TheraTryke
Project Proposal and Feasibility Study
Calvin College Engineering
Team 5
David Evenhouse
Jack Kregel
Nick Memmelaar
Connor VanDongen
Advisor
Professor David Wunder
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 2
Table of Contents
1.
Introduction ......................................................................................................................... 8
1.1
Calvin College Engineering Department ...................................................................... 8
1.2
Senior Design Project .................................................................................................. 8
1.3
Objective ...................................................................................................................... 8
1.3.1 Ease of Use ............................................................................................................... 8
1.3.2 Speed ........................................................................................................................ 9
1.3.3 Safety......................................................................................................................... 9
1.3.4 Therapeutic Benefits .................................................................................................. 9
1.3.5 Outdoor Usage ........................................................................................................... 9
1.3.6 Economic Sustainability ............................................................................................. 9
1.3.7 Pass the Class ........................................................................................................... 9
2.
1.4
Motivation .................................................................................................................... 9
1.5
Group Members ..........................................................................................................10
1.6
Client ..........................................................................................................................12
Project Requirements.........................................................................................................12
2.1
Functional ...................................................................................................................12
2.2
Mechanical .................................................................................................................13
2.2.1
Height and Weight Capacity.................................................................................13
2.2.2
Product Weight ....................................................................................................13
2.2.3
Size .....................................................................................................................13
2.2.4
Material ................................................................................................................13
2.2.5
Seat .....................................................................................................................13
2.2.6
Mounting ..............................................................................................................13
2.2.7
Maintenance ........................................................................................................13
2.2.8
Environmental ......................................................................................................14
2.2.9 Speed .......................................................................................................................14
2.3
Safety .........................................................................................................................14
2.3.1
Brakes .................................................................................................................14
2.3.2
Harnessing ..........................................................................................................14
2.3.3
Stability ................................................................................................................14
2.3.4
Flag Slot ..............................................................................................................14
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 3
2.4 Design Norms ..................................................................................................................15
3. Research .............................................................................................................................15
3.1 Similar Products ..............................................................................................................15
3.1.1 TerraTrike .................................................................................................................15
3.1.2 Top End Trikes ..........................................................................................................16
3.1.3 Rehatri Tikes by Gomier............................................................................................17
3.1.4 AmTryke ...................................................................................................................18
3.1.5 Catrike ......................................................................................................................18
3.2 Past Projects ...................................................................................................................19
3.2.1 Achieving Mobility .....................................................................................................19
3.3 External Resources .........................................................................................................20
3.3.1 TerraTrike .................................................................................................................20
3.3.2 Boston Square Community Bikes ..............................................................................20
4. Mechanical Design ................................................................................................................20
4.1 Frame ..............................................................................................................................20
4.1.1 Research ..................................................................................................................20
4.1.2 Requirements............................................................................................................21
4.1.3 Material Selection......................................................................................................22
4.1.4 Design Alternatives ...................................................................................................26
4.1.5 Cost Considerations ..................................................................................................28
4.2 Steering ...........................................................................................................................29
4.2.1 Research ..................................................................................................................29
4.2.2 Requirements............................................................................................................29
4.2.3 Design Alternatives ...................................................................................................29
4.2.4 Turning Circle Calculations .......................................................................................32
4.2.5 Cost Considerations ..................................................................................................33
4.3 Wheels ............................................................................................................................33
4.3.1 Research ..................................................................................................................33
4.3.2 Requirements............................................................................................................34
4.3.3 Design Alternatives ...................................................................................................34
4.3.4 Cost Considerations ..................................................................................................35
4.4 Seat .................................................................................................................................35
4.4.1 Research ..................................................................................................................35
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 4
4.4.2 Requirements............................................................................................................35
4.4.3 Design Alternatives ...................................................................................................36
4.4.4 Cost Considerations ..................................................................................................37
4.5 Gear and Chain System ..................................................................................................37
4.5.1 Research ..................................................................................................................37
4.5.2 Requirements............................................................................................................38
4.5.3 Design Alternatives ...................................................................................................38
4.5.4 Cost Considerations ..................................................................................................42
4.6 Hand Pedals ....................................................................................................................43
4.6.1 Research ..................................................................................................................43
4.6.2 Requirements............................................................................................................43
4.6.3 Design Alternatives ...................................................................................................43
4.6.4 Cost Considerations ..................................................................................................45
4.7 Foot Pedals .....................................................................................................................45
4.7.1 Research ..................................................................................................................45
4.7.2 Requirements............................................................................................................46
4.7.3 Design Alternatives ...................................................................................................46
4.7.4 Cost Considerations ..................................................................................................47
4.8 Leg Brace and Support ....................................................................................................47
4.8.1 Research ..................................................................................................................47
4.8.2 Requirements............................................................................................................49
4.8.3 Design Alternatives ...................................................................................................49
4.8.4 Cost Considerations ..................................................................................................50
4.9 Brakes .............................................................................................................................51
4.9.1 Research ..................................................................................................................51
4.9.2 Requirements............................................................................................................51
4.9.3 Design Alternatives ...................................................................................................51
4.9.4 Cost Considerations ..................................................................................................54
5. Testing ..................................................................................................................................54
5.1 Ease of Use .....................................................................................................................54
5.1.1 Timing transfer and positioning on trike .....................................................................54
5.2 Safety ..............................................................................................................................54
5.3 Speed ..............................................................................................................................55
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 5
5.3.1 Time top speed on trike on level ground....................................................................55
5.3.2 Acceleration of trike from standstill ............................................................................55
5.4 Therapeutic Benefits ........................................................................................................55
