TheraTryke - Calvin · PDF fileTheraTryke Project Proposal and Feasibility Study Calvin...

TheraTryke

Project Proposal and Feasibility Study

Calvin College Engineering

Team 5

David Evenhouse

Jack Kregel

Nick Memmelaar

Connor VanDongen

Advisor

Professor David Wunder


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

1.4 Motivation .................................................................................................................... 9

1.5 Group Members ..........................................................................................................10

1.6 Client ..........................................................................................................................12

2. 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



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


4.2.4 Turning Circle Calculations .......................................................................................32


4.3 Wheels ............................................................................................................................33

4.3.1 Research ..................................................................................................................33

4.3.2 Requirements ............................................................................................................34



4.4 Seat .................................................................................................................................35

4.4.1 Research ..................................................................................................................35



4.4.2 Requirements ............................................................................................................35



4.5 Gear and Chain System ..................................................................................................37

4.5.1 Research ..................................................................................................................37

4.5.2 Requirements ............................................................................................................38



4.6 Hand Pedals ....................................................................................................................43

4.6.1 Research ..................................................................................................................43

4.6.2 Requirements ............................................................................................................43



4.7 Foot Pedals .....................................................................................................................45

4.7.1 Research ..................................................................................................................45

4.7.2 Requirements ............................................................................................................46



4.8 Leg Brace and Support ....................................................................................................47

4.8.1 Research ..................................................................................................................47

4.8.2 Requirements ............................................................................................................49



4.9 Brakes .............................................................................................................................51

4.9.1 Research ..................................................................................................................51

4.9.2 Requirements ............................................................................................................51



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



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



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



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



1. Introduction

1.1 Calvin College Engineering Department

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.



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



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)



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 closed-

loop 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.

http://www.progressivesurface.com/shotpeening.php

http://www.progressivesurface.com/gritblasting.php



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.



2.2 Mechanical

2.2.1 Height and Weight Capacity

The vehicle will be designed to be used by riders ranging from heights of 5’ to 6’4” 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.



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.



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.



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.



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



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.



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



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]

Yield Strength [MPa]

Mod. of Elasticity [GPa]

Elongation [%]

Hardness [Brinell]

Corrosion

4130 Chromoly Steel 7850 435 205 25.5 197 Yes? Aluminum 6061-T6 2700 276 68.9 12

95 Yes?

Titanium Alloy 3AL-2.5V

4480 500 100 15 256 Yes?



Table 2. English material properties

Material Density [lbf/ft^3]

Yield Strength [psi]

Mod. of Elasticity [ksi]

Elongation [%]

Hardness [Brinell]

Corrosion Resistance

4130 Chromoly Steel

490.752 63100 29700 25.5 197 Yes?

Aluminum 6061-T6 168.480 40000 10000 12 95 Yes? Titanium Alloy 3AL-2.5V

279.936 72500 14500 15 256 Yes?

4.1.2 Requirements

4.1.2.1 Strength

The frame material and design must be strong enough in order to withstand a weight of 250

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.



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.



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.



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.



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 Weight [lbf] Weight [N]

Aluminum 6061-T6 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



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.



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



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.



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.


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.



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



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.



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.



Figure 15. Turning angle diagram

Equation 1 is used in order to calculate the turning circle of a vehicle:

𝑇𝑢𝑟𝑛𝑖𝑛𝑔 𝐶𝑖𝑟𝑐𝑙𝑒 = (𝑊𝑇

2) + (

𝑊𝐵

sin(𝐴𝑇𝐴)) (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.


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.



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.


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

http://www.prc68.com/I/Images/SunEZ-3USXHDTrike68611w.jpg



Another design would consist of using two different sized wheels. This would consist of having

two 20” tires in front and one 26” tire in back. There are many different benefits for using this

design. The large wheel in the back gives the trike more of an upright bicycle type road feel. In

addition to the improved feel, the larger tire allows for the tire to hold its speed better, and

remain stable while maneuvering over obstacles.


Table 13. Cost considerations for wheels


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.




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




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


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



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.


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.



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



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

𝑁𝑐𝑒𝑛𝑡𝑒𝑟.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.



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



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


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.



Table 17. Gear system components and cost


Nuvinci system $399 Buy from Terratrike

(3) 20 tooth sprocket 3 x $30 Price from Alger Bikes

80 tooth sprocket Still Need to check Avalability

SRAM X0 2x10 Low Direct Mount Front Derailleur

$35 http://www.competitivecyclist.com/

3 cassette stack (12, 24, 36) Still Need to check Avalability

(3) Bike chains 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.


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.



