Author: Sam Brady, 24th June 2021

If you look at most modern elite-level sports wheelchairs – such as the ones used for basketball, racing, rugby or tennis – you will likely notice one thing. They have prominent angled wheels – in which the top end, closest to the user, is angled inwards, and the bottom end, touching the ground, is angled outwards. This is a huge difference compared to the non-sporting wheelchairs you might be used to seeing, like everyday or hospital wheelchairs, with their straight wheel alignment. This difference – known as a negatively cambered rear wheel - is an important factor in the development of dedicated sporting wheelchairs. But how was camber introduced to wheelchairs, and who made these developments? By considering the design of early wheelchairs and one example of modification used to give wheelchair negative camber, we can see not only the development of this technology, but also recognise wider patterns of user-led modifications.

  

Wheelchair basketball in the 1950s ©WheelPower and at the Beijing 2008 Paralympics ©Getty Images

Cambered wheels have wide-ranging advantages. Firstly, by increasing the space between the bottom half of the rear wheels, wheelchairs gain lateral stability and improve handling for users. As the wheelchair becomes wider and sits lower, the centre of gravity is lowered, and it becomes more stable. As well, the position the wheels sit in when negatively cambered provide a more natural pushing motion, and reportedly leaves less strain in the shoulders.[1] In an interview for my research, former wheelchair racer and chair modifier, Paul Clark, stated this about the introduction of camber:

That was something that was used in wheelchair basketball, because for stability ... we wanted to have the lower stance of the chair wider, so the chair wouldn't tip over so much, and now you'll see quite an exaggerated camber to the basketball chairs, but back then even a little bit of camber was worth a lot. So that was the first change to wheelchair basketball chairs. And then from that, we started to use the same modification for wheelchair racing chairs...[2]

The addition of camber was important for sport, although too much camber reduced the chair’s usefulness in everyday life. It is vital to remember that the distinction between sporting and everyday wheelchairs did not exist during the early development of wheelchair-based sport, and the first steps in cambering wheels came via the modification of wheelchairs used for sport and day-to-day life. As chairs became more specialised for sport, however, camber increased, making them less suited for everyday life – for example, they became too wide to manoeuvre through standard door frames.[3] And so, the development of camber around the late 1970s and early 1980s shows the origins of the divide between everyday wheelchairs and sporting chair varieties.

One of the major innovations in wheelchair technology was the development of the folding wheelchair, made famous by Everest and Jennings in the 1930s.[4] This became a popular design, as it allowed for easier transportation compared to the fixed frames of older wheelchairs, and quickly became the norm for many wheelchair designs across the world. Folding wheelchairs function by having two side frames for the chair, connected by a fabric seat and two bars which crossed to either side of the frame in an ‘X’ shape. The two cross bars are connected by a bar going through the crossing point, allowing the chair to be folded. Many chairs had one set of crossing bars in the folding mechanism, although some had two sets – one at the front of the chair and one at the back. Below is the ‘Model 8’, a wheelchair used in Britain approximately between the 1950s and 1960s, to provide an idea of what these wheelchairs looked like at this time. Although, there were many different varieties in design, materials, shape and functionality nationally and globally, so not all chairs looked like this. 

Model 8 folding wheelchair, England, 1953-1963. ©Science Museum Group Collection Online

However, wheelchair technology largely remained static, despite the growing demand for better wheelchairs by users – particularly athletes who wanted to improve their speed in racing or performance in basketball.[5] Wheelchair users ultimately became the architects of improved wheelchairs, tinkering and modifying their wheelchairs to make them lighter and more responsive. Eventually, the folding mechanism would be removed as users created their own box or rigid style chair frames, increasing the move towards lighter, stronger and more responsive devices. However, before this, the folding mechanism facilitated an important step in chair evolution by allowing the introduction of negative camber in the rear wheels.

Wheelchair athletes modified the folding mechanism with an incredibly simple modification – a small piece of metal with two holes in it, known as a camber plate. This modification to the folding mechanism changed the angle of the rear wheels, giving them a degree of negative camber. As Paul Clark said:

...simply by taking a plate, which has two holes in it, that match the size of the hole at the crossing, you could put the camber plate so that it would change the crossing to be higher up essentially. And that would spread the bottom of the X and narrow the top of the X. And so really, what you were doing is you were sitting in a chair that had a partially collapsed seat ... your wheels would be wider at the bottom, which you wanted. And the backrest would be more slack, which would allow your whole body weight to be more over the back wheels than the front.[6]

Camber plate used by Paul Clark, placed next to a pen for size comparison. Image ©Paul Clark

Example of a modified chair for racing. Camber plate provides slight cambering of wheels. 1977. Image ©John Brewer, via History of Wheelchair Racing Facebook group.

As previously stated, camber provided a huge advantage in sport, starting in basketball and racing, but continuing into other chairs, such as those used for tennis and rugby. However, the camber plate demonstrates the revolutionary, yet also seemingly minor changes wheelchair athletes made to their devices. Superficially small changes had huge implications for the performance and feel of wheelchairs, especially in sport, and small iterations continued to be experimented with and refined – until the built in, extreme camber we are used to seeing today. As well, the example of the camber reinforces the importance of users being at the heart of this innovation, drawing on their lived experience to advance the technology and the sport.

As such, the wide shape of the modern basketball wheelchair can trace its origins back to the introduction of the camber plate. Despite the less extreme angle used initially, the benefits provided to athletes via negatively cambered wheels can’t be underestimated – only made initially possible via the introduction of this small modification. Adaptions like this were key to advancing wheelchair technology and highlight the importance of users’ input and design ingenuity.

[1] Invacare Passionate People. ‘What Is Camber? Why It Matters for Your Wheelchair’.
[2] Interview with Paul Clark, conducted by the author, 25/03/2021.
[3] Invacare Passionate People.
[4] In Pursuit of Standardization, Woods and Watson, p 546.; A Sociotechnical History of the Ultralightweight Wheelchair, Stewart and Watson, p 6.
[5] Stewart and Watson, pp 6-7.
[6] Interview with Paul Clark, conducted by the author, 31/03/2021.

References:

• Brian Woods and Nick Watson, In Pursuit of Standardization: The British Ministry of Health's Model 8F Wheelchair, 1948-1962 (Technology and Culture, 2004, Volume 45, No.3)
• Camber plate image provided by Paul Clark.
• Hilary Stewart and Nick Watson, A Sociotechnical History of the Ultralightweight Wheelchair: A Vehicle of Social Change (Science, Technology & Human Values, 2019, Volume 45, No.6)
• Interview with Paul Clark, conducted by the author, 25/03/2021.
• Interview with Paul Clark, conducted by the author, 31/03/2021.
• Invacare Passionate People. ‘What Is Camber? Why It Matters for Your Wheelchair’. https://www.passionatepeople.invacare.eu.com/camberwhy-matters-wheelchair/
• Modified racing chair picture provided by John Brewer, via History of Wheelchair Racing Facebook group.
• Science Museum Group. 'Model 8' folding wheelchair, England, 1953-1963. 1979-811 Pt11Science Museum Group Collection Online. Accessed June 12, 2021. https://collection.sciencemuseumgroup.org.uk/objects/co127502/model-8-folding-wheelchair-england-1953-1963-wheelchair.