5.4.1 Comfort .....................................................................................................................55
5.4.2 Avoiding spasms .......................................................................................................56
5.5 Outdoor usage .................................................................................................................56
5.6 Economic Sustainability ...................................................................................................56
5.7 Pass the Class.................................................................................................................57
6. Business Analysis .................................................................................................................57
6.1 Market Research .............................................................................................................57
6.1.1 Existing Competitors .................................................................................................57
6.1.2 Target Markets ..........................................................................................................58
6.2 Financials ........................................................................................................................58
6.2.1 Budget ......................................................................................................................58
6.2.2 Funding .....................................................................................................................59
6.2.3 Potential Profits .........................................................................................................59
7. Project Management .............................................................................................................60
7.1 Work Division ..................................................................................................................60
7.2 Team Organization and Management..............................................................................60
7.3 Scheduling and Milestones ..............................................................................................61
8. Acknowledgements ...............................................................................................................62
9. References ...........................................................................................................................64
10. Conclusion ..........................................................................................................................66
11. Appendices .........................................................................................................................67
A. Excel sheet on gears .........................................................................................................67
B. Work Breakdown Schedule ...............................................................................................68
C. User Experience Definition ................................................................................................71
D. Business Analysis Calculations .........................................................................................72
E. Frame Design Analysis .....................................................................................................78
E.1 Weight Determination ..................................................................................................78
E.2. Maximum Deflection and Stress .................................................................................81
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 6
Figures
Figure 1. Team members ..........................................................................................................10
Figure 2. TerraTrike Tour II model.............................................................................................16
Figure 3. TerraTrike Rover model .............................................................................................16
Figure 4. Top End Force K handcycle .......................................................................................17
Figure 5. Gomier Rehatri Therapy Trike 16" ..............................................................................17
Figure 6. AmTryke AM-16" Therapeutic Tricycle .......................................................................18
Figure 7. Catrike 700 Recumbent Racing Trike .........................................................................19
Figure 8. Past engineering senior design stroller project ...........................................................19
Figure 9. Color schemes as designed in Adobe Color CC .........................................................22
Figure 10. Trike frame with constraints and forces applied ........................................................24
Figure 11. SolidWorks model of trike.........................................................................................27
Figure 12. Top End trike design ................................................................................................30
Figure 13. Terratrike trike design ..............................................................................................30
Figure 14. Ratcheting cable drive concept drawing ...................................................................32
Figure 15. Turning angle diagram .............................................................................................33
Figure 16. Trike design with 20" tires ........................................................................................34
Figure 17. Seat adjustability (TerraTrike model) ........................................................................36
Figure 18. Stationary seating (Utah Trikes) ...............................................................................36
Figure 19. Gear ratio options.....................................................................................................40
Figure 20. Diagram of gear design selections ...........................................................................41
Figure 21. Bike speed calculator ...............................................................................................42
Figure 22. Top End hand pedal design .....................................................................................44
Figure 23. Brake and shifter placement .....................................................................................44
Figure 24. Alternating hand pedaling.........................................................................................45
Figure 25. Standard foot pedal styles ........................................................................................46
Figure 26. Adjustable Ergonomic Knee Brace ...........................................................................47
Figure 27. Example of therapeutic bracing from Trulife .............................................................48
Figure 28. Motocross articulating knee brace, listed at $1,400 per pair .....................................48
Figure 29. Leg bracing sketch ...................................................................................................50
Figure 30. Rim, drum, and disk brake .......................................................................................53
Figure 31. Bike acceleration test results ....................................................................................55
Figure 32. Comfort scale ...........................................................................................................56
Figure 33. Overall team organization ........................................................................................61
Figure 34. Current progress of the project .................................................................................61
Figure 35. Distribution of work time ...........................................................................................62
Figure 36. Aluminum 6061-T6 frame weight ..............................................................................78
Figure 37. Chromoly 4130 alloy steel frame weight ...................................................................79
Figure 38. Al 6061-T6 Von Mises Stress Analysis .....................................................................81
Figure 39. Al 6061-T6 Displacement Analysis ...........................................................................81
Figure 40. Ti 3AL-2.5V Von Mises Stress Analysis ...................................................................82
Figure 41. Ti 3AL-2.5V Displacement Analysis..........................................................................82
Figure 42. Chromoly 4130 Steel Alloy Von Mises Analysis........................................................83
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 7
Figure 43. Chromoly 4130 Steel Alloy Displacement Analysis ...................................................83
Tables
Table 1. Metric material properties ............................................................................................20
Table 2. English material properties ..........................................................................................21
Table 3. Cost of materials for trike.............................................................................................23
Table 4. Maximum stress calculations .......................................................................................25
Table 5. Weight of trike frame based in SolidWorks ..................................................................25
Table 6. Maximum deflection calculations .................................................................................26
Table 7. Design decisions for arm length based on human measurements ...............................27
Table 8. Design decisions for leg length based on human measurements ................................28
Table 9. Design decisions for seat size based on human measurements..................................28
Table 10. Trike frame decision matrix .......................................................................................28
Table 11. Design options for the steering mechanism ...............................................................31
Table 12. Cost considerations for steering ................................................................................33
Table 13. Cost considerations for wheels ..................................................................................35
Table 14. Cost considerations for the seat ................................................................................37
Table 15. Gear ratio possibilities for a 27-speed gear system ...................................................37
Table 16. Gearing system options .............................................................................................39
Table 17. Gear system components and cost ...........................................................................43
Table 18. Design fabrication alternatives for ergonomic bracing ...............................................49
Table 19. Cost consideration for leg braces ..............................................................................50
Table 20. Advantages and disadvantages of brake options.......................................................52
Table 21. Indepth decision for the specific project .....................................................................52
Table 22. Cost comparison for brake types ...............................................................................54
Table 23. Estimated project cost ...............................................................................................58
Table 24. Excel sheet for gear considerations ...........................................................................67
Table 25. Project work breakdown schedule .............................................................................68
Table 26. Income Statement for TheraTryke .............................................................................72
Table 27. Cash Flow Statement for TheraTryke ........................................................................73
Table 28. Break Even Analysis for TheraTryke .........................................................................74
Table 29. Depreciation and Interest Calculations ......................................................................75
Table 30. Ratios and EBITDA Calculations ...............................................................................75
Table 31. Fixed Operating Costs for TheraTryke.......................................................................76
Table 32. Variable Operating Costs for TheraTryke ..................................................................76
Table 33. Variable COGS for TheraTryke .................................................................................77
Table 34. Fixed COGS for TheraTryke ......................................................................................77
Project Proposal and Feasibility Study
Team 5: TheraTryke
1.
