final Project Cost
Estimated Production Cost
Estimated Retail Price
Value
$1,113.94
$1,538.37
$3,000.00
Final Report
Team 5: TheraTryke
page i
Table of Contents
1.
Introduction ......................................................................................................................... 1
1.1
Calvin College Engineering Department ...................................................................... 1
1.2
Senior Design Project .................................................................................................. 1
1.3
Objective ...................................................................................................................... 1
1.3.1 Ease of Use ............................................................................................................... 1
1.3.2 Speed ........................................................................................................................ 2
1.3.3 Safety......................................................................................................................... 2
1.3.4 Therapeutic Benefits .................................................................................................. 2
1.3.5 Outdoor Usage ........................................................................................................... 2
1.3.6 Economic Sustainability ............................................................................................. 2
2.
1.4
Motivation .................................................................................................................... 2
1.5
Group Members ........................................................................................................... 3
1.6
Client ........................................................................................................................... 5
Project Requirements.......................................................................................................... 5
2.1
Functional .................................................................................................................... 5
2.2
Mechanical .................................................................................................................. 5
2.2.1
Height and Weight Capacity.................................................................................. 5
2.2.2
Product Weight ..................................................................................................... 6
2.2.3
Size ...................................................................................................................... 6
2.2.4
Material ................................................................................................................. 6
2.2.5
Seat ...................................................................................................................... 6
2.2.6
Mounting ............................................................................................................... 6
2.2.7
Maintenance ......................................................................................................... 6
2.2.8
Environmental ....................................................................................................... 6
2.2.9 Speed ........................................................................................................................ 6
2.3
Safety .......................................................................................................................... 7
2.3.1
Brakes .................................................................................................................. 7
2.3.2
Harnessing ........................................................................................................... 7
2.3.3
Stability ................................................................................................................. 7
2.3.4
Flag Slot ............................................................................................................... 7
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Team 5: TheraTryke
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2.4 Design Norms ................................................................................................................... 7
3. Market Research ................................................................................................................... 8
3.1 Similar Products ............................................................................................................... 8
3.1.1 TerraTrike .................................................................................................................. 8
3.1.2 Top End Trikes ........................................................................................................... 9
3.1.3 Rehatri Trikes by Gomier ..........................................................................................10
3.1.4 AmTryke ...................................................................................................................10
3.1.5 Catrike ......................................................................................................................11
3.2 Past Projects ...................................................................................................................12
3.2.1 Achieving Mobility .....................................................................................................12
3.3 External Resources .........................................................................................................12
3.3.1 TerraTrike .................................................................................................................12
3.3.2 Boston Square Community Bikes ..............................................................................12
3.3.3 Foot & Ankle Specialists............................................................................................13
3.3.4 Calvin Bike Garage ...................................................................................................13
3.3.5 Progressive Surfaces ................................................................................................13
3.3.6 Custom Frame Coatings ...........................................................................................13
4. Mechanical Design ................................................................................................................13
4.1 Frame ..............................................................................................................................13
4.1.1 Research ..................................................................................................................13
4.1.2 Requirements............................................................................................................14
4.1.3 Design Process .........................................................................................................15
4.1.4 Final Design ..............................................................................................................24
4.1.5 Components..............................................................................................................27
4.2 Steering ...........................................................................................................................27
4.2.1 Research ..................................................................................................................27
4.2.2 Requirements............................................................................................................29
4.2.3 Design Process .........................................................................................................29
4.2.4 Final Design ..............................................................................................................31
4.2.5 Components..............................................................................................................32
4.3 Wheels ............................................................................................................................32
4.3.1 Research ..................................................................................................................32
4.3.2 Requirements............................................................................................................32
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4.3.3 Design Process .........................................................................................................32
4.3.4 Final Design ..............................................................................................................33
4.3.5 Components..............................................................................................................34
4.4 Seat .................................................................................................................................35
4.4.1 Research ..................................................................................................................35
4.4.2 Requirements............................................................................................................36
4.4.3 Design Process .........................................................................................................36
4.4.4 Final Design ..............................................................................................................36
4.4.5 Components..............................................................................................................37
4.5 Gear and Chain System ..................................................................................................37
4.5.1 Research ..................................................................................................................37
4.5.2 Requirements............................................................................................................38
4.5.3 Design Process .........................................................................................................38
4.5.4 Final Design ..............................................................................................................43
4.5.5 Components..............................................................................................................44
4.6 Hand Pedals ....................................................................................................................44
4.6.1 Research ..................................................................................................................44
4.6.2 Requirements............................................................................................................45
4.6.3 Design Process .........................................................................................................45
4.6.4 Final Design ..............................................................................................................47
4.6.5 Components..............................................................................................................51
4.8 Leg Brace and Support ....................................................................................................52
4.8.1 Research ..................................................................................................................52
4.8.2 Requirements............................................................................................................54
4.8.3 Design Alternatives ...................................................................................................54
4.8.4 Initial Design .............................................................................................................55
4.8.5 Final Design ..............................................................................................................56
4.8.6 Components..............................................................................................................58
4.9 Brakes .............................................................................................................................58
4.9.1 Research ..................................................................................................................58
4.9.2 Requirements............................................................................................................59
4.9.3 Design Process .........................................................................................................59
4.9.4 Final Design ..............................................................................................................62
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4.9.5 Components..............................................................................................................64
5. Testing ..................................................................................................................................64
5.1 Ease of Use .....................................................................................................................64
5.1.1 Timing transfer and positioning on trike .....................................................................64
5.2 Safety ..............................................................................................................................64
5.3 Speed ..............................................................................................................................65
5.3.1 Time top speed on trike on level ground....................................................................65
5.3.2 Acceleration of trike from standstill ............................................................................65
5.4 Turning ............................................................................................................................66
5.5 Weight .............................................................................................................................67
5.6 Client Satisfaction ............................................................................................................67
5.6.1 Satisfaction Survey ...................................................................................................67
5.6.2 Avoiding spasms .......................................................................................................67
5.7 Outdoor usage .................................................................................................................68
5.8 Economic Sustainability ...................................................................................................68
6. Business Analysis .................................................................................................................68
6.1 Market Research .............................................................................................................68
6.1.1 Existing Competitors .................................................................................................68
6.1.2 Target Markets ..........................................................................................................69
6.2 Financials ........................................................................................................................70
6.2.1 Budget ......................................................................................................................70
6.2.2 Funding .....................................................................................................................74
6.2.3 Potential Profits. ........................................................................................................74
7. Project Management .............................................................................................................74
7.1 Work Division ..................................................................................................................74
7.2 Team Organization and Management..............................................................................75
7.3 Scheduling and Milestones ..............................................................................................77
8. Acknowledgements ...............................................................................................................78
9. References ...........................................................................................................................80
10. Conclusion ..........................................................................................................................82
11. Appendices .........................................................................................................................83
A. Gearing Calculations .........................................................................................................83
A.1 Excel sheet on gears ...................................................................................................83
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Team 5: TheraTryke
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A.2. Power calculations and top speeds .............................................................................84
A.3 Gearing Ranges Considered .......................................................................................86
B. Work Breakdown Schedule ...............................................................................................87
C. User Experience Definition ................................................................................................91
D. Business Analysis Calculations .........................................................................................93
E. Frame Design Analysis .....................................................................................................98
E.1 Weight Determination ..................................................................................................98
E.2. Maximum Deflection and Stress ...............................................................................101
F. Steering and Pedaling Concept .......................................................................................106
G. Final Prototype Images ...................................................................................................107
Final Report
Team 5: TheraTryke
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Figures
Figure 1. Team members ........................................................................................................... 3
Figure 2. TerraTrike Tour II model.............................................................................................. 8
Figure 3. TerraTrike Rover model .............................................................................................. 9
Figure 4. Top End Force K handcycle ........................................................................................ 9
Figure 5. Gomier Rehatri Therapy Trike 16" ..............................................................................10
Figure 6. AmTryke AM-16" Therapeutic Tricycle .......................................................................11
Figure 7. Catrike 700 Recumbent Racing Trike .........................................................................11
Figure 8. Past engineering senior design stroller project ...........................................................12
Figure 9. Trike frame with constraints and forces applied ..........................................................16
Figure 10. SolidWorks original model of trike ............................................................................19
Figure 11. Small body interference sketch ................................................................................21
Figure 12. Large body interference sketch ................................................................................22
Figure 13. Al 6061-0 Von Mises stress analysis English units (psi) ...........................................22
Figure 14. Al 6061-0 displacement analysis metric units (mm) ..................................................23
Figure 15. Initial 3D trike model .................................................................................................24
Figure 16. Final SolidWorks design ...........................................................................................25
Figure 17. Push bar ..................................................................................................................26
Figure 18. Push bar application .................................................................................................26
Figure 19. Direct steering ..........................................................................................................28
Figure 20. Linkage steering .......................................................................................................28
Figure 21. Hand pedaled recumbent trike .................................................................................29
Figure 22. Turning angle diagram .............................................................................................31
Figure 23. Trike design with 20" tires ........................................................................................33
Figure 24: Final trike layout .......................................................................................................34
Figure 25. Seat with adjustable positioning (TerraTrike model) .................................................35
Figure 26. Seat with fixed positioning (Utah Trikes) ..................................................................35
Figure 27: TerraTrike seat with added restraints .......................................................................36
Figure 28. Diagram of gear design selections ...........................................................................41
Figure 29. Components of the central gear hub ........................................................................42
Figure 30. Central gear hub on frame .......................................................................................42
Figure 31. Final gear setup .......................................................................................................43
Figure 32. Top End hand pedal design .....................................................................................45
Figure 33. Brake and shifter placement .....................................................................................46
Figure 34. Alternating hand pedaling.........................................................................................47
Figure 35. Final hand pedal design ...........................................................................................47
Figure 36. Hand crank to fix interference..................................................................................48
Figure 37. Hand pedal final 3D design .....................................................................................48
Figure 38. Manufactured hand pedals ......................................................................................49
Figure 39. Disassembly of foot pedal .......................................................................................50
Figure 40. Components used in hand pedals ...........................................................................50
Figure 41. Hand pedal with gear shifter ....................................................................................51
Figure 42. Standard foot pedal styles ........................................................................................52
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Team 5: TheraTryke
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Figure 43. Adjustable ergonomic knee brace ............................................................................53
Figure 44. Example of therapeutic bracing from Trulife .............................................................53
Figure 45. Motocross articulating knee brace, listed at $1,400 per pair .....................................54
Figure 46. Leg bracing concept sketch ......................................................................................56
Figure 47: Example walking boot ..............................................................................................57
Figure 48: Modified walking boot with pedal ..............................................................................57
Figure 49. Rim, drum, and disc brake .......................................................................................61
Figure 50. Close up of brake integration site .............................................................................63
Figure 51. Brake and housing design ........................................................................................63
Figure 52. Bike acceleration test results ....................................................................................66
Figure 53. First semester team organization .............................................................................76
Figure 54. Second semester team organization ........................................................................76
Figure 55. Work log ...................................................................................................................77
Figure 56. Distribution of work time ...........................................................................................77
Figure 57: Power Calculations ..................................................................................................84
Figure 58. Bike speed calculator ...............................................................................................85
Figure 59. Gear ranges considered ...........................................................................................86
Figure 60. Aluminum 6061-T6 frame weight ..............................................................................98
Figure 61. Chromoly 4130 alloy steel frame weight ...................................................................99
Figure 62: E.3 Titanium alloy 3AL-2.5V frame weight ..............................................................100
Figure 63. Al 6061-T6 Von Mises stress analysis ....................................................................101
Figure 64. Al 6061-T6 displacement analysis ..........................................................................101
Figure 65. Ti 3AL-2.5V Von Mises stress analysis ..................................................................102
Figure 66. Ti 3AL-2.5V displacement analysis.........................................................................102
Figure 67. Chromoly 4130 Steel Alloy Von Mises stress analysis............................................103
Figure 68. Chromoly 4130 Steel Alloy displacement analysis..................................................103
Figure 69. Al 6061-0 Von Mises stress analysis english units (psi)..........................................104
Figure 70. Al 6061-0 Von Mises stress analysis metric units (𝑁𝑚2) ........................................104
Figure 71. Al 6061-0 displacement analysis english units (in) .................................................105
Figure 72. Al 6061-0 displacement analysis metric units (mm) ................................................105
Figure 73. Concept to combine steering and pedaling.............................................................106
Figure 74. Final prototype .......................................................................................................107
Figure 75. Top view of prototype .............................................................................................107
Final Report
Team 5: TheraTryke
page viii
Tables
Table 1. Metric material properties ............................................................................................14
Table 2. English material properties ..........................................................................................14
Table 3. Cost of materials for trike.............................................................................................15
Table 4. Maximum stress calculations .......................................................................................17
Table 5. Weight of basic trike frame based in SolidWorks .........................................................17
Table 6. Maximum deflection calculations for basic frame .........................................................18
Table 7. Design decisions for arm length based on human measurements (Notice, deemed
inaccurate) ................................................................................................................................19
Table 8. Design decisions for leg length based on human measurements (Notice, deemed
inaccurate) ................................................................................................................................20
Table 9. Design decisions for seat size based on human measurements..................................20
Table 10. Trike frame decision matrix .......................................................................................20
Table 11. FEA results................................................................................................................23
Table 12. Frame BOM...............................................................................................................27
Table 13. Design options for the steering mechanism ...............................................................30
Table 14. Cost considerations for steering ................................................................................32
Table 15. Cost considerations for wheels ..................................................................................34
Table 16. Cost considerations for the seat ................................................................................37
Table 17. Gear ratio possibilities for a 27-speed gear system ...................................................38
Table 18. Gearing system options .............................................................................................39
Table 19. Power distribution and top speeds.............................................................................40
Table 20. Gear system components and cost ...........................................................................44
Table 21. Hand pedal manufacturing decision chart ..................................................................49
Table 22. Costing for hand pedals.............................................................................................51
Table 23. Design fabrication alternatives for ergonomic bracing ...............................................55
Table 24. Cost consideration for leg braces ..............................................................................58
Table 25. Advantages and disadvantages of brake options.......................................................59
Table 26. In-depth decision for the specific project ....................................................................60
Table 27. Cost comparison for brake types ...............................................................................61
Table 28. Pros and Cons of Braking Arrangements .................................................................62
Table 29. Brake BOM component list ........................................................................................64
Table 30. Loading and unloading times .....................................................................................64
Table 31. Braking distance from top speed ...............................................................................65
Table 32. Top speed test results ...............................................................................................65
Table 33. Acceleration data.......................................................................................................66
Table 34. Turning circle results .................................................................................................66
Table 35. Satisfaction survey given to client ..............................................................................67
Table 36. Estimated project cost ...............................................................................................70
Table 37. Actual money spent on prototype ..............................................................................71
Table 38. Final BOM of the trike................................................................................................72
Table 39. Excel sheet for gear considerations ...........................................................................83
Table 40. Project work breakdown schedule .............................................................................87
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Team 5: TheraTryke
page ix
Table 41. Income Statement for TheraTryke .............................................................................93
Table 42. Cash Flow Statement for TheraTryke ........................................................................93
Table 43. Break Even Analysis for TheraTryke .........................................................................94
Table 44. Depreciation and Interest Calculations ......................................................................95
Table 45. Ratios and EBITDA Calculations ...............................................................................95
Table 46. Fixed Operating Costs for TheraTryke.......................................................................96
Table 47. Variable Operating Costs for TheraTryke ..................................................................96
Table 48. Variable COGS for TheraTryke .................................................................................97
Table 49. Fixed COGS for TheraTryke ......................................................................................97
Final Report
Team 5: TheraTryke
1.
Introduction
1.1
Calvin College Engineering Department
page 1
The Calvin College Engineering Department combines a world-class liberal arts education
curriculum with knowledge of technology and engineering to provide for the best learning
environment for students. The faculty and staff work with students to help produce intuitive
designs and great products. The incorporation of a reformed Christian worldview also
challenges the students and allows for development or characteristics necessary to be
successful in the field of engineering. The main goal of the engineering department is to make
an impact for God’s kingdom and the world around us.
1.2
Senior Design Project
Senior Design is a required class taken by all engineering students at Calvin College. The
purpose of this course is to allow senior engineering students to design and implement their
own ideas. These ideas are carried out from cradle to grave in terms of the design process.
This design process includes filling a need with a new idea or an improved design innovation,
implementing a project plan, identifying project requirements and constraints, coming up with
design alternatives, and possibly manufacturing a prototype of the final design. Throughout the
entire process, teams are to report to an appointed advisor in the Calvin engineering program
who will provide the design team with professional advice. At the end of the fall semester, the
team is required to present a Project Proposal and Feasibility Study (PPFS) to the department.
This report includes an introduction to the design, design plans, and all research and initial tests
done that have been recorded. At the end of the spring semester, a final report is due which
builds off of the PPFS and all other work done in order to finalize the project and create a
working apparatus.
1.3
Objective
The objective of this project is to design and build a therapeutic trike for those with little or no
use of their legs. The trike will have the capability of pumping the legs via energy transferred
from hand pedaling. This device will have therapeutic benefits that no other outdoor vehicle
currently in the market has. The specific goals that pertain to this objective are as follows:
1.3.1 Ease of Use
The storage, moving, loading, accelerating, and braking should be not significantly more difficult
or strenuous for a handicapped user when compared to a regular hand trike. The loading time
which consists of transferring into the trike, strapping in the legs, and securing the body
restraints should not take more than 5 minutes.
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1.3.2 Speed
The trike will be able to travel at a steady speed of 10 mph on flat ground, while being supplied
60 watts of power from the rider. This can also be seen in section 2.2.9. The team will test the
trike for its ability to get up to speed. Further details on this testing can be seen in the testing
section.
