[geeks] Electric bike?

[Francois Dion]

On 7/19/06, Gregory Leblanc <gleblanc at linuxweasel.com> wrote:
> 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

I tought the whole grouppo was called positron.

Sheldon Brown's site to the rescue:

http://www.sheldonbrown.com/shimano1982/pages/36.html

Apparently this positron derailleur was offered along with:

http://www.sheldonbrown.com/shimano1982/pages/35.html

a front freewheel system which allowed to shift while coasting.
Positron was a hard link so this was required.


Francois