Wheelchair Design in Developing Countries

2007 Public Service Design Seminar

Amos Winter, Graduate Student, Dept. of Mechanical Engineering

Supported by Amy Smith, Senior Lecturer in Mechanical Engineering

Introduction

James is a teenager in Tanzania. As a young child, he was disabled by polio. His family

cannot afford a wheelchair. James’s only means of transportation is crawling on the

ground. He wears sandals on his hands for protection. James rarely leaves the house

because his family is ashamed of him. While intelligent, James does not go to school

because he is physically incapable and his family forbids it. James will grow up with no

marketable skills and will most probably end up begging on the street.

There are hundreds of children and youth like James who are either forced to stay in their

home or crawl on the ground because appropriate and affordable wheelchair technology is

not accessible. Well-intentioned organizations from the United States and Europe donate

wheelchairs, but they are not designed for the rough conditions in rural East Africa, and

often break down after just one or two months. Locally-made wheelchairs and other

mobility aids provide a much more appropriate solution, but are relatively expensive and

cannot compete with the donated chairs on price. Furthermore, many design

improvements can be implemented to make them stronger, lighter and more

maneuverable. A sound understanding of engineering concepts can be taught in the

redesign of these chairs, benefiting the students doing the design work as well as the

potential builders and users of the chairs.

This document is a proposal for funds to establish a Public Service Design Seminar

entitled Wheelchair Design in Developing Countries (WDDC). The purpose of the class is

to educate MIT students about engineering and cultures in the developing world through

the innovation of appropriate wheelchair technology. I am proposing this class because I

believe that MIT is in the unique position to solve the problem of appropriate wheelchair

technology. By combining the resources, brainpower, and credibility of MIT with the

experience of established community partners already making chairs in developing

countries, wheelchair technology can be advanced to fully suit user needs.

WDDC will inspire students by providing a significant real-world engineering application

and showing them the power they have to improve the lives of others. During the course,

students will conceive appropriate wheelchair design solutions using sound engineering

practices while learning about cultural, economic, and resource considerations in the

developing world. The technology produced in the class will have far-reaching effects.

Through community partners Whirlwind Wheelchair International (WWI), an organization

which has designed developing world wheelchairs for over 30 years, and the Tanzania

Training Center for Orthopedic Technologies (TATCOT), the leader in wheelchair

manufacturing education in Africa, technology developed in WDDC will be disseminated

and implemented in wheelchair workshops around the world.

Background

Motivation to teach this class arises from my own experience with inadequate wheelchair

technology in Tanzania. I spent the summer of 2006 conducting a study entitled

“Assessment of Wheelchair Technology in Tanzania,”1 which was funded by a Public

Service Center Fellowship and supervised by WWI and TATCOT. The project included

interviewing a variety of stakeholders involved with Tanzanian wheelchairs, including

users, manufacturers, and advocacy groups. Over the entire study, approximately 100

interviews were conducted throughout Tanzania in both rural and urban locations.

The results of my assessment showed that wheelchair technology in Tanzania is

insufficiently meeting the needs of users. Many chairs break down prematurely because of

improper design, as shown by the example in Figure 1, where the frame has bent because

the tubing was not strong enough to support the load. Further analysis showed that the

failure occurred where the bending moment was at its maximum. Other problems with

currently produced chairs include underutilization of building materials, improper

1 “Assessment of wheelchair technology in Tanzania.” 2005. Amos Winter. 23 Mar. 2006

<http://web.mit.edu/awinter/Public/Assesment%20of%20TZ%20WC%20technology%20-%20final.pdf>

mounting of bearings, inaccurately predicting stresses and failure points, using inefficient

manufacturing methods, and not taking advantage of locally available components.

Frame weakness

Mo

men

t

Position along chair

Max Moment

FReactionFReaction

Position along chair

Center of

gravity

Figure 1 Example of a poorly designed frame buckling and corresponding bending moment

Additionally, many people rely on donated wheelchairs which may be inexpensive but are

not designed and built to suit the needs of users in developing countries. Some of the

organizations that distribute free chairs judge success by the number of chairs donated,

rather than how many people obtain a sustainable mobility solution. Many of these chairs

break down in the first year and cannot be repaired because replacement parts are

unavailable. Even worse, many chairs are given away without proper fitting, which can be

extremely dangerous for the user. Hard surfaces, like the plastic seat on the donated

wheelchair in Figure 2, or improper chair geometry, can cause pressure sores which can

lead to infection and sometimes even result in death.

