Assessment of Wheelchair Technology in Tanzania

The purpose of this assessment was to determine the current state of wheelchair 
technology in Tanzania and the factors that prevent Tanzania’s disabled from utilizing wheelchair technology. Ninety-nine interviews of wheelchair and tricycle users, wheelchair and tricycle manufacturers, and advocacy groups for the disabled were conducted 
throughout Tanzania during the summer of 2005. Technical issues identified included: tricycles are more popular and much less expensive than wheelchairs; most disabled people rely on donations to buy a mobility aid; production costs can be decreased by using bicycle components and outsourcing tasks; bicycle components are available in rural areas and are attractive for use in wheelchairs; and donated wheelchairs are often irresponsibly distributed and poorly designed for their operating environment. The assessment was 
conducted under the supervision of the Tanzania Training Center for Orthopedic Technologists and Whirlwind Wheelchair International.


INTRODUCTION
People with physical disabilities in developing countries face many challenges integrating into everyday life.If these people cannot obtain a wheelchair they are sometimes forced to stay trapped in their home or use crawling as their only means of transportation.Disability KaR i , 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 Ta nzania Association of the Disabled (CHAWATA) estimates there are 30,000 people who need wheelchairs in Tanzania and only 2,000 who have one.ii Immobility adversely affects the lives of disabled people by, for example, making it near impossible to attend school, participate in the community, or earn an income.The terrain in developing countries can further impede integration into society; in urban environments doorways and bathrooms are typically not handicapped accessible, and in rural settings roadway quality can be hilly, rough, and muddy.
Efforts have been made in Tanzania to improve wheelchair technology, fabrication, and the channels through which wheelchairs are distributed.The Wheelchair Technologists Training Course (WTTC) at the Training Center for Orthopedic Technologists (TATCOT) iii in Moshi, developed in part by the NGO Motivation, iv is a one-year course for a Certificate for Wheelchair Technologists.The WTTC covers manufacturing and fitting of wheelchairs designed for African countries, which can be produced in small-scale, self-sustained shops.Whirlwind Wheelchair International (WWI) v , a US-based non-profit NGO that develops appropriate wheelchair technology for developing countries, has helped establish 21 wheelchair manufacturing shops around the world.One of the wheelchair designs taught in the WTTC is based on a WWI model.
Although chairs are being produced in Tanzania, most people only have accessibility to imports that are poorly made, improperly fitted, and dangerous to the user.Wheelcha irs need to be fitted with the consideration of the user's size, age, and nature of disability, among other factors.If improperly fitted, the chair can cause pressure sores -breaks in the skin produced by a person's weight pressing against an unyielding surface.These sores can develop almost immediately upon contact.If left untreated they can become infected and lead to death.
The purpose of this assessment is to elucidate the factors in current wheelchair design, manufacturing, distribution, and use that are prohibiting Tanzanian wheelchair users from accessing and utilizing appropriate wheelchair technology.Such factors can be in the form of technological inadequacies for the operating environment, inefficient manufacturing practices, lack of competitive pricing, ineffective or limited cost subsidizing, inefficient distribution practices, etc.
This document summarizes the findings of the full report written on the assessment, which is available for download vi .The assessment was supervised by TATCOT and WWI and was meant to provide feedback to both organizations to aid in future wheelchair planning strategies in Tanzania.To the knowledge of the author, TATCOT, and WWI, such an assessment has never been conducted in Tanzania.Written permission was granted from each interviewee before interviews were conducted.

Interview Content
The aim of this assessment was to inspect the current state of wheelchair technology from multiple angles by interviewing the primary parties involved with wheelchair design, manufacturing, and use.Three types of questionnaires were developed by the author, in conjunction with TATCOT and WWI, to interview individual wheelchair users, wheelchair advocacy groups, and wheelchair manufacturers.In this paper the terms "wheelchair" and "tricycle" are both used to describe types of mobility aids.Common examples of these machines are shown in Figure 1.

A) WHEELCHAIR B) TRICYCLE FIGURE 1 COMMON MOBILITY AIDS
International Journal for Service Learning in Engineering Vol. 2, No. 1, pp. 60-77, Fall 2006ISSN 1555-9033 A short content summary of each party's questionnaire is below.Full versions of the questionnaires can be found in the original report vii .

Interview Locations
Interview locations were chosen in an effort to represent both urban and rural wheelchair operating environments.The primary interview locations were Dar es Salaam, Moshi, Arusha, and Stone Town, Zanzibar.Visiting remote villages and interviewing disabled was logistically impossible.Advocacy groups working in rural areas provided most of the information about rural wheelchair use.Some rural information was contributed by urban interviewees who had lived much of their life in a village.The majority of interviews were conducted in the Dar es Salaam area because it has the highest population density and concentration of wheelchair related organizations in the country.

