Calvin College Engineering Design... · Calvin College Engineering THERATRYKE Final Report Team 5...

Calvin College Engineering

THERATRYKE Final Report

Team 5 David Evenhouse

Jack Kregel Nick Memmelaar

Connor VanDongen

Advisor David Wunder

ENGR 340: Senior Design May 13, 2015


TheraTryke David Evenhouse, Jack Kregel, Nick Memmelaar, Connor VanDongen

Executive Summary Project Brief: The goal of team TheraTryke was to create a tricycle that would provide a unique mix of

recreational and therapeutic benefits for persons of low or limited mobility. The resulting trike is

primarily hand pedaled, but was designed with an original gear train that incorporates foot

pedals as well. This design boasts two significant advantages over traditional hand powered

tricycles. For persons living with paraplegia, the tricycle passively moves their legs through a full

range of motion by transferring some power from the hand pedals to the foot pedals. This

realizes significant therapeutic benefits while allowing the user to be active outside. For persons

with limited mobility in all limbs, this design allows them to power the trike using both their arms,

and their legs. This is not only therapeutic, but also provides people with a viable outdoor

recreation alternative.

Problem Overview: Physical disabilities, and the costs or limitations associated with such conditions, effect a wide

variety of people across the globe. The treatment of many of these conditions requires

therapeutic exercise, even while the condition acts to limit the individual’s ability to move. Due to

the relatively small market demographic and high product development costs, there are few

recreational and therapeutic options available to people living with disability.

Historically, there has been limited interaction between those living with disability, and the

manufacturers developing products for use by persons with limited mobility. This divide between

the designer and the end-user has led to the creation of somewhat inferior products, while

simultaneously encouraging a “helping hand” mentality in regards to designing for disability. In

order to mitigate stereotyping and dismissal of the disabled community, and encourage free

access and independent living for disabled persons, a tradition of collaborative design needs to

be established within the therapeutic products industry.

Problem Setting: Senior Design 2014-2015 Team 5 entered into the class with two main goals. First, they wanted

to work on a project that would directly benefit the Calvin community in some way. Second, they

wanted to have fun doing it. To accomplish this, the team members conducted extensive

research in the Calvin College community in order to encounter problems or needs that could be

addressed. It was through this process that the team was put in contact with members of the

disability community. It was through one of these conversations that the team was made aware

of the need for economical recreation alternatives that incorporate therapeutic benefits.


Problem Solution: Team TheraTryke worked to develop a trike that may be used by persons living with low mobility

for recreational and therapeutic purposes. The goal was to be able to accommodate a variety of

users including spinal-cord injury patients, persons living with low mobility conditions, and

persons with paraplegia. To accomplish this, TheraTryke kept in frequent conversation with

disabled persons, medical professionals, local manufacturers, and bike shops, in order to

acquire the information and skills necessary to produce a quality and useful product. The team

also worked with Nancy Remelts, a member of the Calvin Community living with Multiple

Sclerosis (MS). Acting as their main client, Nancy gave recommendations and insights

concerning the trike’s design, and will be the principal user of the product after the end of the

2014-2015 school year.

Design Specifications: The trike designed to be recumbent and incorporates crank-sets for both the hands and feet.

The frame is in the tadpole style, and is manufactured almost entirely from 1/8’’ thick Al-6061-T6

tubing. Components of the trike include parts that were purchased, hand-manufactured, or

scavenged from existing bicycles. These include but are not limited to: independent linkage

steering mechanism, simultaneously actuated disc brakes, adjustable reclining seat, adjustable

4-point harness, integrated leg supports, internal hub gear shifter, and removable push-bar.

Further specifications may be seen in the table below.

TheraTryke Specifications

Trait Name Value

Weight 67 lbs

Wheelbase 55.375 in

Wheeltrack 31.75 in

Seat Height 14 in

Overall Length 89 in

Overall Height 41 in

Turning Circle 21 ft

Hand-to-Foot Revolution Ratio

2:1

Speeds 7

Load Limit 250 lbs

A full cost breakdown may be found at the end of each design section, or compiled in section

6.2.1. Of particular note is the final Bill of Materials (BOM), which may be found in Table 38. An

abbreviated table of values has been included below for the sake of convenience.

Abbreviated Cost Summary

Trait Name Value

Final Project Cost $1,113.94

Estimated Production Cost $1,538.37

Estimated Retail Price $3,000.00

Final Report

Team 5: TheraTryke page i

Table of Contents

1. Introduction ......................................................................................................................... 1

1.1 Calvin College Engineering Department ...................................................................... 1

1.2 Senior Design Project .................................................................................................. 1

1.3 Objective ...................................................................................................................... 1

1.3.1 Ease of Use ............................................................................................................... 1

1.3.2 Speed ........................................................................................................................ 2

1.3.3 Safety ......................................................................................................................... 2

1.3.4 Therapeutic Benefits .................................................................................................. 2

1.3.5 Outdoor Usage ........................................................................................................... 2

1.3.6 Economic Sustainability ............................................................................................. 2

1.4 Motivation .................................................................................................................... 2

1.5 Group Members ........................................................................................................... 3

1.6 Client ........................................................................................................................... 5

2. Project Requirements.......................................................................................................... 5

2.1 Functional .................................................................................................................... 5

2.2 Mechanical .................................................................................................................. 5

2.2.1 Height and Weight Capacity .................................................................................. 5

2.2.2 Product Weight ..................................................................................................... 6

2.2.3 Size ...................................................................................................................... 6

2.2.4 Material ................................................................................................................. 6

2.2.5 Seat ...................................................................................................................... 6

2.2.6 Mounting ............................................................................................................... 6

2.2.7 Maintenance ......................................................................................................... 6

2.2.8 Environmental ....................................................................................................... 6

2.2.9 Speed ........................................................................................................................ 6

2.3 Safety .......................................................................................................................... 7

2.3.1 Brakes .................................................................................................................. 7

2.3.2 Harnessing ........................................................................................................... 7

2.3.3 Stability ................................................................................................................. 7

2.3.4 Flag Slot ............................................................................................................... 7

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2.4 Design Norms ................................................................................................................... 7

3. Market Research ................................................................................................................... 8

3.1 Similar Products ............................................................................................................... 8

3.1.1 TerraTrike .................................................................................................................. 8

3.1.2 Top End Trikes ........................................................................................................... 9

3.1.3 Rehatri Trikes by Gomier ..........................................................................................10

3.1.4 AmTryke ...................................................................................................................10

3.1.5 Catrike ......................................................................................................................11

3.2 Past Projects ...................................................................................................................12

3.2.1 Achieving Mobility .....................................................................................................12

3.3 External Resources .........................................................................................................12

3.3.1 TerraTrike .................................................................................................................12

3.3.2 Boston Square Community Bikes ..............................................................................12

3.3.3 Foot & Ankle Specialists ............................................................................................13

3.3.4 Calvin Bike Garage ...................................................................................................13

3.3.5 Progressive Surfaces ................................................................................................13

3.3.6 Custom Frame Coatings ...........................................................................................13

4. Mechanical Design ................................................................................................................13

4.1 Frame ..............................................................................................................................13

4.1.1 Research ..................................................................................................................13

4.1.2 Requirements ............................................................................................................14

4.1.3 Design Process .........................................................................................................15

4.1.4 Final Design ..............................................................................................................24

4.1.5 Components ..............................................................................................................27

4.2 Steering ...........................................................................................................................27

4.2.1 Research ..................................................................................................................27

4.2.2 Requirements ............................................................................................................29

4.2.3 Design Process .........................................................................................................29

4.2.4 Final Design ..............................................................................................................31

4.2.5 Components ..............................................................................................................32

4.3 Wheels ............................................................................................................................32

4.3.1 Research ..................................................................................................................32

4.3.2 Requirements ............................................................................................................32

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4.3.3 Design Process .........................................................................................................32

4.3.4 Final Design ..............................................................................................................33

4.3.5 Components ..............................................................................................................34

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

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

4.4.2 Requirements ............................................................................................................36

4.4.3 Design Process .........................................................................................................36

4.4.4 Final Design ..............................................................................................................36

4.4.5 Components ..............................................................................................................37

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

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

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

4.5.3 Design Process .........................................................................................................38

4.5.4 Final Design ..............................................................................................................43

4.5.5 Components ..............................................................................................................44

4.6 Hand Pedals ....................................................................................................................44

4.6.1 Research ..................................................................................................................44

4.6.2 Requirements ............................................................................................................45

4.6.3 Design Process .........................................................................................................45

4.6.4 Final Design ..............................................................................................................47

4.6.5 Components ..............................................................................................................51

4.8 Leg Brace and Support ....................................................................................................52

4.8.1 Research ..................................................................................................................52

4.8.2 Requirements ............................................................................................................54

4.8.3 Design Alternatives ...................................................................................................54

4.8.4 Initial Design .............................................................................................................55

4.8.5 Final Design ..............................................................................................................56

4.8.6 Components ..............................................................................................................58

4.9 Brakes .............................................................................................................................58

4.9.1 Research ..................................................................................................................58

4.9.2 Requirements ............................................................................................................59

4.9.3 Design Process .........................................................................................................59

4.9.4 Final Design ..............................................................................................................62

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4.9.5 Components ..............................................................................................................64

5. Testing ..................................................................................................................................64

5.1 Ease of Use .....................................................................................................................64

5.1.1 Timing transfer and positioning on trike .....................................................................64

5.2 Safety ..............................................................................................................................64

5.3 Speed ..............................................................................................................................65

5.3.1 Time top speed on trike on level ground ....................................................................65

5.3.2 Acceleration of trike from standstill ............................................................................65

5.4 Turning ............................................................................................................................66

5.5 Weight .............................................................................................................................67

5.6 Client Satisfaction ............................................................................................................67

5.6.1 Satisfaction Survey ...................................................................................................67

5.6.2 Avoiding spasms .......................................................................................................67

5.7 Outdoor usage .................................................................................................................68

5.8 Economic Sustainability ...................................................................................................68

6. Business Analysis .................................................................................................................68

6.1 Market Research .............................................................................................................68

6.1.1 Existing Competitors .................................................................................................68

6.1.2 Target Markets ..........................................................................................................69

6.2 Financials ........................................................................................................................70

6.2.1 Budget ......................................................................................................................70

6.2.2 Funding .....................................................................................................................74

6.2.3 Potential Profits. ........................................................................................................74

7. Project Management .............................................................................................................74

7.1 Work Division ..................................................................................................................74

7.2 Team Organization and Management ..............................................................................75

7.3 Scheduling and Milestones ..............................................................................................77

8. Acknowledgements ...............................................................................................................78

9. References ...........................................................................................................................80

10. Conclusion ..........................................................................................................................82

11. Appendices .........................................................................................................................83

A. Gearing Calculations .........................................................................................................83

A.1 Excel sheet on gears ...................................................................................................83

Final Report

Team 5: TheraTryke page v

A.2. Power calculations and top speeds .............................................................................84

A.3 Gearing Ranges Considered .......................................................................................86

B. Work Breakdown Schedule ...............................................................................................87

C. User Experience Definition ................................................................................................91

D. Business Analysis Calculations .........................................................................................93

E. Frame Design Analysis .....................................................................................................98

E.1 Weight Determination ..................................................................................................98

E.2. Maximum Deflection and Stress ............................................................................... 101

F. Steering and Pedaling Concept ....................................................................................... 106

G. Final Prototype Images ................................................................................................... 107

Final Report

Team 5: TheraTryke page vi

Figures

Figure 1. Team members ........................................................................................................... 3

Figure 2. TerraTrike Tour II model .............................................................................................. 8

Figure 3. TerraTrike Rover model .............................................................................................. 9

Figure 4. Top End Force K handcycle ........................................................................................ 9

Figure 5. Gomier Rehatri Therapy Trike 16" ..............................................................................10

Figure 6. AmTryke AM-16" Therapeutic Tricycle .......................................................................11

Figure 7. Catrike 700 Recumbent Racing Trike .........................................................................11

Figure 8. Past engineering senior design stroller project ...........................................................12

Figure 9. Trike frame with constraints and forces applied ..........................................................16

Figure 10. SolidWorks original model of trike ............................................................................19

Figure 11. Small body interference sketch ................................................................................21

Figure 12. Large body interference sketch ................................................................................22

Figure 13. Al 6061-0 Von Mises stress analysis English units (psi) ...........................................22

Figure 14. Al 6061-0 displacement analysis metric units (mm) ..................................................23

Figure 15. Initial 3D trike model .................................................................................................24

Figure 16. Final SolidWorks design ...........................................................................................25

Figure 17. Push bar ..................................................................................................................26

Figure 18. Push bar application .................................................................................................26

Figure 19. Direct steering ..........................................................................................................28

Figure 20. Linkage steering .......................................................................................................28

Figure 21. Hand pedaled recumbent trike .................................................................................29

Figure 22. Turning angle diagram .............................................................................................31

Figure 23. Trike design with 20" tires ........................................................................................33

Figure 24: Final trike layout .......................................................................................................34

Figure 25. Seat with adjustable positioning (TerraTrike model) .................................................35

Figure 26. Seat with fixed positioning (Utah Trikes) ..................................................................35

Figure 27: TerraTrike seat with added restraints .......................................................................36

Figure 28. Diagram of gear design selections ...........................................................................41

Figure 29. Components of the central gear hub ........................................................................42

Figure 30. Central gear hub on frame .......................................................................................42

Figure 31. Final gear setup .......................................................................................................43

Figure 32. Top End hand pedal design .....................................................................................45

Figure 33. Brake and shifter placement .....................................................................................46

Figure 34. Alternating hand pedaling .........................................................................................47

Figure 35. Final hand pedal design ...........................................................................................47

Figure 36. Hand crank to fix interference ..................................................................................48

Figure 37. Hand pedal final 3D design .....................................................................................48

Figure 38. Manufactured hand pedals ......................................................................................49

Figure 39. Disassembly of foot pedal .......................................................................................50

Figure 40. Components used in hand pedals ...........................................................................50

Figure 41. Hand pedal with gear shifter ....................................................................................51

Figure 42. Standard foot pedal styles ........................................................................................52

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Team 5: TheraTryke page vii

Figure 43. Adjustable ergonomic knee brace ............................................................................53

Figure 44. Example of therapeutic bracing from Trulife .............................................................53

Figure 45. Motocross articulating knee brace, listed at $1,400 per pair .....................................54

Figure 46. Leg bracing concept sketch ......................................................................................56

Figure 47: Example walking boot ..............................................................................................57

Figure 48: Modified walking boot with pedal ..............................................................................57

Figure 49. Rim, drum, and disc brake .......................................................................................61

Figure 50. Close up of brake integration site .............................................................................63

Figure 51. Brake and housing design ........................................................................................63

Figure 52. Bike acceleration test results ....................................................................................66

Figure 53. First semester team organization .............................................................................76

Figure 54. Second semester team organization ........................................................................76

Figure 55. Work log ...................................................................................................................77

Figure 56. Distribution of work time ...........................................................................................77

Figure 57: Power Calculations ..................................................................................................84

Figure 58. Bike speed calculator ...............................................................................................85

Figure 59. Gear ranges considered ...........................................................................................86