Figure 2 Foreign made, donated wheelchair with no custom fitting and dangerous plastic seat

MIT students’ specialties are sound engineering and innovation, which are the ingredients

needed to solve many of the technological problems identified in Tanzanian-made chairs.

By improving in-country technology, locally made wheelchairs can be better built,

correctly fitted to users, and affordably priced. This not only helps wheelchair users, but

also stimulates the local economy by increasing business for local manufacturers.

Class description

WDDC will be a seminar in which engineering fundamentals are taught in the context of

wheelchair engineering. The lectures will introduce the cultural, economic, and resource

considerations in wheelchair design, and show how sound engineering can be used to form

robust, appropriate design solutions. The class will be divided into groups of 3 to 5

students for term-long projects with a specific wheelchair technical problem to be solved.

The students will learn engineering fundamentals to properly analyze their problem and

appropriately design a solution. Several members of the MIT mechanical engineering

faculty have already agreed to be guest speakers, as well as WWI founder Ralf Hotchkiss,

and a wheelchair manufacturer in Tanzania.

The intention of the class is to interest students in engineering through practical

application of theory, interaction with members of the faculty, and learning the broader

context in which their knowledge and talents can be applied. The course material will be

presented from both the social and technical standpoint of wheelchair engineering. Social

considerations such as understanding cultural stigmas associated with the disabled and

common causes of disability will be examined. The students will learn how to connect

social constraints and requirements to technical design parameters, and then apply

engineering knowledge to develop appropriate designs. Technical topics will span many

engineering disciplines including machine design, materials science, mechanics of

materials, biomedical engineering, and product/ergonomic design. The proposed syllabus

is included in Appendix A.

The text for WDDC will be a manual on engineering principles used in wheelchair design

that I will write during the summer of 2006. Ralf Hotchkiss, the founder of WWI, will be

a co-author on this project. In addition to serving as the text for the class, this manual will

also provide African wheelchair manufacturers with the knowledge to improve and adapt

their products instead of relying solely on the designs of others. The manual will be

presented in the fall of 2006 at the African Wheelchair Congress to be held in Arusha,

Tanzania. As the manual will provide simple, qualitative explanations geared towards

people with little or no engineering training, more rigorous theory will be derived and

presented in WDDC classes.

Proposed projects

The following projects are based on the assessment of wheelchair technology in Tanzania.

Each focuses on a specific technical problem that is of suitable scope, which a solution

can be designed and prototyped in one semester. Some or all of these projects will be

pursued in WDDC:

• Tanzanian hand-powered tricycle frame re-design: Current tricycle frames will be

analyzed and re-designed to increase strength and reduce weight through more

effective use of moment of inertia and local materials.

• Optimization of hand-powered tricycle gear train: The gear ratios of current

tricycles vary significantly, as shown in Figure 3. Human hand power output will

be determined to predict the best hand crank position and gear ratio.

• Folding 3-wheeled frame: A frame will be designed to be kinematically

constrained to ground by 3 points, yet still foldable for transport in busses.

• Rear axle/hub design using bicycle bearings: Different axle/hub/bearing

configurations will be explored. Bicycle bearings are better suited to wheelchair

loads, are cleanable, and are readily replaceable throughout Tanzania. A concept

for a rear hub/axle design is shown in Figure 4.

• Creating testing metrics: Tests using local materials will be developed to

determine the safety of wheelchairs.

d2

d1

d3

d4

Fout

Fin

d2

d1

d3d4

Fin

Fout

A) Tricycle made in Canada B) DAGE Tricycle made in Tanzania Figure 3 Gear ratios of two tricycles used in Tanzania

Upper cup

assembly

Threaded axle

Frame

Lower cup

assembly

Single part

hub/axle

Figure 4 Concept of single part hub/axle and bearing configuration, assembled and exploded view

This proposal includes the request for funds to allow three students to continue their

projects during the summer of 2007. These students will travel to one or multiple

community partners producing wheelchairs and implement the technology developed in

WDDC. Providing travel opportunities to the students enhances their educational

experience while also greatly facilitating the dissemination of technology. WDDC

students may be able to collaborate with MIT Public Service Fellows to establish joint

projects and maximize technology implementation.

