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«Making Mobility  A Folding Tricycle Attachment for Standard  Wheelchairs in Tanzania      ...»

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Making Mobility 

A Folding Tricycle Attachment for Standard 

Wheelchairs in Tanzania 



Brian Holcomb, Alex Klonick, Michael Swift, and Michael Tran 

Mentor: Mr. Amos Winter, Massachusetts Institute of Technology  

Sponsor: Professor Kathleen Sienko , ME 450 

University of Michigan  


Thousands of Tanzanians are unable to attend school, work, or participate in the community due to an immobilizing

disability. Those lucky enough to have a wheelchair are frustrated by long trips across rough terrain. Hand-powered tricycles are easier for long trips but are too big to use inside or on a bus. The goal of this project is to produce a low- cost, foldable and stowable tricycle attachment for standard wheelchairs in collaboration with an MIT course. This hybrid design will allow users to travel freely between regions and more effectively function within their community.



Current wheelchairs and hand-tricycles do not provide the affordable range of mobility required to participate fully in Tanzanian life. Wheelchairs are difficult to use to travel long distances on the rough terrain found in Tanzania and standalone hand-tricycles are too bulky for transit in cars, buses, and inside buildings. We have worked with Mr.

Amos Winter at MIT to develop an easily foldable and stowable tricycle attachment for the Whirlwind Roughrider wheelchair. This attachment provides the long range and stability of a tricycle with the compact comfort of a folding wheelchair. The current MIT attachment design works but is not foldable and stowable. This is an issue when the user wants to travel long distances and does not have a place to put the attachment away after using it.

The key specifications include a folded width of 6 inches, 60 second attachment and detachment time, a gain ratio between the wheel and the hand cranks of about 1.6, and a weight of less than 25 pounds. These specifications were decided based upon literature research and engineering judgment based on comfort and practicality.

The concept chosen in our final design is a two-chain fold over drive system that stows beneath the wheelchair. The two chain system allows the steering column to fold in half while keeping tension in the chain system. Ideally in a two chain system, no chain tensioners are needed. An attachment arm folding system was also used in order to reduce the width down to 6 inches. This allows the user to more easily place the device past the legs and underneath the wheelchair while folded. The attachment arms simply slide and rest on top of the wheelchair cross brace.

In order to simulate the manufacturing environment in Tanzania, the prototype was created using only materials and processes available in Tanzania. The materials used were scrap bicycle parts, fasteners, and standard mild steel pieces.

The processes used included grinding, cutting, drilling, and welding. Since precision machining is widely available in Tanzania, no use of a lathe or mill was used on the prototype.

While the prototype is in working condition, there are still a number of outstanding issues related. The coupling system could be made more robustly to ensure a more secure attachment. The chain alignment is currently off and can cause the chain all off. A last minute addition in adding adjustability to the prototype has a tendency to cause bending in the bar. While all of these issues affect the performance of the attachment, they can all be rectified with further work. Due to time constraints, we were not able to fully address these issues on our prototype.

Figure 1(a): The prototype in its in-use state Figure 1(b): The prototype in its stowed away state

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Appendix A: Updated DR3 Document

Appendix B: Bill of Materials

Appendix C: Description of Changes since DR3

Appendix D: Design Analysis Assignment from lecture

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– Thousands of Tanzanians are unable to attend school, work, or participate in the community due to an immobilizing disability. Those lucky enough to have a wheelchair are frustrated by long trips across rough terrain. Hand-powered tricycles are easier for long trips but are too big to use inside or on a bus. The goal of this project is to produce a low-cost, foldable and storable tricycle attachment for the Whirlwind RoughRider Wheelchair. This hybrid design will allow users to travel freely between regions and more effectively function within their community.

Throughout the course of this project, there were efforts to simulate the materials and manufacturing capability available in Tanzania. The project made no use of precision machining and limited its materials to bicycle parts and mild steel. This document describes the development process and makes recommendations for future development of a folding mobility aid.

Index Terms - developing countries, handcycle, mobility aid, tricycle, wheelchair, manufacture

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Wheelchairs are excellent devices for providing mobility to handicapped persons worldwide. The typical wheelchair can navigate the paved streets and halls of any American town with relative ease. However, without the intricate system of lifts, ramps, and roads even the most basic travel can be almost impossible.

This is the challenge faced by thousands of wheelchair users in developing countries such as Tanzania, where only 8.3% of roads are paved. Most of the wheelchairs are old, damaged US-style four-wheeled devices, designed to navigate the typical American town (United States. Central Intelligence Agency 2006).

As a result, these wheelchairs do not solve the problem of mobility aid in Tanzania.

4 More robust hand powered tricycles are the preferred solution for long distance travel on rough terrain.

These tricycles are more commonly seen on the streets and villages of developing nations. The problem with tricycles is that they often are too bulky for use indoors, and present great problems with space and fees when using mass transit (Winters 2006).

The best option for improving mobility for the 30,000 people in need of a mobility aid in Tanzania is a foldable combination of a tricycle and standard wheelchair, in order to allow for excellent mobility indoors, on streets, as well as on different means of transportation (Winters 2005). The goal of this project was to explore the option of having a foldable attachment that allows a standard wheelchair to turn into a hand powered tricycle while traveling long distances.

