FA info icon.svgAngle down icon.svgProject data
Authors Ana Lise Herrera
Location Kingston, Canada
Status Designed
Instance of Wheelchair
OKH Manifest Download

In many areas of the developing world the conditions under which wheelchairs are used are significantly rough and damaging to the equipment. While companies such as Whirlwind and Next Mobility have adapted wheelchair design to be more suitable for extreme terrain, the access to these wheelchairs is limited. Many of the disabled are accommodated with manual wheelchairs that have been donated from hospitals and, in most cases, are ill fitting.

Studies conducted in El Salvador, with wheelchair users and technicians, illuminated common problems affecting ideal wheelchair function and user comfort. This project has used this feedback in designing a maintenance and repair kit that gives manual wheelchair users and technicians the ability to perform repairs and adjustments as necessary.

Problem definition[edit | edit source]

The main objective of this Mech425 AT Project was taken from a trip report compiled by Lisa Catana after visiting wheelchair users in El Salvador. The report outlined the need to develop a maintenance and repair kit that includes basic tools for repair, lubrication and low cost seating construction with easily accessible materials such that wheelchairs users and technicians can properly maintain and repair wheelchairs, preventing damages and extending the life of the wheelchair.[1]

Background[edit | edit source]

Whirlwind has developed wheelchair technology to improve the lives of the many persons worldwide living with physical disabilities. The highly publicized roughrider wheelchairas shown in figure 1 has added features that compensate for discomfort due to vibrations and others that increase mobility in and around uneven surfaces.[2]

Wheelchair 1.JPG

Figure 1: Showing the Whirlwind Wheelchair; RoughRider, specifically designed to weather rougher terrains

Despite the best efforts of whirlwind, roughrider wheelchairs cannot be made accessible to all those in need and instead, wheelchairs show in figure 2 are more likely to be found in developing countries.

Wheelchair basic 1.JPG

Figure 2: Showing the more likely wheelchair used

The harsh terrain, lack of wheelchair accessible buildings and humid climate mean that wheelchair users are pushing the physical limits of their chairs. Furthermore the widespread use of basic wheelchairs, which lack ergonomic features, result in the general discomfort of the user. The more frequent failures that can be addressed from a maintenance and repair kit involve the functionality of the brake and tires as well as issues of lubrication and adjustable seating options.[1]

Wheelchair Brakes[edit | edit source]

The braking system of wheelchairs is unlike that of a bicycle, whereby the brakes are used to lock the chair in position rather than slow its motion. Many wheelchair brakes are similar to that shown in figure 3, such that pulling a lever initiates contact between the brake and the tire with enough pressure to inhibit motion.[3]


Figure 3: Showing one example of brakes found on a wheelchair

The cause of failure could be speculated to be due to material failure, rust, improper use of device, etc, but in this case is unknown and is likely to vary from one user to another.

Tires[edit | edit source]

There are two types of tires for manual wheelchairs; pneumatic and solid both of which have their own advantages and disadvantages. Pneumatic tires, like those found on bicycles have air filled tubes. These tires provide a smooth ride, absorbing shocks from uneven surfaces but are more likely to be damaged by rough and sharp objects. Issues of leaking can arise from poor sealing, small punctures and malfunctioning nozzles.[4]

Operating the wheelchair with poorly inflated or flat tires can have destructive effects on the rim of the wheel. Correctly inflated tires will prevent pinch flats.[5]

Solid rubber tires, are well solid, and therefore have no issues with punctures. However are less comfortable as the user feels the effects of every bump and uneven surface along their path.[4]

Lubrication[edit | edit source]

As with any other moving mechanism, joints and junctures need to be lubricated for optimum performance.[6] This is the case with all wheelchairs where lubricants are used to reduce wear and prolong the use of the device. Dry lubricants are more user friendly and are most compatible with wheelchair materials, although wet lubricants are still appropriate.[7]

Similar to over inflation of tires, it is important not to over lubricate parts as the excess grease binds dirt and other particles that will prevent proper function.[7]

Seating Adjustments[edit | edit source]

Ideally wheelchairs would be customized for each user so that their arm rests, foot rests, and angle of inclination and position of wheels would compliment their desired posture while sitting in their wheelchair. This is not the case with those buying new wheelchairs, much less those using secondhand chairs.

One adjustment that can be made is providing appropriate cushions for the wheelchair. Due to the significant amount of time spent in the wheelchairs, failure to do so results not only in discomfort of the user but can cause the development of sores and ulcers which can worsen the physical condition of the user and in extreme cases causes death.[8]

User Manual[edit | edit source]

The purpose of having a wheelchair user manual is to provide an added resource for the user. While every wheelchair manufacturer has a manual for each of its chairs, the target user in this study is using a second hand chair/ refurbished chair and is unlikely to possess the manual. Many of the users want to know how to maintain and repair the chairs themselves so by giving them this kind of resource allows them to understand the function of the major components of the wheelchair, easily recognize problems and suggested maintenance and damage mitigation.