Introduction
1.1
Calvin College Engineering Department
page 8
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 from a
previous one, implementing a project plan for the idea, 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 includes 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 five minutes.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 9
1.3.2 Speed
The trike will be able to travel at a steady speed of 10mph on flat ground, while being supplied
60W 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 25 feet while operating at 10 mph with a
250lb rider. The trike should be able to have a ten 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 Terra Trike 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.
1.3.7 Pass the Class
Pass the Senior Design class as determined by the Calvin College Office of the Registrar and
reflected in each team member's Academic Evaluation Report (AER).
1.4
Motivation
Our team has been introduced to many individuals with paralysis. This is a brutal living condition
that affects many people’s mobility. We have heard story after story from these individuals about
how they got to where they are at. A few causes that we learned about were from tragic vehicle
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 10
accidents, unfortunate shootings, and genetic characteristics. We have 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 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, our 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 our 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, David Evenhouse)
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 11
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. This past summer, Nick successfully implemented a spare
parts inventory system at Ventura Manufacturing while also gaining much more 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 plans on working after
graduation and getting a couple years of industry experience. He would love to continue to
design products that are a huge benefit to others. 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 plans to work in industry 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 wants to work in industry before earning a
M.B.A and transitioning to more of a business related career, with the goal of starting his own
company.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 12
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
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 future, he hopes to earn a PhD and to work in
industry for a number of years, thus gaining the experience necessary to better teach the next
generation of engineering students.
1.6
Client
This trike will be designed and built for Nancy Remelts. She is the wife of Glenn Remelts, who is
the Dean of the Library here at Calvin College and who originally connected us with Nancy.
Nancy is diagnosed with multiple sclerosis (MS). 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.
Nancy’s muscles respond nowhere as well as ours would, but she is fighting this disease with all
that she has got. She is in the Calvin gym every weekday morning at 7:30am 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 meeting with her
once, it was clear that she could see a benefit from the product. It is an honor to work with her
on this project and to supply her with more ammunition to aid in her perpetual battle against MS.
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 and user error. 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.
Project Proposal and Feasibility Study
Team 5: TheraTryke
2.2
page 13
Mechanical
2.2.1 Height and Weight Capacity
The vehicle will be designed to be used by riders ranging from heights of 5’ to 6’4” and weights
of 90 to 250 lbs.
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 60lbs 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
The vehicle will be made with components that will not rust under normal operating conditions
for a minimum of 5 years. 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.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 14
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 10 years of regular use.
2.2.9 Speed
The trike should be able to travel at least 10 mph while supplying 60W of energy to the hand
pedals on flat ground.
2.3
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 rollaways and facilitate easy entry.
2.3.1.1 Stopping
The vehicle traveling at 15 mph will have a stopping distance of 25 ft 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 degrees.
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.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 15
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 our neighbors 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.
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, of the money put into the project, and the satisfaction of the client. We want to
select materials that will make the vehicle last.
3. 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. One type is direct steering and the other is linkage steering, both of
which have their pros and cons. They also integrate several different gearing mechanisms
including the Nuvinci internal gearing system. Shown below 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 below 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 $3999.00 for their high end models.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 16
Figure 2. TerraTrike Tour II model
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.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 17
Figure 4. Top End Force K handcycle
http://www.invacare.com/product_files/FRCK_400.jpg
3.1.3 Rehatri Tikes by Gomier
Rehatri is a line of trikes from Gomier with a mission statement much like our own. 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
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 18
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.
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 6 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 2300 bikes annually. Prices at Catrike range from $2150.00 for their
low end models to $2950.00 for high end models. Figure 7 shows an example of a Catrike trike.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 19
Figure 7. Catrike 700 Recumbent Racing Trike
http://www.utahtrikes.com/PROD-11617573.html
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
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 20
3.3 External Resources
3.3.1 TerraTrike
The team has met with TerraTrike at their facility in Grand Rapids. The team as applied for their
sponsorship program. Whether or not that is accepted, they have still offered to be a resource
for parts needed and for knowledge of trikes.
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.
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 seriously be considered when
designing the frame. Safety and comfort are key when designing a product for therapeutic and
recreational use. Several different materials will be 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. These properties,
as well as cost and weldability, were factored into a decision matrix to determine what the final
material would be.
Table 1. Metric material properties
Material
Density
[kg/m^3]
Mod. of
Elasticity
[GPa]
205
68.9
Elongation
[%]
Hardness
[Brinell]
7850
2700
Yield
Strength
[MPa]
435
276
4130 Chromoly Steel
Aluminum 6061-T6
Titanium Alloy
3AL-2.5V
Corrosion
25.5
12
197
95
Yes?
Yes?
4480
500
100
15
256
Yes?
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 21
Table 2. English material properties
Material
Density
[lbf/ft^3]
4130 Chromoly
Steel
Aluminum 6061-T6
Titanium Alloy
3AL-2.5V
Yield
Strength
[psi]
Mod. of
Elasticity
[ksi]
Elongation
[%]
Hardness
[Brinell]
Corrosion
Resistance
490.752
63100
29700
25.5
197
Yes?
168.480
279.936
40000
72500
10000
14500
12
15
95
256
Yes?
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
pounds. 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 pounds.
This being said, the final design of the trike must not weigh more than 50 pounds 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.