Figure 60. Aluminum 6061-T6 frame weight ..............................................................................98

Figure 61. Chromoly 4130 alloy steel frame weight ...................................................................99

Figure 62: E.3 Titanium alloy 3AL-2.5V frame weight .............................................................. 100

Figure 63. Al 6061-T6 Von Mises stress analysis .................................................................... 101

Figure 64. Al 6061-T6 displacement analysis .......................................................................... 101

Figure 65. Ti 3AL-2.5V Von Mises stress analysis .................................................................. 102

Figure 66. Ti 3AL-2.5V displacement analysis......................................................................... 102

Figure 67. Chromoly 4130 Steel Alloy Von Mises stress analysis............................................ 103

Figure 68. Chromoly 4130 Steel Alloy displacement analysis .................................................. 103

Figure 69. Al 6061-0 Von Mises stress analysis english units (psi) .......................................... 104

Figure 70. Al 6061-0 Von Mises stress analysis metric units (𝑁𝑚2) ........................................ 104

Figure 71. Al 6061-0 displacement analysis english units (in) ................................................. 105

Figure 72. Al 6061-0 displacement analysis metric units (mm) ................................................ 105

Figure 73. Concept to combine steering and pedaling............................................................. 106

Figure 74. Final prototype ....................................................................................................... 107

Figure 75. Top view of prototype ............................................................................................. 107

Final Report

Team 5: TheraTryke page viii

Tables

Table 1. Metric material properties ............................................................................................14

Table 2. English material properties ..........................................................................................14

Table 3. Cost of materials for trike.............................................................................................15

Table 4. Maximum stress calculations .......................................................................................17

Table 5. Weight of basic trike frame based in SolidWorks .........................................................17

Table 6. Maximum deflection calculations for basic frame .........................................................18

Table 7. Design decisions for arm length based on human measurements (Notice, deemed

inaccurate) ................................................................................................................................19

Table 8. Design decisions for leg length based on human measurements (Notice, deemed

inaccurate) ................................................................................................................................20

Table 9. Design decisions for seat size based on human measurements..................................20

Table 10. Trike frame decision matrix .......................................................................................20

Table 11. FEA results ................................................................................................................23

Table 12. Frame BOM ...............................................................................................................27

Table 13. Design options for the steering mechanism ...............................................................30

Table 14. Cost considerations for steering ................................................................................32

Table 15. Cost considerations for wheels ..................................................................................34

Table 16. Cost considerations for the seat ................................................................................37

Table 17. Gear ratio possibilities for a 27-speed gear system ...................................................38

Table 18. Gearing system options .............................................................................................39

Table 19. Power distribution and top speeds .............................................................................40

Table 20. Gear system components and cost ...........................................................................44

Table 21. Hand pedal manufacturing decision chart ..................................................................49

Table 22. Costing for hand pedals.............................................................................................51

Table 23. Design fabrication alternatives for ergonomic bracing ...............................................55

Table 24. Cost consideration for leg braces ..............................................................................58

Table 25. Advantages and disadvantages of brake options.......................................................59

Table 26. In-depth decision for the specific project ....................................................................60

Table 27. Cost comparison for brake types ...............................................................................61

Table 28. Pros and Cons of Braking Arrangements .................................................................62

Table 29. Brake BOM component list ........................................................................................64

Table 30. Loading and unloading times .....................................................................................64

Table 31. Braking distance from top speed ...............................................................................65

Table 32. Top speed test results ...............................................................................................65

Table 33. Acceleration data.......................................................................................................66

Table 34. Turning circle results .................................................................................................66

Table 35. Satisfaction survey given to client ..............................................................................67

Table 36. Estimated project cost ...............................................................................................70

Table 37. Actual money spent on prototype ..............................................................................71

Table 38. Final BOM of the trike ................................................................................................72

Table 39. Excel sheet for gear considerations ...........................................................................83

Table 40. Project work breakdown schedule .............................................................................87

Final Report

Team 5: TheraTryke page ix

Table 41. Income Statement for TheraTryke .............................................................................93

Table 42. Cash Flow Statement for TheraTryke ........................................................................93

Table 43. Break Even Analysis for TheraTryke .........................................................................94

Table 44. Depreciation and Interest Calculations ......................................................................95

Table 45. Ratios and EBITDA Calculations ...............................................................................95

Table 46. Fixed Operating Costs for TheraTryke .......................................................................96

Table 47. Variable Operating Costs for TheraTryke ..................................................................96

Table 48. Variable COGS for TheraTryke .................................................................................97

Table 49. Fixed COGS for TheraTryke ......................................................................................97

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Team 5: TheraTryke page 1

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 innovation,

implementing a project plan, identifying project requirements and constraints, coming up with

design alternatives, and possibly manufacturing a prototype of the final design. Throughout the

entire process, teams are to report to an appointed advisor in the Calvin engineering program

who will provide the design team with professional advice. At the end of the fall semester, the

team is required to present a Project Proposal and Feasibility Study (PPFS) to the department.

This report includes an introduction to the design, design plans, and all research and initial tests

done that have been recorded. At the end of the spring semester, a final report is due which

builds off of the PPFS and all other work done in order to finalize the project and create a

working apparatus.

1.3 Objective

The objective of this project is to design and build a therapeutic trike for those with little or no

use of their legs. The trike will have the capability of pumping the legs via energy transferred

from hand pedaling. This device will have therapeutic benefits that no other outdoor vehicle

currently in the market has. The specific goals that pertain to this objective are as follows:

1.3.1 Ease of Use

The storage, moving, loading, accelerating, and braking should be not significantly more difficult

or strenuous for a handicapped user when compared to a regular hand trike. The loading time

which consists of transferring into the trike, strapping in the legs, and securing the body

restraints should not take more than 5 minutes.

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1.3.2 Speed

The trike will be able to travel at a steady speed of 10 mph on flat ground, while being supplied

60 watts of power from the rider. This can also be seen in section 2.2.9. The team will test the

trike for its ability to get up to speed. Further details on this testing can be seen in the testing

section.

1.3.3 Safety

The trike will be able to come to a complete stop within 10 feet while operating at 10 mph with a

250 lb rider. The trike should be able to have a 10 foot turning radius and shoot be able to safely

make this turn at 5 mph.

1.3.4 Therapeutic Benefits

The trike will provide therapeutic benefits to those using it as confirmed by experts in the field of

physical therapy and rehabilitation while in collaboration with patients diagnosed with

paraplegia. The team will test the trike’s ability to deter spams and atrophy by having a people

with paraplegia use it as a direct substitution for stretching for several days.

1.3.5 Outdoor Usage

The trike will be able to endure a variety of outdoor and environmental conditions without seeing

a major loss in performance. This includes exposure to water without corrosion and weathering

impact stresses caused by road use. Specific criteria for measuring these goals can be found in

Section 2.2. The team will accept prior knowledge on material properties.

1.3.6 Economic Sustainability

The trike must fall within reasonable market price values of both current recreational trike

models as sold by TerraTrike and current therapeutic machinery as used by hospitals and

medical personnel. The standard trike market price from TerraTrike is approximately $1,749.

The RT300 Leg Cycle system used for in-home and hospital purposes is approximately

$10,499. The comparative price for the therapeutic trike must be within or below the range of

these price variations.

1.4 Motivation

The team has been introduced to many individuals with paralysis. This is a brutal living condition

that affects many people’s mobility. A few causes that the team learned about were from tragic

vehicle accidents, unfortunate shootings, and genetic characteristics. The team has been

constantly reminded of just how life altering such a condition can be. When paralyzed, it

becomes hard to keep the motivation to exercise the body you can no longer use. Additionally,

when the body is kept in one position for an extended period of time, there are symptoms that

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arise such as leg spasms, sores, stiffness, and atrophy. This has become the reality of many

people living in the Calvin community as well as elsewhere in the world.

The goal of this design project is to minimize a variety of the symptoms that result from

paraplegia and others like it. In order to accomplish this, the idea is to introduce a leg pumping

function into a hand-pedaled trike. The concept is that while the rider cranks their hands to drive

the trike, a simultaneous gear drive will rotate the legs at a desired cycle speed. Below is the

design of a standard racing trike. The key difference is that TheraTryke will be used for

therapeutic purposes in addition to recreational usage.

1.5 Group Members

Figure 1. Team members

(From left to right: Nick Memmelaar, Connor VanDongen, Jack Kregel, and David Evenhouse)

Nick Memmelaar

Nick Memmelaar is a senior engineering student in the mechanical concentration from

Caledonia, MI. Nick has had two engineering internships - the first at Knape & Vogt and the

second at Ventura Manufacturing. During Nick’s summer working at Ventura Manfucaturing,

Nick successfully implemented a spare parts inventory system while also gaining much more

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manufacturing and machine design experience. In January of 2014, Nick had the opportunity to

use his engineering experience in Kenya. He, along with three other students and a professor,

were given the task of fixing a broken bore-hole hand pump for a native community in Sedai,

Kenya. They were successful in fixing the well. Nick was able to experience just how significant

and helpful he can be with the position and education that he is a part of. Nick has accepted a

Mechanical Design Engineer I position at Extol in Zeeland, MI. They are a machine design

company that specializes in plastic joining. He may consider further schooling if the need arises.

Connor VanDongen

Connor VanDongen is a senior engineering student in the mechanical concentration from

Galesburg, MI. From a young age Connor has always had the passion to use his hands in

building something that will benefit the kingdom of God. Whether it was working on his

grandfather’s airplane or tinkering on his dirt bike, Connor always felt like engineering was his

destined career path and decided to take his talents to Calvin. During his time at Calvin, Connor

has held one engineering internship with two different job titles. The company, Progressive

Surface, is a global leader in the design and manufacturing of automated machinery and 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 will be working at Plascore in Zeeland, MI. He plans on working

there for a few years while hopefully working towards his dream job in the field of aerospace

engineering.

Jack Kregel

Jack Kregel is a senior engineering student in the mechanical concentration from Iowa City, IA.

The past two summers Jack has had two different engineering internships. The first was at

Virtual Soldier Research a branch of the University of Iowa Computer Aided-Design program.

While at VSR, Jack worked on Department of Defense funded projects involving software

development for digital human modeling and simulation. During Jacks most recent internship at

Gordon Manufacturing, he worked with a variety of different departments on the development of

height adjustable table legs. Both internships gave Jack knowledge about all aspects of

engineering, ranging from design, production and manufacturing to the business aspects behind

all engineering decisions. After graduation, Jack has accepted a job working as a Production

Support Engineer at Gentex Corporation in Zeeland, MI. He plans on getting several years of

experience before pursuing a Masters of Business Administration and hopefully starting his own

company.

David Evenhouse

David Evenhouse is a senior engineering student in the mechanical concentration from Grand

Rapids, MI. David was inspired at a young age to pursue engineering as a profession and has

notable experience in the manufacturing industry. This includes two summers working as an

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

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

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Assembler Fitter, and two summers working as an Engineering Intern at two separate

engineering companies. From these experiences, he learned how to properly handle tools and

machinery, methods of manufacture, quality engineering systems, and many other practical

engineering skills. Additionally, he studied engineering in Spain during the spring of his junior

year, gaining international experience and reinforcing his knowledge of the Spanish language. A

strong communicator and huge proponent of hands-on engineering work, David looks forward to

tackling the design problem at hand. In the coming years he will be pursuing a PhD in

Engineering Education at the Purdue College of Engineering Education in West Lafayette.

1.6 Client

This trike will be designed and built for Nancy Remelts, a lady with multiple sclerosis (MS) that

is connected to the Calvin community. The cause for MS is unknown, but it is known that the

immune system mistakenly attacks the central nervous system, specifically the myelin coating

around nerve fibers. This damage causes distortion in nerve impulses traveling to and from the

brain, producing a wide variety of symptoms.

The client is fighting this disease with all that she has got. She is in the Calvin gym every

weekday morning at 7:30 am to keep her strength up in case a cure for this disease is found.

She realizes how unpredictable her symptoms can be day by day, but this has turned into her

motivation. After a single meeting with her, it was clear that she could see herself using the

proposed product. It is an honor to work with her on this project and to supply her with more

ammunition to aid her in her fight.

2. Project Requirements

2.1 Functional

The vehicle will be able to be used outside with ease on well-maintained roads or sidewalks,

with some allowance for uneven surfaces. This will be considered the standard operating

condition of the vehicle. The user will be able to enter the trike without assistance, with a

parking brake aiding stable transition. He/she will be able to pedal him/herself by cycling his/her

hands. This pedaling of the hands will cause the legs to cycle, while additional power may be

provided via the legs as permitted by the user’s physical capabilities. The legs will see a

therapeutic benefit regardless of their ability to provide power to the drive assembly.

2.2 Mechanical

2.2.1 Height and Weight Capacity

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

maximum weight of 250 lbs.

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2.2.2 Product Weight

The vehicle will be light enough to promote easy transportation and ease of use for people with

low mobility. Thus, it should not exceed 60 lb of net weight.

2.2.3 Size

The vehicle will be as small as possible while accommodating for rider safety and full range of

motion in all limbs for riders representing a variety of body-types. More specific sizing data can

be found in Section 4.1.4.2.

2.2.4 Material

Component material will be strong enough to support the maximum stated rider weight in

standard operating conditions while also being light enough to promote ease of transportation.

2.2.5 Seat

The seat will be comfortable as well as rugged. The backrest will come up to at least the

shoulder blades of the occupant. It will be adjustable to accommodate for different body lengths.

2.2.6 Mounting

Gears will need to be positioned correctly to allow for linear chain movement. Brakes need to be

mounted correctly. Gear and brake controls will be mounted in user-friendly positions that

promote both ease of use and operational safety.

2.2.7 Maintenance

Maintenance requirements will be similar to that of a bicycle. Gears and chains should be

lubricated. Tire pressure should be checked. Moving components and critical systems such as

braking should be checked regularly for excessive wear due to use.

2.2.8 Environmental

The trike will be made with materials and components that do not normally rust or wear under

normal operating conditions, allowing for at least 5 years of regular use.

2.2.9 Speed

The trike should be able to travel at least 10 mph while supplying 60 watts of energy to the hand

pedals on flat ground.

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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 rollaway and facilitate easy entry.

2.3.1.1 Stopping

The vehicle traveling at 15 mph will have a stopping distance of 10 feet or less while carrying a

load of 90 to 250 lbs.

2.3.1.2 Parking Brake

Applying the parking brake will prevent rollaway of the vehicle under any loading condition up to

250 lbs, positioned on a decline of up to 25°.

2.3.2 Harnessing

The vehicle will include multiple adjustable straps to secure the operator during use including,

but not limited to, a seat belt.

2.3.3 Stability

The vehicle will be stable during normal operation due to the location of the center of gravity and

the wheel placement.

2.3.4 Flag Slot

One side of the backrest will have slots to attach a flag that will be visible to bystanders over a

hill during vehicle operation.

2.4 Design Norms

There are several guidelines that Calvin engineering students strive to follow in their work.

These guidelines help students do an outstanding job in the work that is done as well as keep

things in perspective with God and each other in the picture.