1.3.3 Safety
The trike will be able to come to a complete stop within 10 feet while operating at 10 mph with a
250 lb rider. The trike should be able to have a 10 foot turning radius and shoot be able to safely
make this turn at 5 mph.
1.3.4 Therapeutic Benefits
The trike will provide therapeutic benefits to those using it as confirmed by experts in the field of
physical therapy and rehabilitation while in collaboration with patients diagnosed with
paraplegia. The team will test the trike’s ability to deter spams and atrophy by having a people
with paraplegia use it as a direct substitution for stretching for several days.
1.3.5 Outdoor Usage
The trike will be able to endure a variety of outdoor and environmental conditions without seeing
a major loss in performance. This includes exposure to water without corrosion and weathering
impact stresses caused by road use. Specific criteria for measuring these goals can be found in
Section 2.2. The team will accept prior knowledge on material properties.
1.3.6 Economic Sustainability
The trike must fall within reasonable market price values of both current recreational trike
models as sold by TerraTrike and current therapeutic machinery as used by hospitals and
medical personnel. The standard trike market price from TerraTrike is approximately $1,749.
The RT300 Leg Cycle system used for in-home and hospital purposes is approximately
$10,499. The comparative price for the therapeutic trike must be within or below the range of
these price variations.
1.4
Motivation
The team has been introduced to many individuals with paralysis. This is a brutal living condition
that affects many people’s mobility. A few causes that the team learned about were from tragic
vehicle accidents, unfortunate shootings, and genetic characteristics. The team has been
constantly reminded of just how life altering such a condition can be. When paralyzed, it
becomes hard to keep the motivation to exercise the body you can no longer use. Additionally,
when the body is kept in one position for an extended period of time, there are symptoms that
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Team 5: TheraTryke
page 3
arise such as leg spasms, sores, stiffness, and atrophy. This has become the reality of many
people living in the Calvin community as well as elsewhere in the world.
The goal of this design project is to minimize a variety of the symptoms that result from
paraplegia and others like it. In order to accomplish this, the idea is to introduce a leg pumping
function into a hand-pedaled trike. The concept is that while the rider cranks their hands to drive
the trike, a simultaneous gear drive will rotate the legs at a desired cycle speed. Below is the
design of a standard racing trike. The key difference is that TheraTryke will be used for
therapeutic purposes in addition to recreational usage.
1.5
Group Members
Figure 1. Team members
(From left to right: Nick Memmelaar, Connor VanDongen, Jack Kregel, and David Evenhouse)
Nick Memmelaar
Nick Memmelaar is a senior engineering student in the mechanical concentration from
Caledonia, MI. Nick has had two engineering internships - the first at Knape & Vogt and the
second at Ventura Manufacturing. During Nick’s summer working at Ventura Manfucaturing,
Nick successfully implemented a spare parts inventory system while also gaining much more
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page 4
manufacturing and machine design experience. In January of 2014, Nick had the opportunity to
use his engineering experience in Kenya. He, along with three other students and a professor,
were given the task of fixing a broken bore-hole hand pump for a native community in Sedai,
Kenya. They were successful in fixing the well. Nick was able to experience just how significant
and helpful he can be with the position and education that he is a part of. Nick has accepted a
Mechanical Design Engineer I position at Extol in Zeeland, MI. They are a machine design
company that specializes in plastic joining. He may consider further schooling if the need arises.
Connor VanDongen
Connor VanDongen is a senior engineering student in the mechanical concentration from
Galesburg, MI. From a young age Connor has always had the passion to use his hands in
building something that will benefit the kingdom of God. Whether it was working on his
grandfather’s airplane or tinkering on his dirt bike, Connor always felt like engineering was his
destined career path and decided to take his talents to Calvin. During his time at Calvin, Connor
has held one engineering internship with two different job titles. The company, Progressive
Surface, is a global leader in the design and manufacturing of automated machinery and closedloop process controls for shot peening, abrasive grit blasting, among many others for
applications in the aerospace, energy, medical, military, and general manufacturing industries.
Connor was given the title of Floor Engineer as his first job at Progressive. This position allowed
him to work as a middleman between design and manufacturing personnel refining and
implementing new and improved products. His most recent position as a Junior Design
Engineer has allowed for the development of leadership skills as well as product development
skills. After graduation, Connor will be working at Plascore in Zeeland, MI. He plans on working
there for a few years while hopefully working towards his dream job in the field of aerospace
engineering.
Jack Kregel
Jack Kregel is a senior engineering student in the mechanical concentration from Iowa City, IA.
The past two summers Jack has had two different engineering internships. The first was at
Virtual Soldier Research a branch of the University of Iowa Computer Aided-Design program.
While at VSR, Jack worked on Department of Defense funded projects involving software
development for digital human modeling and simulation. During Jacks most recent internship at
Gordon Manufacturing, he worked with a variety of different departments on the development of
height adjustable table legs. Both internships gave Jack knowledge about all aspects of
engineering, ranging from design, production and manufacturing to the business aspects behind
all engineering decisions. After graduation, Jack has accepted a job working as a Production
Support Engineer at Gentex Corporation in Zeeland, MI. He plans on getting several years of
experience before pursuing a Masters of Business Administration and hopefully starting his own
company.
David Evenhouse
David Evenhouse is a senior engineering student in the mechanical concentration from Grand
Rapids, MI. David was inspired at a young age to pursue engineering as a profession and has
notable experience in the manufacturing industry. This includes two summers working as an
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page 5
Assembler Fitter, and two summers working as an Engineering Intern at two separate
engineering companies. From these experiences, he learned how to properly handle tools and
machinery, methods of manufacture, quality engineering systems, and many other practical
engineering skills. Additionally, he studied engineering in Spain during the spring of his junior
year, gaining international experience and reinforcing his knowledge of the Spanish language. A
strong communicator and huge proponent of hands-on engineering work, David looks forward to
tackling the design problem at hand. In the coming years he will be pursuing a PhD in
Engineering Education at the Purdue College of Engineering Education in West Lafayette.
1.6
Client
This trike will be designed and built for Nancy Remelts, a lady with multiple sclerosis (MS) that
is connected to the Calvin community. The cause for MS is unknown, but it is known that the
immune system mistakenly attacks the central nervous system, specifically the myelin coating
around nerve fibers. This damage causes distortion in nerve impulses traveling to and from the
brain, producing a wide variety of symptoms.
The client is fighting this disease with all that she has got. She is in the Calvin gym every
weekday morning at 7:30 am to keep her strength up in case a cure for this disease is found.
She realizes how unpredictable her symptoms can be day by day, but this has turned into her
motivation. After a single meeting with her, it was clear that she could see herself using the
proposed product. It is an honor to work with her on this project and to supply her with more
ammunition to aid her in her fight.
2.
Project Requirements
2.1
Functional
The vehicle will be able to be used outside with ease on well-maintained roads or sidewalks,
with some allowance for uneven surfaces. This will be considered the standard operating
condition of the vehicle. The user will be able to enter the trike without assistance, with a
parking brake aiding stable transition. He/she will be able to pedal him/herself by cycling his/her
hands. This pedaling of the hands will cause the legs to cycle, while additional power may be
provided via the legs as permitted by the user’s physical capabilities. The legs will see a
therapeutic benefit regardless of their ability to provide power to the drive assembly.
2.2
Mechanical
2.2.1 Height and Weight Capacity
The vehicle will be designed to be used by riders ranging from heights of 5’ to 6’5” and a
maximum weight of 250 lbs.
Final Report
Team 5: TheraTryke
page 6
2.2.2 Product Weight
The vehicle will be light enough to promote easy transportation and ease of use for people with
low mobility. Thus, it should not exceed 60 lb of net weight.
2.2.3 Size
The vehicle will be as small as possible while accommodating for rider safety and full range of
motion in all limbs for riders representing a variety of body-types. More specific sizing data can
be found in Section 4.1.4.2.
2.2.4 Material
Component material will be strong enough to support the maximum stated rider weight in
standard operating conditions while also being light enough to promote ease of transportation.
2.2.5 Seat
The seat will be comfortable as well as rugged. The backrest will come up to at least the
shoulder blades of the occupant. It will be adjustable to accommodate for different body lengths.
2.2.6 Mounting
Gears will need to be positioned correctly to allow for linear chain movement. Brakes need to be
mounted correctly. Gear and brake controls will be mounted in user-friendly positions that
promote both ease of use and operational safety.
2.2.7 Maintenance
Maintenance requirements will be similar to that of a bicycle. Gears and chains should be
lubricated. Tire pressure should be checked. Moving components and critical systems such as
braking should be checked regularly for excessive wear due to use.
2.2.8 Environmental
The trike will be made with materials and components that do not normally rust or wear under
normal operating conditions, allowing for at least 5 years of regular use.
2.2.9 Speed
The trike should be able to travel at least 10 mph while supplying 60 watts of energy to the hand
pedals on flat ground.
Final Report
Team 5: TheraTryke
2.3
page 7
Safety
2.3.1 Brakes
The vehicle will have a hand operated brake similar to a bicycle. The vehicle will also have
parking brakes that secure the trike to avoid rollaway and facilitate easy entry.
2.3.1.1 Stopping
The vehicle traveling at 15 mph will have a stopping distance of 10 feet or less while carrying a
load of 90 to 250 lbs.
2.3.1.2 Parking Brake
Applying the parking brake will prevent rollaway of the vehicle under any loading condition up to
250 lbs, positioned on a decline of up to 25°.
2.3.2 Harnessing
The vehicle will include multiple adjustable straps to secure the operator during use including,
but not limited to, a seat belt.
2.3.3 Stability
The vehicle will be stable during normal operation due to the location of the center of gravity and
the wheel placement.
2.3.4 Flag Slot
One side of the backrest will have slots to attach a flag that will be visible to bystanders over a
hill during vehicle operation.
2.4 Design Norms
There are several guidelines that Calvin engineering students strive to follow in their work.
These guidelines help students do an outstanding job in the work that is done as well as keep
things in perspective with God and each other in the picture.
One design norm that characterizes the project is justice. One main goal for this project is to
design a means of exercise for those who would otherwise not have access to such an
opportunity due to their physical limitations. Providing a fun and exhilarating alternative to their
normal daily routine can make all the difference to someone struggling with a physical
impairment. Those with limited or no leg mobility can have few opportunities to go outside and
enjoy nature.
Final Report
Team 5: TheraTryke
page 8
Caring is another design norm that fits the project. The client’s well-being is at the forefront of
each decision. Past experiences and skills will be used to create a vehicle that the client will
enjoy using and be thoroughly grateful for the work put into the project.
Thirdly, stewardship should shine through this project. The team wants to take care of the
environment, the money put into the project, and the satisfaction of the client. The team want to
select materials that will make the vehicle last.
3. Market Research
3.1 Similar Products
3.1.1 TerraTrike
TerraTrike is a recumbent tricycle company based in Grand Rapids, MI. They were founded in
1996 by originally Jack Wiswell and Wayne Oom. The goal of their company is to create a
vehicle that does not create air, noise, or sight pollution. Their main goal is to produce high end
recumbent trikes that are mainly used for recreational usage. TerraTrike offers many different
types of trikes with a variety of different mechanisms. For their frames they use high tensile
steel, 4130 chromoly steel, and 6061 T6 Heat Treated Aluminum. They also have two different
steering mechanisms, direct and linkage. They also integrate several different gearing
mechanisms including the Nuvinci internal gearing system. Shown in Figure 2 is TerraTrike’s
Tour II model, their high end long distance model. It is outfitted with 4130 Chromoly Steel, and
linkage steering. Also shown in Figure 3 is TerraTrike’s Rover model, their lower lever trike.
The Rover is outfitted with high tensile steel and direct steering. Prices at TerraTrike range from
$899.00 for low end models to $3,999.00 for their high end models.
Figure 2. TerraTrike Tour II model
Final Report
Team 5: TheraTryke
page 9
www.terratrike.com
Figure 3. TerraTrike Rover model
www.terratrike.com
3.1.2 Top End Trikes
Top End Trikes produces high performance arm, chest, and abdominally driven hand-powered
trikes. They are designed for individuals who want to be not only recreational, but even
competitive, despite physical disability. Prices can range from $2,300 for a standard recreational
trike to $7,500 for a trike used in racing applications, not including additional optional
accessories. Their target market is adults who still retain a high degree of strength and mobility
in their upper bodies, allowing for the use of such high performance products. Figure 4 shows a
Top End example.
Figure 4. Top End Force K handcycle
http://www.invacare.com/product_files/FRCK_400.jpg
Final Report
Team 5: TheraTryke
page 10
3.1.3 Rehatri Trikes by Gomier
Rehatri is a line of trikes from Gomier with a mission statement much like TheraTryke’s. Their
goal is to provide therapeutic recreational options to individuals with disability. Their primary
target market is the parents of children with Cerebral Palsy, although a range of trikes are
available for various users. The trikes are designed for use on flat, level pavement only, and
have little adjustability in the gear drive. However, they do incorporate a positive drive system
that rotates the user’s legs for therapeutic purposes, much like the proposed TheraTryke. The
trikes are designed to be recreational, but within a controlled environment, having straight
seatbacks and handles on the back for support and supervision. Trikes range from $895.99 to
$1,250.00, not including optional accessories. Figure 5 is an example of a Rehatri trike.
Figure 5. Gomier Rehatri Therapy Trike 16"
http://www.bikeexchange.com.au/a/recumbent-bikes-trikes/gomier/vic/ravenhall/rehatri-therapy-adult-handicap-red-16/102558814
3.1.4 AmTryke
AmTryke LLC, a therapeutic trike manufacturer, is an affiliate of AMBUCS Inc. AMBUCS is a
national nonprofit organization dedicated to empower disabled persons to achieve greater
degrees of mobility and independence. The trikes produced by this company are also dual drive
operated, meaning that they can be hand and/or foot powered when in use. AmTryke works with
both volunteer members and Physical or Occupational therapists in order to provide these trikes
to individuals to improve motor skills, strength, and self-esteem. AmTryke products are similar in
both appearance and operation to Rehatri products. However, AmTryke markets primarily to
American customers, while Rehatri appears to operate chiefly overseas. Like Rehatri, AmTryke
utilizes vertical backrests and optional accessories to improve performance for physically
impaired users. Prices may range from $800 to $1,250 depending upon the application. Figure 6
is an AmTryke example.
Final Report
Team 5: TheraTryke
page 11
Figure 6. AmTryke AM-16" Therapeutic Tricycle
http://www.rehabmart.com/product/amtryke-am16-therapeutic-tricycle-41127.html?gclid=CKW4wZL1scICFczm7AodeR0AfQ
3.1.5 Catrike
Catrike is a recumbent trike company created in 2000 by Paulo Camasmine, a Brazilian
Mechanical Engineer. Their vision is to create new high quality products to improve people’s
lives. Catrike has received six awards for Trike of the Year by the readers of Bent Rider online.
They try and focus on product development, engineering and process design. Their goal is to
create beautiful and flawless products that are user friendly and require little maintenance.
They are currently making 2,300 bikes annually. Prices at Catrike range from $2,150.00 for
their low end models to $2,950.00 for high end models. Figure 7 shows an example of a Catrike
trike.
Figure 7. Catrike 700 Recumbent Racing Trike
http://www.utahtrikes.com/PROD-11617573.html
Final Report
Team 5: TheraTryke
page 12
3.2 Past Projects
3.2.1 Achieving Mobility
Achieving Mobility was a Calvin College senior design project back in 2010-2011. Their goal
was to design and distribute a motorized stroller that could easily be controlled using one finger.
Their project was developed to help Issac Postma, a young boy diagnosed with Spinal Muscular
Atrophy. The team has drawn a lot of motivation from Achieving Mobility. Their desire to help
an individual with physical limitations inspired the team to pursue a similar product. The team
and their project can be seen in Figure 8.
Figure 8. Past engineering senior design stroller project
http://www.mlive.com/news/grand-rapids/index.ssf/2011/06/how_calvin_college_engineering.html
3.3 External Resources
3.3.1 TerraTrike
The team has met with TerraTrike at their facility in Grand Rapids. They have been very helpful
in explaining what is and is not possible for bike parts, gave recommendations on parts, and
have graciously supplied parts that were used in the final product.
3.3.2 Boston Square Community Bikes
The team did a service learning experience at Boston Square in Grand Rapids. The team were
able to get hands on experience with bikes as well as another great source for parts at a
discounted rate.
Final Report
Team 5: TheraTryke
page 13
3.3.3 Foot & Ankle Specialists
Foot and ankle has provided the team with walking boots for the bracing system designed for
the legs.
3.3.4 Calvin Bike Garage
The Calvin bike garage has been helpful in supplying recommendations and parts on braking
and shifting systems.
3.3.5 Progressive Surfaces
Welders at Progressive Surfaces have been extremely helpful in welding the frame of the
prototype. The team also used SolidWorks at Progressive to design the frame. They are located
in Grand Rapids, MI.
3.3.6 Custom Frame Coatings
Custom Frame coatings offered to powder coat the frame for free. They loved the idea of the
trike and that it will actually help someone. They are located in Zeeland, MI.
4. Mechanical Design
The mechanical design of the product consists of all structural components including but not
limited to the frame, gear design, ergonomics, and braking components. Each of these portions
is divided into subsections for the mechanical design of the project. All components are
dependent on each other meaning that timeliness is of the utmost importance in staying on task.
4.1 Frame
The frame provides the primary structure of the design that supports all other components. The
frame supports the gear train, seating, and other mounting components which will hold the
individual using the device. Weight and strength capabilities must be seriously considered when
designing the frame. Safety and comfort are key when designing a product for therapeutic and
recreational use. Several different materials were analyzed for the final design of the frame.