Eliminating all sharp corners and edges and making the frame design as sleek and
aerodynamic as possible is vital to in the design. Additional aesthetic considerations will be
implemented as time and budget allow. Some sample color schemes are included below.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 22
Figure 9. Color schemes as designed in Adobe Color CC
https://color.adobe.com
4.1.3 Material Selection
Having the proper material for the frame is very important. Most trikes currently use standard
carbon steel, high-tensile steel, chromoly, and aluminum. In order to determine which material
to use for the frame a decision matrix will be made comparing the various materials in terms of
corrosion resistance, cost, weldability, strength, weight, and deflection.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 23
4.1.3.1 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 must be 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. Aluminum oxide is impermeable. Aluminum will automatically repair itself if
damaged. Chromoly is considered an alloy steel and not yet stainless. Chromoly is resistant
to corrosion but will not repel it. According to the Engineering ToolBox, Titanium is a very
good corrosion resistor.
4.1.3.2 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
4.1.3.3 Weldability
This trike will need quality welds. The team has been practicing welding and will be able to do
most of it. Connor’s work, Progressive Surface, will be considered as a resource for welding.
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.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 24
4.1.3.4 Strength
The strength of the trike frame was determined using finite element analysis. 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 we have set for our design which is 250lbs. 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 10 is the basic model of the trike frame showing fixed points and force
application.
Figure 10. Trike frame with constraints and forces applied
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
Table 4 are the materials given with each of their maximum Von Mises stress values.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 25
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 is 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, as seen in the table
above, that the stress on the frame for all materials has passed this test. But all materials will be
considered in the decision matrix for deciding the final material.
4.1.3.5 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 our 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 specifications with weight.
Table 5. Weight of 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
All SolidWorks material properties used and weight calculation can be found in Appendix E. The
material specified must be lightweight in order to minimize the effort required by the rider to
pedal. All materials are within reason to be considered as the final material, therefore they
will be factored into the decision matrix for the final material.
4.1.3.6 Deflection
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 26
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 English standard units of
inches and metric standard units of mm.
Table 6. Maximum deflection calculations
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, as stated earlier, must not be excessive for our goal is to build a
durable stiff trike. Each of the deflections shown for the the frame materials is quite minimal
and is actually expected when a 250 pound rider gets on the trike. Deflection will be
considered in the decision matrix for the final chosen material.
4.1.4 Design Alternatives
4.1.4.1 Frame Setup
The team has 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.
This will mean that we will use an independent steering system that steers 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. A SolidWorks
model of the trike can be seen in Figure 11. This model is a work in progress and will be
modified in later events.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 27
Figure 11. SolidWorks model of trike
4.1.4.2 Sizing and User Accommodation
Data on human measurements in Table 7, Table 8, and Table 9 was taken from a study
performed by Catherine R. Harrison and Kathleen M. Robinette. This was a study performed in
June of 2002 and consists of data taken from 2380 subjects across the United States.
Table 7. Design decisions for arm length based on human measurements
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 28
Table 8. Design decisions for leg length based on human measurements
Table 9. Design decisions for seat size based on human measurements
4.1.5 Cost Considerations
These three materials were put into a decision matrix to help us decide the best option. This can
be seen in Table 10.
Table 10. Trike frame decision matrix
After all calculations have been done and each factor of the frame material has been
weighted, the final decision for the material of the TheraTrike will be Aluminum 6061-T6.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 29
This material will be purchased, cut, welded and heat-treated. The estimated length needed
will be 7.5 feet. Adding one foot for cutting variation, the total cost for the frame material is
$70.13.
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. This makes design of the steering mechanism absolutely crucial to the
design process of any commercial vehicle or means of transportation. Without steering, the trike
would essentially become a glorified sled.
The process of steering is accomplished by a steering mechanism, which can take a variety of
different forms depending upon the application. Flaps on an airplane, the tiller on a boat, and
the tie rod linkage in cars are each examples of steering mechanisms.
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 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 Alternatives
Traditionally, steering in bikes is accomplished by turning the handle bars, thus angling the front
wheel of the vehicle. Additionally, leaning in the direction of the turn can cause the bike to
change direction while traveling at speed. Although this cannot be directly translated into trike
steering, there are some similar designs available.
The recumbent, hand powered trikes produced by Top End utilize a similar mechanism. In order
to turn, the user is required to provide a torque on their hand pedals. These pedals then act as
the “handlebars” of the trike, causing the front wheel to turn. This design can be seen in Figure
12.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 30
Figure 12. Top End trike design
TerraTrike on the other hand utilizes a linkage system. Two handles are located at seat level,
and moving these handles are what causes the trike to change direction. They also
experimented with an elevated set of handlebars, but phased out that design over time. This
design can be seen in Figure 13.
Figure 13. Terratrike trike design
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 31
Additionally, the team needed to consider the possibility of having the steering of the trike be
independent of the drive system. This possibility arose in response to a concern over the
amount of torque that would be put on the drive chains using standard steering methods. Table
11 demonstrates the various design options that were considered to accompany a chain drive
system.
Table 11. Design options for the steering mechanism
At present, the team has decided to design around an independent linkage steering system.
This will prevent torque on the chains while allowing for sensitive steering and easier entry into
the vehicle. The key disadvantage of this approach is that the user will have to move their arms
a considerable distance 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 while turning. Additional considerations include maintaining a forward direction
of movement while on a slight slope, and routing braking to both the steering and the pedaling
grips.
Another alternative would be to explore the possibility of a drive system that does not depend on
gears and sprockets. To this end, the team has been exploring design options for a ratcheting
cable-drive pedaling system. This would enable the user to steer using the hand pedals without
endangering the drive train. The concept is still in its preliminary design phase. However, the
team will be further exploring this option in order to ascertain in this is a viable design
alternative. This design can be seen in Figure 14.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 32
Figure 14. Ratcheting cable drive concept drawing
4.2.4 Turning Circle Calculations
“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 radial 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 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 15.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 33
Figure 15. Turning angle diagram
Equation 1 is used in order to calculate the turning circle of a vehicle:
𝑊𝑇
𝑊𝐵
) + (sin(𝐴𝑇𝐴))
2
𝑇𝑢𝑟𝑛𝑖𝑛𝑔 𝐶𝑖𝑟𝑐𝑙𝑒 = (
(1)
By designing around a desired Turning Circle of 10 to 13 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 degrees at maximum.