Guest lecturers

Guest lecturers will be included in WDDC to 1) give students the chance to interact one-

on-one with engineering faculty, 2) learn about each faculty member’s specialties in the

context of wheelchair design, 3) see the perspective of engineers from the developed

world designing for the developing world, and 4) understand the challenges of being a

wheelchair manufacturer in the developing world. The following people have already

agreed to be guest lecturers in WDDC and present the described topics:

Prof. Mary Boyce

MIT Dept. Mechanical Engineering, Mechanics of Materials

• Performance of common steels

• Material weakening due to welding

• Stress concentrations

• Fracture toughness

Ralf Hotchkiss

Founder and Chief Engineer, Whirlwind Wheelchair International

• 30+ years of WC design in developing countries

• Factors specific to developing world wheelchair design

o Technical factors encountered

o Social factors encountered

• History of WWI designs

Abdulah Munish

Wheelchair Technician, KCMC Wheelchair Workshop

Instructor, TATCOT Wheelchair Technologists Training Course

• Issues facing developing country wheelchair manufacturers

• Materials/parts available for wheelchair manufacturing in Tanzania

• Problems with designs of current wheelchairs

• Competition of poorly made, imported wheelchairs

• Intent/usage mismatch of Tanzanian-made chairs

Prof. Alexander Slocum

MIT Dept. of Mechanical Engineering, Precision Machine Design

• Exact constraint design

• Structural loops/frame compliance

• Bearing choice

• Structures/trusses

Amy Smith

D-Lab Founder and Senior Instructor, MIT Dept. Of Mechanical Engineering

• Process of designing in a developing country

• Past successes and failures of D-Lab projects

• Contrasting design in the developed and developing world

Prof. David Wallace

MIT Dept. of Mechanical Engineering, Product Design

• Design for attractiveness with limited materials

• General product design methods

• Design considerations for the developing world

Educational significance and MIT impact

WDDC will be a class aimed at freshmen but open to any student at MIT. It is meant to

introduce students to concepts from a variety of engineering fields including machine

design, materials science, mechanics of materials, biomedical engineering, and

product/ergonomic design. By combining many engineering fields and hopefully

attracting people from a variety of backgrounds, WDDC will foster interdisciplinary

relationships between students and faculty.

Service learning is a proven effective method of teaching engineering. Using wheelchair

design as a project medium will engage students not only because it is a challenging

technical issue, but also because it has a large human interest component. By conducting

hands-on projects, the students will see the power of their engineering knowledge through

direct application.

Giving the students an opportunity to continue projects through the summer adds another

dimension to the educational experience. The students will learn the challenges of

bringing an idea to final product and along the way gain the teaching experience of

transferring their technology to wheelchair manufacturers. Most importantly, the students

will meet in-country wheelchair users. Fully understanding the struggles disabled people

face in the developing world is a lesson that can never be fully conveyed in a classroom.

The satisfaction of giving the freedom of mobility to another person will teach the

students the power they have to improve the lives of others by using their technical skills.

Impact beyond MIT

Technology produced in WDDC will help one of the most disadvantaged populations in

the world: disabled people in the developing countries. Disability KaR2, which is helping

to oversee wheelchair projects in developing countries, reports that only 2% of people in

Africa who need a wheelchair actually have one. The Tanzania Association of the

Disabled (CHAWATA) estimates there are 30,000 people who need wheelchairs in

Tanzania alone.3 WDDC will help in bringing appropriate, affordable wheelchair

technology to thousands of disabled people. These are people who are frequently denied

education, jobs, and dignity through no fault of their own. Giving mobility to a disabled

person sets them free; in developing countries this means freedom in the most basic and

literal sense. A wheelchair can allow a child to attend schools and participate with his

peers, or an adult to find a job and provide for his family.

2 Disability KaR. 10 June 2005 <www.disabilitykar.net>

3 Conversations with CHAWATA (Tanzanian Association of the Disabled). 15 June 2005.

Locally-built wheelchairs have many benefits over imported chairs. Customers can be fit

by trained technicians who know about pressure points that can cause open sores and

infections. By improving the product of workshops, locally made wheelchairs can be

competitive in price compared to chairs produced in other countries. This will give

donation groups more incentive to buy locally instead of importing low cost, poor quality

foreign chairs.

