Bryan Stenson (Northwestern University)
Currently, there is no effective and comfortable way to transport immobilized patients to clinics over rough terrain in townships and rural areas of South Africa. Common methods involve transportation of handicapped patients by elderly women using either body bags or wheelbarrows; however, these methods are labor-intensive and undignified. To overcome the difficulties, we have developed the Trekker, a collapsible device with the following features: ISO bicycle wheels; a rigid frame; adjustable width to accommodate all sized patients and pathways; a mesh, reclined seating with a low center of gravity. Shonaquip, our client in South Africa, can produce the device using locally available, inexpensive steel tubing and bicycle parts. Such a device has a potential to serve an estimated market of 85 million people in the developing world, giving the Trekker commercial viability. The Trekker provides a novel solution that is both dignified and effective for transporting patients in South Africa.
Immobilized patients living in rural and township areas of Cape Town currently have no efficient method of traveling to health clinics, which are located 1.2 to 1.9 miles away in more industrialized areas. Most health clinics are located in developed urban areas, while the majority of patients live in nearby townships. This presents a problem for patients whose conditions, including diabetes, HIV/AIDS and amputations, have left them immobilized. Many must travel considerable distances over rough terrain to get to clinics. Multiple weekly clinic trips are a necessity for these patients in order to receive drug regimens or other treatments. While these clinic visits are non-emergency situations, they are nonetheless critical to the health and quality of life of these patients.
Currently, patients are transported via very labor-intensive and undignified methods. One method is to carry patients in body bags. This places a large physical burden on the 3 to 4 required transport assistants. Wheelbarrows are also used with fewer transport assistants, but are still labor intensive and leave the patient feeling undignified. The demographic of people available to transport the patients are those who are at home during daytime, namely elderly women and children. The device’s total operational force must also be lower than what is currently expected for the existing methods, and must offer a safer, more dignified means of transport, as well as low center of gravity. Finally, patients will not be engaged in operating the device to ensure that they do not have to physically exert themselves.
Townships are constructed in a disorderly fashion; shacks have an average distance of approximately 2’ between them. In addition, many of these walkways have 90º turns that must be steered. This factor places restrictions on the length of the transporter, as well as emphasizes the need for a tight turning radius. The uneven ground is often strewn with human waste, barbed wire, and garbage . Because of the inconsistency of these obstacles, we have modeled them all to be 6” tall bumps.
The rural environment presents different challenges from the urban setting; patients must be transported 1.2-1.9 miles, through hilly environments along 1’ to 1.5’ wide footpaths, 2.5” deep. This makes transportation of patients by elderly assistants challenging. The towns are often sporadically placed atop 20-30 degree inclines, while others are constructed in sandy dunes or flatlands.
High traffic roads surround townships and are located several miles from the rural areas. A consistent paid taxi service to the clinics runs on these roads. The patients must be effectively transported to these roads, and then the remainder of the journey to the clinic can be completed effortlessly in the comfort of a taxicab. Therefore, the device must be collapsible and fit into the trunks of these cabs in order to be a viable option.
Our client in Cape Town, Shonaquip, is a for-profit assistive device company. The owner, Shona McDonald, has developed markets in Cape Town specifically for her products and has suppliers that can provide low cost materials for manufacturing these assistive devices. One of Shonaquip’s supporting resources is the Western Cape Rehabilitation Centre, which provides prototyping services such as laser cutting, welding, angle bending, and curve bending. Additionally, Shonaquip is offering the use of its on-site facilities for prototyping as well as access to its wholesale suppliers to reduce production costs. The target cost to produce our device is $40-55 USD or approximately one week’s pay for the target demographic, with a slightly larger final retail price to account for profit margins and a 14% value added tax. Because of this financial constraint, the device must be constructed on-site from low cost materials currently available at Shonaquip.
There are approximately 3 million people living in or around Cape Town, and of those, roughly 10-20 thousand people would benefit from a transporter device for non-emergency trips to clinics. Shonaquip has networking connections and capabilities to expand this device throughout South Africa, as well as to the neighboring countries of Namibia, Botswana, Zimbabwe, and Mozambique, which presents a market in the hundreds of thousands. Additionally, 1% of the world’s population requires a wheelchair, and an additional 2% of the world population is old, sick, or weak, and would also benefit from our transporter.
Upon considering the client requirements, as well as advice from designers who worked on this problem previously, three core principles were determined to define a successful device. The device must tackle rough terrain with ease; it must be collapsible and adjustable; and it needs to greatly increase patient comfort and dignity.
Given the variability in the terrain, one of the biggest concerns is a device’s ability to travel over everything from unpaved roads to sand to vegetation. The device must be able to clear obstacles of about 6” height, and also afford lifting modes in case of an excessively large obstacle. The device weight must be distributed as low to the ground as possible and its components should function successfully outdoors. It must also be easily maneuverable by a standard assistant. Additionally, the device must minimize exertions required of the assistant beyond normal pushing and pulling; for example, in the current wheelbarrow method, the assistant still must exert an upward force to counter the downward moment of the patient. The proposed device must balance forces and distribute weight over the wheels.