4.2.5 Cost Considerations
Table 12. Cost considerations for steering
Component
Cost
Source
Catrike tie rod assembly
$75 x 2
http://www.utahtrikes.com
Various hardware components
$30
http://www.utahtrikes.com
Serfas Connector Grips (Black)
$15
http://www.amain.com/
Total: $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 the decision of the wheel selection an important part of the design
process.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 34
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 using in a variety of weather
conditions.
4.3.3 Design Alternatives
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
because of the size and weight, they don’t hold their speed as well. 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 16
shown below is an example of a sport edition trike with three 20” tires.
Figure 16. Trike design with 20" tires
http://www.prc68.com/I/Images/SunEZ-3USXHDTrike68611w.jpg
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 35
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.
4.3.4 Cost Considerations
Table 13. Cost considerations for wheels
Component
Cost
Source
SUN MACH 4 MACH IV REAR BIKE
WHEEL 26"
$70
ebay.com
Tailor-Made 20" 406 Front & Rear
Wheelset LitePro K Fun Disc Brake
32/32 Spokes
$189
ebay.com
Total: $259
4.4 Seat
4.4.1 Research
The team as investigated several different types of seating options. There is padded seating,
mesh seating, fixed seating, and adjustable seating. The options the team are considering can
be seen in the Requirements section.
4.4.2 Requirements
The seating of the trike must satisfy two requirements including adjustability and comfort.
4.4.2.1 Adjustability
Adjustability is important because the trike being designed is intended for a range of heights in
users. The boom on the frame cannot correct for much of the change in height because it will
cause a lot of slop in the gear chain system. In order to compensate for this variance elsewhere,
the seat must be adjustable. The seat will be able to move along the main base of the frame into
variable pinned positions. The seat will also have adjustability in the angle of the backrest.
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 riders back. Comfortable and light materials are preferred.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 36
4.4.3 Design Alternatives
Figure 17 shows an adjustable design option, while Figure 18 shows a fixed option.
Figure 17. Seat adjustability (TerraTrike model)
www.terratrike.com
Figure 18. Stationary seating (Utah Trikes)
www.utahtrikes.com
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 37
4.4.4 Cost Considerations
To manufacture the seat, the team can considers building the seat. The team found a website
with instructions in doing this.
Purchasing considerations can be seen in Table 14.
Table 14. Cost considerations for the seat
Component
Cost
Source
KMX Bucket Seat (Steel)
$50
utahtrikes.com
Hardware
$12
utahtrikes.com
Total: $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 15, 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 15. 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
is the fastest and most difficult pedaling option. This is represented in red in Table 15. The gear
ratios represent how many rotations the wheel will to with one cycle of the pedals.
Table 15. Gear ratio possibilities for a 27-speed gear system
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 38
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, but it will not be guaranteed that solely foot pedaling is enough
for a comfortable ride.
4.5.3 Design Alternatives
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 of 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 all 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 legroom to work with for the leg supports.
Table 16 shows different options for gearing systems. Each option has a specific bonus for
specific connections between the hands, feet, and wheels.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 39
Table 16. 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. The uniform pedaling option is the final
design decision. Because of power distribution calculations done later in this section, the ratio is
reduced to 1/4 so that less energy is necessary to rotate the legs.
A centralized gear set will be used to connect the hands, feet, and back wheel. For the
connection between the hands and feet to the wheels, four total options are 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 a Nuvinci internal pulley system by Fallbrook Technologies. This option allows for
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 40
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. The fourth
option would be similar to the second; it will only have one shifter controlling the Nuvinci system.
The equivalent gear teeth for the Nuvinci shifter is a 10 tooth minimum and a 36 tooth
maximum. Figure 19 shows many different ratio options for all four of these considerations.
Values for this graph can be found in the Appendix. The y-axis varies the size of the gear in the
central gear hub that connects to the back wheel. A minimum low gearing needs to be less than
a regular bike because of the added resistance from the legs. A large range is desirable to
move faster. Equation 2 is used to find a revolution ratio between the back wheel and the
hands.
𝑅𝑒𝑣𝑤ℎ𝑒𝑒𝑙
𝑅𝑒𝑣ℎ𝑎𝑛𝑑𝑠
𝑁ℎ𝑎𝑛𝑑.𝑝𝑒𝑑𝑎𝑙𝑠
= (𝑁
𝑐𝑒𝑛𝑡𝑒𝑟.𝑡𝑜.ℎ𝑎𝑛𝑑𝑠
𝑁𝑐𝑒𝑛𝑡𝑒𝑟.𝑡𝑜.𝑤ℎ𝑒𝑒𝑙
)
𝑁𝑤ℎ𝑒𝑒𝑙
)(
(2)
Figure 19. Gear ratio options
Figure 20 shows a diagram of the design selected. The gear teeth can be seen in this figure and
the range of hand-to-wheel rotations can also be seen in the figure.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 41
Figure 20. Diagram of gear design selections
The calculations done were based off of conservation of power. So the power needed from the
legs and wheels has to equal the power coming from the hands. Equations 3, 4, and 5 were
considered in the power distribution. The size of the gears also needed to be considered. Ratios
between diameter and number of teeth were used to find separate gear sizing.
𝑃 = 𝑇𝝎
(3)
𝑇 = 𝐹𝑟
(4)
𝐹 = 𝑚𝑎
(5)
Figure 21 shows speeds of a bike at a fixed power input. While using the gym at Calvin, an
average wattage value for the hand pedaled stationary bike at a resistance allowing for 60 rpm
is 60W. This value is found from a team member using the stationary bike. The figure says that
someone would be able to travel at about 12 mph. So travel at this speed, the wheel needs 60W
of power. The legs will be rotating at about 30 rpm (this value will be a little higher because the
hands will have to pedal faster to compensate for the added leg resistance. Assuming that one
leg is 20% the weight of a 160 lb person, 32 lb need to be brought up. Assuming the pedal arm
is 6 in from the axis, 192 in-lb of torque will be resisting rotation. At 30 rpm (π radians/sec),
using Equation 2 and converting to watts, the legs will need 68W. Because this means that
more than half of the energy will be going to the legs, the ratio of 1/2 was reduced to 1/4. This
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 42
will mean that a little more than 1/3 of the energy from the hands will be going to the legs. The
team expects the top speed of the trike to be close to 8 mph.
