Good Thinking

Hand-cranked wheelchair is claimed to be safer and more efficient

Hand-cranked wheelchair is cla...
The wheelchair features dual drive cranks, and dual disc brakes
The wheelchair features dual drive cranks, and dual disc brakes
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The crank levers change length throughout each revolution, resulting in a cranking pattern that is oval instead of perfectly circular
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The crank levers change length throughout each revolution, resulting in a cranking pattern that is oval instead of perfectly circular
The wheelchair features dual drive cranks, and dual disc brakes
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The wheelchair features dual drive cranks, and dual disc brakes
Prof. Margit Gföhler (right) with colleague Markus Puchinger
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Prof. Margit Gföhler (right) with colleague Markus Puchinger

According to researchers from Austria's Technische Universität Wien (Vienna University of Technology), propelling conventional wheelchairs puts users' joints in unnatural and potentially injury-causing positions. They've developed what is claimed to be a more ergonomic alternative, in the form of a hand-cranked wheelchair.

Created by a team led by Prof. Margit Gföhler, the new prototype certainly isn't the first wheelchair to substitute a crank system for the traditional hand-rims on the wheels. It is, however, set apart by some unique features.

The chair was developed using a biomechanical computer model that analyzed various upper-body motion sequences. This resulted in a drive system that incorporates two armrest-mounted cranks. Turned by separate arms, each of those cranks is linked to the wheels via toothed belt-drives (stopping is handled by dual hand-lever-activated disc brakes).

The crank levers change length throughout each revolution, resulting in a cranking pattern that is oval instead of perfectly circular
The crank levers change length throughout each revolution, resulting in a cranking pattern that is oval instead of perfectly circular

This arrangement allows for continuous propulsion – as opposed to the series of pushes delivered to hand-rims – along with smaller-diameter wheels than those used on regular wheelchairs. The chair itself isn't any wider than traditional models.

Additionally, the crank levers change length throughout each revolution, resulting in a cranking pattern that is oval instead of perfectly circular. This apparently maximizes power transfer to the wheels, as it compensates for the fact that users' arms don't deliver a consistent amount of power throughout their range of motion.

Prof. Margit Gföhler (right) with colleague Markus Puchinger
Prof. Margit Gföhler (right) with colleague Markus Puchinger

The prototype met with good reviews when assessed by users at an Austrian rehabilitation center, and its drive system is now the subject of a pending patent. "Our new wheelchair concept really could improve many people's quality of life," says Gföhler. "We hope to find a partner in the industry soon to develop our design into a commercial product."

Wheelchair users looking for alternative forms of propulsion might want to also check out models are "rowed" using arm levers.

Source: TU Wien

5 comments
Nobody
50 years ago I remember a young man with a hand cranked wheelchair who traveled all over town. He had massive arms that made Charles Atlas look like a wimp. I don't know who built the wheelchair special for him but it seemed very efficient and quite speedy. The crank was centered in front of him at arms length. It must have folded to the side for him to get in and out. This article reminded me of seeing that young man cranking down the sidewalk many years ago.
Deres
I wonder if the front wheels shall not be bigger or to use double wheels side by side. Such small whells may have issues with obstacles and pot holes.
Nik
While the principle may be good, the method to achieve it, is a production engineering and maintenance nightmare, and all the components, belts and pulleys etc, are potential failures, from wear, which would cause belts to slip, and need adjustment, and collection of debris and dust. The existing belts and pulleys have the potential for trapping clothing or fingers. The engineers motto...'KISS' = ''Keep It Simple, Stupid,'' My solution would be two flexible drives from the hand cranks to the wheels. This would allow an enclosed gearbox, perhaps similar to a bicycle wheel hub type, operated by finger control, to be included if needed.
Martin Winlow
Off topic, but I'm puzzled why the 'self-balancing machine' (think Segway etc) hasn't made it big in conveying disabled people around, yet. Theoretically, such a device could take up no more room than an able-bodied person and conceivably could 'transform' from standing to a more conventional sitting arrangement, and Vv, at the will of the operator.
Daishi
@Martin Winlow That is exactly how the Segway started. Dean Kamen was an inventor of medical technologies and built a wheelchair called iBot that does that and climbs stairs. The technology that allowed the wheelchair is what was used to create the Segway.