One design norm that characterizes the project is justice. One main goal for this project is to

design a means of exercise for those who would otherwise not have access to such an

opportunity due to their physical limitations. Providing a fun and exhilarating alternative to their

normal daily routine can make all the difference to someone struggling with a physical

impairment. Those with limited or no leg mobility can have few opportunities to go outside and

enjoy nature.

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Caring is another design norm that fits the project. The client’s well-being is at the forefront of

each decision. Past experiences and skills will be used to create a vehicle that the client will

enjoy using and be thoroughly grateful for the work put into the project.

Thirdly, stewardship should shine through this project. The team wants to take care of the

environment, the money put into the project, and the satisfaction of the client. The team want to

select materials that will make the vehicle last.

3. Market Research

3.1 Similar Products

3.1.1 TerraTrike

TerraTrike is a recumbent tricycle company based in Grand Rapids, MI. They were founded in

1996 by originally Jack Wiswell and Wayne Oom. The goal of their company is to create a

vehicle that does not create air, noise, or sight pollution. Their main goal is to produce high end

recumbent trikes that are mainly used for recreational usage. TerraTrike offers many different

types of trikes with a variety of different mechanisms. For their frames they use high tensile

steel, 4130 chromoly steel, and 6061 T6 Heat Treated Aluminum. They also have two different

steering mechanisms, direct and linkage. They also integrate several different gearing

mechanisms including the Nuvinci internal gearing system. Shown in Figure 2 is TerraTrike’s

Tour II model, their high end long distance model. It is outfitted with 4130 Chromoly Steel, and

linkage steering. Also shown in Figure 3 is TerraTrike’s Rover model, their lower lever trike.

The Rover is outfitted with high tensile steel and direct steering. Prices at TerraTrike range from

$899.00 for low end models to $3,999.00 for their high end models.

Figure 2. TerraTrike Tour II model

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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

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3.1.3 Rehatri Trikes by Gomier

Rehatri is a line of trikes from Gomier with a mission statement much like TheraTryke’s. Their

goal is to provide therapeutic recreational options to individuals with disability. Their primary

target market is the parents of children with Cerebral Palsy, although a range of trikes are

available for various users. The trikes are designed for use on flat, level pavement only, and

have little adjustability in the gear drive. However, they do incorporate a positive drive system

that rotates the user’s legs for therapeutic purposes, much like the proposed TheraTryke. The

trikes are designed to be recreational, but within a controlled environment, having straight

seatbacks and handles on the back for support and supervision. Trikes range from $895.99 to

$1,250.00, not including optional accessories. Figure 5 is an example of a Rehatri trike.

Figure 5. Gomier Rehatri Therapy Trike 16"

http://www.bikeexchange.com.au/a/recumbent-bikes-trikes/gomier/vic/ravenhall/rehatri-therapy-adult-handicap-red-16/102558814

3.1.4 AmTryke

AmTryke LLC, a therapeutic trike manufacturer, is an affiliate of AMBUCS Inc. AMBUCS is a

national nonprofit organization dedicated to empower disabled persons to achieve greater

degrees of mobility and independence. The trikes produced by this company are also dual drive

operated, meaning that they can be hand and/or foot powered when in use. AmTryke works with

both volunteer members and Physical or Occupational therapists in order to provide these trikes

to individuals to improve motor skills, strength, and self-esteem. AmTryke products are similar in

both appearance and operation to Rehatri products. However, AmTryke markets primarily to

American customers, while Rehatri appears to operate chiefly overseas. Like Rehatri, AmTryke

utilizes vertical backrests and optional accessories to improve performance for physically

impaired users. Prices may range from $800 to $1,250 depending upon the application. Figure 6

is an AmTryke example.

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Figure 6. AmTryke AM-16" Therapeutic Tricycle

http://www.rehabmart.com/product/amtryke-am16-therapeutic-tricycle-41127.html?gclid=CKW4wZL1scICFczm7AodeR0AfQ

3.1.5 Catrike

Catrike is a recumbent trike company created in 2000 by Paulo Camasmine, a Brazilian

Mechanical Engineer. Their vision is to create new high quality products to improve people’s

lives. Catrike has received six awards for Trike of the Year by the readers of Bent Rider online.

They try and focus on product development, engineering and process design. Their goal is to

create beautiful and flawless products that are user friendly and require little maintenance.

They are currently making 2,300 bikes annually. Prices at Catrike range from $2,150.00 for

their low end models to $2,950.00 for high end models. Figure 7 shows an example of a Catrike

trike.

Figure 7. Catrike 700 Recumbent Racing Trike

http://www.utahtrikes.com/PROD-11617573.html

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3.2 Past Projects

3.2.1 Achieving Mobility

Achieving Mobility was a Calvin College senior design project back in 2010-2011. Their goal

was to design and distribute a motorized stroller that could easily be controlled using one finger.

Their project was developed to help Issac Postma, a young boy diagnosed with Spinal Muscular

Atrophy. The team has drawn a lot of motivation from Achieving Mobility. Their desire to help

an individual with physical limitations inspired the team to pursue a similar product. The team

and their project can be seen in Figure 8.

Figure 8. Past engineering senior design stroller project

http://www.mlive.com/news/grand-rapids/index.ssf/2011/06/how_calvin_college_engineering.html

3.3 External Resources

3.3.1 TerraTrike

The team has met with TerraTrike at their facility in Grand Rapids. They have been very helpful

in explaining what is and is not possible for bike parts, gave recommendations on parts, and

have graciously supplied parts that were used in the final product.

3.3.2 Boston Square Community Bikes

The team did a service learning experience at Boston Square in Grand Rapids. The team were

able to get hands on experience with bikes as well as another great source for parts at a

discounted rate.

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3.3.3 Foot & Ankle Specialists

Foot and ankle has provided the team with walking boots for the bracing system designed for

the legs.

3.3.4 Calvin Bike Garage

The Calvin bike garage has been helpful in supplying recommendations and parts on braking

and shifting systems.

3.3.5 Progressive Surfaces

Welders at Progressive Surfaces have been extremely helpful in welding the frame of the

prototype. The team also used SolidWorks at Progressive to design the frame. They are located

in Grand Rapids, MI.

3.3.6 Custom Frame Coatings

Custom Frame coatings offered to powder coat the frame for free. They loved the idea of the

trike and that it will actually help someone. They are located in Zeeland, MI.

4. Mechanical Design

The mechanical design of the product consists of all structural components including but not

limited to the frame, gear design, ergonomics, and braking components. Each of these portions

is divided into subsections for the mechanical design of the project. All components are

dependent on each other meaning that timeliness is of the utmost importance in staying on task.

4.1 Frame

The frame provides the primary structure of the design that supports all other components. The

frame supports the gear train, seating, and other mounting components which will hold the

individual using the device. Weight and strength capabilities must be seriously considered when

designing the frame. Safety and comfort are key when designing a product for therapeutic and

recreational use. Several different materials were analyzed for the final design of the frame.

4.1.1 Research

Past trike frame materials have been researched and all important properties for each material

are provided in both Metric and English in Table 1 and Table 2, respectively.

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Table 1. Metric material properties

Material Density [kg/m^3]

Yield Strength [MPa]

Mod. of Elasticity [GPa]

Elongation [%]

Hardness [Brinell]

Corrosion

4130 Chromoly Steel 7850 435 205 25.5 197 Yes

Aluminum 6061-T6 2700 276 68.9 12 95 Yes

Titanium Alloy 3AL-2.5V 4480 500 100 15 256 Yes

Table 2. English material properties

Material Density [lbf/ft^3]

Yield Strength [psi]

Mod. of Elasticity [ksi]

Elongation [%]

Hardness [Brinell]

Corrosion Resistance

4130 Chromoly Steel 490.752 63100 29700 25.5 197 Yes

Aluminum 6061-T6 168.480 40000 10000 12 95 Yes

Titanium Alloy 3AL-2.5V 279.936 72500 14500 15 256 Yes

4.1.2 Requirements

4.1.2.1 Strength

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

This trike will be designed for individuals with a range of height from 5-0’ to 6-5’. In addition to

these requirements, the frame must be able to withstand any impact from uneven roads. The

welds on the frame must be continuous in order to prevent any cracks or fractures to occur at

the weak joints. The weld thickness must be equal the thickness of the material it is being

applied to. Thicker welds will induce material heating issues.

4.1.2.2 Weight

Weight must be minimal in the trike in order to reduce the amount of force necessary to pump

the arm and leg handles. Those with limited strength or mobility cannot create enough force to

crank the handles if the trike exceeds in weight. According to TerraTrike’s specifications for their

entry level Rover variation of trike express the total weight as a range from 47 to 49 lbs.

Because of the additional weight for a hand pedal column, the final design of the trike must not

weigh more than 60 lbs including all components.

4.1.2.3 Aesthetics

Aesthetics are very important in the final design of the trike. It must be pleasing to the eye

because it is a form of transportation and recreation bringing in a concept of pride in the ride.

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Eliminating all sharp corners and edges and making the frame design as sleek and

aerodynamic as possible are important considerations for the design. Additional aesthetic

considerations will be implemented as time and budget allow. The color for the frame that the

team chose was blue, the client’s favorite color.

4.1.3 Design Process

4.1.3.1 Material Selection

Having the proper material for the frame was very important. Most trikes currently use standard

carbon steel, high-tensile steel, chromoly, or aluminum. In order to determine which material to

use for the frame a decision matrix was made comparing the various materials in terms of

corrosion resistance, cost, weldability, strength, weight, and deflection.

4.1.3.1.1 Corrosion Resistance

Corrosion resistance of the frame material is key to having a reliable and safe trike. The

trike will be exposed to rain and salt on the roads. These weather products have the

capability to produce rust which will degrade the mechanical properties of the material. With

this in mind, a material was chosen that is not affected, or is minimally affected, by the

weather products. Corrosive Resistance is considered in the decision matrix for the final

material. Aluminum is generally a very choice of material if corrosion resistance is

necessary. The aluminum oxide layer that forms on the part is impermeable and self-

sustaining. Chromoly is considered an alloy steel and not yet stainless, therefore it is

resistant to corrosion but will not repel it. According to the Engineering ToolBox, Titanium is

a very good corrosion resistor.

4.1.3.1.2 Cost

Costs were calculated for each possible material and can be seen in Table 3.

Table 3. Cost of materials for trike

Material O.D. [in] Wall Thickness [in] Cost [$/ft]

Al 6061-T6 2-0 ⅛ 8.25

Al 6061-T6 2-0 ¼ 13.48

Chromoly 4130 2-0 ⅛ 15.95

Chromoly 4130 2-0 ¼ 64.13

Ti 3AL-2.5V 2-0 ⅛ 35.82

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4.1.3.1.3 Weldability

This trike will need quality welds. The team initially wanted to do all the welding themselves but

determined that Connor’s employer, Progressive Surface, would be able to give us the highest

quality welds. The design of a good weld is one that matches the thickness of the part being

welded and that has no breaks or gaps which would cause weak joints in the frame. Titanium

welding is generally very good. The single issue with welding titanium is finding a way to

eliminate atmospheric contamination. Titanium reacts quickly with oxygen so there must be very

good ventilation. Aluminum welding is much more difficult because of the thermal conductivity of

the material. Aluminum has a low melting point and therefore you can burn through it very

quickly if not paying attention. Chromoly is an alloy form of steel. This material is easiest to weld

and generally has no complications.

4.1.3.1.4 Strength

The strength of the trike frame was determined using finite element analysis (FEA). The trike

frame model was analyzed in the Autodesk package MultiPhysics. In order to determine the

strength, the model had a brick mesh defined. In order to keep the part constrained, fixed points

were applied to each wheel connection because that is where no deflection will occur and the

trike remains stationary. Forces were also applied to the trike frame. This force was equivalent

to the maximum weight potential that the team had set for the design which is 250 lbs. The force

has been applied to where the rider will be seated, for all the weight will be concentrated in the

seating mount. Below in Figure 9 is the basic model of the trike frame showing fixed points and

force application.

Figure 9. Trike frame with constraints and forces applied

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The same fixed points and force locations were used for each material being analyzed.

Provided in Appendix E are stress analysis figures showing the stress throughout the entire

frame. Below in in both metric and English units.

Table 4 are the materials given with each of their maximum Von Mises stress values in both

metric and English units.

Table 4. Maximum stress calculations

Material Von Mises Stress [ksi]

Yield Strength [ksi]

Von Mises Stress [kPa]

Yield Strength [kPa]

Aluminum 6061-T6 2.478 40.0 17085.178 435000

Chromoly 4130 Alloy Steel 2.169 63.1 14954.702 276000

Titanium Alloy 3AL-2.5V 2.172 72.5 14975.386 500000

The goal of analyzing the Von Mises stress of the trike frame was to compare it to the yield

strength of the material. The yield strength of the material is the point at which material leaves

its elastic deformation and begins its plastic deformation state. It is at this point which the

material can no longer return to its original state and will eventually wear out. This is crucial that

the maximum stress in the frame does not exceed the yield strength. It is apparent that the

stress on the frame for all materials have passed this test.

4.1.3.1.5 Weight

In order to determine what the weight of the frame would be for each given material, a model

was made for the frame. The frame assembly was taken independently from the trike model in

SolidWorks. The material was defined providing all necessary material properties. With all of

these properties, SolidWorks was able to determine the total weight of the assembly. Below is

Table 5 providing each material specification with weight given the initial basic model of the trike

in SolidWorks

Table 5. Weight of basic trike frame based in SolidWorks

Material 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

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All SolidWorks material properties used and weight calculations can be found in Appendix E.

The material specified had to be lightweight in order to minimize the effort required by the

rider to pedal.

4.1.3.1.6 Deflection

Deflection is important because the intention of a trike is to be stiff. A ductile material would

result in an unstable ride. Deflection was determined through using finite element analysis in

Autodesk MultiPhysics. Along with the Von Mises stress analysis, deflection is embedded in the

program. Found in Appendix E are figures showing color orientated photos of the deflection

analysis. In Table 6 are the maximum deflection values provided in both metric and English

units of measurement.

Table 6. Maximum deflection calculations for basic frame

Material Deflection [in]

Deflection [mm]

Aluminum 6061-T6 0.0396 0.894

Chromoly 4130 Alloy Steel 0.0133 0.307

Titanium Alloy 3AL-2.5V 0.0263 0.602

The deflection of the frame must not be excessive because the goal is to build a durable

stiff trike. Each of the deflections shown for the frame materials is quite minimal and is

actually expected when a 250 lb rider gets on the trike. Deflection analysis was done later

on the final model of the trike as well. New displacement measurements were taken

according to the model as well as the fabricated prototype.

4.1.3.2 Design Alternatives

4.1.3.2.1 Frame Setup

The team decided on going forward with a tadpole styled trike. This means that there are two

wheels in front and one in the back. This will keep the gear chains linear to avoid torsion. An

independent steering system will control the front two wheels. This setup will also provide

optimal space for the cycling of the legs. A setup with one wheel in front and two wheels in

back, also known as a delta frame design, even without the chain twisting problem, would be

difficult to place the foot pedals around a steering front wheel. Due to limitations of motion in the

legs, the tadpole design was the finalized decision. The basic SolidWorks design of the trike can

be seen in Figure 10.