4.1.1 Research
Past trike frame materials have been researched and all important properties for each material
are provided in both Metric and English in Table 1 and Table 2, respectively.
Final Report
Team 5: TheraTryke
page 14
Table 1. Metric material properties
Material
Density
[kg/m^3]
Yield
Strength
[MPa]
Mod. of
Elasticity
[GPa]
Elongation
[%]
Hardness
[Brinell]
Corrosion
4130 Chromoly Steel
7850
435
205
25.5
197
Yes
Aluminum 6061-T6
2700
276
68.9
12
95
Yes
Titanium Alloy
3AL-2.5V
4480
500
100
15
256
Yes
Table 2. English material properties
Material
Density
[lbf/ft^3]
Yield
Strength
[psi]
Mod. of
Elasticity
[ksi]
Elongation
[%]
Hardness
[Brinell]
Corrosion
Resistance
4130 Chromoly Steel
490.752
63100
29700
25.5
197
Yes
Aluminum 6061-T6
168.480
40000
10000
12
95
Yes
Titanium Alloy
3AL-2.5V
279.936
72500
14500
15
256
Yes
4.1.2 Requirements
4.1.2.1 Strength
The frame material and design must be strong enough in order to withstand a weight of 250 lbs.
This trike will be designed for individuals with a range of height from 5-0’ to 6-5’. In addition to
these requirements, the frame must be able to withstand any impact from uneven roads. The
welds on the frame must be continuous in order to prevent any cracks or fractures to occur at
the weak joints. The weld thickness must be equal the thickness of the material it is being
applied to. Thicker welds will induce material heating issues.
4.1.2.2 Weight
Weight must be minimal in the trike in order to reduce the amount of force necessary to pump
the arm and leg handles. Those with limited strength or mobility cannot create enough force to
crank the handles if the trike exceeds in weight. According to TerraTrike’s specifications for their
entry level Rover variation of trike express the total weight as a range from 47 to 49 lbs.
Because of the additional weight for a hand pedal column, the final design of the trike must not
weigh more than 60 lbs including all components.
4.1.2.3 Aesthetics
Aesthetics are very important in the final design of the trike. It must be pleasing to the eye
because it is a form of transportation and recreation bringing in a concept of pride in the ride.
Final Report
Team 5: TheraTryke
page 15
Eliminating all sharp corners and edges and making the frame design as sleek and
aerodynamic as possible are important considerations for the design. Additional aesthetic
considerations will be implemented as time and budget allow. The color for the frame that the
team chose was blue, the client’s favorite color.
4.1.3 Design Process
4.1.3.1 Material Selection
Having the proper material for the frame was very important. Most trikes currently use standard
carbon steel, high-tensile steel, chromoly, or aluminum. In order to determine which material to
use for the frame a decision matrix was made comparing the various materials in terms of
corrosion resistance, cost, weldability, strength, weight, and deflection.
4.1.3.1.1 Corrosion Resistance
Corrosion resistance of the frame material is key to having a reliable and safe trike. The
trike will be exposed to rain and salt on the roads. These weather products have the
capability to produce rust which will degrade the mechanical properties of the material. With
this in mind, a material was chosen that is not affected, or is minimally affected, by the
weather products. Corrosive Resistance is considered in the decision matrix for the final
material. Aluminum is generally a very choice of material if corrosion resistance is
necessary. The aluminum oxide layer that forms on the part is impermeable and selfsustaining. Chromoly is considered an alloy steel and not yet stainless, therefore it is
resistant to corrosion but will not repel it. According to the Engineering ToolBox, Titanium is
a very good corrosion resistor.
4.1.3.1.2 Cost
Costs were calculated for each possible material and can be seen in Table 3.
Table 3. Cost of materials for trike
Material
O.D. [in]
Wall Thickness [in]
Cost [$/ft]
Al 6061-T6
2-0
⅛
8.25
Al 6061-T6
2-0
¼
13.48
Chromoly 4130
2-0
⅛
15.95
Chromoly 4130
2-0
¼
64.13
Ti 3AL-2.5V
2-0
⅛
35.82
Final Report
Team 5: TheraTryke
page 16
4.1.3.1.3 Weldability
This trike will need quality welds. The team initially wanted to do all the welding themselves but
determined that Connor’s employer, Progressive Surface, would be able to give us the highest
quality welds. The design of a good weld is one that matches the thickness of the part being
welded and that has no breaks or gaps which would cause weak joints in the frame. Titanium
welding is generally very good. The single issue with welding titanium is finding a way to
eliminate atmospheric contamination. Titanium reacts quickly with oxygen so there must be very
good ventilation. Aluminum welding is much more difficult because of the thermal conductivity of
the material. Aluminum has a low melting point and therefore you can burn through it very
quickly if not paying attention. Chromoly is an alloy form of steel. This material is easiest to weld
and generally has no complications.
4.1.3.1.4 Strength
The strength of the trike frame was determined using finite element analysis (FEA). The trike
frame model was analyzed in the Autodesk package MultiPhysics. In order to determine the
strength, the model had a brick mesh defined. In order to keep the part constrained, fixed points
were applied to each wheel connection because that is where no deflection will occur and the
trike remains stationary. Forces were also applied to the trike frame. This force was equivalent
to the maximum weight potential that the team had set for the design which is 250 lbs. The force
has been applied to where the rider will be seated, for all the weight will be concentrated in the
seating mount. Below in Figure 9 is the basic model of the trike frame showing fixed points and
force application.
Figure 9. Trike frame with constraints and forces applied
Final Report
Team 5: TheraTryke
page 17
The same fixed points and force locations were used for each material being analyzed.
Provided in Appendix E are stress analysis figures showing the stress throughout the entire
frame. Below in in both metric and English units.
Table 4 are the materials given with each of their maximum Von Mises stress values in both
metric and English units.
Table 4. Maximum stress calculations
Material
Von Mises Stress
[ksi]
Yield Strength
[ksi]
Von Mises Stress
[kPa]
Yield Strength
[kPa]
Aluminum 6061-T6
2.478
40.0
17085.178
435000
Chromoly 4130 Alloy Steel
2.169
63.1
14954.702
276000
Titanium Alloy 3AL-2.5V
2.172
72.5
14975.386
500000
The goal of analyzing the Von Mises stress of the trike frame was to compare it to the yield
strength of the material. The yield strength of the material is the point at which material leaves
its elastic deformation and begins its plastic deformation state. It is at this point which the
material can no longer return to its original state and will eventually wear out. This is crucial that
the maximum stress in the frame does not exceed the yield strength. It is apparent that the
stress on the frame for all materials have passed this test.
4.1.3.1.5 Weight
In order to determine what the weight of the frame would be for each given material, a model
was made for the frame. The frame assembly was taken independently from the trike model in
SolidWorks. The material was defined providing all necessary material properties. With all of
these properties, SolidWorks was able to determine the total weight of the assembly. Below is
Table 5 providing each material specification with weight given the initial basic model of the trike
in SolidWorks
Table 5. Weight of basic trike frame based in SolidWorks
Material
Aluminum 6061-T6
Weight [lbf]
Weight [N]
6.86
30.51
Chromoly 4130 Alloy Steel
19.93
88.65
Titanium Alloy 3AL-2.5V
11.38
50.62
Final Report
Team 5: TheraTryke
page 18
All SolidWorks material properties used and weight calculations can be found in Appendix E.
The material specified had to be lightweight in order to minimize the effort required by the
rider to pedal.
4.1.3.1.6 Deflection
Deflection is important because the intention of a trike is to be stiff. A ductile material would
result in an unstable ride. Deflection was determined through using finite element analysis in
Autodesk MultiPhysics. Along with the Von Mises stress analysis, deflection is embedded in the
program. Found in Appendix E are figures showing color orientated photos of the deflection
analysis. In Table 6 are the maximum deflection values provided in both metric and English
units of measurement.
Table 6. Maximum deflection calculations for basic frame
Material
Deflection
[in]
Deflection
[mm]
Aluminum 6061-T6
0.0396
0.894
Chromoly 4130 Alloy Steel
0.0133
0.307
Titanium Alloy 3AL-2.5V
0.0263
0.602
The deflection of the frame must not be excessive because the goal is to build a durable
stiff trike. Each of the deflections shown for the frame materials is quite minimal and is
actually expected when a 250 lb rider gets on the trike. Deflection analysis was done later
on the final model of the trike as well. New displacement measurements were taken
according to the model as well as the fabricated prototype.
4.1.3.2 Design Alternatives
4.1.3.2.1 Frame Setup
The team decided on going forward with a tadpole styled trike. This means that there are two
wheels in front and one in the back. This will keep the gear chains linear to avoid torsion. An
independent steering system will control the front two wheels. This setup will also provide
optimal space for the cycling of the legs. A setup with one wheel in front and two wheels in
back, also known as a delta frame design, even without the chain twisting problem, would be
difficult to place the foot pedals around a steering front wheel. Due to limitations of motion in the
legs, the tadpole design was the finalized decision. The basic SolidWorks design of the trike can
be seen in Figure 10.
Final Report
Team 5: TheraTryke
page 19
Figure 10. SolidWorks original model of trike
4.1.3.2.2 Sizing and User Accommodation
Data on human measurements in Table 7, Table 8, and Table 9 was taken from a study of 2380
subjects across the United States (Harrison and Robinette, 2002).
Table 7. Design decisions for arm length based on human measurements (Notice, deemed inaccurate)
Final Report
Team 5: TheraTryke
page 20
Table 8. Design decisions for leg length based on human measurements (Notice, deemed inaccurate)
Table 9. Design decisions for seat size based on human measurements
It is important to keep in mind that Table 7 and Table 8 are deemed inaccurate according to
user definition.
4.1.3.3 Cost Considerations
These three materials were put into a decision matrix to help decide the best option. This can be
seen in Table 10.
Table 10. Trike frame decision matrix
Criteria
Weighted Scale
(0-10)
Corrision
Cost
Weldability
Strength
Weight
Deflection
8
10
5
6
9
4
Sum
Rank
Aluminum 6061-T6
Score
Weighted
(0-10)
Score
8
64
9
90
5
25
9
54
9
81
7
28
342
1
Chromoly 4130
Score
Weighted
(0-10)
Score
6
48
6
60
9
45
9
54
6
54
9
36
297
2
Titanium 3Al-2.5V
Score
Weighted
(0-10)
Score
10
80
3
30
7
35
9
54
7
63
8
32
294
3
Final Report
Team 5: TheraTryke
page 21
After all calculations were done and each factor of the frame material was weighted, the
final decision for the material of the trike was decidedly Aluminum 6061-T6. This material
was purchased, cut and welded.
4.1.3.4 Prototype Frame Design
During prototype design and fabrication of the frame, there were many mistakes and learning
opportunities that presented themselves. In the following section, the frame fabrication process
will be explained along with all of the rework that was done to correct initial mistakes made.
Additional components applied after initial testing will be explained as well.
4.1.3.4.1 Initial Frame Design
The initial frame design was made based off of ergonomic human body length data received
from on online research article which can be found in Table 7, Table 8 and Table 9. All modeling
was done in SolidWorks 2015. The only components not provided in the 3D model are the
gears, chains, and brake lines. Making sure the frame would fit a human body was vital to the
design process. That is why the referenced scholarly article was used. Below are figures
showing the initial frame design with sketches marked in the model. These are sketches
representing the limb interference. This had to be considered in order to eliminate any limb
interference while cycling the hands and feet simultaneously on the trike.
Figure 11. Small body interference sketch
Final Report
Team 5: TheraTryke
page 22
Figure 12. Large body interference sketch
As seen in Figure 11 and Figure 12, there is no interference between the knee joint and hand
cycling motion. This allowed us to move to the next step in the process which was to complete a
secondary FEA using the proper frame design to test the stress and displacement of the new
design. Note, under all analysis a 250 lb force was used as the standard case for the weight of
the rider. This force was applied only to the base of the frame which will be seen in the following
figures.
Figure 13. Al 6061-0 Von Mises stress analysis English units (psi)
Final Report
Team 5: TheraTryke
page 23
Figure 14. Al 6061-0 displacement analysis metric units (mm)
Aluminum 6061-0 was used as the defaulted material for this analysis rather than the actual
Aluminum 6061-T6 temper state. This was done to compensate for the lower temper levels after
welding. It is unknown what the temper will be exactly after welding is done because it depends
on the state of the weld. To consider worst case scenarios, 6061-0 was used which is the
softest state that Aluminum 6061 can exist in. This compensates for any poor welds that may
have been done during welding. In the following table are the outcome results for both stress
and displacement. These are compared to the yield strength of the material.
Table 11. FEA results
Stress
Model
2.626
18.106
Yield Strength
8.000
55.158
Displacement
Units
ksi
MPa
Model
0.088
2.242
Actual
0.063
1.588
Units
in
mm
The FEA results that were expected and allowed us to proceed with the final fabrication of the
frame. The maximum stress that the frame will undergo is 3 times less than the yield strength of
the aluminum frame based on worst case scenario. This allows for a safety factor of 3. The
maximum deflection that the FEA shows the trike will undergo is approximately 0.1 in.
Displacement is seriously considered because aluminum will fatigue over time if the
displacement of the material is significant. 0.1 in deflection for any material for this trike is far
less than anything that would bring concern.
Once all of this analysis has been completed, the final trike model could be assembled in
SolidWorks as a full 3D model. Again, this model does not detail any components that are
Final Report
Team 5: TheraTryke
page 24
unnecessary for dimensional analysis and component interference analysis. The model can be
seen below in Figure 15.
Figure 15. Initial 3D trike model
Welding of the initial frame was done by Phil Savickas at Progressive Surface. Phil is an expert
at welding aluminum. It was crucial that the welding was done right in order to maintain the
strength of the 6061-T6 material as much as possible. The entire setup process, alignment of
parts, and welding took approximately 8 hours.
4.1.4 Final Design
Below is the explanation of both the rework of the frame and the additional components applied
to the frame after testing.
4.1.4.1 Reworking the Frame
After the initial frame design and fabrication, some issues arose which had to be solved before
any further assembly could be done. The initial design was mocked up according to given
human body dimensions from a research article. These dimensions were not double-checked or
cross-referenced with any other human body dimensions. This was a mistake on the team’s part
because all body dimensions were off by approximately 12 in. A redesign was needed for the
entire front end of the trike including locations for the foot cycling bottom bracket and central
gear hub.
In order to re-dimension the trike, the current welded trike was used. One of the team members
was similar in height to the client’s height and all re-dimensioning of the trike frame components
were considered using actual human body dimensions. The process of re-dimensioning was as
follows.
The first step was to locate and position the seat where the rider would need it in the final
prototype stage. Once the seat was place in its final location, exact dimensions were taken of
the leg and arm lengths needed. Footing was positioned by extending feet out including a 2 in
Final Report
Team 5: TheraTryke
page 25
reduction to eliminate full leg extension. Dimensions were taken to accommodate the new
position according to components on the current welded frame. The hand cycling bottom
bracket was relocated in the same fashion as the footing. New dimensions were taken using
actual body dimensions and compensating those dimensions with the current frame status.
After all proper re-dimensioning had been completed, the redesign was configured in
SolidWorks to second check all possible interference points. An FEA analysis was not produced
using the new frame design because the base of the frame remained unchanged. All previous
FEA work had been completed on the base of the frame. Below in Figure 16, is the final frame
model of the trike.
Figure 16. Final SolidWorks design
All necessary rework on the frame had to be done. This included re-welding the frame to the
new design. Welding was done by Greg Parlmer at Progressive Surface. Greg is also an expert
at welding aluminum materials.
4.1.4.2 Additional Components
As a result of testing, as seen in Section 5, additional components were added to the framework
of the trike. After the end client was able to test and ride the trike at Calvin’s Tennis and Track
facilities, it was requested that some bar be implemented onto the frame so as to make the ride
easier for the rider if they became fatigued or are unable to make it up steep hills.
The single addition to the frame was denoted a push bar. Below in Figure 17 is the
manufactured push bar. It was designed to fit into the rear wheel support of the frame. The
intention of the bar is to allow a spouse, friend, or therapist to walk along side of the rider and
support them by pushing the trike forward to alleviate the stress on the rider.
Final Report
Team 5: TheraTryke
page 26
Figure 17. Push bar
This push bar was manufactured out of an aluminum pipe used as the shaft and a steel bike
handle bar used as the bar itself. These two components were bolted and epoxied together in
order to eliminate any instability and slop between the two materials. The aluminum pipe is
simply fitted into the rear support bar of the frame and locked in place using a simple pin and
lock. Below in Figure 18 is an example of how the push bar might be used.
Figure 18. Push bar application
Final Report
Team 5: TheraTryke
page 27
4.1.5 Components
All frame materials are listed below in the BOM in Table 12.
Table 12. Frame BOM
Component
Unit
Unit Cost
Quantity
Total
Cost
Supplier
1-3/4” OD x 1/8”
thk pipe
24 ft
$126.00
55.4%
$69.80
ALRO Steel
Rear Wheel Frame
Material
EA
$10.00
1
$10.00
ALRO Steel
Central Hub
Aluminum Shell
EA
$14.24
1
$14.24
ALRO Steel
Bottom Bracket
Aluminum Shell
EA
$28.48
2
$56.96
ALRO Steel
Welding
hr
$22.80
8
$182.4
In house assumption
Powder Coat –
Blue (1509)
EA
$75.00
1
$75.00
Custom Frame Powder
Coating
Push Bar
(Aluminum Shaft)
4 ft
$23.20
1
$23.20
Metals Depot
Push Bar (Bike
Handle
EA
$35.00
1
$35.00
Cambria Bicycle
Total: $391.60 (estimated was $70)
4.2 Steering
4.2.1 Research
Steering is the mechanism by which the operator of a vehicle is able to direct their movement
into a desired course. For trikes, or more specifically recumbent foot trikes, there are two types
of steering: direct and linkage. These different styles can be seen in Figure 19 and Figure 20.
