September 19, 2010
File under "Better Mouse Trap"
I've watched this video several times, but still haven't quite gotten a handle on, well, the pedal and crank and cable on this reimagined bicycle propulsion system.
The gears and chain we all know from our childhoods have been replaced, their familiar round-and-round circuit replaced by an irregular elliptical path at the front crank, and cables rising and falling, winding twining around the rear hub.
How the gearing works -- can it even be called "gearing" when there aren't anything with teeth? -- is still a mystery to me.
Eccentric discs. The pedal axis rotates these discs at both sides of the frame. The discs has a specific, kidney like shape which determines the driving characteristic i.e. the angular displacement of the rear wheel of the bicycle as a function of the angular position of the pedal shaft. The chosen shape provides for a conventional driving characteristic i.e. the same as if a chain-driven bike with circular gears were used. In a more expensive model the discs can be changed with other ones having different shapes, whereby the driving characteristic can be changed in a tour or in a contest, to load different muscle groups.
The swinging unit, comprising a pair of oppositely swinging arms arranged for swinging movement around a pivoted auxiliary axis. The rotation of the eccentric discs results in the swinging movement of the arms in forward and backward direction.
Transmission (speed) changer. This unit is a controlled slide. It changes the longitudinal position (height) of respective pulleys guided along the swinging arms. The height of the two pulleys is always the same. When the pulley is in the outermost position, the transmission ratio is at maximum, while in the innermost position this ratio is at minimum.
The design is supposed to offer a number of benefits, the least of which is no dirty chain to lubricate -- and mess up your pants.
The rest, along with photos, are here.
Posted by Mike Lief at September 19, 2010 11:00 PM