Evaluation

We will formally survey all students and community partners at the end of the class. The

surveys are based on models used for measuring service learning outcomes, and so are

particularly relevant for a project-based course with a social service theme. All surveys are

approved by the Research and Assessment Coordinator for the MIT Public Service Center,

Sumi Gupta Ariely. The surveys include both open-ended qualitative questions and scored

quantitative questions relating to the class objectives, students attitudes, and the success of

the team projects. The surveys will be independently evaluated by Public Service Center

staff.

At the end of the course, each project team will formally present their work to the rest of

the class as well as demonstrate a prototype. The students will be required to write a final

report in which they outline plans for implementing their technology in a wheelchair

workshop. These presentations highlight team productivity and outcomes, and will be

evaluated with a standard scoring rubric.

In subsequent years of WDDC, students and instructors will return to field sites used

during previous summers. Consequently, future teams can evaluate the adoption and

dissemination of WDDC projects into their target communities by observation, as well as

interviews and surveys. If field evaluation shows a WDDC project is not working as

hoped, further work can be done by the original team as part of a continuing project or by

a new WDDC team. In addition, our on-site community partners can provide on-going

feedback and evaluation.

Long-term goals

WDDC is meant to be a seed project in a longer-term goal of establishing a center for

wheelchair technology at MIT. This center will approach wheelchair technology in

developing countries on a larger scale by 1) engineering complete wheelchair re-designs to

fully satisfy user needs, 2) developing a full set of standards for in-country testing, 3)

continuing classes on wheelchair technology, 4) facilitating projects for independent

study, and 5) providing topics and supervision for senior theses.

MIT is an ideal location for such a center, as it would serve as a hub for wheelchair

innovation. Through a combination of MIT’s resources, people, and reputation for

excellence with the practical knowledge of organizations like WWI and the in-country

experience of community partners like TATCOT, each aspect of wheelchair design can be

addressed to produce an optimal product, appropriate for use in developing countries.

Conclusion

WDDC will enrich the learning experience of MIT students by combining engineering

with service learning. This class has the potential for far-reaching positive effects: The

students will experience new cultures and learn sound engineering practices, while the

partnering organizations in developing countries will benefit from resources and

technology that would otherwise not be available. The students will produce real,

measurable results by developing technology that can be immediately implemented into

wheelchair manufacturing in the developing world. WDDC students or other members of

the MIT community can choose to continue a hands-on role in implementing the

technology by traveling to community partners during IAP and summer fellowships.

This class will engage students through the application of engineering skills to a real and

very important problem while helping out one of the most disadvantaged populations.

Inviting guest lecturers with years of experience working with wheelchairs in developing

countries will show the students the boundless opportunities within engineering and

beyond. By including faculty as guest lecturers, students will have the chance to interact

with some of the most prominent engineering faculty and see how their research and

theoretical expertise can be used to address an interesting and real-life problem.

Budget and time-line

Development and implementation of WDDC will be broken up into three phases. In the

first phase during the summer of 2006, travel to Tanzania will be necessary to procure

locally made wheelchairs and tricycles, as well as raw materials and machine components,

to be used for analysis in the class. The equipment will have to be shipped back to the US,

as the tricycles have a large fixed frame that prohibits them from being carried onto a

plane. Pictures, video, and statements from wheelchair manufacturers and users will also

be gathered on this trip for use as class materials.

The fall of 2006 will be used for curriculum development. Lectures will be designed and

related reading materials will be assembled. The course website will be contracted and

built. Using the materials procured in Tanzania, and with the help of community partners,

the course projects will be finalized.

During the second phase when the class is in session, the funds required to fly Abdulah

Munish and Ralf Hotchkiss to MIT justify the value these people will add to the class.

Both will give a perspective on wheelchair design and manufacturing that could not be

obtained from a faculty member. Prototyping materials are required for the class, as the

students will build and test their design concepts.

In the final phase students will travel to a community partner and implement their designs

from WDDC. Allowing students to travel to the country for which they are developing

technology will provide them with a valuable cultural experience while ensuring the

technology is disseminated to wheelchair manufacturers. Additional prototyping materials

will be necessary during this time to allow the students to test their technology on multiple

wheelchairs.