Direct steering is generally more responsive than linkage steering, while linkage steering will be
able to buffer any shaking and rattling from riding.
Final Report
Team 5: TheraTryke
page 28
Figure 19. Direct steering
Figure 20. Linkage steering
For a hand pedaled recumbent trike, the steering is incorporated into the single front wheel. This
can be seen in Figure 21. This is a great way to incorporate the steering and pedaling but not
terribly practical for the TheraTryke prototype. This will be further discussed in the design
alternatives.
Final Report
Team 5: TheraTryke
page 29
Figure 21. Hand pedaled recumbent trike
Turning ability is measured using a metric called Turning Circle (also called Turning Radius).
This is a measure of the diameter of a circle that the vehicle traces at its maximum turning
condition. It is measured using the outside of the frame rather than the center or inside. Further
analysis of turning circle can be seen in the design alternatives section.
4.2.2 Requirements
It is required that the user be able to maintain full control of the vehicle under standard operating
conditions. This means that the trike will turn freely, move forward in a straight line, and provide
responsive handling at all operating speeds. The steering mechanism must be robust in nature
and easily accessible to the user at all times. The turning circle of the vehicle must allow for
driving on roadways and sidewalks without issue. The goal for turning circle is 26 feet. The
steering and frame design must interact such that the trike will not overbalance if the user
makes a turn, or is forced to avoid an obstruction at speed.
4.2.3 Design Process
The team needed to consider the possibility of having the steering of the trike be independent of
the drive system. With the hands, feet, and drive wheel gears all having to stay aligned, steering
must be separate unless the legs turn with the hands and legs. The team is uncomfortable in
turning and bending legs that are limited in mobility. Table 13 demonstrates the various design
options that were considered to accompany a chain drive system.
Final Report
Team 5: TheraTryke
page 30
Table 13. Design options for the steering mechanism
The team decided to design around an independent linkage steering system. Separating
steering from hand-pedaling will prevent chains from falling off gears. The key disadvantage of
this approach is that the user will have to move their arms in order to transfer their hands from
pedaling to steering. This will decrease their ability to respond in a crisis situation, and will
prevent them from being able to power the trike with both hands while turning. The team also
considered how the trike while on a slight slope.
The team did try to consider a way to combine the steering and pedaling. The team did find a
way that seamed feasible, but would be too difficult to manufacture with the time and experience
available. For this system, the team explored using a ratcheting cable-drive pedaling system.
This would enable the user to steer using the hand pedals without endangering the drive train.
Sketches of this design can be seen in Appendix F. Steering and Pedaling Concept. This design
alternative was rejected due to difficulty of design and manufacture, as well as the possible
power losses.
The team also needed to calculate how much the wheels need to turn to get the desired turning
circle. “Turning Circle” is a term that has commonly replaced the term “Turning Radius” in
steering design applications. The turning circle of a vehicle describes the amount of space
needed for the vehicle to execute a large turn and is, in fact, a diametric measure. This
calculation is dependent upon three main factors. First, the Wheel Base (WB) of the vehicle,
which is the distance between the front and rear axles. Second, the Wheel Track (WT) of the
vehicle, which is the distance between the two turning wheels. Finally, the Average Turning
Final Report
Team 5: TheraTryke
page 31
Angle (ATA) which is the average of the turning angles realized by each of the turning wheels. A
diagram of these values can be seen in Figure 22.
Figure 22. Turning angle diagram
Equation 6 is used in order to calculate the turning circle of a vehicle:
𝑊𝑇
𝑊𝐵
)+(
)
2
sin(𝐴𝑇𝐴)
𝑇𝑢𝑟𝑛𝑖𝑛𝑔 𝐶𝑖𝑟𝑐𝑙𝑒 = (
(6)
By designing around a desired Turning Circle of 20 to 26 feet and using nominal values for the
Wheel Track and Wheel Base, the team was able to calculate a desired Average Turning Angle
of 25° to 30° at maximum.
4.2.4 Final Design
The team decided to buy a linkage steering system from TerraTrike. The team chose to go with
a linkage system because less vibrations will travel to the hands, allowing for a more
comfortable ride. In order to achieve the desired turning circle, the team had to remove material
on the part of the frame attached to the wheel to create clearance for moving parts.
The measured turning circle of the trike upon completion of the prototype was just under 21 feet,
and the average turning angle was calculated to be 26.6 degrees.
Final Report
Team 5: TheraTryke
page 32
4.2.5 Components
Table 14. Cost considerations for steering
Component
Unit Cost
Quantity
Total Cost
Supplier
Tie rod end, M8 Male LH
$5
2
$10
TerraTrike
Tie rod end, M8 Male RH
$5
2
$10
TerraTrike
M8 hex nut, Tie rod end nut, LH
$0.25
2
$0.50
TerraTrike
M8 hex nut, Tie rod end nut, RH
$0.25
2
$0.50
TerraTrike
Tie Rod, Tour II, linkage steer
$17.50
2
$35
TerraTrike
Steering Brace, Tour II w/bolts and nuts
$30
1
$30
TerraTrike
HandleBar
$20
1
$20
TerraTrike
Total: $160 (estimate was $270)
4.3 Wheels
4.3.1 Research
Wheels are the components of the design that are pivotal to the maneuverability and safety of
the vehicle. This makes wheel selection an important part of the design process.
Traditionally there are three common wheel set size combinations used in recumbent tricycle
applications. The first common size combination uses three 16” wheels. This combination is
common in sport models. The second combination uses three 20” wheels. This combination is
popular in touring models. The third combination utilizes two 20” wheels and one 26” wheel. As
the development of recumbent tricycles has become more popular, companies have
transitioned towards the 26”/20” combination because of its versatility.
4.3.2 Requirements
For the wheels, it is required that they provide high quality performance under all operating
conditions. This means that the wheels will be able to perform at both high and low speeds
while making tight turns, operating on varied terrain, and traveling in a variety of weather
conditions.
4.3.3 Design Process
The main design alternatives involve the sizing of the wheels. One potential design is to use
three common sized wheels, either 16” or 20” diameters. Traditionally this is how sport and
touring recumbent bikes are designed. The small tire size allows for easier acceleration but
Final Report
Team 5: TheraTryke
page 33
because of the size and weight, they don’t hold their speed as well and won't get a top speed as
high as a bike with bigger wheels. In addition, the materials tend to wear out sooner than larger
tires. One reason to use three equally sized small wheels would be to accommodate a more
compact bike designed for high speed capabilities. Figure 23 shown below is an example of a
sport edition trike with three 20” tires.
Figure 23. Trike design with 20" tires
http://www.prc68.com/I/Images/SunEZ-3USXHDTrike68611w.jpg
Another design would consist of using two different sized wheels. This would consist of having
two 20” tires in front and one 26” tire in back. There are many different benefits for using this
design. The large wheel in the back gives the trike more of an upright bicycle type road feel. In
addition to the improved feel, the larger tire allows for the tire to hold its speed better, and
remain stable while maneuvering over obstacles.
The team decided to use two 20" wheel in front, and one 26” wheel in back. This was chosen
because the team thought a bigger back wheel would look good and because the gearing is
slightly low so having a bigger wheel makes the trike go faster than it would with a smaller
wheel.
4.3.4 Final Design
The team decided to go with two 20” wheels in the front, and one 26” wheel in the back. This
was partially influenced by the how the gearing was set up. The team also chose a larger back
wheel for aesthetic reasons.
Final Report
Team 5: TheraTryke
page 34
Figure 24: Final trike layout
4.3.5 Components
Table 15. Cost considerations for wheels
Component
Unit Cost
Quantity
Total Cost
Supplier
20” Wheel
$45
2
$90
TerraTrike
26” Wheel
(price included
in Gear and
Chain System)
1
(price included
in Gear and
Chain System)
West Michigan Bike
and Fitness
Axle Bolt
$2.50
2
$5
TerraTrike
20” Tire
$5
2
$10
Boston Square
Community Bikes
26” Tire
$5
1
$5
Boston Square
Community Bikes
20” Tire innertube and
protective band
$2
2
$4
Boston Square
Community Bikes
26” Tire innertube and
protective band
$2
1
$2
Boston Square
Community Bikes
Total: $116 (estimated was $259)
Final Report
Team 5: TheraTryke
page 35
4.4 Seat
4.4.1 Research
The team has investigated several different types of seating options. There is padded seating,
mesh seating, fixed seating, and adjustable seating. Figure 25 shows an adjustable design
option, while Figure 26 shows a fixed option. Adjustable seating is considerably easier to design
around than an adjustable frame, since adjusting frame length will also adjust chain length.
Figure 25. Seat with adjustable positioning (TerraTrike model)
Figure 26. Seat with fixed positioning (Utah Trikes)
Final Report
Team 5: TheraTryke
page 36
4.4.2 Requirements
The seating of the trike must satisfy the adjustability requirements for the trike, as well as
providing the rider with sufficient comfort when in use.
4.4.2.1 Adjustability
The trike needs to be adjustable for the target range of body heights.
4.4.2.2 Comfort
The seating of the trike must be made for a comfortable ride. No user will want to ride the trike if
they are uncomfortable. The seat frame must be made to fit the entire back of the user so as to
not have bars driving into the rider’s back. Comfortable and light materials are preferred.
4.4.3 Design Process
The team considered fabricating the seat on their own. When the team was setting up an order
from TerraTrike, the seat was included. It covers nearly everything that is needed on the trike.
The one thing about this seat is that it cost more than the team budgeted for. The team decided
that it would be worth it because there is great savings in other sections of the trike, and the
team could use more time for fabricating and testing rather than designing and building a seat.
4.4.4 Final Design
The team decided it would be best to go with TerraTrike’s adjustable seat. It has a wide range of
adjustability, it is light, and it is very comfortable. The team decided that adding a seatbelt
system would be necessary because potential users may not have any use of their abs. An
over-the-shoulder seatbelt system (4-point harness) will keep them securely in the seat.
Figure 27: TerraTrike seat with added restraints
Final Report
Team 5: TheraTryke
page 37
4.4.5 Components
The components of the seat can be seen in Table 16.
Table 16. Cost considerations for the seat
Component
Unit Cost
Quantity
Total Cost
Supplier
Seat Frame
$90
1
$90
Terratrike
Seat Mesh
$27.50
1
$27.50
Terratrike
Seat Clamp
$17.50
1
$17.50
Terratrike
Seat Stay Pin
$1
2
$2
Terratrike
Seat Stays Set
$25
1
$25
Terratrike
M8 Nyloc Nut, SS
$0.50
3
$1.50
Terratrike
M8x40mm SHSCS
SS
$0.50
3
$1.50
Terratrike
M8x20 Low Head,
SS
$0.50
2
$1
Terratrike
M5x30mm SHCS SS
$0.50
2
$1
Terratrike
M5 Nyloc nut SS
$0.15
2
$0.30
Terratrike
M5x12mm SHCS SS
$0.20
2
$0.40
Terratrike
Seatbelt
$26.99
1
$26.99
Amazon
Total: $194.69 (estimated was $62)
4.5 Gear and Chain System
4.5.1 Research
Gears are what give the user of a bike the ability to vary the strength or simplicity of moving the
vehicle forward. In Table 17, the possible options for a bike with three gear cassettes attached
to the pedals and nine gear cassettes connected to the wheel are presented. If the number of
gear teeth are equal from the pedaling gears to the wheel gears, one pedal will cause one
rotation of the wheel. If the number of teeth in the pedaling gear is lower than the number of
teeth in the wheel gear, the operator will need to pedal more than one cycle to get a full rotation
of the wheel. This is the easiest and slowest pedaling option and is represented in green in
Table 17. When the number of teeth in the pedaling gear is much higher than the number of
teeth in the wheel gear, one rotation of the pedals will cause multiple rotations of the wheel. This
Final Report
Team 5: TheraTryke
page 38
is the fastest and most difficult pedaling option. This is represented in red in Table 17. The gear
ratios represent how many rotations the wheel will go with one cycle of the pedals.
Table 17. Gear ratio possibilities for a 27-speed gear system
For a recumbent hand powered trike, it is generally accepted to have the hand pedaling cause
the front wheel to cycle. For a recumbent foot powered trike, it is typical to have the feet pedals
cause the back wheel or wheels to cycle.
4.5.2 Requirements
It is necessary that hand strength alone is enough to power this vehicle. The added power
necessary to cycle the feet will have an effect on what type of gearing system that will be
necessary. The gears between the hands, feet, and wheels all need to remain parallel through
turning motions so binding is not a problem. Assisted pedaling from the feet is something that
will be possible in this vehicle.
4.5.3 Design Process
At first, it was assumed that the hand pedals, hand steering, feet pedals, and driven wheel(s)
would all be linked together. One problem that arises with this is the steering with the hands.
The front wheel could also pivot, but there is no clear way for the legs to rotate comfortably to
keep all the chains inline. All three parts need to stay straight or all rotate together. The design
alternative selected for this problem was to have hand steering independent of all the gears and
chains. The gears stay in the middle of the vehicle connecting to the back single wheel. The
steering is hand controlled and pivots the front two wheels. One would not be able to hand
pedal and steer at the same time unless they choose to use one hand for each. The design with
two wheels in front and one in back is ideal for this independent steering option and provides
plenty of leg room to work with for the leg supports.
Table 18 shows different options for gearing systems. Each option has a specific bonus for
specific connections between the hands, feet, and wheels.
Final Report
Team 5: TheraTryke
page 39
Table 18. Gearing system options
Preferably, the hand pedals should be directly connected to both the wheel and the foot pedals.
The ratio between the hands and feet should remain constant for comfort and rhythm purposes.
With alternating hand pedaling, a 1/1 teeth ratio between the hands and feet would be ideal so
the legs would alternate and the arms would alternate, similar to a running motion. For uniform
hand pedaling, a 1/2 teeth ratio between the hands and feet would be ideal so every time one
pedals down, one leg would also go down. A 1/2 teeth ratio would make the feet rotate slower,
making less power necessary for rotating the legs. A 1/4 teeth ratio would mean that even more
power can be used for moving the trike forward. Calculations for power distribution and top
speeds can be found in Appendix A.2. Power calculations and top speeds. These calculations
were based off of the following equations:
𝑃 = 𝑇𝝎
(2)
𝑇 = 𝐹𝑟
(3)
𝐹 = 𝑚𝑎
(4)
They are also based off of the fact that someone can pedal with 60 watts of power through their
arms. This number comes from pedaling at 60 rpm at level of difficulty that provides a workout
on a stationary hand pedaled recumbent bike in Calvin’s gym. The top speeds are based off of a
Final Report
Team 5: TheraTryke
page 40
calculator that can also be found in Appendix A.2. Power calculations and top speeds. The top
speeds and power distributions can be found in Table 19.
Table 19. Power distribution and top speeds
1/2 ratio
47%
5.6 mph
Power to wheel
Top speed
1/4 ratio
64%
7.7 mph
Now for the actual layout of the gears on the trike. A centralized gear set was used to connect
the hands, feet, and back wheel. For the connection between the hands and feet to the wheels,
four total options were considered. The first one is having multiple cassette gears on the forcing
and forced sides of the system. This would allow for a large range of options for speed and
incline variations. Two derailleurs will be necessary for this option: one connected to the
centralized gear set and one connected to the back wheel. Cable shifters can be used for
varying the cassettes used. The second option would be to have only the gear set on the back
wheel variable. This would make the gearing range smaller, but would eliminate the need to
mount a derailleur on the central gear hub. The third option would be similar to the first, but the
cassette stack on the back wheel would be replaced with an internal gearing hub. This option
allows for smooth, immediate shifting without the bulk of a gear train and derailleur. The internal
pulley system is the ideal design option for this project because of the smooth shifting. A user
does not need to be pedaling to change gears. The fourth option would be similar to the second;
it will only have one shifter controlling the internal gearing system. The equivalent gear teeth for
a Nuvinci (internal gearing system) shifter is a 10 tooth minimum and a 36 tooth maximum.
Appendix A.3 Gearing Ranges Considered shows many different ratio options for all four of
these considerations. The y-axis varies the size of the gear in the central gear hub that connects
to the back wheel. A minimum low gearing should be less than a regular bike because of the
added resistance from the legs. A large range is desirable to move at an enjoyable speed.
Equation 5 is used to find a revolution ratio between the back wheel and the hands. Equation 6
is used to find the set ratio between the hands and feet.
𝑅𝑒𝑣𝑤ℎ𝑒𝑒𝑙
𝑅𝑒𝑣ℎ𝑎𝑛𝑑𝑠
𝑁ℎ𝑎𝑛𝑑.𝑝𝑒𝑑𝑎𝑙𝑠
= (𝑁
𝑐𝑒𝑛𝑡𝑒𝑟.𝑡𝑜.ℎ𝑎𝑛𝑑𝑠
𝑅𝑒𝑣𝑓𝑒𝑒𝑡
𝑅𝑒𝑣ℎ𝑎𝑛𝑑𝑠
𝑁𝑐𝑒𝑛𝑡𝑒𝑟.𝑡𝑜.𝑤ℎ𝑒𝑒𝑙
) (%𝑖𝑛𝑡𝑒𝑟𝑛𝑎𝑙.𝑔𝑒𝑎𝑟𝑖𝑛𝑔 )
𝑁𝑤ℎ𝑒𝑒𝑙
)(
𝑁
𝑁𝑐𝑒𝑛𝑡𝑒𝑟.𝑡𝑜.𝑓𝑒𝑒𝑡
= (𝑁 ℎ𝑎𝑛𝑑.𝑝𝑒𝑑𝑎𝑙𝑠 ) (
𝑐𝑒𝑛𝑡𝑒𝑟.𝑡𝑜.𝑓𝑒𝑒𝑡
𝑁𝑤ℎ𝑒𝑒𝑙
)
(5)
(6)
The first semester gear design can be seen in Figure 28 with the range of hand-to-wheel
rotation ratios provided.