Figure 21. Bike speed calculator
www.bikecalculator.com
4.5.4 Cost Considerations
Table 17 shows the components needed, and their costs for the gear system. Availability of
some of the parts still need to be assessed. Some of the sprockets may need to be custom
made.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 43
Table 17. Gear system components and cost
Component
Cost
Source
Nuvinci system
$399
Buy from Terratrike
(3) 20 tooth sprocket
3 x $30
Price from Alger Bikes
80 tooth sprocket
SRAM X0 2x10 Low Direct
Mount Front Derailleur
Still Need to check Avalability
$35
3 cassette stack (12, 24, 36)
(3) Bike chains
http://www.competitivecyclist.com/
Still Need to check Avalability
3 x $16
Price from Alger Bikes
Total Cost: more than $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 degrees from
horizontal. The rotating handles are made of aluminum and keep the hands slightly off of a
vertical position. This position allows for the least amount of exertion. A user of the Top end trike
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 shifter and hand brake on the right hand grip.
4.6.3 Design Alternatives
One alternative would be to do something very similar to Top End’s design. Their design can be
seen in Figure 22 and Figure 23.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 44
Figure 22. Top End hand pedal design
Figure 23. Brake and shifter placement
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 45
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 Nuvinci shifter is a dial, so
that will need to 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 24.
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. Most of the target customer will not be able to do that
because they will not have any strength in their abdomen.
Figure 24. Alternating hand pedaling
http://www.bikecare.co.uk/special-needs-tricycles.html
4.6.4 Cost Considerations
These pedal arms can be fabricated in the engineering shop. Progressive Surfaces may be able
to help us make these as well.
4.7 Foot Pedals
4.7.1 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
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 46
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 25.
Figure 25. Standard foot pedal styles
www.nashbar.com
www.performancebike.com
www.aurora-collective.com
4.7.2 Requirements
The requirements for the pedals in the 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.
4.7.3 Design Alternatives
The stability and hold that the application requires could be accomplished through any number
of strapping or bracing options, many of which will be eliminated during design iterations.
However, one major design decision discussed was whether to utilize an adjustable boot, or a
series of straps.
The adjustable boot would be similar to a ski boot in nature, but with more adjustability and ease
of use. The principle advantage of this option would be that the team could carefully control the
range of motion of the foot. Additionally, there would be absolutely no chance of the foot moving
or sliding during use.
A series of straps could also be used, and would allow for greater range and ease of
adjustability for the user. A heel strap, combined with straps at the ankle and mid-foot, could
provide for a hold that rivals the boot in solidity. Additionally, it would be much easier for the
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 47
user to get into, and more comfortable during long rides. However, it would most likely prove
more difficult to integrate with the leg braces.
The team has decided to go with the strapping option. Despite the lower degree of control, the
team believes that this design will be more user friendly.
4.7.4 Cost Considerations
The pedals will most likely have to be either fully fabricated in shop, or adapted from an existing
set of pedals. The assumption now is that the team will be able to use pedals from used bikes.
4.8 Leg Brace and Support
4.8.1 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 26.
Figure 26. 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 our application. 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 our application are generally fairly large, intrusive, and
difficult to put on. Specifics on these braces can be seen in Figure 27.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 48
Figure 27. 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
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 28.
Figure 28. Motocross articulating knee brace, listed at $1,400 per pair
http://evs-sports.com/index.php/moto/knee-braces/axis-series/axis-pro.html
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 49
4.8.2 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 our bracing solution. Originally, it was
assumed that we 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 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 18.
Table 18. Design fabrication alternatives for ergonomic bracing
At the moment, the team is 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 team is currently looking at a bracing design that is integrated with the foot pedals, and
allows for the braces to be loaded from above. This means that the user will simply be able to lift
their legs and place them directly into the braces. The legs will then be strapped into place, and
the brace will guide the limb throughout its full range of motion. One point of adjustability will be
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 50
designed into the brace, allowing for differing leg lengths. Brainstorming considerations can be
seen in Figure 29.
Figure 29. Leg bracing sketch
4.8.4 Cost Considerations
Table 19 shows an estimate of the cost of leg braces based off of research.
Table 19. Cost consideration for leg braces
Components
Leg braces
Cost
$100
Total: $100
Source
Educated guess
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 51
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 disk
brakes on the front two tires. In addition to active brakes, parking brakes had to be researched.
Many disk 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.
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 15 mph while carrying a load of 90 to
250 lb. The required stopping distance for this application will be 25 ft.
4.9.3 Design Alternatives
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. For this hand braking mechanism, a brake handle will
be mounted to both the hand crank as well as the steering handles. These brakes will require
pressure from the operator to provide adequate power to stop the wheels. In addition to having
a 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
4.15 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 20 while a more in-depth
decision matrix showing how the team got to the final design is shown in Table 21.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 52
Table 20. 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
Table 21. Indepth 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. Disk brakes work by pressing two pads against a metal
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 53
disk that is attached to the axle of the wheel.
representation of the different brake options.
Shown below in Figure 30 is a visual
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 disk 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 disk brakes outweighed the benefits of the other systems. It was also
determined that the disk 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.
Figure 30. Rim, drum, and disk brake
http://img.hisupplier.com
http://www.amazon.com
http://www.mountainbikestoday.com
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 54
4.9.4 Cost Considerations
Table 22 shows multiple price considerations for brake systems.
Table 22. Cost comparison for brake types
Total Cost of two Hayes Prime Dyno Comp Disc Brakes: $160
5. Testing
5.1 Ease of Use
5.1.1 Timing transfer and positioning on trike
The team will take turns to transfer from a wheelchair to the trike, strap themselves into the
seat, position limp legs correctly, and strap them in. A time study will be done on this process to
get each components time. The full transfer time should be less than five minutes.