From the trip report it was observed that most wheelchairs were made by Invacare however, other manufactures include Pride Mobility, Sunrise Medical, Colours in Motion and Quickie Wheelchairs.

Here are links to a couple wheelchair user manuals from different manufactures.

Eclipse wheelchair manual.pdf

Esteem wheelchair manual.pdf

Excel wheelchair manual.pdf

Invacare wheelchair manual.pdf

Pride manual.pdf

Maintenance and Repair Kits[edit | edit source]

Each problem area has been assessed and tools necessary to fix the problems have been identified. Furthermore a design for an alternative brake system and tools and materials necessary to build this break have also been identified. All these tools and materials have been recommended to be included in a maintenance and repair kit for wheelchair users and technicians, specifically, in El Salvador. The kit itself can be customized based on price, size and weight constraints. To do so open the spreadsheet in the 'Final Kit' section below, selecting product combinations and viewing the size, price and weight on the kit.

Below is a more detailed description of the materials and tools included, instructions as to how to use some of the components as well as alternative materials that can be used in the place of those suggested.

Basic Tools[edit | edit source]

Two basic tools for repair are an adjustable wrench and multi tip screw driver. These are essential in all aspects of maintenance; checking bolts and nuts, adjusting leg rests, footrests, armrests and backrests, adjusting wheel alignment as well as changing tires or removing the wheel.[9]

A Suggested Manual Wheelchair Maintenance Guide outlines the types of maintenance checks that should be performed on a daily, weekly, monthly and annual basis.

Brake Design[edit | edit source]

An alternative brake system was designed to replace existing brakes broken beyond repair.[1]The brake design compensates for limited access to materials and resources and was conceived using a simple approach.

The basic concept behind this design is that the brake is enabled by sliding two pins along a slot until the brake arm locks into place while simultaneously making contact with the tire and preventing rotation of the wheel. The braking system comprises of 3 components; the brake arm, the slotted base and an attachment device to the frame of the wheelchair.

The brake arm, as shown in figure 4, consists of a lever, 2 pins of varying diameters and the brake material (not included in diagram) which is to be attached to the base of the arm.

Slottedbase new.JPG

Figure 4:Brake arm (left) and slotted base (right)

The base contains a slot along which brake arm slides, as illustrated in figure 4 above. The pins are constrained within the slot by a stopper. The stopper allows for horizontal and vertical movement of the arm along the plane of the base while preventing the arm moving perpendicularly to the base.

A simple representation of how the brake arm and slotted base interact with each other when the brake is initiated is shown in figure 5 below.

Figure 5: Illustration of brake as it moves from the off to on position

During normal use of the wheelchair the brake remains in the 'off' position as shown in image (a) of figure 5 above. To initiate the brake the user lifts and rotates the arm through positions shown in images (b), (c) and (d), allowing the pins to follow the slot. Finally with the the arm in position shown in image (e), the brake is then in contact with the tire and rotation of the wheel is prevented.

The brake can be made from any strong, rigid material. Using a wooden base would allow for easy cutting of the slot and metal nails as pins would provide for smooth sliding along slot while ensuring the stability of the device.

The material used to inhibit motion of the wheel, that is the brake material, must have a high coefficient of friction when in contact with the wheel, be resistant to wear and environmental effects.[10] Rubber, old tires, brake pads from old cars or bicycles or a dense, rough plastic material are all appropriate materials for this application. When attaching the material to the arm, a point to consider is the shape of the material. Figure 6 below shows two options with diagram a showing the more preferable shape.

Matrerial shape.JPG

Figure 6: Showing the shape options for the brake material when attached to brake arm

No prototype was done and hence no testing of this design has been performed, however, figure 7 below shows the suggested dimensions for the brake arm and base.

Figure 7: Showing a dimensioned drawing of the brake arm and base

The brake material is to be attached to the arm. The length of this attachment will vary depending on the location of the brake base on the wheelchair frame. Similarly, the length of the lever can be adjusted to suit the user.

While the ratio of diameters for the large and small pins is 1:2, this need not be the case. Any two pins of differing diameters can be used, once the slot has been adjusted (with appropriate tolerances) to accommodate the diameters, such that the larger pin is constrained to only move vertically.

For simplicity of producing this design on varying scales, Pythagorean numbers were used when dimensioning the slot on the base.

