Imagine if the only way of propelling yourself on a bicycle was to reach down and turn one of the wheels with your hand. It would be pretty inefficient, yet that's essentially how a wheelchair works.

"I wanted to create a new electric power-drive accessory for a manual wheelchair," said an inventor, from Buffalo, N.Y., "so ...

Normally, wheelchair users move themselves along by pushing the rims of the two large wheels forward. But installing a set of Rowheels allows them to pull back on the rims, and still move forward.

When the RoChair first appeared back in 2011, the wheelchair used an unorthodox center-mounted drive lever, operated with a rowing motion, to propel it forwards. Four years later the RoChair has been ...