Figure 22. Top End hand pedal design

Figure 23. Brake and shifter placement



The arms of the hand pedals will need to be shortened slightly, and the hand pedals will need to

be raised so that there is enough clearance for the legs to cycle. The 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


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



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.


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

http://www.nashbar.com/

http://www.performancebike.com/

http://www.aurora-collective.com/



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.


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.



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



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.


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



designed into the brace, allowing for differing leg lengths. Brainstorming considerations can be

seen in Figure 29.

Figure 29. Leg bracing sketch


Table 19 shows an estimate of the cost of leg braces based off of research.

Table 19. Cost consideration for leg braces

Components Cost Source

Leg braces $100 Educated guess

Total: $100



4.9 Brakes

4.9.1 Research

For recumbent trikes, there are several types of brakes currently used by market companies.

The type of brake depends on the main purpose of the trike, and the goal of the company

developing the specific trike. For a lower level vehicle, with the main purpose being leisure

activities, the common brake type is a simple rim brake. They are sold at a low cost and allow

for easy, hassle free operation. For higher level trikes, disk brakes are common. They allow for

better stopping power which will allow for higher speed operations and they also perform better

on rugged terrain. Another type often used on recumbent trikes is a drum brake. Drum brakes

are most commonly used in applications where variable weather will occur and require very low

maintenance. In addition to brake types, common locations of brake placement had to be

researched. Many recumbent trike applications employ the brakes on the front wheels while

others employ the brakes on the rear wheels. The most popular trike in industry employs 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: user-

controlled 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.


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.



Table 20. Advantages and disadvantages of brake options

Brake Type Advantages Disadvantages

Rim Brake ● Lightweight ● Low cost ● Simple Operation

● 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



disk that is attached to the axle of the wheel. Shown below in Figure 30 is a visual

representation of the different brake options.

For the final design, disk brakes operated by a hand brake controller were chosen. This was

because of several different benefits. Many benefits surround the 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

http://img.hisupplier.com/

http://www.amazon.com/

http://www.mountainbikestoday.com/




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.



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/s2 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



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



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


6.1.1.3 Rehatri


6.1.1.4 Amtryke


6.1.1.5 Catrike




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.



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.



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



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.

Figure 34. Current progress of the project

0

50

100

150

200

250

8/29/2014 9/13/2014 9/28/2014 10/13/2014 10/28/2014 11/12/2014 11/27/2014 12/12/2014

Tota

l Ho

urs

Date

Total

Nick

Connor

Jack

David



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.

0

10

20

30

40

50

60

70

80

90

Tota

l Ho

urs



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.



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/disc-

brakes.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.restorative-

therapies.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.arc-

zone.com/blog/joewelder/2009/01/08/metal-of-the-month-chromoly/

Welding of titanium and its alloys. (n.d.). Retrieved from TWI: http://www.twi-

global.com/technical-knowledge/job-knowledge/welding-of-titanium-and-its-alloys-part-1-

109/



What is the practical advantage of disk brakes over rim brakes? (n.d.). Retrieved from

StackExchange: http://bicycles.stackexchange.com/questions/3855/what-is-the-

practical-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



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.



11. Appendices

A. Excel sheet on gears

Table 24. Excel sheet for gear considerations



B. Work Breakdown Schedule

Table 25. Project work breakdown schedule

Task Name Duration Estimated

Start

Estimated

Finish

TheraTryke 180 days Mon 9/8/14 Fri 5/15/15

Milestones 180 days Mon 9/8/14 Fri 5/15/15

Project Definition and Client

Choice

39 days Mon 9/8/14 Thu 10/30/14

Planning Complete 60 days Mon 9/8/14 Fri 11/28/14

Research Complete 67 days Tue 9/30/14 Wed 12/31/14

Prototyping Complete 95 days Fri 11/28/14 Thu 4/9/15

Finishing Complete 27 days Thu 4/9/15 Fri 5/15/15

Presentations 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

PPFS 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 Mon 10/13/14

Team Members 1 day? Tue 10/14/14 Tue 10/14/14

Client 7 days Tue 10/14/14 Wed 10/22/14

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

Material Properties 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



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

Gear Train System 12 days Mon 11/10/14 Tue 11/25/14

Ergonomics 12 days Mon 11/10/14 Tue 11/25/14

Braking 12 days Mon 11/10/14 Tue 11/25/14

Wheels 12 days Mon 11/10/14 Tue 11/25/14

Financials 35 days Wed 10/15/14 Tue 12/2/14

Website Creation 45 days Thu 10/2/14 Wed 12/3/14

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

Mechanical Characteristics 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 10 days Fri 12/19/14 Thu 1/1/15



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

Control

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

Testing 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



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.