WDDC budget

Curriculum Development (Summer & Fall 2006)

Personnel

instructor $15,000 (covered by industry-sponsored RA)

web page designer $500

assessment coordinator $1,000

Travel

airfare to Tanzania $2,000

ground transportation $200

accommodation $250

Materials

digital camcorder $1,200 (on loan from Edgerton Center)

digital video tapes $50

wheelchairs $800

shipping $1,200

prototyping materials $500

reference materials $400

posters & flyers $150

Total $23,250

Requested from Alumni Funds $7,050

Course Implementation (Spring 2007)

Personnel

instructor $10,000 (covered by industry-sponsored RA)

webmaster $250

assessment coordinator $1,000

Travel

airfare from Tanzania (Abdulah Munish) $2,000

airfare from San Francisco (Ralf Hotchkiss) $500

ground transportation $50

accommodation in Boston $800

Materials

prototyping materials $2,000

demonstration materials $1,000

course handouts $250

Total $17,850

Requested from Alumni Funds $7,850

Project Implementation (Summer 2007)

Travel

airfare from Tanzania (3 students) $6,000

ground transportation $250

accommodation $500

translator $500

Materials

prototyping materials $1,000

Total $8,250

Requested from Alumni Funds $8,250

Total requested from Alumni Funds $23,150

Appendix A: Class Syllabus

Week# Date Wheelchair Topics Engineering Topics

Guest Lecturer Assignments

1 2/5/2007

Introduction to wheelchairs in Developing Country

Deterministic design process

Statistics on underserved populations

Strategy, Concepts, Modules, Parts

Review of common causes of disability

Presentation of possible projects

Wheelchair user habits

2 2/12/2007 Review of currently used wheelchairs

Structural calculations

Abdulah Munish TATCOT

wheelchairs currently being built in country (brought back from Tanzania)

design/statics/trusses/buckling

Draw free-body-diagrams for all the wheelchairs

Imported wheelchairs and US wheelchairs (brought back from Tanzania and borrowed from MIT medical)

Calculate loads on major components

Review of means of purchasing/obtaining wheelchairs in developing countries

3 2/19/2007 Examples of engineering in the developing world Idea to product

Amy Smith MIT

Examples of successful and unsuccessful engineering in the developing world

Stakeholder analysis Determination of user needs

Form project teams, choose projects

Factors to consider when designing for developing countries

Implementation in the field

4 2/26/2007 Constraints/freedoms in design Outlining a design

identification of design constraints specific to the developing world

Determining functional requirements, constraints, freedoms

Identification of design shortcomings in currently built wheelchairs

Identification of design opportunities and freedoms that can be utilized in the developing world

Outlining of functional requirements

common operation environments encountered in the developing world

5 3/5/2007 Methods of propulsion

Biomedical engineering/ Conservation laws

efficiency of wheelchair vs. tricycle

Biomechanics of hand-powered propulsion

Presentation of strategies

Benefits and shortcomings of 3 and 4 wheel chairs

Anatomical considerations, posture, body loads

Justification of best strategy

Conservation laws: power, energy, efficiency

6 3/12/2007 Operating a wheelchair in the developing world

Material science/ mechanics of materials

Prof. Mary Boyce MIT

Review of materials available in the developing world

Stress/strain of materials, material behavior, metal processing, fracture toughness, stress concentrations.

Concept sketches of design parameters of projects

Material choice for design. Defining performance requirements

7 3/19/2007

Manufacturing technologies in the developing world

Manufacturing technologies

What is currently being used

A focus on what is available in the developing world

Presentation on chosen concept

What is available and underutilized

Lean manufacturing techniques

8 3/26/2007 Spring Break

9 4/2/2007 Review of locally available components Machine elements

Prof. Alex Slocum MIT

Inspection of materials procured in Tanzania

bearings, bushings, wheels, tires, tubes

10 4/9/2007

Comparison of 3-wheeled wheelchairs vs. 4-wheeled

Exact constraint design

Field Trip to wheelchair user group meeting

11 4/16/2007 Personal identity and wheelchairs

Product design/ Ergonomic design

Prof. David Wallace MIT

12 4/23/2007 Fitting a wheelchair Ergonomic design

Ralf Hotchkiss Whirlwind

Presentation of engineering prototypes

Avoiding pressure sores and correctly matching chair and user body geometry

Design review by Ralf Hotchkiss

Making the chair stable

13 4/30/2007 Project work Project work

14 5/7/2007 Project work Project work

15 5/14/2007 Project work Project work

Final presentation of project with a working prototype