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Figure 10. SolidWorks original model of trike

4.1.3.2.2 Sizing and User Accommodation

Data on human measurements in Table 7, Table 8, and Table 9 was taken from a study of 2380

subjects across the United States (Harrison and Robinette, 2002).

Table 7. Design decisions for arm length based on human measurements (Notice, deemed inaccurate)

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Table 8. Design decisions for leg length based on human measurements (Notice, deemed inaccurate)

Table 9. Design decisions for seat size based on human measurements

It is important to keep in mind that Table 7 and Table 8 are deemed inaccurate according to

user definition.

4.1.3.3 Cost Considerations

These three materials were put into a decision matrix to help decide the best option. This can be

seen in Table 10.

Table 10. Trike frame decision matrix

Score

(0-10)

Weighted

Score

Score

(0-10)

Weighted

Score

Score

(0-10)

Weighted

Score

Corrision 8 8 64 6 48 10 80

Cost 10 9 90 6 60 3 30

Weldability 5 5 25 9 45 7 35

Strength 6 9 54 9 54 9 54

Weight 9 9 81 6 54 7 63

Deflection 4 7 28 9 36 8 32

Rank

342

1

297

2

294

3

Aluminum 6061-T6 Chromoly 4130 Titanium 3Al-2.5V

CriteriaWeighted Scale

(0-10)

Sum

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After all calculations were done and each factor of the frame material was weighted, the

final decision for the material of the trike was decidedly Aluminum 6061-T6. This material

was purchased, cut and welded.

4.1.3.4 Prototype Frame Design

During prototype design and fabrication of the frame, there were many mistakes and learning

opportunities that presented themselves. In the following section, the frame fabrication process

will be explained along with all of the rework that was done to correct initial mistakes made.

Additional components applied after initial testing will be explained as well.

4.1.3.4.1 Initial Frame Design

The initial frame design was made based off of ergonomic human body length data received

from on online research article which can be found in Table 7, Table 8 and Table 9. All modeling

was done in SolidWorks 2015. The only components not provided in the 3D model are the

gears, chains, and brake lines. Making sure the frame would fit a human body was vital to the

design process. That is why the referenced scholarly article was used. Below are figures

showing the initial frame design with sketches marked in the model. These are sketches

representing the limb interference. This had to be considered in order to eliminate any limb

interference while cycling the hands and feet simultaneously on the trike.

Figure 11. Small body interference sketch

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Figure 12. Large body interference sketch

As seen in Figure 11 and Figure 12, there is no interference between the knee joint and hand

cycling motion. This allowed us to move to the next step in the process which was to complete a

secondary FEA using the proper frame design to test the stress and displacement of the new

design. Note, under all analysis a 250 lb force was used as the standard case for the weight of

the rider. This force was applied only to the base of the frame which will be seen in the following

figures.

Figure 13. Al 6061-0 Von Mises stress analysis English units (psi)

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Figure 14. Al 6061-0 displacement analysis metric units (mm)

Aluminum 6061-0 was used as the defaulted material for this analysis rather than the actual

Aluminum 6061-T6 temper state. This was done to compensate for the lower temper levels after

welding. It is unknown what the temper will be exactly after welding is done because it depends

on the state of the weld. To consider worst case scenarios, 6061-0 was used which is the

softest state that Aluminum 6061 can exist in. This compensates for any poor welds that may

have been done during welding. In the following table are the outcome results for both stress

and displacement. These are compared to the yield strength of the material.

Table 11. FEA results

Stress Displacement

Model Yield Strength Units Model Actual Units

2.626 8.000 ksi 0.088 0.063 in

18.106 55.158 MPa 2.242 1.588 mm

The FEA results that were expected and allowed us to proceed with the final fabrication of the

frame. The maximum stress that the frame will undergo is 3 times less than the yield strength of

the aluminum frame based on worst case scenario. This allows for a safety factor of 3. The

maximum deflection that the FEA shows the trike will undergo is approximately 0.1 in.

Displacement is seriously considered because aluminum will fatigue over time if the

displacement of the material is significant. 0.1 in deflection for any material for this trike is far

less than anything that would bring concern.

Once all of this analysis has been completed, the final trike model could be assembled in

SolidWorks as a full 3D model. Again, this model does not detail any components that are

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unnecessary for dimensional analysis and component interference analysis. The model can be

seen below in Figure 15.

Figure 15. Initial 3D trike model

Welding of the initial frame was done by Phil Savickas at Progressive Surface. Phil is an expert

at welding aluminum. It was crucial that the welding was done right in order to maintain the

strength of the 6061-T6 material as much as possible. The entire setup process, alignment of

parts, and welding took approximately 8 hours.

4.1.4 Final Design

Below is the explanation of both the rework of the frame and the additional components applied

to the frame after testing.

4.1.4.1 Reworking the Frame

After the initial frame design and fabrication, some issues arose which had to be solved before

any further assembly could be done. The initial design was mocked up according to given

human body dimensions from a research article. These dimensions were not double-checked or

cross-referenced with any other human body dimensions. This was a mistake on the team’s part

because all body dimensions were off by approximately 12 in. A redesign was needed for the

entire front end of the trike including locations for the foot cycling bottom bracket and central

gear hub.

In order to re-dimension the trike, the current welded trike was used. One of the team members

was similar in height to the client’s height and all re-dimensioning of the trike frame components

were considered using actual human body dimensions. The process of re-dimensioning was as

follows.

The first step was to locate and position the seat where the rider would need it in the final

prototype stage. Once the seat was place in its final location, exact dimensions were taken of

the leg and arm lengths needed. Footing was positioned by extending feet out including a 2 in

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reduction to eliminate full leg extension. Dimensions were taken to accommodate the new

position according to components on the current welded frame. The hand cycling bottom

bracket was relocated in the same fashion as the footing. New dimensions were taken using

actual body dimensions and compensating those dimensions with the current frame status.

After all proper re-dimensioning had been completed, the redesign was configured in

SolidWorks to second check all possible interference points. An FEA analysis was not produced

using the new frame design because the base of the frame remained unchanged. All previous

FEA work had been completed on the base of the frame. Below in Figure 16, is the final frame

model of the trike.

Figure 16. Final SolidWorks design

All necessary rework on the frame had to be done. This included re-welding the frame to the

new design. Welding was done by Greg Parlmer at Progressive Surface. Greg is also an expert

at welding aluminum materials.

4.1.4.2 Additional Components

As a result of testing, as seen in Section 5, additional components were added to the framework

of the trike. After the end client was able to test and ride the trike at Calvin’s Tennis and Track

facilities, it was requested that some bar be implemented onto the frame so as to make the ride

easier for the rider if they became fatigued or are unable to make it up steep hills.

The single addition to the frame was denoted a push bar. Below in Figure 17 is the

manufactured push bar. It was designed to fit into the rear wheel support of the frame. The

intention of the bar is to allow a spouse, friend, or therapist to walk along side of the rider and

support them by pushing the trike forward to alleviate the stress on the rider.

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Figure 17. Push bar

This push bar was manufactured out of an aluminum pipe used as the shaft and a steel bike

handle bar used as the bar itself. These two components were bolted and epoxied together in

order to eliminate any instability and slop between the two materials. The aluminum pipe is

simply fitted into the rear support bar of the frame and locked in place using a simple pin and

lock. Below in Figure 18 is an example of how the push bar might be used.

Figure 18. Push bar application

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4.1.5 Components

All frame materials are listed below in the BOM in Table 12.

Table 12. Frame BOM

Component Unit Unit Cost Quantity Total Cost

Supplier

1-3/4” OD x 1/8” thk pipe

24 ft $126.00 55.4% $69.80 ALRO Steel

Rear Wheel Frame Material

EA $10.00 1 $10.00 ALRO Steel

Central Hub Aluminum Shell

EA $14.24 1 $14.24 ALRO Steel

Bottom Bracket Aluminum Shell

EA $28.48 2 $56.96 ALRO Steel

Welding hr $22.80 8 $182.4 In house assumption

Powder Coat – Blue (1509)

EA $75.00 1 $75.00 Custom Frame Powder Coating

Push Bar (Aluminum Shaft)

4 ft $23.20 1 $23.20 Metals Depot

Push Bar (Bike Handle

EA $35.00 1 $35.00 Cambria Bicycle

Total: $391.60 (estimated was $70)

4.2 Steering

4.2.1 Research

Steering is the mechanism by which the operator of a vehicle is able to direct their movement

into a desired course. For trikes, or more specifically recumbent foot trikes, there are two types

of steering: direct and linkage. These different styles can be seen in Figure 19 and Figure 20.

Direct steering is generally more responsive than linkage steering, while linkage steering will be

able to buffer any shaking and rattling from riding.

Final Report


Figure 19. Direct steering

Figure 20. Linkage steering

For a hand pedaled recumbent trike, the steering is incorporated into the single front wheel. This

can be seen in Figure 21. This is a great way to incorporate the steering and pedaling but not

terribly practical for the TheraTryke prototype. This will be further discussed in the design

alternatives.

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Figure 21. Hand pedaled recumbent trike

Turning ability is measured using a metric called Turning Circle (also called Turning Radius).

This is a measure of the diameter of a circle that the vehicle traces at its maximum turning

condition. It is measured using the outside of the frame rather than the center or inside. Further

analysis of turning circle can be seen in the design alternatives section.

4.2.2 Requirements

It is required that the user be able to maintain full control of the vehicle under standard operating

conditions. This means that the trike will turn freely, move forward in a straight line, and provide

responsive handling at all operating speeds. The steering mechanism must be robust in nature

and easily accessible to the user at all times. The turning circle of the vehicle must allow for

driving on roadways and sidewalks without issue. The goal for turning circle is 26 feet. The

steering and frame design must interact such that the trike will not overbalance if the user

makes a turn, or is forced to avoid an obstruction at speed.


The team needed to consider the possibility of having the steering of the trike be independent of

the drive system. With the hands, feet, and drive wheel gears all having to stay aligned, steering

must be separate unless the legs turn with the hands and legs. The team is uncomfortable in

turning and bending legs that are limited in mobility. Table 13 demonstrates the various design

options that were considered to accompany a chain drive system.

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Table 13. Design options for the steering mechanism

The team decided to design around an independent linkage steering system. Separating

steering from hand-pedaling will prevent chains from falling off gears. The key disadvantage of

this approach is that the user will have to move their arms in order to transfer their hands from

pedaling to steering. This will decrease their ability to respond in a crisis situation, and will

prevent them from being able to power the trike with both hands while turning. The team also

considered how the trike while on a slight slope.

The team did try to consider a way to combine the steering and pedaling. The team did find a

way that seamed feasible, but would be too difficult to manufacture with the time and experience

available. For this system, the team explored using a ratcheting cable-drive pedaling system.

This would enable the user to steer using the hand pedals without endangering the drive train.

Sketches of this design can be seen in Appendix F. Steering and Pedaling Concept. This design

alternative was rejected due to difficulty of design and manufacture, as well as the possible

power losses.

The team also needed to calculate how much the wheels need to turn to get the desired turning

circle. “Turning Circle” is a term that has commonly replaced the term “Turning Radius” in

steering design applications. The turning circle of a vehicle describes the amount of space

needed for the vehicle to execute a large turn and is, in fact, a diametric measure. This

calculation is dependent upon three main factors. First, the Wheel Base (WB) of the vehicle,

which is the distance between the front and rear axles. Second, the Wheel Track (WT) of the

vehicle, which is the distance between the two turning wheels. Finally, the Average Turning

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Angle (ATA) which is the average of the turning angles realized by each of the turning wheels. A

diagram of these values can be seen in Figure 22.

Figure 22. Turning angle diagram

Equation 6 is used in order to calculate the turning circle of a vehicle:

𝑇𝑢𝑟𝑛𝑖𝑛𝑔 𝐶𝑖𝑟𝑐𝑙𝑒 = (𝑊𝑇

2) + (

𝑊𝐵

sin(𝐴𝑇𝐴)) (6)

By designing around a desired Turning Circle of 20 to 26 feet and using nominal values for the

Wheel Track and Wheel Base, the team was able to calculate a desired Average Turning Angle

of 25° to 30° at maximum.

4.2.4 Final Design

The team decided to buy a linkage steering system from TerraTrike. The team chose to go with

a linkage system because less vibrations will travel to the hands, allowing for a more

comfortable ride. In order to achieve the desired turning circle, the team had to remove material

on the part of the frame attached to the wheel to create clearance for moving parts.

The measured turning circle of the trike upon completion of the prototype was just under 21 feet,

and the average turning angle was calculated to be 26.6 degrees.

Final Report


4.2.5 Components

Table 14. Cost considerations for steering

Component Unit Cost Quantity Total Cost Supplier

Tie rod end, M8 Male LH $5 2 $10 TerraTrike

Tie rod end, M8 Male RH $5 2 $10 TerraTrike

M8 hex nut, Tie rod end nut, LH $0.25 2 $0.50 TerraTrike

M8 hex nut, Tie rod end nut, RH $0.25 2 $0.50 TerraTrike

Tie Rod, Tour II, linkage steer $17.50 2 $35 TerraTrike

Steering Brace, Tour II w/bolts and nuts $30 1 $30 TerraTrike

HandleBar $20 1 $20 TerraTrike

Total: $160 (estimate was $270)

4.3 Wheels

4.3.1 Research

Wheels are the components of the design that are pivotal to the maneuverability and safety of

the vehicle. This makes wheel selection an important part of the design process.

Traditionally there are three common wheel set size combinations used in recumbent tricycle

applications. The first common size combination uses three 16” wheels. This combination is

common in sport models. The second combination uses three 20” wheels. This combination is

popular in touring models. The third combination utilizes two 20” wheels and one 26” wheel. As

the development of recumbent tricycles has become more popular, companies have

transitioned towards the 26”/20” combination because of its versatility.

4.3.2 Requirements

For the wheels, it is required that they provide high quality performance under all operating

conditions. This means that the wheels will be able to perform at both high and low speeds

while making tight turns, operating on varied terrain, and traveling in a variety of weather

conditions.


The main design alternatives involve the sizing of the wheels. One potential design is to use

three common sized wheels, either 16” or 20” diameters. Traditionally this is how sport and

touring recumbent bikes are designed. The small tire size allows for easier acceleration but

Final Report


because of the size and weight, they don’t hold their speed as well and won't get a top speed as

high as a bike with bigger wheels. In addition, the materials tend to wear out sooner than larger

tires. One reason to use three equally sized small wheels would be to accommodate a more

compact bike designed for high speed capabilities. Figure 23 shown below is an example of a

sport edition trike with three 20” tires.

Figure 23. Trike design with 20" tires

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

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

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

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

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

remain stable while maneuvering over obstacles.

The team decided to use two 20" wheel in front, and one 26” wheel in back. This was chosen

because the team thought a bigger back wheel would look good and because the gearing is

slightly low so having a bigger wheel makes the trike go faster than it would with a smaller

wheel.

4.3.4 Final Design

The team decided to go with two 20” wheels in the front, and one 26” wheel in the back. This

was partially influenced by the how the gearing was set up. The team also chose a larger back

wheel for aesthetic reasons.

