(Chalo) writes:

It looks like the fella behind this CVT hydraulic bike is trying to
raise some capital by selling off his prototype:

http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3641257316

http://www.powerengine.com

It seems like a cool artifact, if not particularly practical.

Quick summary of the mechanism as I understand it from reading the
website :

The basic unit consists of an opposed two cylinder 'boxer' layout. The
unit can be used either as a pump or as a motor. Two 'bottom bracket'
actuators are illustrated, one with a single two cylinder unit, and
the other with two units mounted at ninety degrees to one another, and
thus presumably providing substantially smoother flow as at least one
piston is on its pump stroke at all times.

So far I've described components of a fixed ratio transmission.

The CVT bit comes from a very cool idea: a variable offset crank-pin
at the pump end. As the crankpin offset increases, so the volume of
fluid moved per rotation increases, so the effective ratio
increases. So far so good. But now for the disappointing bit: It's
manual. You have a lever on your handlebar which varies the offset on
the crankpin. I really don't see that that's a significant benefit
over, say, a Rohloff. Yes, I appreciate that the transmission is
stepless, but as you have to move the lever to change the ratio, you
experience a step, and the difference between 14 steps and stepless
isn't much.

It surely shouldn't be beyond the wit of man to manage feedback from
the high-pressure side of the system to the crankpin offset to get
fully automatic CVT, which would be a significant win.


--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

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