5.2 Safety
The team will do stopping distance tests for breaking. The stopping distance is the length
traveled from when a user decides to stop to when he/she actually stops, so reflexes play a
part. A signal will be given to the rider to stop. The distance from where the trike was at that
signal to the stopped position will be measured. These tests will be done at top speed, which
the team will either measure or estimate. The goal of the stopping distance is to be less than 25
feet.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 55
5.3 Speed
5.3.1 Time top speed on trike on level ground
Each team member will take a turn at traveling a short, measured distance. The rider will be at
top speed for the entirety of the length. The time to get through the length will be recorded and
calculations will be done to find the mph value. This will be done on level ground. The target
stop speed is 10 mph.
5.3.2 Acceleration of trike from standstill
Each team member will take a turn at traveling a short, measured distance. The user will start at
a stopped position. The user will be able to use the gears however they feel fit. According to a
report by Figliozzi, Wheeler, and Monsere, the average acceleration of a bike is 5.5 ft/s 2 on flat
ground. Figure 31. Using the calculation that about 2/3 of the energy from the hands will be
going to the wheel, the team expects an acceleration value of 3.6 ft/s2. The team will record the
time to complete the length and calculate the acceleration.
Figure 31. Bike acceleration test results
http://www.its.pdx.edu/upload_docs/1368048473.pdf
5.4 Therapeutic Benefits
5.4.1 Comfort
Having a 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, to ensure that the ride is enjoyable, as that is one goal of the project. Since you can't
measure comport using numeric tests, the team has designed a simple test that will better
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 56
quantify the level of comfort of riders. Riders will be subject to a 30 minute test ride in the trike.
At the start of the ride, and at 5 minute intervals throughout the entire ride, the subjects will be
shown Figure 32, and asked the question, “How are you feeling based in comparison these
pictures?”. The subjects will be instructed to answer these questions based off of feeling in their
arms, legs, back and bottom. This will ensure that the seat, leg bracing and hand pedals are
comfortable for any user.
Figure 32. Comfort scale
http://www.hospiceworld.org/book/images/happy-faces.gif
5.4.2 Avoiding spasms
To test the therapeutic benefits of the leg cycling aspect of this trike, the team will have some of
the paraplegics that we have been in contact use the trike. The team will need to make sure that
the trike is safe for use before conducting this test. 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.
5.5 Outdoor usage
The team will record each other going over various types of terrains. These terrains include
going up a sloped road, going down a sloped road, traveling along a banked road, riding on a
rainy day, riding through flat grass, and riding through hilly grass. Unique riding conditions from
each terrain will be recorded and improvements will be considered.
5.6 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 be complete. 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
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 57
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.
5.7 Pass the Class
The Calvin College Engineering Department has high academic standards, as does all Calvin
departments. Because of these high standards, a passing grade in all engineering classes is a
C. To fulfill the goal of passing the class, students will use their official transcript as a
measuring device.
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
Indepth analysis shown in Section 3
6.1.1.2 Top End Trikes
Indepth analysis shown in Section 3
6.1.1.3 Rehatri
Indepth analysis shown in Section 3
6.1.1.4 Amtryke
Indepth analysis shown in Section 3
6.1.1.5 Catrike
Indepth analysis shown in Section 3
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 58
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.
6.2 Financials
6.2.1 Budget
Since the team is actually developing the product throughout the entire year, the budget has the
potential to change. The budget shown below in Table 23 also reflects numbers for only one
production unit. For actual production applications, the budget is expected to decrease.
Table 23. 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 cost of producing one unit for the final product, it doesn’t
account for the fact that the team plans to develop multiple prototypes for testing purposes.
These prototypes should have a relatively small cost considering the fact that many components
will be 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 will be used. Because of this, the developmental costs were not considered in the
final budget.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 59
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. These values stand to
change as the team is in the process of determining alternate sources for the parts.
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.
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.
6.2.2.2 Exterior Sources
The team is currently looking into exterior funding opportunities. The team is in consideration
for the Eric DeGroot Engineering Fund Scholarship. This fund has the potential to be worth up
to $1,000 which would be a great help in the project. The team has also submitted proposals
for two other grants. The first is from Western Michigan University. It is a grant from the
Sammons Center for Innovation and Research in Occupation Based Technology. The team
also submitted a proposal to TerraTrike for their semi-annual sponsorship.
6.2.3 Potential Profits
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 five 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.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 60
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
member has certain visions in mind about what the overall design will look like. At the
beginning of the semester, 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 the 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 semester. 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 can be seen below in Figure 33. Because of all the
relationships between each part of the project, there will have to be clear communication
between the team members. Each team member should have a good understanding of the
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 61
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.
Figure 33. Overall team organization
7.3 Scheduling and Milestones
In Figure 34, it shows the progress of the project currently. Figure 35 shows time distribution
between parts of the project. A detailed WBS can be found in Appendix B.
250
Total Hours
200
150
Total
Nick
Connor
100
Jack
David
50
0
8/29/2014 9/13/2014 9/28/2014 10/13/2014 10/28/2014 11/12/2014 11/27/2014 12/12/2014
Date
Figure 34. Current progress of the project
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 62
90
80
70
Total Hours
60
50
40
30
20
10
0
Figure 35. Distribution of work time
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:
Calvin College
Calvin College provides the team with many different resources including workspace and
materials along with providing a generous portion of the budget.
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.
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 Ermer
Professor Ermer provides the team with great information regarding the development of the
gear system.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 63
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.
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.
TerraTrike
TerraTrike provide the team with great information regarding all aspects of trike design. This
included braking, steering, and frame design.
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.
Pierre Vos-Camy
Pierre, a paraplegic, shares his thoughts on what would make our 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.
Jeff Yonker
Jeff, a paraplegic and user of a hand powered recumbent trike, provids the team with advice
regarding the design and use of the trike.
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.
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.