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

Final Report


Figure 24: Final trike layout

4.3.5 Components

Table 15. Cost considerations for wheels


20” Wheel $45 2 $90 TerraTrike

26” Wheel (price included in Gear and Chain System)

1 (price included in Gear and Chain System)

West Michigan Bike and Fitness

Axle Bolt $2.50 2 $5 TerraTrike

20” Tire $5 2 $10 Boston Square Community Bikes


20” Tire inner-tube and protective band

$2 2 $4 Boston Square Community Bikes

26” Tire inner-tube and protective band

$2 1 $2 Boston Square Community Bikes

Total: $116 (estimated was $259)

Final Report


4.4 Seat

4.4.1 Research The team has investigated several different types of seating options. There is padded seating,

mesh seating, fixed seating, and adjustable seating. Figure 25 shows an adjustable design

option, while Figure 26 shows a fixed option. Adjustable seating is considerably easier to design

around than an adjustable frame, since adjusting frame length will also adjust chain length.

Figure 25. Seat with adjustable positioning (TerraTrike model)

Figure 26. Seat with fixed positioning (Utah Trikes)

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4.4.2 Requirements

The seating of the trike must satisfy the adjustability requirements for the trike, as well as

providing the rider with sufficient comfort when in use.

4.4.2.1 Adjustability

The trike needs to be adjustable for the target range of body heights.

4.4.2.2 Comfort

The seating of the trike must be made for a comfortable ride. No user will want to ride the trike if

they are uncomfortable. The seat frame must be made to fit the entire back of the user so as to

not have bars driving into the rider’s back. Comfortable and light materials are preferred.


The team considered fabricating the seat on their own. When the team was setting up an order

from TerraTrike, the seat was included. It covers nearly everything that is needed on the trike.

The one thing about this seat is that it cost more than the team budgeted for. The team decided

that it would be worth it because there is great savings in other sections of the trike, and the

team could use more time for fabricating and testing rather than designing and building a seat.

4.4.4 Final Design

The team decided it would be best to go with TerraTrike’s adjustable seat. It has a wide range of

adjustability, it is light, and it is very comfortable. The team decided that adding a seatbelt

system would be necessary because potential users may not have any use of their abs. An

over-the-shoulder seatbelt system (4-point harness) will keep them securely in the seat.

Figure 27: TerraTrike seat with added restraints

Final Report


4.4.5 Components

The components of the seat can be seen in Table 16.

Table 16. Cost considerations for the seat


Seat Frame $90 1 $90 Terratrike

Seat Mesh $27.50 1 $27.50 Terratrike

Seat Clamp $17.50 1 $17.50 Terratrike

Seat Stay Pin $1 2 $2 Terratrike

Seat Stays Set $25 1 $25 Terratrike

M8 Nyloc Nut, SS $0.50 3 $1.50 Terratrike

M8x40mm SHSCS SS

$0.50 3 $1.50 Terratrike

M8x20 Low Head, SS

$0.50 2 $1 Terratrike

M5x30mm SHCS SS $0.50 2 $1 Terratrike

M5 Nyloc nut SS $0.15 2 $0.30 Terratrike

M5x12mm SHCS SS $0.20 2 $0.40 Terratrike

Seatbelt $26.99 1 $26.99 Amazon

Total: $194.69 (estimated was $62)

4.5 Gear and Chain System

4.5.1 Research

Gears are what give the user of a bike the ability to vary the strength or simplicity of moving the

vehicle forward. In Table 17, the possible options for a bike with three gear cassettes attached

to the pedals and nine gear cassettes connected to the wheel are presented. If the number of

gear teeth are equal from the pedaling gears to the wheel gears, one pedal will cause one

rotation of the wheel. If the number of teeth in the pedaling gear is lower than the number of

teeth in the wheel gear, the operator will need to pedal more than one cycle to get a full rotation

of the wheel. This is the easiest and slowest pedaling option and is represented in green in

Table 17. When the number of teeth in the pedaling gear is much higher than the number of

teeth in the wheel gear, one rotation of the pedals will cause multiple rotations of the wheel. This

Final Report


is the fastest and most difficult pedaling option. This is represented in red in Table 17. The gear

ratios represent how many rotations the wheel will go with one cycle of the pedals.

Table 17. Gear ratio possibilities for a 27-speed gear system

For a recumbent hand powered trike, it is generally accepted to have the hand pedaling cause

the front wheel to cycle. For a recumbent foot powered trike, it is typical to have the feet pedals

cause the back wheel or wheels to cycle.

4.5.2 Requirements

It is necessary that hand strength alone is enough to power this vehicle. The added power

necessary to cycle the feet will have an effect on what type of gearing system that will be

necessary. The gears between the hands, feet, and wheels all need to remain parallel through

turning motions so binding is not a problem. Assisted pedaling from the feet is something that

will be possible in this vehicle.


At first, it was assumed that the hand pedals, hand steering, feet pedals, and driven wheel(s)

would all be linked together. One problem that arises with this is the steering with the hands.

The front wheel could also pivot, but there is no clear way for the legs to rotate comfortably to

keep all the chains inline. All three parts need to stay straight or all rotate together. The design

alternative selected for this problem was to have hand steering independent of all the gears and

chains. The gears stay in the middle of the vehicle connecting to the back single wheel. The

steering is hand controlled and pivots the front two wheels. One would not be able to hand

pedal and steer at the same time unless they choose to use one hand for each. The design with

two wheels in front and one in back is ideal for this independent steering option and provides

plenty of leg room to work with for the leg supports.

Table 18 shows different options for gearing systems. Each option has a specific bonus for

specific connections between the hands, feet, and wheels.

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Table 18. Gearing system options

Preferably, the hand pedals should be directly connected to both the wheel and the foot pedals.

The ratio between the hands and feet should remain constant for comfort and rhythm purposes.

With alternating hand pedaling, a 1/1 teeth ratio between the hands and feet would be ideal so

the legs would alternate and the arms would alternate, similar to a running motion. For uniform

hand pedaling, a 1/2 teeth ratio between the hands and feet would be ideal so every time one

pedals down, one leg would also go down. A 1/2 teeth ratio would make the feet rotate slower,

making less power necessary for rotating the legs. A 1/4 teeth ratio would mean that even more

power can be used for moving the trike forward. Calculations for power distribution and top

speeds can be found in Appendix A.2. Power calculations and top speeds. These calculations

were based off of the following equations:

𝑃 = 𝑇𝝎 (2)

𝑇 = 𝐹𝑟 (3)

𝐹 = 𝑚𝑎 (4)

They are also based off of the fact that someone can pedal with 60 watts of power through their

arms. This number comes from pedaling at 60 rpm at level of difficulty that provides a workout

on a stationary hand pedaled recumbent bike in Calvin’s gym. The top speeds are based off of a

Final Report


calculator that can also be found in Appendix A.2. Power calculations and top speeds. The top

speeds and power distributions can be found in Table 19.

Table 19. Power distribution and top speeds

1/2 ratio 1/4 ratio

Power to wheel 47% 64%

Top speed 5.6 mph 7.7 mph

Now for the actual layout of the gears on the trike. A centralized gear set was used to connect

the hands, feet, and back wheel. For the connection between the hands and feet to the wheels,

four total options were considered. The first one is having multiple cassette gears on the forcing

and forced sides of the system. This would allow for a large range of options for speed and

incline variations. Two derailleurs will be necessary for this option: one connected to the

centralized gear set and one connected to the back wheel. Cable shifters can be used for

varying the cassettes used. The second option would be to have only the gear set on the back

wheel variable. This would make the gearing range smaller, but would eliminate the need to

mount a derailleur on the central gear hub. The third option would be similar to the first, but the

cassette stack on the back wheel would be replaced with an internal gearing hub. This option

allows for smooth, immediate shifting without the bulk of a gear train and derailleur. The internal

pulley system is the ideal design option for this project because of the smooth shifting. A user

does not need to be pedaling to change gears. The fourth option would be similar to the second;

it will only have one shifter controlling the internal gearing system. The equivalent gear teeth for

a Nuvinci (internal gearing system) shifter is a 10 tooth minimum and a 36 tooth maximum.

Appendix A.3 Gearing Ranges Considered shows many different ratio options for all four of

these considerations. The y-axis varies the size of the gear in the central gear hub that connects

to the back wheel. A minimum low gearing should be less than a regular bike because of the

added resistance from the legs. A large range is desirable to move at an enjoyable speed.

Equation 5 is used to find a revolution ratio between the back wheel and the hands. Equation 6

is used to find the set ratio between the hands and feet.

𝑅𝑒𝑣𝑤ℎ𝑒𝑒𝑙

𝑅𝑒𝑣ℎ𝑎𝑛𝑑𝑠= (

𝑁ℎ𝑎𝑛𝑑.𝑝𝑒𝑑𝑎𝑙𝑠

𝑁𝑐𝑒𝑛𝑡𝑒𝑟.𝑡𝑜.ℎ𝑎𝑛𝑑𝑠) (

𝑁𝑐𝑒𝑛𝑡𝑒𝑟.𝑡𝑜.𝑤ℎ𝑒𝑒𝑙

𝑁𝑤ℎ𝑒𝑒𝑙) (%𝑖𝑛𝑡𝑒𝑟𝑛𝑎𝑙.𝑔𝑒𝑎𝑟𝑖𝑛𝑔) (5)

𝑅𝑒𝑣𝑓𝑒𝑒𝑡

𝑅𝑒𝑣ℎ𝑎𝑛𝑑𝑠= (

𝑁ℎ𝑎𝑛𝑑.𝑝𝑒𝑑𝑎𝑙𝑠

𝑁𝑐𝑒𝑛𝑡𝑒𝑟.𝑡𝑜.𝑓𝑒𝑒𝑡) (

𝑁𝑐𝑒𝑛𝑡𝑒𝑟.𝑡𝑜.𝑓𝑒𝑒𝑡

𝑁𝑤ℎ𝑒𝑒𝑙) (6)

The first semester gear design can be seen in Figure 28 with the range of hand-to-wheel

rotation ratios provided.

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Figure 28. Diagram of gear design selections

After attempting to acquire parts for gearing, it appears that there is not a large enough range of

standard sized gears to get the desired 1/4 revolution ratio between hands and feet. The team

went back to the 1/2 revolution ratio because of this. The team worked with TerraTrike and

acquired two crank assemblies with 32 teeth on the gears attached. The team has acquired a

40 tooth, 28 tooth, and 20 tooth gear for the central gear hub. The team used a Shimano Nexus

7 internal gear hub instead of the Nuvinci for cost reasons. This reduces the gearing from a

360% to 245%.

The central gear hub was built off of a bottom bracket with a steel crank set. Aluminum spacers

were manufactured with the mill at Calvin, and the gears connecting to the hands and feet were

drilled and tapped to the aluminum spacer. The foot crank used did not have enough space to fit

the additional gears, so the arms were cut off, and keyways were made in the shaft and the

aluminum spacers so that the gears spin with the shaft. The gear connecting to the back wheel

was connected to the opposite side of the shaft with a similar aluminum spacer and keyway.

The lathe was used to make the shaft even. Bolts were threaded into the ends of the shaft to

hold the gears in place. The components for the central gear hub can be seen in Figure 29 and

the final assembly can be seen in Figure 30.

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Figure 29. Components of the central gear hub

Figure 30. Central gear hub on frame

Final Report


4.5.4 Final Design

The final design for the gearing can be seen in Figure 31.

Figure 31. Final gear setup

The final gear range can be seen in Appendix A.3 Gearing Ranges Considered along with other

ranges considered. Although the graph does not specifically show, it would be more beneficial

to start the range even lower. This information was acquired from testing.

Final Report


4.5.5 Components

Table 20 shows the components needed, and their costs in order to produce this gear system.

For the prototype, $430.10 was actually spent.

Table 20. Gear system components and cost


Shimano Nexus 7 speed $299.98 1 $299.98 West Michigan Bike and Fitness

20 tooth sprocket $10 1 $10 Alger Bikes



Crankset $17.50 2 $35 Terratrike

Crankset screws (M8x1) $2 4 $8 Terratrike

Bike chains (1/8) $12 5 $60 Boston Square Community Bikes/Amazon

Bottom Bracket Shells $10.06 2 $20.12 Amazon.com

RPM sealed bearing BB, 68X118 ENG

$7.50 2 $15 Terratrike

Central Gear Hub Shaft $15 1 $15 Bikewagon.com (Scrapped off of old bike and machined)

Central Gear Hub Bottom Bracket with bearings

$10 1 $10 Bikewagon.com (Scrapped off of old bike)

Custom aluminum spacing/joining discs

$1 2 $2 Machined

Washer $0.10 5 $0.50 From Calvin’s Shop

Bolt (1/4-20) $0.10 1 $0.10 From Calvin’s Shop

Bolt (5/16-18) $0.10 1 $0.10 From Calvin’s Shop

Screws (6-32) $0.10 9 $0.90 From Calvin’s Shop

Total Cost: $501.7 (estimate was $572)

4.6 Hand Pedals

4.6.1 Research

For a Top End trike, the hand pedals used are pedaled in tandem. This allows for a balanced

pedaling motion. The angle of the bars jutting out are probably around 60° from horizontal. The

rotating handles are made of aluminum and keep the hands slightly off of a vertical position.

Final Report


This position allows for the least amount of exertion. A user of the Top end trike that the team

encountered commented that he would like the pedals closer together. This would make the

pedaling even easier, but the space occupied by the gears need to be considered.

4.6.2 Requirements

The pedals need to be simple and comfortable. Hands closer together will allow for more power.

Hands near a vertical position will also allow for easier pedaling. The hand grips need to stay at

a constant angle and have room for a gear shifter. Initially the team though a hand brake would

be placed on the right hand, but decided to have the braking system on the steering. Since the

hand pedals will have a gear shifter connected to gear changing cables, they must be placed in

a manner that minimizes interference between the hand pedals, the gear shifter, the gear shifter

cables, and the gear located near the hand pedals.


One alternative would be to do something very similar to Top End’s design. Their design can be

seen in Figure 32 and Figure 33.

.

Figure 32. Top End hand pedal design

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Figure 33. Brake and shifter placement

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

be raised so that there is enough clearance for the legs to cycle. The shifter will be attached to a

handle. The handle will need to be extended slightly so that accidental shifting does not happen.

A second alternative would to have pedals that alternate. This style can be seen in Figure 34.

This style would mean that each hand would have to work by itself half the time. This design is

not preferred because it encourages a side-to-side motion. This side-to-side rocking motion will

not be attractive to the target customer. Some of the target customers will not be able to do that

because they will not have any strength in their abdomen.

Final Report


Figure 34. Alternating hand pedaling

http://www.bikecare.co.uk/special-needs-tricycles.html

4.6.4 Final Design

Through considering all the variables involved in the design of the hand pedals, the team

determined that best design involved a design where both hands were pedaled in tandem. This

will allow for the body to stay stable and minimize core strength required to use the trike, thus

improving the safety. As shown below in Figure 35, it can be seen how the hands will work

together to propel the bike forward.