The placement of the brake is intended for a horizontal bar on the frame of the wheelchair, below the seat (shown by the red box in figure 8 below). The following suggestions can be used as an attachment device: clamp or permanent attachment to the frame using screws. The clamp is likely to be the more reasonable option as adjustments can be made more easily and will not compromise the structural integrity of the frame.

Location of brake.JPG

Figure 8: Showing the intended location for the brake described above

Tire Repair[edit | edit source]

The main issue with inflatable tires is leaking and hence deflation.[1]The use of the wheelchair on unpaved, uneven surfaces increases the chance of punctures and small holes developing. Patching tires will fix holes and therefore reduce the frequency that the user needs to re-inflate their tires.

The basic components for tire repair, patches and glue, have been included in this kit. Due to the adhesives necessary to patch tires it is unlikely that there is a natural substitute that can be used in its place. The number of patches in the kit should be adequate and should all be used then the wheels of the chair should be replaced all together.

Under the likely circumstances where replacing faulty wheels is not an option, the alternative is to remove and replace the air tube with solid materials. Ideally this solid material would be rubber however here a some suggestions for other materials:

  • Foam; firm foam would help absorb shocks from bumps and uneven surfaces. It would have to be densely packed into the tire so that when loaded the wheelchair is not rolling on its rims.
  • Coconut husks; it would also have to be densely packed to prevent damage to the rims. Special attention would be necessary to ensure evenly packing husks around entire wheel.

One way to ensure that damages are minimized is maintain properly inflated tires at all times.

Seating/ cushioning[edit | edit source]

The option for seat cushioning for the kit is to either include a sizable piece of foam that can further be cut or re-sized by the user, to better suit the user. A standard wheelchair has a seat depth of 16" and a seat width of 16 ", 18" or 20".[11] The cut of foam included in the kit can be specified in the spreadsheet below. The thickness should depend on the firmness of the foam where for a firm grade, a thinner thickness can be used. Generally, the type of foam used and the manner in which it is cut depends on the user's comfort.

Due to the variability in the size of each wheelchair cushion, a case for the cushion was not considered for the kit. Instead, suggestions for casing include cloth found in the house; towels, sheets, t-shirts.[12]

For additional designs for seating cushions made from low cost, locally accessible materials, RESNA has received many [low-cost seating designs], within those constraints, from inventors around the world.

Lubrication[edit | edit source]

There are several options for lubricating the wheelchair; wet and dry lubricants and vegetable oils. The advantages of using generic lubricants are that there are variations of lubricants for many specific applications and therefore the most appropriate, cost effective lubricant has thus been included into the kit. There is always the option of not including it in the kit and the other alternatives can also be appropriate.

Vegetable oils have become popular with those looking for natural and easily accessible lubricants. Their properties include good resistance to shear, high flash point and high viscosity index. Caster oil is one such vegetable whose viscous nature and thermal properties, where it is unlikely to dry or harden under the conditions of use, make it a good lubricant for wheelchair applications. Industrial caster oil is the best choice however, household caster oil found in pharmacies can also be used.[13]

Some cooking oils can be used as viable options.[14] While they are more expensive than industrial oils or lubricants, they are more likely to be found within the house than the other two options.

The Final Maintenance and Repair Kit[edit | edit source]

The potential maintenance and repair kit to be distributed to wheelchair users in El Salvador, and from there, anywhere else in the world, has been presented in the form of a spreadsheet. The spreadsheet allows users to customize the kits and include or exclude unncessary tools or materials and thus choose an appropriate kit based on size, weight or price constraints. Factors affecting the decisions made, especially with respect to product selection, has been included in the spreadsheet and will be elaborated on further in this article.

The spreadsheet can be downloaded using the following link. Please see notes in the discussion tab regarding the downloading of different versions of this spreadsheet.

Limitations and Recommendations[edit | edit source]

The most significant limitation of the design and construction of this kit is that it has been constructed using materials and tools found and priced within Canada. This presents a couple problems. Firstly is the affordability of the kit. Especially when converted into the El Salvador Colon it is clear that even the most basic kit will be out of the price range of many of the wheelchair users most in need of it.

Secondly, if considering the given maintenance kit as a guideline for tools and materials, which are to be sourced locally, then the economic analysis performed is a poor representation of the actual cost of the kit. How much a kit that has been assembled in El Salvador would be is unknown. Furthermore, the question of access to and availability of the same/ similar materials and tools included in the Canadian assembled kit poses itself. With regards especially to using low cost, easily accessible materials in El Salvador, there is no doubt that all maintenance can be performed using local materials. However, being unaware of what materials are accessible it has been difficult to suggest with confidence specific materials.