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 Year 2 Year 3

Sales revenue 3,000,000 3,500,000 3,500,000 4,000,000

Variable Cost of Goods Sold 861,200 991,440 1,164,300

Fixed Cost of Goods Sold 290,000 290,000 290,000

Depreciation 20,000 32,000 19,200

Gross Margin 1,828,800 2,186,560 2,526,500

Variable Operating Costs 450,000 525,000 600,000

Fixed Operating Costs 600,000 600,000 600,000

Operating Income 778,800 1,061,560 1,326,500

Interest Expense 75,000 135,000 98,250

Income Before Tax 703,800 926,560 1,228,250

Income tax (40%) 281,520 370,624 491,300

Net Income After Tax 422,280 555,936 736,950



Table 27. Cash Flow Statement for TheraTryke

TheraTryke

Pro-Forma Statement of Cash Flows


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



Table 28. Break Even Analysis for TheraTryke

TheraTryke

Break - Even Analysis


Sales revenue 3,000,000

3,500,000

4,000,000

Less: Variable Costs:

Variable Cost of Goods Sold

861,200

991,440

1,164,300

Variable Operating Costs

450,000

525,000

600,000

Total Variable Costs

1,311,200

1,516,440

1,764,300

Contribution Margin 1,688,800

1,983,560

2,235,700

Less: Fixed Costs

Fixed Cost of Goods Sold

290,000

290,000

290,000

Fixed Operating Costs

600,000

600,000

600,000

Depreciation 20,000

32,000

19,200

Interest Expense 75,000

135,000

98,250

Total Fixed Costs

985,000

1,057,000

1,007,450

Income Before Tax 703,800

926,560

1,228,250


Total Fixed Costs 985,000

1,057,000

1,007,450

Contribution Margin % 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



Table 29. Depreciation and Interest Calculations

Equipment Depreciation

Purchases Year 1 Year 2 Year 3

Equipment Purchases Year 1 100,000

20,000

32,000

19,200

Equipment Purchases Year 2 -

-

-

Equipment Purchases Year 3 -

-

20,000

32,000

19,200

MACRS Rates (5-year recovery period) 0.2 0.32 0.192

Interest Expense:

Annual interest rate on debt 10%


Average debt balance 750,000

1,350,000

982,500

Interest expense 75,000

135,000

98,250

Table 30. Ratios and EBITDA Calculations

Ratios

Profit Margin % 0.14076 0.158838857 0.1842375

Gross Margin % 0.62 0.63 0.64

Contribution Margin % 56% 57% 56%

Debt to Equity Ratio 1.875 3.375 2.45625

EBITDA 798,800 1,093,560 1,345,700

4X EBITDA 5,382,800

4X EBITDA AFTER TAXES 3,229,680.0



Table 31. Fixed Operating Costs for TheraTryke

Fixed Operating Costs

Building 250000

Advertising 100000

General and administrative salaries 150000

Selling 100000

Total 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


525,000.00

Year 3

Sales comissions

200,000.00


600,000.00


Units Sold 3,000 3,500

4,000



Table 33. Variable COGS for TheraTryke

Variable Cost of Goods Sold


Direct Materials 800,000

920,000

1,077,500

Direct Labor $51,200 $61,440 $76,800

Variable manufacturing overhead 10000 10000 10000

861200 991440 1164300

Leg Bracing 100000 115000 137500

Frame Material 150000 172500 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


Wage $10 12 15

People 2 2 2

hour/day 8 8 8

day/year 320 320 320

$51,200 $61,440 $76,800

Table 34. Fixed COGS for TheraTryke

Fixed Costs of Good Sold

Manufacturing Facilities 15000

Manufacturing management salaries 100000

Benefits 100000

Rent 75000

290000



E. Frame Design Analysis

E.1 Weight Determination

Figure 36. Aluminum 6061-T6 frame weight

SolidWorks



Figure 37. Chromoly 4130 alloy steel frame weight

SolidWorks



SolidWorks

Figure E.3 Titanium alloy 3AL-2.5V frame weight



E.2. Maximum Deflection and Stress

Figure 38. Al 6061-T6 Von Mises Stress Analysis

Figure 39. Al 6061-T6 Displacement Analysis



Figure 40. Ti 3AL-2.5V Von Mises Stress Analysis

Figure 41. Ti 3AL-2.5V Displacement Analysis



Figure 42. Chromoly 4130 Steel Alloy Von Mises Analysis

Figure 43. Chromoly 4130 Steel Alloy Displacement Analysis

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