Final Report
Team 5: TheraTryke
page 41
Figure 28. Diagram of gear design selections
After attempting to acquire parts for gearing, it appears that there is not a large enough range of
standard sized gears to get the desired 1/4 revolution ratio between hands and feet. The team
went back to the 1/2 revolution ratio because of this. The team worked with TerraTrike and
acquired two crank assemblies with 32 teeth on the gears attached. The team has acquired a
40 tooth, 28 tooth, and 20 tooth gear for the central gear hub. The team used a Shimano Nexus
7 internal gear hub instead of the Nuvinci for cost reasons. This reduces the gearing from a
360% to 245%.
The central gear hub was built off of a bottom bracket with a steel crank set. Aluminum spacers
were manufactured with the mill at Calvin, and the gears connecting to the hands and feet were
drilled and tapped to the aluminum spacer. The foot crank used did not have enough space to fit
the additional gears, so the arms were cut off, and keyways were made in the shaft and the
aluminum spacers so that the gears spin with the shaft. The gear connecting to the back wheel
was connected to the opposite side of the shaft with a similar aluminum spacer and keyway.
The lathe was used to make the shaft even. Bolts were threaded into the ends of the shaft to
hold the gears in place. The components for the central gear hub can be seen in Figure 29 and
the final assembly can be seen in Figure 30.
Final Report
Team 5: TheraTryke
page 42
Figure 29. Components of the central gear hub
Figure 30. Central gear hub on frame
Final Report
Team 5: TheraTryke
page 43
4.5.4 Final Design
The final design for the gearing can be seen in Figure 31.
Figure 31. Final gear setup
The final gear range can be seen in Appendix A.3 Gearing Ranges Considered along with other
ranges considered. Although the graph does not specifically show, it would be more beneficial
to start the range even lower. This information was acquired from testing.
Final Report
Team 5: TheraTryke
page 44
4.5.5 Components
Table 20 shows the components needed, and their costs in order to produce this gear system.
For the prototype, $430.10 was actually spent.
Table 20. Gear system components and cost
Component
Unit Cost
Quantity
Total Cost
Supplier
Shimano Nexus 7 speed
$299.98
1
$299.98
West Michigan Bike and Fitness
20 tooth sprocket
$10
1
$10
Alger Bikes
40 tooth sprocket
$15
1
$15
Alger Bikes
28 tooth sprocket
$10
1
$10
Alger Bikes
Crankset
$17.50
2
$35
Terratrike
Crankset screws (M8x1)
$2
4
$8
Terratrike
Bike chains (1/8)
$12
5
$60
Boston Square Community
Bikes/Amazon
Bottom Bracket Shells
$10.06
2
$20.12
Amazon.com
RPM sealed bearing BB,
68X118 ENG
$7.50
2
$15
Terratrike
Central Gear Hub Shaft
$15
1
$15
Bikewagon.com (Scrapped off of
old bike and machined)
Central Gear Hub Bottom
Bracket with bearings
$10
1
$10
Bikewagon.com (Scrapped off of
old bike)
Custom aluminum
spacing/joining discs
$1
2
$2
Machined
Washer
$0.10
5
$0.50
From Calvin’s Shop
Bolt (1/4-20)
$0.10
1
$0.10
From Calvin’s Shop
Bolt (5/16-18)
$0.10
1
$0.10
From Calvin’s Shop
Screws (6-32)
$0.10
9
$0.90
From Calvin’s Shop
Total Cost: $501.7 (estimate was $572)
4.6 Hand Pedals
4.6.1 Research
For a Top End trike, the hand pedals used are pedaled in tandem. This allows for a balanced
pedaling motion. The angle of the bars jutting out are probably around 60° from horizontal. The
rotating handles are made of aluminum and keep the hands slightly off of a vertical position.
Final Report
Team 5: TheraTryke
page 45
This position allows for the least amount of exertion. A user of the Top end trike that the team
encountered commented that he would like the pedals closer together. This would make the
pedaling even easier, but the space occupied by the gears need to be considered.
4.6.2 Requirements
The pedals need to be simple and comfortable. Hands closer together will allow for more power.
Hands near a vertical position will also allow for easier pedaling. The hand grips need to stay at
a constant angle and have room for a gear shifter. Initially the team though a hand brake would
be placed on the right hand, but decided to have the braking system on the steering. Since the
hand pedals will have a gear shifter connected to gear changing cables, they must be placed in
a manner that minimizes interference between the hand pedals, the gear shifter, the gear shifter
cables, and the gear located near the hand pedals.
4.6.3 Design Process
One alternative would be to do something very similar to Top End’s design. Their design can be
seen in Figure 32 and Figure 33.
.
Figure 32. Top End hand pedal design
Final Report
Team 5: TheraTryke
page 46
Figure 33. Brake and shifter placement
The arms of the hand pedals will need to be shortened slightly, and the hand pedals will need to
be raised so that there is enough clearance for the legs to cycle. The shifter will be attached to a
handle. The handle will need to be extended slightly so that accidental shifting does not happen.
A second alternative would to have pedals that alternate. This style can be seen in Figure 34.
This style would mean that each hand would have to work by itself half the time. This design is
not preferred because it encourages a side-to-side motion. This side-to-side rocking motion will
not be attractive to the target customer. Some of the target customers will not be able to do that
because they will not have any strength in their abdomen.
Final Report
Team 5: TheraTryke
page 47
Figure 34. Alternating hand pedaling
http://www.bikecare.co.uk/special-needs-tricycles.html
4.6.4 Final Design
Through considering all the variables involved in the design of the hand pedals, the team
determined that best design involved a design where both hands were pedaled in tandem. This
will allow for the body to stay stable and minimize core strength required to use the trike, thus
improving the safety. As shown below in Figure 35, it can be seen how the hands will work
together to propel the bike forward.
Figure 35. Final hand pedal design
Final Report
Team 5: TheraTryke
page 48
The team wanted to model their hand pedal after the design used by Top End. This was
because of the comfort of the pedal. The team developed a SolidWorks model to represent the
final design. The difficult part of this design process was developing a way to build the
extension column for gear shifter. The final design for this is shown below in Figure 36. Another
feature designed in the model is the insertion hole. This hole, also shown in Figure 36, allows
for easy assembly and removal of the hand pedals. The final decision for the design involved
the interference of the hand pedals with the legs. Due to the limited available space between
the legs and the hands as demonstrated in Figure 11, the hand pedal had to be connected to
the crank shaft at the middle actual hand pedal. This design requires the user to split their
fingers to cover the whole pedal, but it also provides enough space to allow for the most space
possible between the top of the knees and the hands. This design feature is shown in Figure
37.
Figure 36. Hand crank to fix interference
Figure 37. Hand pedal final 3D design
Final Report
Team 5: TheraTryke
page 49
The next big step in the process was the manufacturing of the hand pedals. The team initially
thought about using a 3D printer to achieve the complex geometry of the parts but determined
that using aluminum would be a better overall decision based on the high strength over the
lifetime of the part. Input about this decision came from a variety of 3D experts who said that 3D
printing was not a good solution for manufacturing. Table 21 below also outlines some
considerations in the decision.
Table 21. Hand pedal manufacturing decision chart
Method
Aluminum
3D Printer
Cost
Low
High
Labor Time
High
Low
Strength
High
Low
Ability to Redesign
High
High
The actual manufacturing of the hand pedals was done in the Calvin machine shop. Aluminum
rods were machined down to width and hollowed out. After all the components were made,
Nico Ourensma, a fellow senior engineering student, welded the parts together. These parts
are shown below in Figure 38.
Figure 38. Manufactured hand pedals
Another big part of the design process was developing a way to attach the hand pedals to crank
shaft. This was done be disassembling and machining down a foot pedal to access the screw
part of the pedal. A before and after of this process is shown below in Figure 39.
Final Report
Team 5: TheraTryke
page 50
Figure 39. Disassembly of foot pedal
This screw insert from the foot pedal was then inserted into the aluminum welded components
and attached to the crank shaft. Figure 40 shows all the components involved in the assembly
of the hand pedal. Figure 41 shows the final assembly with the gear shifter attached.
Figure 40. Components used in hand pedals
Final Report
Team 5: TheraTryke
page 51
Figure 41. Hand pedal with gear shifter
4.6.5 Components
Table 22. Costing for hand pedals
Component
Unit Cost
Quantity
Total Cost
Supplier
Foot Pedal
$1
2
$2
Boston Square Bikes
2” Aluminum
Bar
$3.55
2
$7.10
OnlineMetals.com
Washer
$0.10
2
$0.20
ALRO Steel
Lock Washer
$0.10
2
$0.20
ALRO Steel
Bolt
$0.15
2
$0.30
ALRO Steel
Total: $9.30
Final Report
Team 5: TheraTryke
page 52
4.8 Leg Brace and Support
4.8.1 Research
4.8.1.1 Foot Pedal Research
Foot pedals on most bikes and trikes come in one of three distinct forms. The first is a simple,
rugged platform on which the foot presses. These pedals are typically textured or rigid in some
manner in order to keep the user’s shoe (and thus the user’s foot) firmly on the pedal throughout
its full range of rotation. Second, there are pedals that are designed to clip directly to specially
manufactured shoes. These allow for much more user freedom of movement and power output
by keeping the foot firmly mounted to the pedal. Finally, there are pedals that strap the foot in
place. These pedals work similarly to the clip pedals, but do not require special footwear.
However, they are larger, heavier, and provide less of a hold on the shoe. All these options can
be seen in Figure 42.
Figure 42. Standard foot pedal styles
www.nashbar.com
www.performancebike.com
www.aurora-collective.com
4.8.1.1 Leg Bracing Research
Leg bracing is not uncommon in physical therapy. There are many pre-existing designs for
braces and splints that limit leg movement. However, it is somewhat rare for these braces to
allow for articulation of the limb. They are generally designed to hold the leg in a single position,
allowing for the body to heal after a traumatic injury. This can be seen in Figure 43.
Final Report
Team 5: TheraTryke
page 53
Figure 43. Adjustable ergonomic knee brace
Royal Medical Co. Patent 277944_A1
Articulating leg bracing is less common as a tool for physical therapy. When used for this
application, the bracing is typically designed to prevent hyperextension of the knee, which could
be very useful for the application of the trike. There are also custom bracing options that are
more robust. However, these bracing solutions are generally cost-preventative. Additionally,
those braces that provide sufficient guidance for the application of this trike are generally fairly
large, intrusive, and difficult to put on. An example of such a brace can be seen in Figure 44.
Figure 44. Example of therapeutic bracing from Trulife
http://trulife.com/Brochures/us-orthopaedics-brochure.pdf
Bracing of this nature can also be found in sports. Typically, this kind of knee bracing takes the
form of a soft, slip-on support and would not prove terribly useful for the team’s application. The
exception to this is the very robust knee protection designed for use in Motocross. Due to the
extreme nature of the sport, some impressive advancements have been made in knee support
and safety. The advantage to these designs is that they are for rapid, repeated movements and
Final Report
Team 5: TheraTryke
page 54
have adjustable hyperextension locks that can be customized to each user. However, these
braces can also be expensive. An example of this brace can be seen in Figure 45.
Figure 45. Motocross articulating knee brace, listed at $1,400 per pair
http://evs-sports.com/index.php/moto/knee-braces/axis-series/axis-pro.html
4.8.2 Requirements
4.8.2.1 Pedal and Support Requirements
The requirements for the pedals in this application will be slightly different than the typical
models one would see on the market. Because this vehicle will be marketed to people suffering
from low mobility or paralysis, the pedals will be required to make up for their possible limited
movement. Thus, the pedals will need to keep the users feet firmly in place throughout their full
range of motion, even if the user has no muscular control.
4.8.2.12 Bracing Requirements
The ergonomic bracing on the system must be able to withstand prolonged, rapid, and repeated
movements during normal operation without failure. It must be able to prevent hyperextension of
the user’s legs while keeping them straight in line with the pedals. They must also not be overly
difficult to enter and exit, preferably allowing users to place their legs into the braces from
above. The braces also cannot be overly expensive, or should be designed in a way that allows
us to fabricate them in house.
4.8.3 Design Alternatives
First, the team must decide in what way to approach the bracing solution. Originally, it was
assumed that the trike would have two full-length, articulating leg braces that would guide the
user’s legs through a full range of motion. While this method would certainly guarantee user
Final Report
Team 5: TheraTryke
page 55
safety, there are many drawbacks to this option, chiefly among them cost, ease of entry, and
power loss. Another option would be to design an integrated foot-pedal and bracing system that
would not fully encapsulate the knee. Hyperextension or locking of the knee would be prevented
either by a separate, wearable brace, or by placing the pedals below the level of the seat.
Secondly, the team must also find the best way to accomplish this task. Put simply, the team
would have three different options; purchasing an existing brace, fabricating a custom brace, or
modifying an existing brace to fit their needs. Each option would have its own advantages and
drawbacks which can be seen in Table 23.
Table 23. Design fabrication alternatives for ergonomic bracing
4.8.4 Initial Design
Originally, the team was leaning towards a design that would integrate the bracing with the
pedals. These braces would be removable, but also easy to install and use for a patient that
requires them.
The design would have to allow for the braces to be loaded from above. This means that the
user would simply be able to lift their legs and place them directly into the braces. The legs
would then be strapped into place, and the brace would guide the limb throughout its full range
of motion. One point of adjustability would be designed into the brace, allowing for differing leg
lengths. Brainstorming considerations can be seen in Figure 46.
Final Report
Team 5: TheraTryke
page 56
Figure 46. Leg bracing concept sketch
4.8.5 Final Design
After weeks of brainstorming, design work, and prototyping, the team realized that a proper and
ergonomic integration of the pedals with the leg braces would not prove to be feasible within the
time allotted for the project. Problems included designing in the adjustability in a way that would
be universally accessible, aligning the bracing with the center of the leg for all users, ensuring
that there was no interference with other trike components, and manufacturing difficulties.
4.8.5.1 Supports Final Design
For the final design of the supports, the team chose to combine a set of existing bike pedals
with a pair of walking boots. Walking boots are padded, boot-shaped braces that incorporate
bracing around the foot, ankle, and calf. They are typically used for therapy and rehabilitation,
allowing the patient to walk around freely with minimal inconvenience. Figure 47 below shows
an image of a walking boot.
Final Report
Team 5: TheraTryke
page 57
Figure 47: Example walking boot
http://runsmartonline.com/blog/wp-content/uploads/2011/09/walking-boot.gif
This design is advantageous because the walking boots have already been designed to
properly brace the leg of the user as they move, ensuring that the design will not break. The
incorporated straps will also allow for easy adjustability. The boots are not so large as to be
obtrusive, but still ensure proper alignment of the leg while the trike is in use. They can easily be
modified to include a bike pedal, and are thus ideal for the use as a rapid and effective
prototype for the project. Finally, this design allows for the use of scavenged and donated parts,
greatly reducing the prospective cost of the leg support system.
Figure 48: Modified walking boot with pedal
Final Report
Team 5: TheraTryke
page 58
4.8.5.2 Bracing Final Design
Although part of the original design, the team decided to forego bracing as a part of their final
prototype. This is due to the inherent complexity of designing an integrated and adjustable leg
brace that could accommodate a variety of body types. Additionally, the client the team was
working with would not require any sort of leg or knee bracing when operating the trike. It was
decided, therefore, that professionally designed leg bracing would be worn independently of the
leg supports when needed.
4.8.6 Components
Table 24 shows an estimate of the cost of leg braces based off of research.
Table 24. Cost consideration for leg braces
Components
Leg braces and
Supports
Unit Cost
$60
Quantity
2
Total Cost
Supplier
$120
Foot & Ankle Specialists
Total: $120 (estimated $100)
4.9 Brakes
4.9.1 Research
For recumbent trikes, there are several types of brakes currently used by market companies.
The type of brake depends on the main purpose of the trike, and the goal of the company
developing the specific trike. For a lower level vehicle, with the main purpose being leisure
activities, the common brake type is a simple rim brake. They are sold at a low cost and allow
for easy, hassle free operation. For higher level trikes, disk brakes are common. They allow for
better stopping power which will allow for higher speed operations and they also perform better
on rugged terrain. Another type often used on recumbent trikes is a drum brake. Drum brakes
are most commonly used in applications where variable weather will occur and require very low
maintenance. In addition to brake types, common locations of brake placement had to be
researched. Many recumbent trike applications employ the brakes on the front wheels while
others employ the brakes on the rear wheels. The most popular trike in industry employs disc
brakes on the front two tires. In addition to active brakes, parking brakes had to be researched.
Many disc brakes can be outfitted with a simple parking brake allowing for safety and assurance
while stopped. Using basic rim brakes, an alternative parking brake system would have to be
implemented.
Final Report
Team 5: TheraTryke
page 59
4.9.2 Requirements
The trikes braking system will have to provide adequate braking for two different functions: usercontrolled braking and locked braking. User-controlled brakes will involve the operator manually
controlling the brakes while the trike is in motion. The parking brake will allow for locking the
trike in place to provide stability while stopped and prevent any unwanted movement.