Literature Supporting a Combination of a Wheelchair and a Tricycle:

In Mr. Amos Winter’s journal article, Assessment of Wheelchair Technology in Tanzania, it is noted that disabled Tanzanians prefer tricycles over standard wheelchairs during outside travel. In fact, Mr. Winter mentions that he did not see a single wheelchair being used outside at all. He attributes this preference for tricycles to requiring much less energy when traveling long distances and a tricycle’s ability to better traverse the rough Tanzanian terrain. During his visit, he got the chance to interview many of the disabled Tanzanians and summarizes his evaluation of the hand powered tricycle by saying “tricycles are much more common and popular than wheelchairs” and “a tricycle is a more sensible choice for long-distance travel” (Winters 2006).

In Uganda, there is a similar need for mobility aids. In an article by Mr. Tone Øderud, Feasibility Study on Production and Provision of Wheelchairs and Tricycles in Uganda, a team reports its findings after visiting and surveying wheelchair users in Uganda. After spending time interviewing the Ugandans, the team found that while standard wheelchairs that were donated from hospitals are foldable and more easily storable, they were not very durable in the rural terrain and broke down easily. This problem is compounded by the fact that spare parts are not readily available to the community. Tricycles are noted to be the preferred method of mobility aid for traveling intermediate distances, but users were often denied access to public transportation because the tricycles are not foldable and easily transportable (Øderud and Hotchkiss 2004).

Research performed by Joe Mellin at Freedom Technology in the Philippines showed that there are many limitations that tricycle users encounter. First, the tricycle could not be used inside a building or home. Many of the tricycle users choose to keep their wheelchair for these situations, because they favored its small turning radius and better maneuverability. Additionally, while many users liked the comfort provided by the tricycle over longer distances, tricycle users could not use public transportation because the tricycle was too large to fit on the bus. In contrast, wheelchair users could fold their wheelchairs and use public transportation (Mellin 2007).

In an article written by Mr. R. Lee Kirby and Mr. Rory A. Cooper, Applicability of the Wheelchair Skills Program to the Indian context, the authors write about their observations on mobility aids used in India.

During their two-week visit, they noticed that hand powered tricycles were the preferred type of mobility aid used to travel. Similarly Tanzania, obstacles were more prevalent and extreme than those seen in North America. While the tricycles were preferred, they noted that they were difficult to maneuver in tight spaces due to a larger turning radius compared to a standard wheelchair (Kirby and Cooper 2007).

Other Literature Useful in Design Process:

The project team used various sources to research the use of wheelchairs and tricycles as mobility aids in Tanzania. The most valuable resources were those taken from the MIT class 784 website. The purpose of this class is to analyze wheelchair design in developing countries. In order to fully understand the demographics and needs of people that will be using our device, the team relied heavily on Mr. Amos 5 Winter’s paper and the materials from the MIT website. These resources are very detailed and include user complaints about wheelchairs and tricycles. These resources were valued highly because the team could not directly interact with the users they were designing for. Other resources that were linked from the MIT website included two videos that documented the manufacturing process that a wheelchair and tricycle manufacturer used in Nairobi, Kenya. Even though this is outside of the target country of Tanzania, manufacturing capabilities are very similar in both countries.

The research was not limited to sources on the MIT website. Details about the ergonomics of the wheelchairs and their users were found in Positioning in a Wheelchair by Mayall and Desharnais.

Additionally, limited data was found on the size of people in the Hadza tribe of Tanzania from Annals of Human Biology. These two sources allowed the team to design a wheelchair attachment that will provide proper ergonomic support to the user while being able to be used by a large variation of user sizes in Tanzania. Additionally, research into current patents of wheelchairs, tricycles and wheelchair attachments was conducted in order to become familiarized with the types of devices similar to this project. These patents aided in understanding the design problem by demonstrating past solutions to similar problems.

Because the team was not able to directly interact with the Tanzanian people, all of the research is secondhand. This created some holes in the research that the team was forced to accept. For example, the team could not find any reliable anthropometric data that describes the height, weight, leg length, and arm reach of the users that we were targeted. Additionally, the demographics concerning the types of users needing mobility aid in Tanzania are taken directly from Mr. Amos Winter’s thesis, Assessment of Wheelchair Technology in Tanzania. He describes how he was only able to see those wheelchair users that were mobile enough to use the streets during the day. Those users who were immobilized to the point where they had to stay indoors could not be counted. For this reason, Mr. Amos Winter believes that there are more users who suffer from spinal injuries than reported (Winter 2006).


The engineering specifications for this project were dynamic throughout the design process. The team began by identifying and ranking the importance of our initial specifications using a quality function deployment (QFD). After discussions with the team’s mentor, Mr. Amos Winter from the Massachusetts Institute of Technology (MIT), the team was able further refine the existing specifications as well as identify new specifications that were not examined previously.

In order to keep the team focused on the key functions of the device throughout the process, they created a functional decomposition of the project. The functional decomposition broke the system down into the most important functions and then listed what sub-functions would contribute to each key function in order to map out the process. The six most important functions were determined from our QFD and were found to be attaching to the wheelchair, propelling the wheelchair, compacting into a smaller size, stowing on the wheelchair, traversing long terrain, and adjusting to different people.

Once all the necessary engineering specifications and functions had been clearly defined the team used them as a solid base from which to generate concepts.

Scoring Matrix:

In order to reach a single design from all of the concepts we generated in brainstorming, the team used a methodical ranking system in order to determine the best concepts for each main component of the attachment. The main components that were used were how the drive system would be folded and the stowing location, and the attachment method.

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