Despite these limitations, the kit design and this article itself provides many resources for not only wheelchair maintenance and repair but also ways to ensure that damage is prevented. For the most part, the design of the brake was done as simply as possible and intended to be made from low cost, locally available materials. If nothing else, users should be able to gain a good understanding of what tools and materials are necessary to address their major issues.

Further work on the maintenance kit should dive further into the different, appropriate resources available, the cost of such resources and perform a price comparison to determine if a kit assembled in El Salvador is indeed cheaper.

With regard to the brake design, more time needs to be extended to test it and make appropriate adjustments.

Another limitation of this article is that it has been prepared for an English speaking audience. All instructions and user manuals would need to be translated, or found in Spanish print, to be understood by the users in El Salvador.

One of the major problems is that there are some problems cannot be fixed. If the wheelchair is too small then other problems will be inherent; chronic discomfort and excessive pressure on the frame and wheels of wheelchair causing structural damage. Even the most elaborate kit will not be able to keep that wheelchair in good, working condition. It might be insulting to suggest proper diet and exercise to the users but doing so would ensure that the wheelchair does not endure unnecessary stresses and strains throughout its daily use. Proper day to day use of the device is the best way to maintain the device.

Summary[edit | edit source]

A maintenance and repair kit was developed based on an analysis of issues associated with faulty tires, inappropriate or uncomfortable seating conditions, lubrication the wheelchair and a functionality of the brake system. The kit was designed to include all tools, materials and instructions necessary to address all of these problem areas. Furthermore the kit can be customized to include or exclude tools due to constraints on size, weight or price. Alternative materials, to those suggested for the kit, have been discussed should the user decide to build their own maintenance and repair kit themselves.

References[edit | edit source]

  1. 1.0 1.1 1.2 1.3 Cantana, L. "Project Acesso Trip Report November 21 - December 1, 2006"
  2. Whirlwind Wheelchair International, RoughRider, http://web.archive.org/web/20110426055429/http://whirlwindwheelchair.org:80/wwi/pages/roughrider.html, Accessed March 23, 2010
  3. Wheelchair.ca Medical Equipment Information & Resources, "Wheelchair Brakes", http://web.archive.org/web/20120406061939/http://wheelchair.ca:80/manualbrakes.php, Accessed March 24, 2010
  4. 4.0 4.1 SpinLife.com Experts in Motion "Wheelchair Tire Tips" http://www.spinlife.com/spintips/details/k/Wheelchair%20Tire%20Tips/a/327/c/3, Accessed March 25, 2010
  5. Brown, S. "Bicycle Tires and Tubes" http://www.sheldonbrown.com/tires.html Acessed March 29, 2010
  6. Esteban, J. Importance of Lubrication http://quazen.com/recreation/autos/the-importance-of-lubrication/ Accessed April 16, 2010
  7. 7.0 7.1 Denison, I., 2006 "Wheelchair Maintenance Series: Lubrication", G.F. Strong Rehab Centre
  8. Krizack, M. "It's Not About Wheelchairs" http://web.archive.org/web/20110728175435/http://www.whirlwindwheelchair.org/articles/current/article_c02.htm Accessed April 2, 2010
  9. SpinLife.com Experts in Motion "Manual Wheelchair Maintenance" http://www.spinlife.com/spintips/details/k/manualwheelchairmaintenance/a/116/c/2 Accessed March 19, 2010
  10. RoyMech "Clutch/ Brake Material Properties" http://web.archive.org/web/20190620181917/http://www.roymech.co.uk:80/Useful_Tables/Drive/Brake_Clutch_mat.html Accessed April 18, 2010
  11. Wheelchair.ca "Standard Wheelchairs" http://web.archive.org/web/20111221041948/http://wheelchair.ca:80/standard.php Accessed March 24, 2010
  12. Disability India Network "Cushion Design for Wheelchair Competition" Accessed April 2, 2010
  13. Amateur Work Magazine Vol5, Miscellaneous Authors "Caster Oil As A Lubricant" http://chestofbooks.com/crafts/popular-mechanics/Amateur-Work-5/Castor-Oil-As-A-Lubricant.html Accessed April 6, 2010
  14. Garret, S. "Vegetable Oil For Lubricating Chain Saws" http://www.fs.fed.us/t-d/pubs/html/98511316/98511316.html Accessed April 6, 2010
FA info icon.svgAngle down icon.svgPage data
Part of Mech425
Keywords wheelchairs, transport, mobility and rehabilitation, appropriate technology
SDG SDG10 Reduced inequalities
Authors Ana Lise Herrera
License CC-BY-SA-3.0
Language English (en)
Translations Indonesian
Related 1 subpages, 8 pages link here
Impact 2,254 page views
Created April 14, 2010 by Ana Lise Herrera
Modified October 23, 2023 by Maintenance script
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