Figure 35. Final hand pedal design

Final Report


The team wanted to model their hand pedal after the design used by Top End. This was

because of the comfort of the pedal. The team developed a SolidWorks model to represent the

final design. The difficult part of this design process was developing a way to build the

extension column for gear shifter. The final design for this is shown below in Figure 36. Another

feature designed in the model is the insertion hole. This hole, also shown in Figure 36, allows

for easy assembly and removal of the hand pedals. The final decision for the design involved

the interference of the hand pedals with the legs. Due to the limited available space between

the legs and the hands as demonstrated in Figure 11, the hand pedal had to be connected to

the crank shaft at the middle actual hand pedal. This design requires the user to split their

fingers to cover the whole pedal, but it also provides enough space to allow for the most space

possible between the top of the knees and the hands. This design feature is shown in Figure

37.

Figure 36. Hand crank to fix interference

Figure 37. Hand pedal final 3D design

Final Report


The next big step in the process was the manufacturing of the hand pedals. The team initially

thought about using a 3D printer to achieve the complex geometry of the parts but determined

that using aluminum would be a better overall decision based on the high strength over the

lifetime of the part. Input about this decision came from a variety of 3D experts who said that 3D

printing was not a good solution for manufacturing. Table 21 below also outlines some

considerations in the decision.

Table 21. Hand pedal manufacturing decision chart

Method Cost Labor Time Strength Ability to Redesign

Aluminum Low High High High

3D Printer High Low Low High

The actual manufacturing of the hand pedals was done in the Calvin machine shop. Aluminum

rods were machined down to width and hollowed out. After all the components were made,

Nico Ourensma, a fellow senior engineering student, welded the parts together. These parts

are shown below in Figure 38.

Figure 38. Manufactured hand pedals

Another big part of the design process was developing a way to attach the hand pedals to crank

shaft. This was done be disassembling and machining down a foot pedal to access the screw

part of the pedal. A before and after of this process is shown below in Figure 39.

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Figure 39. Disassembly of foot pedal

This screw insert from the foot pedal was then inserted into the aluminum welded components

and attached to the crank shaft. Figure 40 shows all the components involved in the assembly

of the hand pedal. Figure 41 shows the final assembly with the gear shifter attached.

Figure 40. Components used in hand pedals

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Figure 41. Hand pedal with gear shifter

4.6.5 Components Table 22. Costing for hand pedals


Foot Pedal $1 2 $2 Boston Square Bikes

2” Aluminum Bar

$3.55 2 $7.10 OnlineMetals.com

Washer $0.10 2 $0.20 ALRO Steel

Lock Washer $0.10 2 $0.20 ALRO Steel

Bolt $0.15 2 $0.30 ALRO Steel

Total: $9.30

Final Report


4.8 Leg Brace and Support

4.8.1 Research

4.8.1.1 Foot Pedal Research

Foot pedals on most bikes and trikes come in one of three distinct forms. The first is a simple,

rugged platform on which the foot presses. These pedals are typically textured or rigid in some

manner in order to keep the user’s shoe (and thus the user’s foot) firmly on the pedal throughout

its full range of rotation. Second, there are pedals that are designed to clip directly to specially

manufactured shoes. These allow for much more user freedom of movement and power output

by keeping the foot firmly mounted to the pedal. Finally, there are pedals that strap the foot in

place. These pedals work similarly to the clip pedals, but do not require special footwear.

However, they are larger, heavier, and provide less of a hold on the shoe. All these options can

be seen in Figure 42.

Figure 42. Standard foot pedal styles

www.nashbar.com www.performancebike.com www.aurora-collective.com

4.8.1.1 Leg Bracing Research

Leg bracing is not uncommon in physical therapy. There are many pre-existing designs for

braces and splints that limit leg movement. However, it is somewhat rare for these braces to

allow for articulation of the limb. They are generally designed to hold the leg in a single position,

allowing for the body to heal after a traumatic injury. This can be seen in Figure 43.

http://www.nashbar.com/

http://www.performancebike.com/

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

Final Report


Figure 43. Adjustable ergonomic knee brace

Royal Medical Co. Patent 277944_A1

Articulating leg bracing is less common as a tool for physical therapy. When used for this

application, the bracing is typically designed to prevent hyperextension of the knee, which could

be very useful for the application of the trike. There are also custom bracing options that are

more robust. However, these bracing solutions are generally cost-preventative. Additionally,

those braces that provide sufficient guidance for the application of this trike are generally fairly

large, intrusive, and difficult to put on. An example of such a brace can be seen in Figure 44.

Figure 44. Example of therapeutic bracing from Trulife

http://trulife.com/Brochures/us-orthopaedics-brochure.pdf

Bracing of this nature can also be found in sports. Typically, this kind of knee bracing takes the

form of a soft, slip-on support and would not prove terribly useful for the team’s application. The

exception to this is the very robust knee protection designed for use in Motocross. Due to the

extreme nature of the sport, some impressive advancements have been made in knee support

and safety. The advantage to these designs is that they are for rapid, repeated movements and

Final Report


have adjustable hyperextension locks that can be customized to each user. However, these

braces can also be expensive. An example of this brace can be seen in Figure 45.

Figure 45. Motocross articulating knee brace, listed at $1,400 per pair

http://evs-sports.com/index.php/moto/knee-braces/axis-series/axis-pro.html

4.8.2 Requirements

4.8.2.1 Pedal and Support Requirements

The requirements for the pedals in this application will be slightly different than the typical

models one would see on the market. Because this vehicle will be marketed to people suffering

from low mobility or paralysis, the pedals will be required to make up for their possible limited

movement. Thus, the pedals will need to keep the users feet firmly in place throughout their full

range of motion, even if the user has no muscular control.

4.8.2.12 Bracing Requirements

The ergonomic bracing on the system must be able to withstand prolonged, rapid, and repeated

movements during normal operation without failure. It must be able to prevent hyperextension of

the user’s legs while keeping them straight in line with the pedals. They must also not be overly

difficult to enter and exit, preferably allowing users to place their legs into the braces from

above. The braces also cannot be overly expensive, or should be designed in a way that allows

us to fabricate them in house.

4.8.3 Design Alternatives

First, the team must decide in what way to approach the bracing solution. Originally, it was

assumed that the trike would have two full-length, articulating leg braces that would guide the

user’s legs through a full range of motion. While this method would certainly guarantee user

Final Report


safety, there are many drawbacks to this option, chiefly among them cost, ease of entry, and

power loss. Another option would be to design an integrated foot-pedal and bracing system that

would not fully encapsulate the knee. Hyperextension or locking of the knee would be prevented

either by a separate, wearable brace, or by placing the pedals below the level of the seat.

Secondly, the team must also find the best way to accomplish this task. Put simply, the team

would have three different options; purchasing an existing brace, fabricating a custom brace, or

modifying an existing brace to fit their needs. Each option would have its own advantages and

drawbacks which can be seen in Table 23.

Table 23. Design fabrication alternatives for ergonomic bracing

4.8.4 Initial Design

Originally, the team was leaning towards a design that would integrate the bracing with the

pedals. These braces would be removable, but also easy to install and use for a patient that

requires them.

The design would have to allow for the braces to be loaded from above. This means that the

user would simply be able to lift their legs and place them directly into the braces. The legs

would then be strapped into place, and the brace would guide the limb throughout its full range

of motion. One point of adjustability would be designed into the brace, allowing for differing leg

lengths. Brainstorming considerations can be seen in Figure 46.

Final Report


Figure 46. Leg bracing concept sketch

4.8.5 Final Design

After weeks of brainstorming, design work, and prototyping, the team realized that a proper and

ergonomic integration of the pedals with the leg braces would not prove to be feasible within the

time allotted for the project. Problems included designing in the adjustability in a way that would

be universally accessible, aligning the bracing with the center of the leg for all users, ensuring

that there was no interference with other trike components, and manufacturing difficulties.

4.8.5.1 Supports Final Design

For the final design of the supports, the team chose to combine a set of existing bike pedals

with a pair of walking boots. Walking boots are padded, boot-shaped braces that incorporate

bracing around the foot, ankle, and calf. They are typically used for therapy and rehabilitation,

allowing the patient to walk around freely with minimal inconvenience. Figure 47 below shows

an image of a walking boot.

Final Report


Figure 47: Example walking boot

http://runsmartonline.com/blog/wp-content/uploads/2011/09/walking-boot.gif

This design is advantageous because the walking boots have already been designed to

properly brace the leg of the user as they move, ensuring that the design will not break. The

incorporated straps will also allow for easy adjustability. The boots are not so large as to be

obtrusive, but still ensure proper alignment of the leg while the trike is in use. They can easily be

modified to include a bike pedal, and are thus ideal for the use as a rapid and effective

prototype for the project. Finally, this design allows for the use of scavenged and donated parts,

greatly reducing the prospective cost of the leg support system.

Figure 48: Modified walking boot with pedal

Final Report


4.8.5.2 Bracing Final Design

Although part of the original design, the team decided to forego bracing as a part of their final

prototype. This is due to the inherent complexity of designing an integrated and adjustable leg

brace that could accommodate a variety of body types. Additionally, the client the team was

working with would not require any sort of leg or knee bracing when operating the trike. It was

decided, therefore, that professionally designed leg bracing would be worn independently of the

leg supports when needed.

4.8.6 Components

Table 24 shows an estimate of the cost of leg braces based off of research.

Table 24. Cost consideration for leg braces

Components Unit Cost Quantity Total Cost Supplier

Leg braces and Supports

$60 2 $120 Foot & Ankle Specialists

Total: $120 (estimated $100)

4.9 Brakes

4.9.1 Research

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

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

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

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

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

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

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

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

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

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

others employ the brakes on the rear wheels. The most popular trike in industry employs disc

brakes on the front two tires. In addition to active brakes, parking brakes had to be researched.

Many disc brakes can be outfitted with a simple parking brake allowing for safety and assurance

while stopped. Using basic rim brakes, an alternative parking brake system would have to be

implemented.

Final Report


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 10 mph while carrying a load of 90 to

250 lb. The required stopping distance for this application will be 10 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. These brakes will require pressure from the operator to

provide adequate power to stop the wheels. In addition to having an operable brake for stopping

the vehicle while moving, a parking brake will be required to keep the bike stopped while not in

operation. The type of brakes in consideration are listed in Table 25. The type of parking brake

will be dependent of what brake type is chosen.

Brake types that were considered are rim brakes, drum brakes, and disk brakes. Simple

advantages and disadvantages of the brakes are listed below in Table 25 while a more in-depth

decisions showing how the team got to the final design is shown in Table 26.

Table 25. Advantages and disadvantages of brake options

Brake Type 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

Final Report


Table 26. In-depth decision for the specific project

Brake Design Pros Cons

-2 rim brakes attached to back wheel.

- RH cycling handle - RH steering handle

-Low Cost -Braking possible with every hand location -Low weight

-Less stability in front wheels -Possible difficulties faced when entering vehicle

- 1 rim brake attached to back wheel

- RH cycling handle -2 disk brakes on front tires

- Brake handles attached to each steering hand pedal

-Increased maneuverability while braking (braking capable for each individual wheel) -Brake locking capabilities for easy entry/exit

-High cost -High weight -Lack of braking capabilities for all hand arrangements

-1 disk brake on back wheel with double clamps

- RH cycling handle - RH steering handle

-Low weight -Low cost

-Lack of balance while entering and exiting -Difficult parking brake arrangement

Rim brakes use two pads that are pressed against the rim of the rotating tire to provide stopping

power. Drum brakes used two pads but those pads are pressed outward against the inside of a

hub shell as compared to the rim itself. Disc brakes work by pressing two pads against a metal

disc that is attached to the axle of the wheel. Shown below in Figure 49 is a visual

representation of the different brake options.

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

because of several different benefits. Many benefits surround the disc brake itself. It has great

stopping power, can easily be fixed or modified for specific riders, requires minimal

maintenance, and most importantly has the ability to work with the chosen gear system and tire

placement. Drum brakes and simple rim brakes would provide good alternatives, but the

benefits of using disc brakes outweighed the benefits of the other systems. It was also

determined that the disc brakes would be operated via a hand brake. A hand brake system as

compared to alternatives such as foot braking was implemented because of its obvious benefits.

Those include easy accessibility for the operator, easily mountable, low costs, and they don’t

require strength beyond grip strength which will allow for the product to fulfill the needs of a

variety of clientele.

Final Report


Figure 49. Rim, drum, and disc brake

http://img.hisupplier.com http://www.amazon.com http://www.mountainbikestoday.com

Table 27 shows multiple price considerations for brake systems.

Table 27. Cost comparison for brake types

Initially the team considered multiple designs for the arrangement of the brake handles. These

designs with pros and cons are laid out in Table 28.

http://img.hisupplier.com/

http://www.amazon.com/

http://www.mountainbikestoday.com/

Final Report


Table 28. Pros and Cons of Braking Arrangements

Design Pros Cons

Handles on both hand pedals and both steering hand locations

Easy accessibility wherever hands are

Maximum safety

Braking capability while steering and pedaling

High costs

Complex design and integration

Handles on only hand pedals Easy accessibility

Good safety

Complex design

Lack of braking while steering

Handles on only steering Easy integration

Good safety

Lack of braking while pedaling

One handle on steering and one handle on hand pedals

Braking capability while pedaling and steering

High safety

Difficulty implementing

Awkward hand positioning

After weighing many of the pros and cons, the team finally decided that the best design would

be to have levers on only the steering handles. This decision was made because it was a

system that could be implemented easily and still accomplished the goals of a braking system.

The only negative of this design was that there could not be braking done while hands are on

the hand pedals. After much thought and consideration, the team realized that a user probably

wouldn’t need to brake while pedaling, so having brakes on the hand pedals would not be

necessary and would actually cause more design issues than it would fix.

The next task in the design of brake system was determining what brake handles would control

which brakes. Since each handle on the steering column had its own brake handle, the team

considered having the left handle control the left brake and the right handle control the right

brake. After thinking about this design, the team realized that there was one big flaw in the

design – the possibility of unbalanced braking. The team considered the fact that a user might

keep one hand on the crank handle and another hand on the steering handle. If this happened

and the user utilized a brake under the independent braking design, only one tire would brake

and consequently the bike might flip or become unstable. Because of this, the team decided

that the best option would be to develop a way that each handle would control both brakes.

Through research the team found brake doublers what would accomplish this task, but due to

the high costs, the team decided to manufacture their own system to accomplish the braking.

This was accomplished by using a clip from a cantilever brake and several crimps.

4.9.4 Final Design

As you can see in Figure 50 and Figure 51, the two cables from each individual brake handle

come together and get crimped into the back end of the cantilever brake clip. The other end of

this clip has a groove which allows for a brake cable that is attached to both disc brakes to be

inserted. Which this design, when a handle is pulled, that brake cable triggers the cantilever clip

to pull on the joining cable which then pulls on the disk brakes and braking is accomplished.

Final Report


Figure 50. Close up of brake integration site

Figure 51. Brake and housing design

Final Report


4.9.5 Components

Table 29. Brake BOM component list


Alhonga Disk Brakes $15 2 $30 TerraTrike

Brake Lever Set $10 1 $10 TerraTrike

Brake Cables with housing

$12.99 2 $25.98 Amazon

Cantilever Brake Clip $1 1 $1 Boston Square Bike

Crimps $0.10 2 $0.20 Lowe’s

Total Cost: $67.18 (Estimate of $160)

5. Testing

5.1 Ease of Use

5.1.1 Timing transfer and positioning on trike

The team timed team members, new abled body users, and the client getting in and out of the

trike. The results for this can be seen in Table 30. The team’s goal was to have someone able

to do the full transfer by themselves in less than 5 minutes.