The brakes will need to accommodate a trike traveling at 10 mph while carrying a load of 90 to
250 lb. The required stopping distance for this application will be 10 ft.
4.9.3 Design Process
When the trike is in operation, a brake system, operated by the rider is required to slow and stop
the vehicle. The chosen system will involve two different components. The first component is a
user operated hand braking mechanism. These brakes will require pressure from the operator to
provide adequate power to stop the wheels. In addition to having an operable brake for stopping
the vehicle while moving, a parking brake will be required to keep the bike stopped while not in
operation. The type of brakes in consideration are listed in Table 25. The type of parking brake
will be dependent of what brake type is chosen.
Brake types that were considered are rim brakes, drum brakes, and disk brakes. Simple
advantages and disadvantages of the brakes are listed below in Table 25 while a more in-depth
decisions showing how the team got to the final design is shown in Table 26.
Table 25. Advantages and disadvantages of brake options
Brake Type
Rim Brake
Advantages
●
●
●
Lightweight
Low cost
Simple Operation
Disadvantages
●
●
●
High Maintenance
Poor performance in
wet conditions
Need for additional
parking brake
Drum Brake
●
●
●
Weather resistant
Good stopping power
Very low maintenance
●
●
Risk of overheating
Heavy
Disk Brake
●
●
●
●
Good heat dissipation
Easy alterations
Great on variety of terrain
Phenomenal stopping
power
●
●
●
Require unique frames
High weight
High costs
Final Report
Team 5: TheraTryke
page 60
Table 26. In-depth decision for the specific project
Brake Design
Pros
Cons
-2 rim brakes attached to
back wheel.
- RH cycling handle
- RH steering handle
-Low Cost
-Braking possible with every
hand location
-Low weight
-Less stability in front wheels
-Possible difficulties faced
when entering vehicle
- 1 rim brake attached to back
wheel
- RH cycling handle
-2 disk brakes on front tires
- Brake handles
attached to each
steering hand pedal
-Increased maneuverability
while braking (braking
capable for each individual
wheel)
-Brake locking capabilities for
easy entry/exit
-High cost
-High weight
-Lack of braking capabilities
for all hand arrangements
-1 disk brake on back wheel
with double clamps
- RH cycling handle
- RH steering handle
-Low weight
-Low cost
-Lack of balance while
entering and exiting
-Difficult parking brake
arrangement
Rim brakes use two pads that are pressed against the rim of the rotating tire to provide stopping
power. Drum brakes used two pads but those pads are pressed outward against the inside of a
hub shell as compared to the rim itself. Disc brakes work by pressing two pads against a metal
disc that is attached to the axle of the wheel. Shown below in Figure 49 is a visual
representation of the different brake options.
For the final design, disk brakes operated by a hand brake controller were chosen. This was
because of several different benefits. Many benefits surround the disc brake itself. It has great
stopping power, can easily be fixed or modified for specific riders, requires minimal
maintenance, and most importantly has the ability to work with the chosen gear system and tire
placement. Drum brakes and simple rim brakes would provide good alternatives, but the
benefits of using disc brakes outweighed the benefits of the other systems. It was also
determined that the disc brakes would be operated via a hand brake. A hand brake system as
compared to alternatives such as foot braking was implemented because of its obvious benefits.
Those include easy accessibility for the operator, easily mountable, low costs, and they don’t
require strength beyond grip strength which will allow for the product to fulfill the needs of a
variety of clientele.
Final Report
Team 5: TheraTryke
page 61
Figure 49. Rim, drum, and disc brake
http://img.hisupplier.com
http://www.amazon.com
http://www.mountainbikestoday.com
Table 27 shows multiple price considerations for brake systems.
Table 27. Cost comparison for brake types
Initially the team considered multiple designs for the arrangement of the brake handles. These
designs with pros and cons are laid out in Table 28.
Final Report
Team 5: TheraTryke
page 62
Table 28. Pros and Cons of Braking Arrangements
Design
Handles on both hand pedals
and both steering hand
locations
Pros

Handles on only hand pedals


Handles on only steering



One handle on steering and
one handle on hand pedals



Easy accessibility
wherever hands are
Maximum safety
Braking capability while
steering and pedaling
Easy accessibility
Good safety
Easy integration
Good safety
Braking capability while
pedaling and steering
High safety
Cons
 High costs
 Complex design and
integration





Complex design
Lack of braking while
steering
Lack of braking while
pedaling
Difficulty implementing
Awkward hand
positioning
After weighing many of the pros and cons, the team finally decided that the best design would
be to have levers on only the steering handles. This decision was made because it was a
system that could be implemented easily and still accomplished the goals of a braking system.
The only negative of this design was that there could not be braking done while hands are on
the hand pedals. After much thought and consideration, the team realized that a user probably
wouldn’t need to brake while pedaling, so having brakes on the hand pedals would not be
necessary and would actually cause more design issues than it would fix.
The next task in the design of brake system was determining what brake handles would control
which brakes. Since each handle on the steering column had its own brake handle, the team
considered having the left handle control the left brake and the right handle control the right
brake. After thinking about this design, the team realized that there was one big flaw in the
design – the possibility of unbalanced braking. The team considered the fact that a user might
keep one hand on the crank handle and another hand on the steering handle. If this happened
and the user utilized a brake under the independent braking design, only one tire would brake
and consequently the bike might flip or become unstable. Because of this, the team decided
that the best option would be to develop a way that each handle would control both brakes.
Through research the team found brake doublers what would accomplish this task, but due to
the high costs, the team decided to manufacture their own system to accomplish the braking.
This was accomplished by using a clip from a cantilever brake and several crimps.
4.9.4 Final Design
As you can see in Figure 50 and Figure 51, the two cables from each individual brake handle
come together and get crimped into the back end of the cantilever brake clip. The other end of
this clip has a groove which allows for a brake cable that is attached to both disc brakes to be
inserted. Which this design, when a handle is pulled, that brake cable triggers the cantilever clip
to pull on the joining cable which then pulls on the disk brakes and braking is accomplished.
Final Report
Team 5: TheraTryke
page 63
Figure 50. Close up of brake integration site
Figure 51. Brake and housing design
Final Report
Team 5: TheraTryke
page 64
4.9.5 Components
Table 29. Brake BOM component list
Component
Unit Cost
Quantity
Total Cost
Supplier
Alhonga Disk Brakes
$15
2
$30
TerraTrike
Brake Lever Set
$10
1
$10
TerraTrike
Brake Cables with
housing
$12.99
2
$25.98
Amazon
Cantilever Brake Clip
$1
1
$1
Boston Square Bike
Crimps
$0.10
2
$0.20
Lowe’s
Total Cost: $67.18 (Estimate of $160)
5. Testing
5.1 Ease of Use
5.1.1 Timing transfer and positioning on trike
The team timed team members, new abled body users, and the client getting in and out of the
trike. The results for this can be seen in Table 30. The team’s goal was to have someone able
to do the full transfer by themselves in less than 5 minutes.
Table 30. Loading and unloading times
User
Jack (team member
acting as paraplegic)
New abled body user
Nancy (client with MS)
Load Time
(min)
2:01
Unload Time
(min)
1:04
Total
(min)
3:05
2:37
2:45
0:29
N/A
3:06
2:45+
5.2 Safety
Braking distance is a key measure that the team thought was very important for safety. To
measure this, a tape measure was laid out in a flat parking lot. A user (abled body male) got to
top speed before the tape measure. Both brake handles were enabled when the user got to the
tape measure, and the distance to stop was measured. Results of this can be seen in Table 31.
Final Report
Team 5: TheraTryke
page 65
The goal of the stopping distance is to be less than 10 feet. The brakes seem to respond very
well, and the team is very happy with the results.
Table 31. Braking distance from top speed
User
Jack (abled body male)
Jack (abled body male)
Jack (abled body male)
AVERAGE:
Braking distance from top speed
(ft)
4 ft 8 in
5 ft 8 in
5 ft
5 ft 1 in
5.3 Speed
5.3.1 Time top speed on trike on level ground
The team timed a team member (abled body male) on the top speed using just their hands to
pedal. A tape thirty foot tape measure was laid out in the parking lot. The user got to top speed
before traveling the thirty feet. This was timed and the top speed was calculated. Results can be
seen in Table 32. The team’s goal was to be able to go 10 mph, and the predicted value was
5.6 mph. The team was close to achieving the initial goal using an abled body person. Results
may have more variation with a variety of potential users of the trike.
Table 32. Top speed test results
User
Nick (abled body male)
Nick (abled body male)
Nick (abled body male)
AVERAGE:
Top Speed (mph)
8.92
8.77
8.24
8.64
5.3.2 Acceleration of trike from standstill
We had one team member (abled body male) do the acceleration test. For this test, the team
had the trike start at a standstill and time how long it takes to travel thirty feet using just their
hands to pedal. This was enough information to calculate the acceleration. To have a goal, the
team found bike acceleration values. These can be seen Figure 52. The average acceleration of
a bike is 5.5 ft/s2 on flat ground. Using the calculation that about half of the energy from the
hands will be going to the wheel, the team expects an acceleration value of 2.75 ft/s2. The
team’s results can be seen in Table 33. These results match and also exceed expectations. A
user with limited mobility may have results less than these.
Final Report
Team 5: TheraTryke
page 66
Figure 52. Bike acceleration test results
http://www.its.pdx.edu/upload_docs/1368048473.pdf
Table 33. Acceleration data
User
Nick (abled body male)
Nick (abled body male)
Nick (abled body male)
AVERAGE:
Acceleration
(ft/s2)
2.92
3.1
3.03
3.02
5.4 Turning
The team measured the turning circle of the trike, both turning left and turning right. The
measurement was taken at a straight distance from the outside of the trike to the outside of the
trike when the path of the trike was parallel to the starting position of the trike. The results can
be seen in Table 34. The goal was to have both sides be no more than 26 feet. The trike does
fall under this goal. Shortening the frame would improve the turning circle even more, but the
team likes the long frame for its stability and does not want to sacrifice that.
Table 34. Turning circle results
Trial
Trail 1
Trial 2
Trial 3
AVERAGE:
Left Turning Circle
(ft)
20 ft 11 in
20 ft 4 in
20 ft 7 in
20 ft 7 in
Right Turning Circle
(ft)
20 ft 2 in
20 ft 7 in
21 ft 6 in
21 ft 1 in
Final Report
Team 5: TheraTryke
page 67
5.5 Weight
The team had the goal of producing a product of weight 60 lbs. After final assembly, the team
weighed the trike and found the final weight to be 67 lbs. This weight could be reduced in the
future by using lighter components such as thin walled aluminum in the manufacturing of the
frame. Although the frame is heavier than expected, there are no negative consequences of a
trike with higher weight.
5.6 Client Satisfaction
5.6.1 Satisfaction Survey
The team had the client test ride the trike in the Tennis and Track Center in Calvin’s field house.
The team gave her some things to rate on a 0-5 scale, 5 being the best and 0 being the worst.
Having an overall comfortable ride for the user is of the utmost importance for TheraTryke. The
team wants the user to maintain comfort levels over extended periods of time while operating
the trike. The client’s ratings on certain aspects of the trike can be seen in Table 35.
Table 35. Satisfaction survey given to client
Section
Steering/hand pedaling interaction
Loading
Unloading
Braking
Parking Brake
Shifting
Enjoyment
Hills
Start moving
Overall Feel
Rating: 5 (Great) – 0 (Bad)
4
2
2
5
3.5
4.5
5
N/A
N/A
4
5.6.2 Avoiding spasms
To test the therapeutic benefits of the leg cycling aspect of this trike, the team wanted to have
some of the paraplegics that the team have been in contact use the trike. For the test, the
paraplegic will use the trike daily for a set amount of time for a set amount of days in a row. The
user will not do any of their stretching routines, so this will be a direct substitute. After each day
of the test, the user will log comments on how well the trike is stretching their legs. The team ran
out of time and did not feel comfortable in having a paraplegic test the trike with the current
bracing option.
Final Report
Team 5: TheraTryke
page 68
5.7 Outdoor usage
The team wanted to test the trike going up hills, down hills, and through grass. The team did not
come up with a way to put a value to what was tested, but a lower gearing would be attractive
for grass and going up hills. Higher gearing going downhill would be a secondary addition. In
addition to developing a lower gearing system, the team also made an easy assist bar with the
capability of pushing the user through difficult terrain (hills, grass, curbs).
5.8 Economic Sustainability
One goal of the project is to determine if this project would be economically sustainable in a full
production environment. In order to determine the economic sustainability, an in depth financial
analysis was to be completed. This financial analysis took into account all fixed and variable
costs associated with the production of the product including materials and labor costs, potential
employee salaries and all costs associated with the manufacturing facilities. Using several
different business statements including a cash flow statement, a break-even analysis, an
income statement, as well as an analysis of several ratios such as the profit margin percentage,
gross margin percentage, and debt to equity ratio, the team was able to determine the potential
profits of the company. It was determined that the potential profits in the first three years of
operation would be $1,715,166. This was also based off of several assumptions. The first
being that the company would start out with 1000 sales in the first year. The next assumption is
that the company will grow at a steady 15% over the first three years of operation. The team
knows that these are optimistic assumptions, but based off of market research and trends, the
team feels like these assumptions are realistic.
6. Business Analysis
6.1 Market Research
6.1.1 Existing Competitors
Several competitors exist to TheraTryke’s product design. This section outlines the competitors
that are in the target market currently. These companies are competitors in the design of hand
and/or foot pedaled trikes. Some of these companies do have products that simultaneously
pump both the hands and feet, but none of them demonstrate the same integration of
therapeutic benefits and recreational activity that the team is attempting to design.
6.1.1.1 Terratrike
TerraTrike is a recumbent tricycle company based in Grand Rapids. They are very well known
in the West Michigan area and are slowly becoming more well-known nationally. Their prices
range from $899.00 for low end models to $3,999.00 for their high end models
Final Report
Team 5: TheraTryke
page 69
6.1.1.2 Top End Trikes
Tope End Trikes produce high performance arm, chest and abdominally driven hand-powered
trikes. They are mainly for recreation and competition for those with physical disability. Prices
range from $2,300 to $7,500.
6.1.1.3 Rehatri
Rehatri is a line of trikes from Gomier with the goal of providing therapeutic recreational options
to individuals with disability, specifically children with Cerebral Palsy. Designs are simple with
the main use being flat, level pavement only and they do not provide adjustment in their gear
drive. Prices range from $895.99 to $1,250.00
6.1.1.4 Amtryke
AmTryke LLC is a therapeutic trike manufacturer. The trikes produced by this company are also
dual drive operated, meaning that they can be hand and/or foot powered when in use. The
prices of an AmTryke device range from $800 to $1,250.
6.1.1.5 Catrike
Catrike is a recumbent trike company created in 2000 by Paulo Camasmine, a Brazilian
Mechanical Engineer. Their vision is to create new high quality products to improve people’s
lives. Prices at Catrike range from $2,150.00 for their low end models to $2,950.00 for high end
models.
6.1.2 Target Markets
The target market for TheraTryke consists of individuals who have paraplegia or that do not
have full mobility in their limbs or core. TheraTryke’s target market pertains to those seeking out
therapeutic rehabilitation with a recreational application.
Final Report
Team 5: TheraTryke
page 70
6.2 Financials
6.2.1 Budget
Table 36 shows the estimated budget for the prototype. Actual production costs are shown in
Table 37.
Table 36. Estimated project cost
Component
Price
Steering
$270
Wheels
$259
Seat
$62
Gearing System
$572
Hand and Leg Pedal
$0
Leg bracing
$100
Brakes
$160
Frame
$70
Total
$1,493
6.2.1.1 Developmental
As the budget above represents the predicted cost of producing one unit for the final product, it
doesn’t account for the fact that the team has sources that will donate parts and services. The
prototype should have a smaller cost because many components have been donated. One of
these donors is Calvin College. They have a variety of scrap material that can be used in
prototyping. In addition to that, friends and colleagues have donated spare parts that have been
used. The actual cost for the prototype can be seen in Table 37.
Final Report
Team 5: TheraTryke
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Table 37. Actual money spent on prototype
Date
9/30/14
1/22/15
2/11/15
2/11/15
2/11/15
2/11/15
2/14/15
2/20/15
3/2/15
4/21/15
4/21/15
5/12/15
Description
Beginning Balance
Steer/Gear/seat components from TerraTrike
Bike chains
Aluminum piping
Back wheel/back gearing system
Brake Cables
Tires from Boston Square Community Bikes
Restraint and Bottom Bracket Shells
Shifting cable
14' shifting cable
parking for DisArt Festival
Screws for Trike
Cost
532.70
29.07
124.56
299.98
25.98
22.00
47.77
5.50
11.65
8.00
6.73
Balance
$500.00
-$32.70
-$61.77
-$186.33
-$486.31
-$512.29
-$534.29
-$582.06
-$587.56
-$599.21
-$607.21
-613.94
The total money spent by the team to make the prototype is $1,113.94.
6.2.1.2 Production
A large majority of the costs will come during the production phase. This includes purchased
parts such as gear systems and brakes. This will also include material costs for the frame and
any other components necessary for the production of the product.
6.2.1.2.1 Fixed Cost
There will be no fixed costs for this project. As the team is using all of Calvin’s facilities, no fixed
costs will associated with housing any phases of production nor the production itself.
6.2.1.2.2 Variable Cost
All of the costs associated with this project will be variable costs. This is because all the costs
will be materials, parts, or services. In Table 38, all the parts for one trike can be seen and all of
the prices associated with the part.