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.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 64
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/
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 65
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
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 66
10. Conclusion
The team believes that this project is feasible. It will be possible to make this trike with
recreational and therapeutic purposes. The team believes that it will be popular because of its
uniqueness. One thing that the team is concerned about is the budget. One other thing that the
team didn’t foresee at the beginning was the difficulty to incorporate steering with the gearing
system. The team is also concerned about factors that will keep the trike from moving fast.
Some of these factors include weight and the gearings system.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 67
11. Appendices
A. Excel sheet on gears
Table 24. Excel sheet for gear considerations
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 68
B. Work Breakdown Schedule
Table 25. Project work breakdown schedule
Task Name
TheraTryke
Duration
Estimated
Start
Estimated
Finish
180 days
Mon 9/8/14
Fri 5/15/15
180 days
Mon 9/8/14
Fri 5/15/15
Project Definition and Client
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
95 days
Fri 11/28/14
Thu 4/9/15
27 days
Thu 4/9/15
Fri 5/15/15
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
Banquet Night
10 days
Mon 4/27/15 Fri 5/8/15
39 days
Wed 10/15/14 Mon 12/8/14
Introduction
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
Team Members
1 day?
Tue 10/14/14 Tue 10/14/14
Client
7 days
Tue 10/14/14 Wed 10/22/14
Project Requirements
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
12 days
Tue 10/28/14 Wed 11/12/14
Seating
12 days
Tue 10/28/14 Wed 11/12/14
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
Safety Requirements
16 days
Wed 10/22/14 Wed 11/12/14
Braking
16 days
Wed 10/22/14 Wed 11/12/14
Milestones
Choice
Finishing Complete
Presentations
PPFS
Material Properties
Mon 10/13/14
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 69
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
Design Norms
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
Steering 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
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
Website Creation
45 days
Thu 10/2/14
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
Donations
30 days
Thu 10/23/14 Wed 12/3/14
Remelts (up to $300)
30 days
Thu 10/23/14 Wed 12/3/14
Partnerships
30 days
Thu 10/23/14 Wed 12/3/14
TerraTrike
30 days
Thu 10/23/14 Wed 12/3/14
Grants
30 days
Thu 10/23/14 Wed 12/3/14
Summons Center
30 days
Thu 10/23/14 Wed 12/3/14
120 days
Thu 10/23/14 Wed 4/8/15
Structure and Drive
120 days
Thu 10/23/14 Wed 4/8/15
Frame
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
Fri 12/19/14
Gear Train System
Mechanical Characteristics
10 days
Wed 12/3/14
Thu 1/1/15
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 70
Decisions
Attachment and Mounting
20 days
Fri 1/2/15
Thu 1/29/15
Frame Prototype
20 days
Thu 2/12/15
Wed 3/11/15
Wheels
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
Seat
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
Gears
110 days
Thu 10/23/14 Wed 3/25/15
Research Regular Bikes
25 days
Thu 10/23/14 Wed 11/26/14
Gear Ratio 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
30 days
Thu 1/29/15
Wed 3/11/15
Braking
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
Trike Functionality
70 days
Thu 1/15/15
Wed 4/22/15
Weight
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
25 days
Thu 3/5/15
Wed 4/8/15
Smoothness
30 days
Thu 3/5/15
Wed 4/15/15
Wheels In-Line
10 days
Thu 3/5/15
Wed 3/18/15
Gear Changing
20 days
Thu 3/5/15
Wed 4/1/15
Ease of Ride
30 days
Thu 3/5/15
Wed 4/15/15
Transfer
20 days
Thu 3/5/15
Wed 4/1/15
Human Functionality
50 days
Fri 1/30/15
Thu 4/9/15
Limb Interference
20 days
Fri 1/30/15
Thu 2/26/15
Joint Flexion
30 days
Fri 2/27/15
Thu 4/9/15
Comfort
20 days
Fri 2/27/15
Thu 3/26/15
Business Plan
20 days
Mon 11/10/14 Fri 12/5/14
Marketing Strategy
2 days
Mon 11/10/14 Tue 11/11/14
Business Strategy
4 days
Wed 11/12/14 Mon 11/17/14
Competitor Analysis
4 days
Tue 11/18/14 Fri 11/21/14
Control
Testing
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 71
Finances
3 days
Mon 11/24/14 Wed 11/26/14
Investments
3 days
Thu 11/27/14 Mon 12/1/14
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. We could put 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.
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 72
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
stowed in the garage in a similar manner to which it was removed. Assistance may be
necessary for stowing away the trike.
D. Business Analysis Calculations
Table 26. 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
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
Year 3
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
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 73
Table 27. 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
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 74
Table 28. 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
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 75
Table 29. 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 30. 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
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 76
Table 31. Fixed Operating Costs for TheraTryke
Fixed Operating Costs
Building
Advertising
General and administrative
salaries
Selling
Total
250000
100000
150000
100000
600000
Table 32. 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
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 77
Table 33. 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 34. Fixed COGS for TheraTryke
Fixed Costs of Good Sold
Manufacturing Facilities
Manufacturing management
salaries
Benefits
Rent
15000
100000
100000
75000
290000
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 78
E. Frame Design Analysis
E.1 Weight Determination
Figure 36. Aluminum 6061-T6 frame weight
SolidWorks
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 79
Figure 37. Chromoly 4130 alloy steel frame weight
SolidWorks
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 80
SolidWorks
Figure E.3 Titanium alloy 3AL-2.5V frame weight
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 81
E.2. Maximum Deflection and Stress
Figure 38. Al 6061-T6 Von Mises Stress Analysis
Figure 39. Al 6061-T6 Displacement Analysis
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 82
Figure 40. Ti 3AL-2.5V Von Mises Stress Analysis
Figure 41. Ti 3AL-2.5V Displacement Analysis
Project Proposal and Feasibility Study
Team 5: TheraTryke
page 83
Figure 42. Chromoly 4130 Steel Alloy Von Mises Analysis
Figure 43. Chromoly 4130 Steel Alloy Displacement Analysis