Table 30. Loading and unloading times

User Load Time (min)

Unload Time (min)

Total (min)

Jack (team member acting as paraplegic)

2:01 1:04 3:05

New abled body user 2:37 0:29 3:06

Nancy (client with MS) 2:45 N/A 2:45+

5.2 Safety

Braking distance is a key measure that the team thought was very important for safety. To

measure this, a tape measure was laid out in a flat parking lot. A user (abled body male) got to

top speed before the tape measure. Both brake handles were enabled when the user got to the

tape measure, and the distance to stop was measured. Results of this can be seen in Table 31.

Final Report


The goal of the stopping distance is to be less than 10 feet. The brakes seem to respond very

well, and the team is very happy with the results.

Table 31. Braking distance from top speed

User Braking distance from top speed (ft)

Jack (abled body male) 4 ft 8 in

Jack (abled body male) 5 ft 8 in

Jack (abled body male) 5 ft

AVERAGE: 5 ft 1 in

5.3 Speed

5.3.1 Time top speed on trike on level ground

The team timed a team member (abled body male) on the top speed using just their hands to

pedal. A tape thirty foot tape measure was laid out in the parking lot. The user got to top speed

before traveling the thirty feet. This was timed and the top speed was calculated. Results can be

seen in Table 32. The team’s goal was to be able to go 10 mph, and the predicted value was

5.6 mph. The team was close to achieving the initial goal using an abled body person. Results

may have more variation with a variety of potential users of the trike.

Table 32. Top speed test results

User Top Speed (mph)

Nick (abled body male) 8.92



AVERAGE: 8.64

5.3.2 Acceleration of trike from standstill

We had one team member (abled body male) do the acceleration test. For this test, the team

had the trike start at a standstill and time how long it takes to travel thirty feet using just their

hands to pedal. This was enough information to calculate the acceleration. To have a goal, the

team found bike acceleration values. These can be seen Figure 52. The average acceleration of

a bike is 5.5 ft/s2 on flat ground. Using the calculation that about half of the energy from the

hands will be going to the wheel, the team expects an acceleration value of 2.75 ft/s2. The

team’s results can be seen in Table 33. These results match and also exceed expectations. A

user with limited mobility may have results less than these.

Final Report


Figure 52. Bike acceleration test results

http://www.its.pdx.edu/upload_docs/1368048473.pdf

Table 33. Acceleration data

User Acceleration (ft/s2)




AVERAGE: 3.02

5.4 Turning The team measured the turning circle of the trike, both turning left and turning right. The

measurement was taken at a straight distance from the outside of the trike to the outside of the

trike when the path of the trike was parallel to the starting position of the trike. The results can

be seen in Table 34. The goal was to have both sides be no more than 26 feet. The trike does

fall under this goal. Shortening the frame would improve the turning circle even more, but the

team likes the long frame for its stability and does not want to sacrifice that.

Table 34. Turning circle results

Trial Left Turning Circle (ft)

Right Turning Circle (ft)

Trail 1 20 ft 11 in 20 ft 2 in

Trial 2 20 ft 4 in 20 ft 7 in

Trial 3 20 ft 7 in 21 ft 6 in

AVERAGE: 20 ft 7 in 21 ft 1 in

Final Report


5.5 Weight The team had the goal of producing a product of weight 60 lbs. After final assembly, the team

weighed the trike and found the final weight to be 67 lbs. This weight could be reduced in the

future by using lighter components such as thin walled aluminum in the manufacturing of the

frame. Although the frame is heavier than expected, there are no negative consequences of a

trike with higher weight.

5.6 Client Satisfaction

5.6.1 Satisfaction Survey

The team had the client test ride the trike in the Tennis and Track Center in Calvin’s field house.

The team gave her some things to rate on a 0-5 scale, 5 being the best and 0 being the worst.

Having an overall comfortable ride for the user is of the utmost importance for TheraTryke. The

team wants the user to maintain comfort levels over extended periods of time while operating

the trike. The client’s ratings on certain aspects of the trike can be seen in Table 35.

Table 35. Satisfaction survey given to client

Section Rating: 5 (Great) – 0 (Bad)

Steering/hand pedaling interaction 4

Loading 2

Unloading 2

Braking 5

Parking Brake 3.5

Shifting 4.5

Enjoyment 5

Hills N/A

Start moving N/A

Overall Feel 4

5.6.2 Avoiding spasms

To test the therapeutic benefits of the leg cycling aspect of this trike, the team wanted to have

some of the paraplegics that the team have been in contact use the trike. For the test, the

paraplegic will use the trike daily for a set amount of time for a set amount of days in a row. The

user will not do any of their stretching routines, so this will be a direct substitute. After each day

of the test, the user will log comments on how well the trike is stretching their legs. The team ran

out of time and did not feel comfortable in having a paraplegic test the trike with the current

bracing option.

Final Report


5.7 Outdoor usage

The team wanted to test the trike going up hills, down hills, and through grass. The team did not

come up with a way to put a value to what was tested, but a lower gearing would be attractive

for grass and going up hills. Higher gearing going downhill would be a secondary addition. In

addition to developing a lower gearing system, the team also made an easy assist bar with the

capability of pushing the user through difficult terrain (hills, grass, curbs).

5.8 Economic Sustainability

One goal of the project is to determine if this project would be economically sustainable in a full

production environment. In order to determine the economic sustainability, an in depth financial

analysis was to be completed. This financial analysis took into account all fixed and variable

costs associated with the production of the product including materials and labor costs, potential

employee salaries and all costs associated with the manufacturing facilities. Using several

different business statements including a cash flow statement, a break-even analysis, an

income statement, as well as an analysis of several ratios such as the profit margin percentage,

gross margin percentage, and debt to equity ratio, the team was able to determine the potential

profits of the company. It was determined that the potential profits in the first three years of

operation would be $1,715,166. This was also based off of several assumptions. The first

being that the company would start out with 1000 sales in the first year. The next assumption is

that the company will grow at a steady 15% over the first three years of operation. The team

knows that these are optimistic assumptions, but based off of market research and trends, the

team feels like these assumptions are realistic.

6. Business Analysis

6.1 Market Research

6.1.1 Existing Competitors

Several competitors exist to TheraTryke’s product design. This section outlines the competitors

that are in the target market currently. These companies are competitors in the design of hand

and/or foot pedaled trikes. Some of these companies do have products that simultaneously

pump both the hands and feet, but none of them demonstrate the same integration of

therapeutic benefits and recreational activity that the team is attempting to design.

6.1.1.1 Terratrike

TerraTrike is a recumbent tricycle company based in Grand Rapids. They are very well known

in the West Michigan area and are slowly becoming more well-known nationally. Their prices

range from $899.00 for low end models to $3,999.00 for their high end models

Final Report


6.1.1.2 Top End Trikes

Tope End Trikes produce high performance arm, chest and abdominally driven hand-powered

trikes. They are mainly for recreation and competition for those with physical disability. Prices

range from $2,300 to $7,500.

6.1.1.3 Rehatri

Rehatri is a line of trikes from Gomier with the goal of providing therapeutic recreational options

to individuals with disability, specifically children with Cerebral Palsy. Designs are simple with

the main use being flat, level pavement only and they do not provide adjustment in their gear

drive. Prices range from $895.99 to $1,250.00

6.1.1.4 Amtryke

AmTryke LLC is a therapeutic trike manufacturer. The trikes produced by this company are also

dual drive operated, meaning that they can be hand and/or foot powered when in use. The

prices of an AmTryke device range from $800 to $1,250.

6.1.1.5 Catrike

Catrike is a recumbent trike company created in 2000 by Paulo Camasmine, a Brazilian

Mechanical Engineer. Their vision is to create new high quality products to improve people’s

lives. Prices at Catrike range from $2,150.00 for their low end models to $2,950.00 for high end

models.

6.1.2 Target Markets

The target market for TheraTryke consists of individuals who have paraplegia or that do not

have full mobility in their limbs or core. TheraTryke’s target market pertains to those seeking out

therapeutic rehabilitation with a recreational application.

Final Report


6.2 Financials

6.2.1 Budget

Table 36 shows the estimated budget for the prototype. Actual production costs are shown in

Table 37.

Table 36. Estimated project cost

Component Price

Steering $270

Wheels $259

Seat $62

Gearing System $572

Hand and Leg Pedal $0

Leg bracing $100

Brakes $160

Frame $70

Total $1,493

6.2.1.1 Developmental

As the budget above represents the predicted cost of producing one unit for the final product, it

doesn’t account for the fact that the team has sources that will donate parts and services. The

prototype should have a smaller cost because many components have been donated. One of

these donors is Calvin College. They have a variety of scrap material that can be used in

prototyping. In addition to that, friends and colleagues have donated spare parts that have been

used. The actual cost for the prototype can be seen in Table 37.

Final Report


Table 37. Actual money spent on prototype

Date Description Cost Balance

9/30/14 Beginning Balance

$500.00

1/22/15 Steer/Gear/seat components from TerraTrike 532.70 -$32.70

2/11/15 Bike chains 29.07 -$61.77

2/11/15 Aluminum piping 124.56 -$186.33

2/11/15 Back wheel/back gearing system 299.98 -$486.31

2/11/15 Brake Cables 25.98 -$512.29

2/14/15 Tires from Boston Square Community Bikes 22.00 -$534.29

2/20/15 Restraint and Bottom Bracket Shells 47.77 -$582.06

3/2/15 Shifting cable 5.50 -$587.56

4/21/15 14' shifting cable 11.65 -$599.21

4/21/15 parking for DisArt Festival 8.00 -$607.21

5/12/15 Screws for Trike 6.73 -613.94

The total money spent by the team to make the prototype is $1,113.94.

6.2.1.2 Production

A large majority of the costs will come during the production phase. This includes purchased

parts such as gear systems and brakes. This will also include material costs for the frame and

any other components necessary for the production of the product.

6.2.1.2.1 Fixed Cost

There will be no fixed costs for this project. As the team is using all of Calvin’s facilities, no fixed

costs will associated with housing any phases of production nor the production itself.

6.2.1.2.2 Variable Cost

All of the costs associated with this project will be variable costs. This is because all the costs

will be materials, parts, or services. In Table 38, all the parts for one trike can be seen and all of

the prices associated with the part.

Final Report


Table 38. Final BOM of the trike


Frame

1-3/4” OD x 1/8” thk pipe $126.00 55.4% $69.80 ALRO Steel

Rear Wheel Frame Material $10.00 1 $10.00 ALRO Steel

Central Hub Aluminum Shell $14.24 1 $14.24 ALRO Steel

Bottom Bracket Aluminum Shell $28.48 2 $56.96 ALRO Steel

Powder Coat – Blue (1509) $75.00 1 $75.00 Custom Frame Powder Coating

Push Bar (Aluminum Shaft) $23.20 1 $23.20 Metals Depot

Push Bar (Bike Handle $35.00 1 $35.00 Cambria Bicycle

Welding $22.80/hr 8 hrs $182.4 In house assumption

Steering

Tie rod end, M8 Male LH $5 2 $10 TerraTrike

Tie rod end, M8 Male RH $5 2 $10 TerraTrike

M8 hex nut, Tie rod end nut, LH $0.25 2 $0.50 TerraTrike

M8 hex nut, Tie rod end nut, RH $0.25 2 $0.50 TerraTrike

Tie Rod, Tour II, linkage steer $17.50 2 35 TerraTrike

Steering Brace, Tour II w/bolts and nuts $30 1 $30 TerraTrike

HandleBar $20 1 $20 TerraTrike

Wheels

20” Wheel $45 2 $90 TerraTrike

26” Wheel (price included in Gear and Chain System)

1 (price included in Gear and Chain System)

West Michigan Bike and Fitness

Axle Bolt $2.50 2 $5 TerraTrike



20” Tire inner-tube and protective band $2 2 $4 Boston Square Community Bikes

26” Tire inner-tube and protective band $2 1 $2 Boston Square Community Bikes

Seat

Seat Frame $90 1 $90 Terratrike

Seat Mesh $27.50 1 $27.50 Terratrike

Seat Clamp $17.50 1 $17.50 Terratrike

Seat Stay Pin $1 2 $2 Terratrike

Final Report


Seat Stays Set $25 1 $25 Terratrike

M8 Nyloc Nut, SS $0.50 3 $1.50 Terratrike

M8x40mm SHSCS SS $0.50 3 $1.50 Terratrike

M8x20 Low Head, SS $0.50 2 $1 Terratrike

M5x30mm SHCS SS $0.50 2 $1 Terratrike

M5 Nyloc nut SS $0.15 2 $0.30 Terratrike

M5x12mm SHCS SS $0.20 2 $0.40 Terratrike

Seatbelt $26.99 1 $26.99 Amazon

Gear and Chain System

Shimano Nexus 7 speed $299.98 1 $299.98 West Michigan Bike and Fitness




Crankset $17.50 2 $35 Terratrike

Crankset screws (M8x1) $2 4 $8 Terratrike

Bike chains (1/8) $12 5 $60 Boston Square Community Bikes/Amazon

Bottom Bracket Shells $10.06 2 $20.12 Amazon.com

Hand Pedals

Foot Pedal $1 2 $2 Boston Square Bikes

2” Aluminum Bar $3.55 2 $7.10 ALRO Steel

Washer $0.10 2 $0.20 ALRO Steel

Lock Washer $0.10 2 $0.20 ALRO Steel

Bolt $0.15 2 $0.30 ALRO Steel

Leg Brace and Support

Leg braces and Supports

$60 2 $120 Foot & Ankle Specialists

Brakes

Alhonga Disk Brakes $15 2 $30 TerraTrike

Brake Lever Set $10 1 $10 TerraTrike

Brake Cables with housing $12.99 2 $25.98 Amazon

Cantilever Brake Clip $1 1 $1 Boston Square Bike

Crimps $0.10 2 $0.20 Lowe’s

Total Cost: $1538.37

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6.2.2 Funding

6.2.2.1 Calvin College

The team is given an initial budget of $500 from Calvin College to use towards any purchases

necessary for the project. The team was able to use more than this from Calvin because not

every team used all of their budget.

6.2.3 Potential Profits.

6.2.3.1 Selling Single Unit

The team determined that the market value of the product is $3,000. This is assuming the total

cost of production to be $1538.37. The selling price of $3,000 also accounts for overhead cost,

shipping costs, and includes a retail markup to allow for a profit margin of 23%.

6.2.3.1 Yearly Selling Forecast

Based off of a variety of calculations that include an income statement, a statement of cash

flows, and a break even analysis, the company was able to determine potential profits for the

product. These calculations used fixed and variable costs, projected sales quantities and costs,

taxes, and interest. After all variables are taken into account profits in the first year were

determined to be $422,280. This was based off of 1000 sales. In the second year, the profits

increased to $555,936, and in the third year, profits increased to $736,950. Over the first three

years, the company is assuming 15% growth. This continual growth shows that within 5 years

after initial production, the team could be seeing profits of almost $1,000,000. The team

realizes that profits will eventually stabilize as the market becomes saturated with similar

products, meaning that the team needs to take advantage of this timing and implement

immediate production.