RESULTS AND DISCUSSION OF WHEELCHAIR USER INTERVIEWS
The following section presents critical results from wheelchair user interviews and provides discussion on issues the data reveals.The full compilation of data from the assessment can be found in the original report viii .In all, seventy-one disabled people were interviewed in the assessment.It is important to note that only people who were available or visible to the author were interviewed.Survivors of birth defects and polio made up 54% of the interviewees.In comparison to the spinally injured, who typically became disabled later in life (~20 years old), birth defect and polio survivors had more time to acclimate to their disability by learning to crawl or use a mobility aid.Thus, the people who were able to work or beg on the street were primarily polio or birth defect survivors and represent a larger portion of the interviewees.

Pre-wheelchair Mobility
As a result of the majority of interviewees becoming disabled early in life, most used crawling as their primary form of mobility before obtaining a wheelchair or tricycle.This trend is seen in Figure 3, with 49% of the interviewees relying on crawling before obtaining their current mobility aid.and many more traveling over 1km.For long distances, a tricycle requires much less energy than a wheelchair.Although Figure 6 shows only slightly more tricycle users than wheelchair users, it is important to note that the author had to make a concerted effort to find wheelchair users, but had to forgo many interviews with tricycle users.On the street, it was much more common to see a tricycle user.Wheelchair users were only interviewed in hospitals, schools, and rehabilitation centers -places that required small distances of movement per day.During the duration of the assessment not a single wheelchair user was seen outside an enclosed facility or organization.The preference of tricycles by Tanzanian disabled can be further explained by comparing Figure 5 and Figure 6 with Figure 3 and Figure 4. Figure 4 shows that most people interviewed did not get a mobility aid until later in life (mean age of 22), and Figure 3 shows many had been forced to crawl small distances.As a result, there is a greater need for many disabled to travel long distances using a mobility aid, such as going from home to work.Since many of the interviewees were capable of crawling short distances, they were willing to forgo the short-range mobility offered by a wheelchair for the multiple-kilometer capabilities of a tricycle.Furthermore, local busses rarely permit disabled people to ride; many interviewees commented on being turned away when trying to ride a bus.The author used city busses as his primary mode of transportation throughout the study and did not once see a wheelchair or tricycle user as a passenger.
Imported wheelchairs were much more common than ones made in-country, with 73% of wheelchair users having a chair made abroad.Only two interviewees used Tanzania-made wheelchairs as their primary mobility aid.The majority of imported wheelchairs observed came from the Wheelchair Foundation ix , which has given thousands of chairs to Tanzania over the past decade.

Wheelchair and Tricycle Purchasing
A problem observed during the assessment was the inability of people to purchase their own mobility aid. Figure 7 shows the distribution of income of the interviewees.The average monthly income was $49US, which is twice Tanzania's national average income of $24 per month.x This discrepancy can be attributed to the following factors: 1) People with jobs were easier to find and interview; 2) Most of the interviews were conducted in urban areas where there are more formal and informal income-generating opportunities and higher average incomes; 3) Only 35% of the national population is urbanized.

Locations of Wheelchair Repair
Bicycle shops were the most common location of wheelchair and tricycle repair reported during the assessment, as shown in Figure 10.In the category of "Other," 14 of the 17 responses were from children at the Salvation Army Rehabilitation Center xii who get their wheelchairs repaired at the on-site workshop.The majority of those children said they have their chairs repaired at bicycle shops when they are at home.The most common complaint about foreign wheelchairs was that spare parts are not available.Tricycles are easily repaired at bicycle shops because they are primarily built from bicycle parts.

Products of Manufacturers
Table 1 reports the wheelchairs and tricycles being produced by the eight Tanzanian manufactures interviewed during the assessment.Contact information for all the manufactures is included within the original report xiii .Table 1 shows that tricycles cost approximately $100US less than the wheelchairs.This most likely contributes to the greater popularity of tricycles over wheelchairs in Tanzania.In order to be competitive, Tanzanian wheelchair manufacturers should lower their prices to the level of tricycles and imported chairs.Price reduction is possible, considering the UWZ workshop is able to sell a wheelchair for $140US that is essentially identical to the Mobility Care 4-wheeler sold at $250.

TABLE 1 WHEELCHAIRS AND TRICYCLES CURRENTLY
Upon inspection of tricycle manufacturing facilities, the following factors were observed to contribute to low production costs.
International Journal for Service Learning in Engineering Vol. 2, No. 1, pp. 60-77, Fall 2006ISSN 1555-9033 The bending stress on the axle is a function of the load and tipping angle, and is expressed in Equation 1.
EQUATION 1 mm The tip-over point of the chair is approximately 31 degrees, where the center of mass is vertically aligned ove r the reaction point of the wheel and the ground.If the frame is made of mild steel, with a yield stress of 330N/mm 2 , the max bending stress at that angle is 59% of the yield strength of the steel.Note that this analysis is static.If a chair were to drop off a curb only a few inches, the shock load could be multiple times greater and cause the axle to yield.One should also consider that the highest stress occurs at the point where the axle is welded to the frame, where the material will be weaker due to the weldment.

