On Jan 13, 1:05 pm, " wrote:
On Jan 13, 6:06 pm, wrote:

On Jan 13, 3:16 am, " wrote:

http://www.google.com/patents?id=Pj5HAAAAEBAJ

What happens here?

As drawn, nothing happens. There's no mechanism to compensate for the
varying chain length, and the chains are either going to bind or
skip. Later proponents of elliptical chain rings have realized that;
a) The sprockets need not also be elliptical, b) There does not need
to be two chains, and c) There needs to be chain slack and some kind
of spring loaded tensioner.

Yes, that's what I thought. I've seen the egg shaped sprockets appear
and disappear over the years. The point of the patent seems to be in
having a chain for both pedals.

Here is a modern patent referencing this one.

"A drive mechanism applicable to bicycles for increasing the
efficiency of pedaling action via independent pedals with a
sinusoidally varying transmission ratio. The drive mechanism achieves
increased efficiency by making the pedals independently synchronized
with a varying transmission ratio"http://www.google.com/patents?id=lUIZAAAAEBAJ

You know of any production bike using that?

No, but that patent was filed by Rotor: http://www.rotorcranksusa.com/
They're not likely to be developing that particular design, but rather
filed the patent to keep some small part of it protected for
themselves.