Final Report
Team 5: TheraTryke
page 72
Table 38. Final BOM of the trike
Component
Frame
1-3/4” OD x 1/8” thk pipe
Rear Wheel Frame Material
Central Hub Aluminum Shell
Bottom Bracket Aluminum Shell
Powder Coat – Blue (1509)
Unit Cost
Quantity
Total Cost
Supplier
$126.00
$10.00
$14.24
$28.48
$75.00
55.4%
1
1
2
1
$69.80
$10.00
$14.24
$56.96
$75.00
Push Bar (Aluminum Shaft)
Push Bar (Bike Handle
$23.20
$35.00
1
1
$23.20
$35.00
Welding
$22.80/hr
8 hrs
$182.4
ALRO Steel
ALRO Steel
ALRO Steel
ALRO Steel
Custom Frame
Powder
Coating
Metals Depot
Cambria
Bicycle
In house
assumption
$5
$5
$0.25
$0.25
$17.50
$30
$20
2
2
2
2
2
1
1
$10
$10
$0.50
$0.50
35
$30
$20
TerraTrike
TerraTrike
TerraTrike
TerraTrike
TerraTrike
TerraTrike
TerraTrike
2
1
2
2
$90
(price
included in
Gear and
Chain
System)
$5
$10
TerraTrike
West Michigan
Bike and
Fitness
Axle Bolt
20” Tire
$45
(price
included in
Gear and
Chain
System)
$2.50
$5
26” Tire
$5
1
$5
20” Tire inner-tube and protective band
$2
2
$4
26” Tire inner-tube and protective band
$2
1
$2
Seat
Seat Frame
Seat Mesh
Seat Clamp
Seat Stay Pin
$90
$27.50
$17.50
$1
1
1
1
2
$90
$27.50
$17.50
$2
Steering
Tie rod end, M8 Male LH
Tie rod end, M8 Male RH
M8 hex nut, Tie rod end nut, LH
M8 hex nut, Tie rod end nut, RH
Tie Rod, Tour II, linkage steer
Steering Brace, Tour II w/bolts and nuts
HandleBar
Wheels
20” Wheel
26” Wheel
TerraTrike
Boston Square
Community
Bikes
Boston Square
Community
Bikes
Boston Square
Community
Bikes
Boston Square
Community
Bikes
Terratrike
Terratrike
Terratrike
Terratrike
Final Report
Team 5: TheraTryke
page 73
Seat Stays Set
M8 Nyloc Nut, SS
M8x40mm SHSCS SS
$25
$0.50
$0.50
1
3
3
$25
$1.50
$1.50
Terratrike
Terratrike
Terratrike
M8x20 Low Head, SS
M5x30mm SHCS SS
$0.50
$0.50
2
2
$1
$1
Terratrike
Terratrike
M5 Nyloc nut SS
M5x12mm SHCS SS
$0.15
$0.20
2
2
$0.30
$0.40
Terratrike
Terratrike
Seatbelt
Gear and Chain System
Shimano Nexus 7 speed
$26.99
1
$26.99
Amazon
$299.98
1
$299.98
20 tooth sprocket
$10
1
$10
West Michigan
Bike and
Fitness
Alger Bikes
40 tooth sprocket
$15
1
$15
Alger Bikes
28 tooth sprocket
$10
1
$10
Alger Bikes
Crankset
$17.50
2
$35
Terratrike
Crankset screws (M8x1)
$2
4
$8
Terratrike
Bike chains (1/8)
$12
5
$60
Bottom Bracket Shells
$10.06
2
$20.12
Boston Square
Community
Bikes/Amazon
Amazon.com
Hand Pedals
Foot Pedal
$1
2
$2
2” Aluminum Bar
$3.55
2
$7.10
Boston Square
Bikes
ALRO Steel
Washer
$0.10
2
$0.20
ALRO Steel
Lock Washer
$0.10
2
$0.20
ALRO Steel
Bolt
$0.15
2
$0.30
ALRO Steel
$60
2
$120
Foot & Ankle
Specialists
$15
2
$30
TerraTrike
Brake Lever Set
$10
1
$10
TerraTrike
Brake Cables with housing
$12.99
2
$25.98
Amazon
Cantilever Brake Clip
$1
1
$1
Crimps
Total Cost:
$0.10
2
$0.20
$1538.37
Boston Square
Bike
Lowe’s
Leg Brace and Support
Leg braces and
Supports
Brakes
Alhonga Disk Brakes
Final Report
Team 5: TheraTryke
page 74
6.2.2 Funding
6.2.2.1 Calvin College
The team is given an initial budget of $500 from Calvin College to use towards any purchases
necessary for the project. The team was able to use more than this from Calvin because not
every team used all of their budget.
6.2.3 Potential Profits.
6.2.3.1 Selling Single Unit
The team determined that the market value of the product is $3,000. This is assuming the total
cost of production to be $1538.37. The selling price of $3,000 also accounts for overhead cost,
shipping costs, and includes a retail markup to allow for a profit margin of 23%.
6.2.3.1 Yearly Selling Forecast
Based off of a variety of calculations that include an income statement, a statement of cash
flows, and a break even analysis, the company was able to determine potential profits for the
product. These calculations used fixed and variable costs, projected sales quantities and costs,
taxes, and interest. After all variables are taken into account profits in the first year were
determined to be $422,280. This was based off of 1000 sales. In the second year, the profits
increased to $555,936, and in the third year, profits increased to $736,950. Over the first three
years, the company is assuming 15% growth. This continual growth shows that within 5 years
after initial production, the team could be seeing profits of almost $1,000,000. The team
realizes that profits will eventually stabilize as the market becomes saturated with similar
products, meaning that the team needs to take advantage of this timing and implement
immediate production.
7. Project Management
Project management is essential in conducting the steps to complete the design and
implementation of a product. Clear goals and structured scheduling will be required to complete
the project under the given time constraints and budget limitations. The management of this
project is allocated to three sub categories which include work division, team organization, and
scheduling.
7.1 Work Division
The team is made up of all mechanical engineers with similar backgrounds which gives
versatility within the team. This has its advantages and disadvantages when it comes to the
distribution of work. Each member is capable of working on all the different jobs necessary to
complete the project which enables overlap in certain areas, but it is difficult because each
Final Report
Team 5: TheraTryke
page 75
member has certain visions in mind about what the overall design will look like. At the
beginning of the school year, the team met to discuss the division of work. They discussed all
the components necessary to make the project a success and then distributed the work so
everyone would have an idea of their tasks for the semester. At the end of each week, tech
memos are assembled so the whole team and the advisor will be aware of what had been
completed, and what would need to be complete in the upcoming weeks. Although each
member has certain responsibilities, all of the tasks overlap allowing for team collaboration on
almost all aspects of research and development.
7.2 Team Organization and Management
Time is a barrier that many teams have struggled with in past years. The team has realized this
at many steps during the school year. Management of time and organization of responsibilities
are both large components of this project to help push for continual progress and to avoid
uncertainty of what should be done next. Professor Wunder, the team’s advisor, has done a
good job in pushing us to hit certain deadlines for design decisions. Weekly technical memos
are submitted to him to show where the team stands. Included in these memos are what has
been done recently, and what the team will be doing in the near future. In addition, a detailed
Work Breakdown Structure (WBS) has been made to outline the tasks for the entire year. The
WBS shows each task, the predicted start date, and the estimated hours of completion. Actual
hours are added in once the task is complete. The project completion percentage is updated
each time progress on a task is made.
The team has a work log that is updated with the person’s name, the task he worked on, the
date he worked on it, and the hours spent doing this task. This is a measure to see where time
has been spent and to see how much time each team member has put into their responsibilities.
The responsibilities of each team member during the first semester can be seen below in Figure
53. This was mostly market research and initial design. Because of all the relationships between
each part of the project, there had to be clear communication between the team members. Each
team member should have a good understanding of the others section. They will not have
decision power over one in charge of a section, but they will have the power to make
suggestions to make sure that each part is working in harmony with their respective sections.
For the second semester, the team was organized slightly different. This can be seen in Figure
54. This semester consisted of acquiring parts and manufacturing the systems. The team also
was more conscious of checking each other’s work. This can be seen by the arrows coming
from the bottom.
Final Report
Team 5: TheraTryke
page 76
Figure 53. First semester team organization
Figure 54. Second semester team organization
Final Report
Team 5: TheraTryke
page 77
7.3 Scheduling and Milestones
In Figure 55, it shows the time dedicated to the project over the school year. The second
semester was not documented as well as the first semester, so team members estimated how
many hours per week they worked during second semester. Figure 56 shows time distribution
between parts of the project for the first semester, the initial design phase. A detailed WBS can
be found in Appendix B.
Figure 55. Work log
90
80
Total Hours
70
60
50
40
30
20
10
0
Figure 56. Distribution of work time
Final Report
Team 5: TheraTryke
page 78
8. Acknowledgements
There are many individuals and organizations have been very helpful and provided great insight
to the team throughout the entire project. The team would like to give a special thanks to the
following:
Boston Square Bikes
Tom Bulten and the whole Boston Square Bike staff provide the team with information about
many aspects of how bikes and trikes work. They provide workspace and help the team
develop hands on experience.
Calvin College
Calvin College provides the team with many different resources including workspace and
materials along with providing a generous portion of the budget.
Custom Frame Coatings
Custom Frame Coatings has generously powder coated the prototype frame for no cost. They
like the idea of the project and wanted to help out.
Cara Masselink
Cara, an occupational therapist at Mary Free Bed Rehabilitation Hospital, provids the team with
information regarding the benefits of therapeutic aspect of the design.
CJ Verbrugge
CJ, an employee at Mary Free Bed Rehabilitation Hospital, helps explain the possible
therapeutic benefits of a therapeutic tricycle.
Dr. Kenyon
Dr. Kenyon, a pediatric physical therapist at GVSU, gives insights to the therapeutic advantages
of a device like the one the team is designing.
Dr. Lisa Van Arragon
Dr. Lisa Van Arragon was involved with the DisArt (disability art) Festival in Grand Rapids. This
is an international art show where the artwork has either disability themes or is made by
someone with a disability. She connected the team with the event. The team had a station to put
pictures of the trike, and the team also gave a collaboration presentation during the event.
Dr. Meyer
Dr. Meyer, a Calvin exercise science professor, has provided the team with information
regarding the physical therapy and therapeutic aspect of the design.
Foot & Ankle Specialists
Foot & Ankle has generously donated three walking boots to be used for the bracing system of
the legs in the prototype.
Final Report
Team 5: TheraTryke
page 79
Jeff Yonker
Jeff, a paraplegic and user of a hand powered recumbent trike, provides the team with advice
regarding the design and use of the trike.
Nancy Remelts
Nancy, acting at the team’s main client, provided guidance in the development of the product.
She helped give the team insights as to what would be most beneficial to potential users.
Phil Jasperse
Phil is the metal and woodshop supervisor at Calvin. He helps the team with many parts of the
project especially involving the development of prototypes.
Pierre Vos-Camy
Pierre, a paraplegic, shares his thoughts on what would make the product useful and
successful. As a user of a recumbent trike, Pierre helps demonstrated aspects of trike design
that the team implemented in their design.
Professor Ermer
Professor Ermer provides the team with great information regarding the development of the
gear system.
Professor Tubergen
Professor Tubergen acts as the team’s industrial consultant. He provides great insight to many
aspects of the project including design, organization, and prototyping.
Professor Wunder
Professor Wunder is the team's faculty advisor. He helps push the team towards success by
providing both advice and criticism. He helps keep the team on task by providing deadlines and
sharing useful project management techniques.
Progressive Surface
Phil Savickas and Greg Parlmer have offered their time after their work hours to weld the frame
together. The welding expertise they have offered is very much appreciated.
TerraTrike
TerraTrike provide the team with great information regarding all aspects of trike design. This
included braking, steering, and frame design.
Final Report
Team 5: TheraTryke
page 80
9. References
Adobe. (n.d.). Retrieved from Adobe: https://color.adobe.com
Allen, J. (n.d.). Disc Brakes. Retrieved from Harris Cyclery: http://sheldonbrown.com/discbrakes.html
Aluminum corrosion resistance. (n.d.). Retrieved from Aluminum Design:
http://www.aluminiumdesign.net/design-support/aluminium-corrosion-resistance/
Amain. (n.d.). Retrieved from Amain: http://www.amain.com/
AmTryke. (n.d.). Retrieved from Ambucs: http://www.ambucs.org/amtryke/
Bike Calculator. (n.d.). Retrieved from Bike Calculator: www.bikecalculator.com
Brown, S. (n.d.). Harris Cyclery. Retrieved from Bicycle Brake Shoices:
http://sheldonbrown.com/brake-choices.html
Building a Recumbent Trike Seat. (n.d.). Retrieved from Instructables:
http://www.instructables.com/id/Building-a-Recumbent-Trike-Seat
Calvin College. (n.d.). Retrieved from Calvin College: http://www.calvin.edu/
Calvin College Engineering. (n.d.). Retrieved from Calvin College:
http://www.calvin.edu/academic/engineering/2010-11-team3/
Calvin College Engineering Senior Design. (n.d.). Retrieved from Calvin College:
http://www.calvin.edu/academic/engineering/senior-design/
Catrike. (n.d.). Retrieved from Catrike: http://www.catrike.com/
Choosing A Recumbent. (n.d.). Retrieved from Recumbent Cyclist News:
http://recumbentcyclistnews.blogspot.com/p/recumbent-101.html
Figliozzi, Wheeler, & Monsere. (n.d.). A Methodology to Estimate Bicyclists’ Acceleration and
Speed. Retrieved from
http://web.cecs.pdx.edu/~maf/Journals/2013_A_Methodology_to_Estimate_Bicyclists%E
2%80%99_Acceleration_and_Speed_Distributions_at_Signalized_Intersections.pdf
Gomier Manufacturing Co., Ltd. (n.d.). Retrieved from Gomier Manufacturing Co., Ltd.:
http://gomier.imb2b.com/
Metals and Corrosion Resistance. (n.d.). Retrieved from The Engineering Toolbox:
http://www.engineeringtoolbox.com/metal-corrosion-resistance-d_491.html
Online Metals. (n.d.). Retrieved from Online Metals: http://www.onlinemetals.com/
Recreational & Excercise Equipment. (n.d.). Retrieved from Fas Equipment:
http://www.fasequipment.com/flipbook/Recreational/index.html#2
Restorative Therapies. (n.d.). Retrieved from Restorative Therapies: http://www.restorativetherapies.com/rt300_series
Terratrike. (n.d.). Retrieved from Terratrike: www.terratrike.com
Top End . (n.d.). Retrieved from Top End: http://www.topendwheelchair.com/
Utah Trikes. (n.d.). Retrieved from Utah Trikes: http://www.utahtrikes.com/
Watson, J. (n.d.). Metal of the Month: Chromoly. Retrieved from Arc-Zone: https://www.arczone.com/blog/joewelder/2009/01/08/metal-of-the-month-chromoly/
Welding of titanium and its alloys. (n.d.). Retrieved from TWI: http://www.twiglobal.com/technical-knowledge/job-knowledge/welding-of-titanium-and-its-alloys-part-1109/
Final Report
Team 5: TheraTryke
page 81
What is the practical advantage of disk brakes over rim brakes? (n.d.). Retrieved from
StackExchange: http://bicycles.stackexchange.com/questions/3855/what-is-thepractical-advantage-of-disk-brakes-over-rim-brakes
Why do you use cantilever brakes when everyone else is using V-brakes or disc brakes? (n.d.).
Retrieved from Rod Bikes: http://www.rodbikes.com/articles/brakes.html
Final Report
Team 5: TheraTryke
page 82
10. Conclusion
The team is very happy with the state of the prototype. The client has given it a test ride and
enjoyed it. If the trike is proven to be reliable, the team is comfortable in handing it off to her. As
for the status of the trike after this class, the team plans on showing to the therapeutic and
recreational department at Mary Free Bed Hospital. The team is eager to hear feedback from
them and will reassess the plans for the project after the feedback. The team will also examine
the possibility of patenting the trike.
Final Report
Team 5: TheraTryke
page 83
11. Appendices
A. Gearing Calculations
A.1 Excel sheet on gears
Table 39. Excel sheet for gear considerations
Final Report
Team 5: TheraTryke
page 84
A.2. Power calculations and top speeds
Figure 57: Power Calculations
Final Report
Team 5: TheraTryke
page 85
Figure 58. Bike speed calculator
www.bikecalculator.com
Final Report
Team 5: TheraTryke
page 86
A.3 Gearing Ranges Considered
Figure 59. Gear ranges considered
Final Report
Team 5: TheraTryke
page 87
B. Work Breakdown Schedule
Table 40. Project work breakdown schedule
Task Name
TheraTryke
Duration
Start
Finish
180 days
Mon 9/8/14
Fri 5/15/15
175 days
Mon 9/8/14
Fri 5/8/15
Project Definition and Client Choice 39 days
Mon 9/8/14
Thu 10/30/14
Planning Complete
60 days
Mon 9/8/14
Fri 11/28/14
Research Complete
67 days
Tue 9/30/14
Wed 12/31/14
Prototyping Complete
96 days
Fri 11/28/14
Fri 4/10/15
Presentation Complete
11 days
Mon 4/6/15
Mon 4/20/15
Final Report Complete
25 days
Thu 4/9/15
Wed 5/13/15
180 days
Mon 9/8/14
Fri 5/15/15
Elevator Pitch
10 days
Sun 9/28/14
Fri 10/10/14
Final 339 Presentation
10 days
Tue 11/11/14
Mon 11/24/14
340 Presentation 1
10 days
Mon 2/2/15
Fri 2/13/15
340 Presentation 2
10 days
Thu 4/2/15
Wed 4/15/15
DisArt
10 days
Tue 4/7/15
Mon 4/20/15
Banquet Night
10 days
Mon 4/27/15
Fri 5/8/15
PPFS and Reports
150 days
Wed 10/15/14 Tue 5/12/15
13 days
Mon 10/6/14
Wed 10/22/14
Department
3 days
Mon 10/6/14
Wed 10/8/14
Project
1 day?