Weakness of X-brace Center Pivot
A number of workshops reported that the holes that hold the bolt for the center pivot of the Xbrace would quickly wear out and open up, decreasing the rigidity of the brace.The widening of the brace hole is the result of high torques being exerted on the pivot pin when the chair is on 3 wheels, such as when rolling over rough ground.A 4-wheeled chair is probably not the best solution for very bumpy operating environments.Unless the frame has a lot of compliance or slack in the joints, only 3 wheels will touch the ground.Vol. 2, No. 1, pp. 60-77, Fall 2006ISSN 1555-9033 Some of the manufacturers said that fixed-frame 3-wheeled chairs are preferred by people who have to travel on rough terrain, as the chair is always kinematically constrained with the ground.One of these manufacturers said that the 4-wheeled WTTC chair is primarily sold to hospitals, where the ground is even and flat.This is unfortunate, as the WTTC 4-wheeler was originally intended for rough terrain.

Tricycle Frame Weakness
Many of the tricycles observed had bent frames, or had frames that had been bent in the past and since repaired.The frame weakness is the result of designing the second moment of area too low in the center of the frame.This problem was observed in the Palray, Jaffery, and DAGE frames.A bucked frame and corresponding moment within the frame are shown in Figure 13.Bending stress is proportional to the applied moment, the distance from the neutral axis, and the inverse of the second moment of area.Thus the highest stress occurs at center of all the Tanzanian tricycle frames.

Inefficient Gearing in Tricycles
Many tricycle users observed traveling seemed to be working much harder than necessary, and during interviews many said that pedaling caused pain in their chest muscles.After riding a tricycle and experiencing the difficulties first hand, it was clear that the gear ratio was not well matched for human force and power capabilities.Figure 14 shows the gear ratio schematics of two tricycle designs, with each critical element characterized by its diameter.Figure 14A shows a Canadian tricycle that has a high mechanical advantage, and Figure 14B shows a DAGE tricycle that takes much more force to move.Using the dimensions of Figure 14, the relationship between the force required by the user, F in , and the output force used to move the chair, F out , is expressed in Equation 2. The DAGE tricycle produces a much lower F out for a given F in than the Canada tricycle, requiring the DAGE user to exert himself much more.
Over-constrained Bearings All of the radial bearings in the WTTC designs are mounted in an over-constrained configuration, including the radial bearings in the caster barrel, shown in Figure 15A.Overconstraining the bearings can greatly decrease their life by inducing high stresses on the balls and races.In Figure 15B one can imagine that if the bearing spacer is too short, the inner race will not hit the spacer.The preload force from the nut will then be transferred through the bearing balls into the outer race.If the nut is tightened further, increasing the preload force, the balls and International Journal for Service Learning in Engineering Vol. 2, No. 1, pp. 60-77, Fall 2006ISSN 1555-9033 races will be sheared, damaging the bearings.Radial bearings are not designed to take high axial loads.If the bearing spacer is too long then the bearings will be under-constrained, allowing the fork to slide up and down.For comparison, Figure 15C shows a mounting configuration that exactly constrains the bearings.Tightening of the nut will not damage the bearings, as the preload force will be transferred through the external faces of the inner races, which are designed to be compressed.The bearings will not slide up and down because the external thread nut will exactly position the bottom bearing, and the upper bearing will be clamped between the spacer and the nut.

Radial
It is important to note that any configuration of radial bearings used in the castor swivel is undesirable, as radial bearings are not meant to support axial loads.Loading them axially can greatly shorten their life.The proper configuration would be to use either two angular contact bearings, like what is used in bicycle hubs, or one radial and one thrust bearing, like what is sometimes used in bicycle stems.

Figure 2
Figure2shows the distribution of disability causes for the interviewees.Polio was the most common disability observed, at 38% of the interview population.Most polio survivors interviewed contracted the virus early in life. xi

Figure 8
FIGURE 7 INCOME OF INTERVIEWEES FIGURE 8 PRICE GAP BETWEEN WHEELCHAIR/TRICYCLE COST AND WHAT USER CAN AFFORD FIGURE 10 DISTRIBUTION OF REPAIR LOCATIONS FIGURE 12 PROJECTION OF MOMENTS IN X-BRACE OF WTTC 4-WHEELER FIGURE 13 BUCKLED FRAME OF A PALRAY TRICYCLE AND CORRESPONDING BENDING MOMENT FIGURE 15 MOUNTING OF CASTER BEARINGS

• Individual wheelchair/tricycle users: How was
200US, but 90% of the people who answered the question said they could only contribute $0US to $50US for a new chair or tricycle.This leaves approximately a $100US gap between what people can afford and what mobility aids cost.The majority of interviewees, 78%, did not contribute any money towards their current mobility aid.Figure9demonstrates how dependent disabled people are on contributions from others to purchase a wheelchair or tricycle.Only 14% of those interviewed were able to purchase their own mobility aid.