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).
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.
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."
Source: TU Wien
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