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).
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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.
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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