Collapsibility is important because the device must fit into the trunk of a taxi. Previous designs failed when they could not be folded and stowed in taxi cab trunks or were too wide to navigate the narrow environments. The device must, therefore, be collapsible and have width adjustability.
Neither body bags nor wheelbarrows provide a sense of dignity to patients as they are transported through their living community. Because both techniques are make-shift solutions, they lack the stability and comfort of manufactured products. While they perform a transportation function, both methods are not legitimate assistive products that the patient is proud to use and own. The device must provide its users with comfortable, dignified seating. Furthermore, the device should also be aesthetically pleasing and be a product that the patient is proud to own.
For our mockup, we used a stretcher made of 2 steel tubes and fabric. This idea was the simplest method of providing comfortable, full body support to the patient. We rested our stretcher in a cut-open steel keg shell with bicycle wheels on either end. This steel shell gave support to our seating while allowing mobility on rougher terrains with large bicycle wheels. However, this design had many issues. It was too heavy, and would be difficult to lift over obstacles. It did not have as much clearance off the ground as we wanted. The device was uncomfortable to sit in, because some metal from the shell pressed into the patient’s sides. In addition, the prototype was neither collapsible nor adjustable.
The final proposed device, the Trekker, consists of a frame made of interfitting steel tubing connected by bicycle clamps, bicycle wheels attached via bicycle forks, and a nylon netting that provides a hammock-style seating. In its operational state, the device has a total length of 6’, an adjustable width between 20” to 26”, and a clearance above the ground of 8” to 12.” The Trekker is not only a light-weight device (15 lbs), but can also easily disassemble into a smaller 26” by 24” configuration. A bungee cord runs throughout the interior of the tubing, holding the disassembled pieces intact. Also, ISO 24” bicycle wheels held within 26” bicycle forks are used in our device.
Because the frame can be grasped at the top or bottom, the device can easily be pushed, pulled, or lifted while a patient is seated. During operation, the device is tilted back by the assistant, which allows the patient to recline comfortably. The assistant need not exert any additional stabilization forces, as the patient’s weight lies over the wheels. The design allows for better leverage going up and down hills, with the assistant facing the same direction as the patient. On level ground, it allows for a rickshaw-style pull or normal pushing. Finally, if an obstacle is encountered that cannot easily be scaled by the wheels (ie. a puddle of mud or animal), the frame can easily be gripped on both ends and lifted.
Interfitting steel tubing was used and connected by bicycle clamps, which require hex L-keys. Clamps were placed at the top and bottom frame portions; these are used to adjust device width. Additional clamps connect the sides of the frames and can be loosened to disassemble the device into a 26” by 24” unit. A bungee cord runs through the interior of the steel tubing to keep the various pieces connected, ensuring that the individual parts would not get lost. The collapsed configuration allows the device to easily fit inside the trunk of a car. In future designs, we anticipate using quick-release bicycle clamps so there is no need to rely on a hex key.
The use of interfitting tubing and clamps also allows for varying device widths. The frame can be pushed all the way in or out at the top and bottom portions of the frames to achieve widths ranging between 20” and 26”. A medium-sized width (23”) should be appropriate for a majority of patients and narrow enough to fit through footpaths and alleys. Adjustability helps give the device the smallest possible size when collapsed. It also allows for the device to be personalized to the size of the patient. Since this device might also occasionally be used for transporting goods and groceries, the adjustable width plays a further role.
With an emphasis on patient dignity and comfort, the device was designed to achieve an “up-right” seating with a proper posture angle and appropriate foot support. A strongly-rated, light-weight Nylon netting was attached around the frame, giving a reclined seating that provided a comfortable posture and allowed the patient to sit upright. The netting also allowed for complete lower body support once the patient was seated.
Maintaining a low center of gravity for the patient was key to ensure device stability. The nylon netting ensured that the patient was low enough to the ground that the device would not topple due to unsteady loading and high enough to clear small obstacles. The use of low-hanging netting meant that it was not possible to use a cross-axle to connect the two wheels, as the patient would be slightly below the center of the wheels. Therefore, we welded bicycle forks to secure the wheels on their respective sides, foregoing the need for a cross-axle and still achieving high stability.
We would like to thank Professor Matthew Glucksberg for his help throughout the design process. We would also like to thank our clients Shona McDonald and Matthieu Chardon.
1. HOPE Cape Town Association <http://www.hopecapetown.com/09English/hiv_situationsa_e.html>. October 9th, 2009
2. Van Nostrand JF, e., Common beliefs about the rural elderly: what do national data tell us? Vital Health Stat 3, 1993.
3. Pharmaceutical Research and Manufacturers of America. Health Care in the Developing World 2006 [cited 2009 Oct 18]; Available from: http://world.phrma.org/.
4. Design Team Interviews. Client Interview with Mr. Chardon. September 30, 2009.
5. Design Team Interviews. Client Skype Interview with Shona. October 14, 2009.
6. Global Oneness Encylcopedia II. http://www.experiencefestival.com/a/Cape_Town_-_Demographics/id/5199080, October 8th, 2009
7. Email correspondence Shona McDonald. Received Dec 5, 2009.
8. Email correspondence Shona McDonald. Received Dec 6, 2009.
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