7. Project Management

Project management is essential in conducting the steps to complete the design and

implementation of a product. Clear goals and structured scheduling will be required to complete

the project under the given time constraints and budget limitations. The management of this

project is allocated to three sub categories which include work division, team organization, and

scheduling.

7.1 Work Division

The team is made up of all mechanical engineers with similar backgrounds which gives

versatility within the team. This has its advantages and disadvantages when it comes to the

distribution of work. Each member is capable of working on all the different jobs necessary to

complete the project which enables overlap in certain areas, but it is difficult because each

Final Report


member has certain visions in mind about what the overall design will look like. At the

beginning of the school year, the team met to discuss the division of work. They discussed all

the components necessary to make the project a success and then distributed the work so

everyone would have an idea of their tasks for the semester. At the end of each week, tech

memos are assembled so the whole team and the advisor will be aware of what had been

completed, and what would need to be complete in the upcoming weeks. Although each

member has certain responsibilities, all of the tasks overlap allowing for team collaboration on

almost all aspects of research and development.

7.2 Team Organization and Management

Time is a barrier that many teams have struggled with in past years. The team has realized this

at many steps during the school year. Management of time and organization of responsibilities

are both large components of this project to help push for continual progress and to avoid

uncertainty of what should be done next. Professor Wunder, the team’s advisor, has done a

good job in pushing us to hit certain deadlines for design decisions. Weekly technical memos

are submitted to him to show where the team stands. Included in these memos are what has

been done recently, and what the team will be doing in the near future. In addition, a detailed

Work Breakdown Structure (WBS) has been made to outline the tasks for the entire year. The

WBS shows each task, the predicted start date, and the estimated hours of completion. Actual

hours are added in once the task is complete. The project completion percentage is updated

each time progress on a task is made.

The team has a work log that is updated with the person’s name, the task he worked on, the

date he worked on it, and the hours spent doing this task. This is a measure to see where time

has been spent and to see how much time each team member has put into their responsibilities.

The responsibilities of each team member during the first semester can be seen below in Figure

53. This was mostly market research and initial design. Because of all the relationships between

each part of the project, there had to be clear communication between the team members. Each

team member should have a good understanding of the others section. They will not have

decision power over one in charge of a section, but they will have the power to make

suggestions to make sure that each part is working in harmony with their respective sections.

For the second semester, the team was organized slightly different. This can be seen in Figure

54. This semester consisted of acquiring parts and manufacturing the systems. The team also

was more conscious of checking each other’s work. This can be seen by the arrows coming

from the bottom.

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Figure 53. First semester team organization

Figure 54. Second semester team organization

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7.3 Scheduling and Milestones

In Figure 55, it shows the time dedicated to the project over the school year. The second

semester was not documented as well as the first semester, so team members estimated how

many hours per week they worked during second semester. Figure 56 shows time distribution

between parts of the project for the first semester, the initial design phase. A detailed WBS can

be found in Appendix B.

Figure 55. Work log

Figure 56. Distribution of work time

0

10

20

30

40

50

60

70

80

90

Tota

l Ho

urs

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8. Acknowledgements

There are many individuals and organizations have been very helpful and provided great insight

to the team throughout the entire project. The team would like to give a special thanks to the

following:

Boston Square Bikes

Tom Bulten and the whole Boston Square Bike staff provide the team with information about

many aspects of how bikes and trikes work. They provide workspace and help the team

develop hands on experience.

Calvin College

Calvin College provides the team with many different resources including workspace and

materials along with providing a generous portion of the budget.

Custom Frame Coatings

Custom Frame Coatings has generously powder coated the prototype frame for no cost. They

like the idea of the project and wanted to help out.

Cara Masselink

Cara, an occupational therapist at Mary Free Bed Rehabilitation Hospital, provids the team with

information regarding the benefits of therapeutic aspect of the design.

CJ Verbrugge

CJ, an employee at Mary Free Bed Rehabilitation Hospital, helps explain the possible

therapeutic benefits of a therapeutic tricycle.

Dr. Kenyon

Dr. Kenyon, a pediatric physical therapist at GVSU, gives insights to the therapeutic advantages

of a device like the one the team is designing.

Dr. Lisa Van Arragon

Dr. Lisa Van Arragon was involved with the DisArt (disability art) Festival in Grand Rapids. This

is an international art show where the artwork has either disability themes or is made by

someone with a disability. She connected the team with the event. The team had a station to put

pictures of the trike, and the team also gave a collaboration presentation during the event.

Dr. Meyer

Dr. Meyer, a Calvin exercise science professor, has provided the team with information

regarding the physical therapy and therapeutic aspect of the design.

Foot & Ankle Specialists

Foot & Ankle has generously donated three walking boots to be used for the bracing system of

the legs in the prototype.

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Jeff Yonker

Jeff, a paraplegic and user of a hand powered recumbent trike, provides the team with advice

regarding the design and use of the trike.

Nancy Remelts

Nancy, acting at the team’s main client, provided guidance in the development of the product.

She helped give the team insights as to what would be most beneficial to potential users.

Phil Jasperse

Phil is the metal and woodshop supervisor at Calvin. He helps the team with many parts of the

project especially involving the development of prototypes.

Pierre Vos-Camy

Pierre, a paraplegic, shares his thoughts on what would make the product useful and

successful. As a user of a recumbent trike, Pierre helps demonstrated aspects of trike design

that the team implemented in their design.

Professor Ermer

Professor Ermer provides the team with great information regarding the development of the

gear system.

Professor Tubergen

Professor Tubergen acts as the team’s industrial consultant. He provides great insight to many

aspects of the project including design, organization, and prototyping.

Professor Wunder

Professor Wunder is the team's faculty advisor. He helps push the team towards success by

providing both advice and criticism. He helps keep the team on task by providing deadlines and

sharing useful project management techniques.

Progressive Surface

Phil Savickas and Greg Parlmer have offered their time after their work hours to weld the frame

together. The welding expertise they have offered is very much appreciated.

TerraTrike

TerraTrike provide the team with great information regarding all aspects of trike design. This

included braking, steering, and frame design.

Final Report


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/

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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

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10. Conclusion

The team is very happy with the state of the prototype. The client has given it a test ride and

enjoyed it. If the trike is proven to be reliable, the team is comfortable in handing it off to her. As

for the status of the trike after this class, the team plans on showing to the therapeutic and

recreational department at Mary Free Bed Hospital. The team is eager to hear feedback from

them and will reassess the plans for the project after the feedback. The team will also examine

the possibility of patenting the trike.

Final Report


11. Appendices

A. Gearing Calculations

A.1 Excel sheet on gears

Table 39. Excel sheet for gear considerations

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A.2. Power calculations and top speeds

Figure 57: Power Calculations

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Figure 58. Bike speed calculator

www.bikecalculator.com

http://www.bikecalculator.com/

Final Report


A.3 Gearing Ranges Considered

Figure 59. Gear ranges considered

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B. Work Breakdown Schedule

Table 40. Project work breakdown schedule

Task Name Duration Start Finish

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

Milestones 175 days Mon 9/8/14 Fri 5/8/15

Project Definition and Client Choice 39 days Mon 9/8/14 Thu 10/30/14

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

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

Prototyping Complete 96 days Fri 11/28/14 Fri 4/10/15

Presentation Complete 11 days Mon 4/6/15 Mon 4/20/15

Final Report Complete 25 days Thu 4/9/15 Wed 5/13/15

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

DisArt 10 days Tue 4/7/15 Mon 4/20/15

Banquet Night 10 days Mon 4/27/15 Fri 5/8/15

PPFS and Reports 150 days Wed 10/15/14 Tue 5/12/15

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

Final Report


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

Stearing Mechanism 5 days Mon 11/10/14 Fri 11/14/14

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

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

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

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

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

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

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

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

Consultant Report 5 days Mon 3/9/15 Fri 3/13/15

Final Design Report 27 days Tue 4/7/15 Wed 5/13/15

Website Creation 160 days Thu 10/2/14 Wed 5/13/15

Budget 35 days Thu 10/23/14 Wed 12/10/14

Fund Distribution 20 days Fri 10/24/14 Thu 11/20/14

Preliminary Cost Estimates 25 days Fri 10/24/14 Thu 11/27/14

Final Budget 5 days Fri 11/28/14 Thu 12/4/14

Exterior Funding 30 days Thu 10/23/14 Wed 12/3/14

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

Final Report


TerraTryke 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 Decisions 10 days Fri 12/19/14 Thu 1/1/15

Frame Prototype 20 days Thu 2/12/15 Wed 3/11/15

Install Steering w/ Front Wheels 2 days Thu 3/12/15 Fri 3/13/15

Install Back Wheel, Foot/Hand

Pedals, Central Hub 2 days Mon 3/23/15 Tue 3/24/15

Install Chain, Shifting Cables 4 days Tue 3/24/15 Fri 3/27/15

Braking Installation 3 days Mon 3/30/15 Wed 4/1/15

Installation of Seat, Pedals,

Bracing 2 days Thu 4/2/15 Fri 4/3/15

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

Attach Seatbelt 3 days Thu 3/12/15 Mon 3/16/15

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 Ration Calculations 20 days Thu 11/27/14 Wed 12/24/14

Positioning of Gears 25 days Thu 12/25/14 Wed 1/28/15

Mounting Options and Control 30 days Thu 1/29/15 Wed 3/11/15

Final Report


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

Tryke 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 30 days Thu 3/5/15 Wed 4/15/15

Smoothness 28 days Thu 3/5/15 Mon 4/13/15

Wheels In-Line 10 days Thu 3/5/15 Wed 3/18/15

Gear Changing 28 days Thu 3/5/15 Mon 4/13/15

Ease of Ride 28 days Thu 3/5/15 Mon 4/13/15

Transfer 28 days Thu 3/5/15 Mon 4/13/15

Human Functionality 50 days Fri 1/30/15 Thu 4/9/15

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C. User Experience Definition

A definition of the “User Experience” as imagined by the TheraTryke team.

The user will exit their house and approach the trike. First, they will reach down and disengage

the parking brake in order to allow them to orient the trike. There will be one parking brake on

each steering handle so that it does not matter which side the user is coming from. In order to

move the trike they will have to push or drag it into the correct position. The easiest way to

move the trike will be to back the trike straight out of the garage. What will be difficult to do

alone will be turning the trike around while holding one steering handle on the side of the trike.

Assistance may be necessary. After positioning the trike, the user will once again engage the

parking brake. The user will properly adjust the seat in order to match their leg length. This may

mean getting in and out to test the distance to the pedals. There could be different height values

on the adjustment options. They will then transfer to the trike from their wheelchair or sit down

directly. Users who lack abdominal control will immediately strap their torso to the seat’s

backrest. After sitting down and orienting themselves, the user will pick up their legs and place

them directly into the leg brace assemblies. With the hand pedal column in front of them, they

will need to bring one leg very close to their body, or the stand will be collapsible. If the stand is

collapsible, something needs to be in reach to bring it back up and to lock it into place. With

their legs stable in the braces, they will first strap in their feet and lower legs. Then, the user will

adjust the knee brace so that it is centered on their knee, and then strap in their lower thigh. If

the user does not have control of their abdominals they will require assistance to strap in their

lower legs and feet. In this way, both the braces and the seat adjustment will protect the user

from hyperextension. The lower leg brace will be detachable from the foot pedal so that the user

will be able to choose to use the bracing system or not.

After properly orienting the trike and transferring to the seat, the user will begin to pedal.

Pedaling will be done with hands. Leg usage is a bonus for people without paraplegia, but that

is not the target user. If the user is initially in too high a gear to start pedaling, they will cycle

down on the Nuvinci variable pulley system in order to make pedaling easier. They will slowly

accelerate to a comfortable rolling speed, adjusting their gear ratio as desired. During use, they

will travel over small bumps, ascend and descend slopes, stop for traffic lights, avoid possible

obstacles, and turn around standard road corners. In addition, they may travel along straight,

crowned roadways, during which their trike will keep traveling forward. In order to turn, the user

will remove one or both of their hands from the pedals and grab the steering handles located at

waist height. After turning, they will remove their hands from the steering handles and expect,

once again, to remain traveling straight. At any point in time during this procedure, the user will

have access to braking. While pedaling, the user’s legs will be traveling through their full range

of motion at a rate directly proportional to the rate of hand pedaling. At no point will they ever be

fully extended in the locked position.

Upon returning to their home, the user will have sufficient control of the trike to be able to pull

directly up to their waiting wheelchair and perform a transfer if needed. The trike will then be

Final Report


stowed in the garage in a similar manner to which it was removed. Assistance may be

necessary for stowing away the trike.

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D. Business Analysis Calculations

Table 41. 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 42. 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

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Table 43. 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

Final Report


Table 44. 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 45. 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

Final Report


Table 46. Fixed Operating Costs for TheraTryke

Fixed Operating Costs

Building 250000

Advertising 100000

General and administrative salaries 150000

Selling 100000

Total 600000

Table 47. Variable Operating Costs for TheraTryke

Variable Operating Costs

Year 1

Sales commissions

150,000.0

Shipping Costs 300,000

450,000.0

Year 2

Sales commissions

175,000.00


525,000.00

Year 3

Sales comissions

200,000.00


600,000.00


Units Sold 3,000 3,500

4,000

Final Report


Table 48. 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 49. Fixed COGS for TheraTryke

Fixed Costs of Good Sold

Manufacturing Facilities 15000

Manufacturing management salaries 100000

Benefits 100000

Rent 75000

290000

Final Report


E. Frame Design Analysis

E.1 Weight Determination

Figure 60. Aluminum 6061-T6 frame weight

SolidWorks

Final Report


Figure 61. Chromoly 4130 alloy steel frame weight

SolidWorks

Final Report


Figure 62: E.3 Titanium alloy 3AL-2.5V frame weight

SolidWorks

Final Report


E.2. Maximum Deflection and Stress

Figure 63. Al 6061-T6 Von Mises stress analysis

Figure 64. Al 6061-T6 displacement analysis

Final Report


Figure 65. Ti 3AL-2.5V Von Mises stress analysis

Figure 66. Ti 3AL-2.5V displacement analysis

Final Report


Figure 67. Chromoly 4130 Steel Alloy Von Mises stress analysis

Figure 68. Chromoly 4130 Steel Alloy displacement analysis

Final Report


Figure 69. Al 6061-0 Von Mises stress analysis english units (psi)

Figure 70. Al 6061-0 Von Mises stress analysis metric units (𝑁

𝑚2)

Final Report


Figure 71. Al 6061-0 displacement analysis english units (in)

Figure 72. Al 6061-0 displacement analysis metric units (mm)

Final Report


F. Steering and Pedaling Concept

Figure 73. Concept to combine steering and pedaling

Final Report


G. Final Prototype Images

Figure 74. Final prototype

Figure 75. Top view of prototype

Calvin College Engineering Design... · Calvin College Engineering THERATRYKE Final Report Team 5...

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