Mon 10/6/14
Mon 10/6/14
Objective
3 days
Mon 10/6/14
Wed 10/8/14
Motivation
3 days
Thu 10/9/14
Mon 10/13/14
Team Members
1 day?
Tue 10/14/14
Tue 10/14/14
Client
7 days
Tue 10/14/14
Wed 10/22/14
16 days
Wed 10/22/14 Wed 11/12/14
Functional Requirements
4 days
Wed 10/22/14 Mon 10/27/14
Mechanical Requirements
12 days
Tue 10/28/14
Wed 11/12/14
Height and Weight
12 days
Tue 10/28/14
Wed 11/12/14
Product Weight
12 days
Tue 10/28/14
Wed 11/12/14
Size
12 days
Tue 10/28/14
Wed 11/12/14
Material Properties
12 days
Tue 10/28/14
Wed 11/12/14
Seating
12 days
Tue 10/28/14
Wed 11/12/14
Milestones
Presentations
Introduction
Project Requirements
Final Report
Team 5: TheraTryke
page 88
Mounting
12 days
Tue 10/28/14
Wed 11/12/14
Maintenance
12 days
Tue 10/28/14
Wed 11/12/14
Environmental
12 days
Tue 10/28/14
Wed 11/12/14
16 days
Wed 10/22/14 Wed 11/12/14
16 days
Wed 10/22/14 Wed 11/12/14
Stopping
16 days
Wed 10/22/14 Wed 11/12/14
Parking
16 days
Wed 10/22/14 Wed 11/12/14
Harnessing
16 days
Wed 10/22/14 Wed 11/12/14
Stability
16 days
Wed 10/22/14 Wed 11/12/14
Flag Slot
16 days
Wed 10/22/14 Wed 11/12/14
16 days
Wed 10/22/14 Wed 11/12/14
Justice
16 days
Wed 10/22/14 Wed 11/12/14
Caring
16 days
Wed 10/22/14 Wed 11/12/14
Stewardship
16 days
Wed 10/22/14 Wed 11/12/14
Major Design Decisions
17 days
Mon 11/10/14 Tue 12/2/14
Stearing Mechanism
5 days
Mon 11/10/14 Fri 11/14/14
Frame
12 days
Mon 11/10/14 Tue 11/25/14
Material
12 days
Mon 11/10/14 Tue 11/25/14
Structure
12 days
Mon 11/10/14 Tue 11/25/14
Gear Train System
12 days
Mon 11/10/14 Tue 11/25/14
Ergonomics
12 days
Mon 11/10/14 Tue 11/25/14
Braking
12 days
Mon 11/10/14 Tue 11/25/14
Wheels
12 days
Mon 11/10/14 Tue 11/25/14
Financials
35 days
Wed 10/15/14 Tue 12/2/14
Consultant Report
5 days
Mon 3/9/15
Fri 3/13/15
Final Design Report
27 days
Tue 4/7/15
Wed 5/13/15
Website Creation
160 days
Thu 10/2/14
Wed 5/13/15
Budget
35 days
Thu 10/23/14
Wed 12/10/14
Fund Distribution
20 days
Fri 10/24/14
Thu 11/20/14
Preliminary Cost Estimates
25 days
Fri 10/24/14
Thu 11/27/14
Final Budget
5 days
Fri 11/28/14
Thu 12/4/14
Exterior Funding
30 days
Thu 10/23/14
Wed 12/3/14
30 days
Thu 10/23/14
Wed 12/3/14
30 days
Thu 10/23/14
Wed 12/3/14
30 days
Thu 10/23/14
Wed 12/3/14
Safety Requirements
Braking
Design Norms
Donations
Remelts (up to $300)
Partnerships
Final Report
Team 5: TheraTryke
TerraTryke
page 89
30 days
Thu 10/23/14
Wed 12/3/14
30 days
Thu 10/23/14
Wed 12/3/14
Summons Center
30 days
Thu 10/23/14
Wed 12/3/14
Mechanical Characteristics
120 days
Thu 10/23/14
Wed 4/8/15
120 days
Thu 10/23/14
Wed 4/8/15
100 days
Thu 10/23/14
Wed 3/11/15
Material Selection
10 days
Mon 11/3/14
Fri 11/14/14
Height and Length
10 days
Mon 11/17/14 Fri 11/28/14
Joint Angle Strength
8 days
Mon 12/1/14
Wed 12/10/14
Welding Techniques
4 days
Thu 12/11/14
Tue 12/16/14
Discussion with Bike Experts
2 days
Wed 12/17/14 Thu 12/18/14
Integration of Design Decisions
10 days
Fri 12/19/14
Thu 1/1/15
Frame Prototype
20 days
Thu 2/12/15
Wed 3/11/15
Thu 3/12/15
Fri 3/13/15
Mon 3/23/15
Tue 3/24/15
Grants
Structure and Drive
Frame
Install Steering w/ Front Wheels 2 days
Install Back Wheel, Foot/Hand
2 days
Pedals, Central Hub
Install Chain, Shifting Cables
4 days
Tue 3/24/15
Fri 3/27/15
Braking Installation
3 days
Mon 3/30/15
Wed 4/1/15
Installation of Seat, Pedals,
Bracing
2 days
Thu 4/2/15
Fri 4/3/15
25 days
Sun 11/30/14
Thu 1/1/15
Research Designs
10 days
Mon 12/1/14
Fri 12/12/14
Wheel Sizing Options
15 days
Mon 12/15/14 Fri 1/2/15
Shock Absorption
3 days
Mon 12/15/14 Wed 12/17/14
15 days
Mon 12/1/14
Fri 12/19/14
Research Current Market
5 days
Mon 12/1/14
Fri 12/5/14
Fixed Position
4 days
Mon 12/1/14
Thu 12/4/14
Adjustability
4 days
Mon 12/1/14
Thu 12/4/14
Cushioning
4 days
Mon 12/1/14
Thu 12/4/14
Attach Seatbelt
3 days
Thu 3/12/15
Mon 3/16/15
110 days
Thu 10/23/14
Wed 3/25/15
Research Regular Bikes
25 days
Thu 10/23/14
Wed 11/26/14
Gear Ration Calculations
20 days
Thu 11/27/14
Wed 12/24/14
Positioning of Gears
25 days
Thu 12/25/14
Wed 1/28/15
Mounting Options and Control
30 days
Thu 1/29/15
Wed 3/11/15
Wheels
Seat
Gears
Final Report
Team 5: TheraTryke
Braking
page 90
25 days
Fri 12/19/14
Thu 1/22/15
Investigate Regular Bikes
10 days
Fri 12/19/14
Thu 1/1/15
Positioning and Control
10 days
Fri 1/2/15
Thu 1/15/15
100 days
Mon 12/15/14 Fri 5/1/15
70 days
Thu 1/15/15
Wed 4/22/15
60 days
Thu 1/15/15
Wed 4/8/15
Lightweight Frame
35 days
Thu 1/15/15
Wed 3/4/15
Capacity
14 days
Thu 3/5/15
Tue 3/24/15
Gear Train is Light
30 days
Thu 3/5/15
Wed 4/15/15
28 days
Thu 3/5/15
Mon 4/13/15
Wheels In-Line
10 days
Thu 3/5/15
Wed 3/18/15
Gear Changing
28 days
Thu 3/5/15
Mon 4/13/15
Ease of Ride
28 days
Thu 3/5/15
Mon 4/13/15
Transfer
28 days
Thu 3/5/15
Mon 4/13/15
50 days
Fri 1/30/15
Thu 4/9/15
Testing
Tryke Functionality
Weight
Smoothness
Human Functionality
Final Report
Team 5: TheraTryke
page 91
C. User Experience Definition
A definition of the “User Experience” as imagined by the TheraTryke team.
The user will exit their house and approach the trike. First, they will reach down and disengage
the parking brake in order to allow them to orient the trike. There will be one parking brake on
each steering handle so that it does not matter which side the user is coming from. In order to
move the trike they will have to push or drag it into the correct position. The easiest way to
move the trike will be to back the trike straight out of the garage. What will be difficult to do
alone will be turning the trike around while holding one steering handle on the side of the trike.
Assistance may be necessary. After positioning the trike, the user will once again engage the
parking brake. The user will properly adjust the seat in order to match their leg length. This may
mean getting in and out to test the distance to the pedals. There could be different height values
on the adjustment options. They will then transfer to the trike from their wheelchair or sit down
directly. Users who lack abdominal control will immediately strap their torso to the seat’s
backrest. After sitting down and orienting themselves, the user will pick up their legs and place
them directly into the leg brace assemblies. With the hand pedal column in front of them, they
will need to bring one leg very close to their body, or the stand will be collapsible. If the stand is
collapsible, something needs to be in reach to bring it back up and to lock it into place. With
their legs stable in the braces, they will first strap in their feet and lower legs. Then, the user will
adjust the knee brace so that it is centered on their knee, and then strap in their lower thigh. If
the user does not have control of their abdominals they will require assistance to strap in their
lower legs and feet. In this way, both the braces and the seat adjustment will protect the user
from hyperextension. The lower leg brace will be detachable from the foot pedal so that the user
will be able to choose to use the bracing system or not.
After properly orienting the trike and transferring to the seat, the user will begin to pedal.
Pedaling will be done with hands. Leg usage is a bonus for people without paraplegia, but that
is not the target user. If the user is initially in too high a gear to start pedaling, they will cycle
down on the Nuvinci variable pulley system in order to make pedaling easier. They will slowly
accelerate to a comfortable rolling speed, adjusting their gear ratio as desired. During use, they
will travel over small bumps, ascend and descend slopes, stop for traffic lights, avoid possible
obstacles, and turn around standard road corners. In addition, they may travel along straight,
crowned roadways, during which their trike will keep traveling forward. In order to turn, the user
will remove one or both of their hands from the pedals and grab the steering handles located at
waist height. After turning, they will remove their hands from the steering handles and expect,
once again, to remain traveling straight. At any point in time during this procedure, the user will
have access to braking. While pedaling, the user’s legs will be traveling through their full range
of motion at a rate directly proportional to the rate of hand pedaling. At no point will they ever be
fully extended in the locked position.
Upon returning to their home, the user will have sufficient control of the trike to be able to pull
directly up to their waiting wheelchair and perform a transfer if needed. The trike will then be
Final Report
Team 5: TheraTryke
page 92
stowed in the garage in a similar manner to which it was removed. Assistance may be
necessary for stowing away the trike.
Final Report
Team 5: TheraTryke
page 93
D. Business Analysis Calculations
Table 41. Income Statement for TheraTryke
TheraTryke
Pro-Forma Statement of Income
Year 1
Sales revenue
Variable Cost of Goods Sold
Fixed Cost of Goods Sold
Depreciation
Gross Margin
Variable Operating Costs
Fixed Operating Costs
Operating Income
Interest Expense
Income Before Tax
Income tax (40%)
Net Income After Tax
3,000,000
861,200
290,000
20,000
1,828,800
450,000
600,000
778,800
75,000
703,800
281,520
422,280
Year 2
3,500,000
Year 3
3,500,000
991,440
290,000
32,000
2,186,560
525,000
600,000
1,061,560
135,000
926,560
370,624
555,936
4,000,000
1,164,300
290,000
19,200
2,526,500
600,000
600,000
1,326,500
98,250
1,228,250
491,300
736,950
Table 42. Cash Flow Statement for TheraTryke
TheraTryke
Pro-Forma Statement of Cash Flows
Year 1
Year 2
Year 3
Beginning Cash Balance
-
2,242,280
2,930,216
Net Income After Tax
422,280
555,936
736,950
Depreciation expense
20,000
32,000
19,200
Invested Capital (Equity)
400,000
400,000
400,000
Increase (decrease) in borrowed funds
1,500,000
(300,000)
(435,000)
Equipment Purchases
(100,000)
-
-
Ending Cash Balance
2,242,280
2,930,216
3,651,366
Final Report
Team 5: TheraTryke
page 94
Table 43. Break Even Analysis for TheraTryke
TheraTryke
Break - Even Analysis
Year 1
Sales revenue
Less: Variable Costs:
Variable Cost of
Goods Sold
Variable
Operating Costs
Total Variable
Costs
Contribution Margin
Less: Fixed Costs
Fixed Cost of
Goods Sold
Fixed Operating
Costs
Year 2
3,000,000
Year 3
3,500,000
4,000,000
861,200
991,440
1,164,300
450,000
525,000
600,000
1,311,200
1,516,440
1,764,300
1,688,800
1,983,560
2,235,700
290,000
290,000
290,000
600,000
600,000
600,000
Depreciation
20,000
32,000
19,200
Interest Expense
Total Fixed
Costs
75,000
135,000
98,250
Income Before Tax
Year 1
985,000
1,057,000
1,007,450
703,800
926,560
1,228,250
Year 2
Year 3
1,057,000
1,007,450
56%
57%
56%
Break Even Sales
Volume
1,749,763
1,865,081
1,802,478
Break Even Units
583.25
621.69
600.83
Total Fixed Costs
Contribution Margin
%
985,000
Final Report
Team 5: TheraTryke
page 95
Table 44. Depreciation and Interest Calculations
Equipment
Purchases
Equipment Purchases Year 1
100,000
Equipment Purchases Year 2
-
Equipment Purchases Year 3
-
Depreciation
Year 2
Year 1
20,000
Year 3
32,000
19,200
-
-
20,000
MACRS Rates (5-year recovery period)
32,000
0.2
Interest Expense:
Annual interest rate on debt
0.32
19,200
0.192
10%
Year 1
Year 2
Year 3
Average debt balance
750,000
1,350,000
982,500
Interest expense
75,000
135,000
98,250
Table 45. Ratios and EBITDA Calculations
Profit Margin %
Gross Margin %
Contribution Margin %
Debt to Equity Ratio
EBITDA
4X EBITDA
4X EBITDA AFTER TAXES
Ratios
0.14076
0.62
56%
1.875
798,800
0.158838857
0.63
57%
3.375
1,093,560
0.1842375
0.64
56%
2.45625
1,345,700
5,382,800
3,229,680.0
Final Report
Team 5: TheraTryke
page 96
Table 46. Fixed Operating Costs for TheraTryke
Fixed Operating Costs
Building
Advertising
General and administrative
salaries
Selling
Total
250000
100000
150000
100000
600000
Table 47. Variable Operating Costs for TheraTryke
Variable
Operating Costs
Year 1
Sales
commissions
150,000.0
Shipping Costs
300,000
450,000.0
Year 2
Sales
commissions
175,000.00
Shipping Costs
350,000
525,000.00
Year 3
Sales
comissions
200,000.00
Shipping Costs
400,000
600,000.00
Year 1
Units Sold
3,000
Year 2
Year 3
3,500
4,000
Final Report
Team 5: TheraTryke
page 97
Table 48. Variable COGS for TheraTryke
Variable Cost of Goods Sold
Year 1
Direct Materials
Direct Labor
Variable manufacturing
overhead
Year 2
Year 3
800,000 920,000 1,077,500
$51,200 $61,440
$76,800
10000
10000
10000
861200
991440
1164300
Leg Bracing
Frame Material
100000
150000
115000
172500
137500
206250
Gears
350,000 402,500 481,250
Braking and Seating
100,000 115,000 115,000
Wheels
100,000 115,000 137,500
800,000 920,000 1,077,500
Year 1
Wage
People
hour/day
day/year
$10
2
8
320
$51,200
Year 2
Year 3
12
15
2
2
8
8
320
320
$61,440 $76,800
Table 49. Fixed COGS for TheraTryke
Fixed Costs of Good Sold
Manufacturing Facilities
Manufacturing management
salaries
Benefits
Rent
15000
100000
100000
75000
290000
Final Report
Team 5: TheraTryke
page 98
E. Frame Design Analysis
E.1 Weight Determination
Figure 60. Aluminum 6061-T6 frame weight
SolidWorks
Final Report
Team 5: TheraTryke
page 99
Figure 61. Chromoly 4130 alloy steel frame weight
SolidWorks
Final Report
Team 5: TheraTryke
page 100
Figure 62: E.3 Titanium alloy 3AL-2.5V frame weight
SolidWorks
Final Report
Team 5: TheraTryke
page 101
E.2. Maximum Deflection and Stress
Figure 63. Al 6061-T6 Von Mises stress analysis
Figure 64. Al 6061-T6 displacement analysis
Final Report
Team 5: TheraTryke
page 102
Figure 65. Ti 3AL-2.5V Von Mises stress analysis
Figure 66. Ti 3AL-2.5V displacement analysis
Final Report
Team 5: TheraTryke
page 103
Figure 67. Chromoly 4130 Steel Alloy Von Mises stress analysis
Figure 68. Chromoly 4130 Steel Alloy displacement analysis
Final Report
Team 5: TheraTryke
page 104
Figure 69. Al 6061-0 Von Mises stress analysis english units (psi)
Figure 70. Al 6061-0 Von Mises stress analysis metric units (
𝑁
𝑚2
)
Final Report
Team 5: TheraTryke
page 105
Figure 71. Al 6061-0 displacement analysis english units (in)
Figure 72. Al 6061-0 displacement analysis metric units (mm)
Final Report
Team 5: TheraTryke
page 106
F. Steering and Pedaling Concept
Figure 73. Concept to combine steering and pedaling
Final Report
Team 5: TheraTryke
page 107
G. Final Prototype Images
Figure 74. Final prototype
Figure 75. Top view of prototype