[geeks] Electric bike?

[Gregory Leblanc]

On Wed, 2006-07-19 at 11:59 -0400, Francois Dion wrote:
> On 7/18/06, Sheldon T. Hall <shel at tandem.artell.net> wrote:
> >  Saith Francois Dion ...
> > > I've just been trying to figure a mechanical way to drive through the
> > > regular chain.
> >
> > You need a co-axial arrangement through the regular bottom bracket.  The
> > motor drives a sleeve inside the BB, and the normal BB axle is inside of
> > that.  Two layers of bearings, of course: BB-sleeve, and sleeve-axle.  The
> > chainrings are on the sleeve, and a one-way clutch lets the BB axle (and
> > thus the pedals) drive the sleeve.
> 
> You'd think this would be a common tandem option. Didn't some BMX work
> this way? And then there was the Shimano positron, but I've actually
> never ever seen one. Went the way of the Biopace.

Positron was just the first generation indexed shifting.  The rear
derailer had bumps on it, that forced it into a particular position.  It
used a solid piece of wire as the shifter cable, which was MUCH stiffer
than the stranded cables that everyone else uses.  No idea what this
would have to do with anything else discussed, though.
	Greg