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When we typically think of evolution, we think of “survival of the fittest”, where evolution is the process of something getting better over time in terms of function. In the case of the most widely used manual wheelchair in the world, the design evolution (improvement) has been geared towards reducing manufacturing and production costs to the detriment of the wheelchairs’ mobility performance.
The core of a wheelchair’s mobility revolves around its wheels. That is why we call it a “wheel chair”. Just like bicycle, the rear wheels of the wheelchair are critical components. Their function is a primary determinant of mobility performance. The most common wheelchair wheel is a mag wheel made almost entirely of plastic and uses solid urethane tires with effectively no tread. The axle is a common steel bolt. Due to its bulky plastic construction, each wheel is heavy, weighing approximately 5 lbs.
Despite being used in a similar urban environment, there is no comparable bicycle wheel to the wheelchair mag wheel. Nobody would put such a wheel on a bicycle due to the combination of poor performance, lack of tread, and excessive weight. The typical bicycle wheel is made of metal rims and spokes for light weight. It uses a rubber tread tire with a pneumatic inner tube. This tried and true method has been around for decades. Metal spoke rim wheels were also commonly used for wheelchairs until the evolution of the injection molded mag wheel which has reduced the wholesale cost from $5-$10 to $2-$6 per wheel (or from the cost of a regular cheese pizza to only a slice or two).
Using a strip of urethane as a tire eliminates the pneumatic inner tube and rubber tread tire. No maintenance is required. There is no inner tube to fill with air, patch or replace. There is no tire tread to wear out and replace. The wheelchair mag wheel is effectively the modern version of the wheels used by the very first bicycles from the 1800’s.
After a few years after the Dandy bicycle, the wooden spokes were replaced with metal wires to lessen wheel weight. In 1887, the pneumatic tire was invented to reduce road jarring by creating air suspension. The pneumatic tire has been the dominant bicycle wheel for well over one hundred years due to its performance characteristics. Yet, the most commonly used wheelchair wheel has devolved from being similar to a bicycle wheel to being similar to a wooden cartwheel used in the 1800’s. The wheelchair mag wheel is the result of “survival of the cheapest”. The design of the plastic mag wheel takes advantage of modern technology to produce mass quantities of wheelchair wheels at the lowest possible manufacturing cost with no regard to the decrease in performance characteristics and user comfort.
The front caster wheels of the cheapest wheelchairs also use injection molded plastic wheels that cost around $1 per wheel. Add in a plastic fork and metal stem axle and the total cost increases to $3.50 or so. At this point, the wholesale cost of all four of the wheelchair wheels is less than $20. Without considering the need for maintaining (or improving) performance characteristics, the singular priority (of evolution) of cheap wheelchairs is to reduce manufacturing costs.
The position of the wheelchair’s rear axle has a tremendous effect on its mobility performance. Think of it like a bicycle seat where proper height adjustment is critical to customization for different people. The cheapest way to make wheelchair axle holder is to fix its position (don’t make it customizable) on the existing metal backrest support of the wheelchair. In this case, there is no need for an extra piece of metal to be used to create a support. Using a fixed position eliminates the need to make an adjustable bracket. The axle holder is literally a reinforced hole in an already present part of the frame. Once again, the priority of reducing high quantity manufacturing costs results in greatly reduced wheelchair mobility and user comfort.
Given that the rear wheels of the wheelchair weigh a total of 10lbs, removing them makes it much easier to physically lift the frame. But a bolt with a nut is the cheapest type of axle (29 cents). Therefore, the most common wheelchairs use common steel bolts rather than quick release axles which cost a little more.
Unlike riding a bicycle, people use wheelchairs for personal mobility because they are unable or have great difficulty walking. Despite the important role that manual wheelchairs play in the lives of millions of people, their low function design has no parallel in the able-bodied world. There is no example of a widespread mobility device used by able-bodied people that is designed as poorly as the Cheap Wheelchair.
In terms of providing mobility, a wheelchair is to non-walking paraplegic as a prosthesis is to a lower limb amputee. The “wooden leg” has evolved into an extremely high tech and high performance and expensive prosthesis made of a wide variety of materials. The cheapest style of prosthesis is not the most widely used. In fact, there is no mass production of prosthetics for widespread use.
Unlike wheelchairs, evolution of prosthetics is not about reducing price; it is about improving function. Society recognizes that is critical that amputees have access to well designed and lightweight protheses to improve their function as much as possible. Yet, society desires to spend as little as possible on manual wheelchairs for the majority of wheelchair users even if the result is their greatly diminished mobility potential.
Put another way, there is no societal desire to enable wheelchair users to be as mobile as possible. History has shown that the economic incentive is to make commonly used manual wheelchairs as inexpensively as possible. For people in the United States, cheap wheelchairs have been made so readily available that it makes more economic sense for consumers to throw them away and replace them rather than attempt to repair them. These wheelchairs ultimately end up in low resource countries where people have no other option but to use them (despite their poor functionality).
Cheap Wheelchairs are designed and manufactured in such an extreme manner that it would cost relatively little to improve their current poor functionality into a more user centered product (something that already exists). But in order to do so, the incentive of evolution in terms of the current “survival of the cheapest” must change to “survival of cheapest AND also appropriately functional”.
Note - I will address the less commonly used and available, Expensive Manual Wheelchair in future posts. The existence of this style of mobility device doesn’t negate the economic reality of Cheap Wheelchairs.