Wheelchair Design in Developing Countries:
Redesigning the Trike Frame
Fiona Hughes, Gina Policelli, Ashley Thomas, and Jodie Wu; Massachusetts Institute of Technology
Most Critical Module
Current Design Facts:
• Strength of the base frame
Introduction:
Each year, tens of thousands of wheelchairs are donated to Africa in hopes of helping
the nearly 20 million people in Africa in need of a wheelchair. However, within
months, these wheelchairs lose their functionality as they cannot survive the harsh
terrain in Africa. In Africa, many of the roads are unpaved and buses are inaccessible
to many wheelchair users, forcing wheelchair users to travel more than 5 km each day
over conditions in which an ordinary wheelchair was not designed for.
Local manufacturers have come up with a tricycle design that allows for easy travel
over long distances through the use of a hand crank and a three-wheel design for
added stability. However, these designs often bend, hindering the movement of the
trike. During this project, a thorough analysis was done to create a strong tricycle
frame that would satisfy the needs of the manufacturerers and the users..
Problem:
Issues with the Current Frame
• too weak to support necessary
weight and retain functionality in
the given conditions
• “one size fits all” (not
adjustable for user)
• too large and bulky to be used
indoors or on public
transportation
• difficult to manufacture, very
difficult to ship
•Most time consuming part of building a frame: Bending the frame
•Most expensive frame material: Round hollow tubing 25 X1.5 mm for
base frame.
•Time required to produce a frame: 5 man-hours
Functional Requirements:
• Strength: strong enough to support the rider and some cargo.
• Strengthen and stiffen high moment areas to withstand at least
350 lbs of load
• Robustness: appropriate for the conditions used in, long life
• Easily Manufactured and Repaired: shops should be able to produce
trike with the tools they already have and repair the frame easily
• Manufacturing time: <5 hours
• Made from parts that are cheap and readily available.
• Adjustable: accomodating people of different ages, disabilities, and
sizes; easy to get in and out of.
• Lightweight: light and compact frame design.
• Size: <= 50” in length and 26” in width (including wheels)
• Low Cost: affordable to produce, ship, and buy.
• Frame Materials: Cost<$100
• Shippable: Stackable Design
Community partner response on reason for current tricycle breakage:
“Our design is made of round tubing having several bends forming a base frame.
If the tube is flattened on bending or the material is a bit thin, then it breaks
easily. Also if the type of tubing frame do not withhold the weight of the
persons then it breaks.”
Key Features
• Adjustable Seat
Goals:
Material Analysis
To improve on the design of the tricycle frames so that they are better
suited and more convenient for the user
 Create a design that is easier and cheaper to build and repair

Initial Design:
Back slanted
to allow stacking
Removable chair
Sturdier base
•Adjustable to user
•Biomechanically optimized
Diameter Thickness Weight Price Cost
(mm)
(mm)
(kg) (KES) (USD)
16
16
20
20
22
22
22
25
25
25
32
32
32
33.5
33.5
38
38
38.7
38.7
42.25
42.25
45
1.2
1.5
1.2
1.5
1.2
1.5
2
1.2
1.5
2
1.2
1.5
2
1.2
1.5
1.2
1.5
1.2
1.5
1.2
1.5
1.5
3.02
3.55
3.61
4.11
3.80
4.55
6.07
4.66
5.76
6.98
5.62
6.78
9.02
5.88
7.14
6.72
8.28
6.80
8.22
7.54
9.06
9.66
312
329
358
396
380
434
460
407
478
527
466
538
683
486
565
564
654
563
650
625
718
773
4.55
4.80
5.22
5.77
5.54
6.33
6.71
5.93
6.97
7.68
6.79
7.84
9.96
7.08
8.24
8.22
9.53
8.21
9.48
9.11
10.47
11.27
• Stackable
•Shippable to more clients
•Lowered shipping cost
Moment of Bending
Stiffness
Stiffness/
Stiffness/ Cost/
Inertia
Moment
BM/Weight
BM/Cost
(N*m^2)
Weight
Cost
Weight
(mm^4)
(N*m)
1537.70
99.39
307.54
32.91
101.83
21.85
67.62
1.51
1815.01
117.32
363.00
33.05
102.25
24.46
75.69
1.35
3143.99
162.58
628.80
45.04
174.18
31.15
120.49
1.45
3754.15
194.13
750.83
47.23
182.68
33.63
130.07
1.40
4254.75
200.01
850.95
52.64
223.93
36.11
153.62
1.46
5101.90
239.84 1020.38
52.71
224.26
37.91
161.29
1.39
6346.02
298.32 1269.20
49.15
209.09
44.49
189.28
1.10
6369.05
263.48 1273.81
56.54
273.35
44.41
214.70
1.27
7675.75
317.53 1535.15
55.13
266.52
45.57
220.32
1.21
9628.20
398.30 1925.64
57.06
275.88
51.85
250.66
1.10
13789.61
445.67 2757.92
79.30
490.73
65.61
405.99
1.21
16753.28
541.45 3350.66
79.86
494.20
69.04
427.24
1.16
21300.00
688.40 4260.00
76.32
472.28
69.14
427.87
1.10
15901.85
490.92 3180.37
83.49
540.88
69.29
448.92
1.20
19344.36
597.20 3868.87
83.64
541.86
72.51
469.74
1.15
23509.65
639.84 4701.93
95.21
699.69
77.82
571.90
1.22
28692.12
780.89 5738.42
94.31
693.05
81.91
601.92
1.15
24875.94
664.78 4975.19
97.76
731.65
81.00
606.21
1.21
30372.85
811.68 6074.57
98.74
739.00
85.66
641.10
1.15
32625.08
798.61 6525.02
105.92
865.39
87.66
716.19
1.21
39913.70
977.02 7982.74
107.84
881.10
93.35
762.70
1.16
48543.94 1115.66 9708.79
115.49
1005.05
99.01
861.61
1.17
Current frames can collapse in on the rider and are not strong
enough to support rider and cargo, so analysis was needed
Design Analysis
•Yield stress of mild steel: 5.17 E8 Pa
•Safety factor: 10 yielding a max stress of 5.17 E7 Pa
•Considerations
• Users will travel over all kinds of terrain
• Heavy loads and/or other people will be carried
• Trike will be used for years in harsh conditions
•SOLUTION: CENTRAL BEAM
Solid Model:
Improvement of Design
• Reduced manufacturing time due to fewer bends and pieces
• Stackable and shippable with angled back
• Compact design, increasing mobility
• Storage beneath and behind for convenience
• Adjustable seat to fit user
• Sturdier Frame due to center beam
Special Thanks to…
Amos Winter for teaching
the course
John Hart for advising this
project
Edgerton Center for
providing machining tools
MIT Foundry for use of
welding equipment