In article ,
(Chalo) wrote:

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.

I know this particular bike has come up for discussion before, with a
certain amount of pooh-poohing of the general concept. Since this
thing surfaced again, I've been reflecting on what hypothetical
advantages a hydraulically driven bike could have over a chain driven
bike, which might offset the drawbacks of what is almost certainly a
heavier, lossier, and more expensive system than chain drive. So far
I've come up with:

1) True continuously variable transmission ratio, which this bike has

Some people insist we want CVT, but hydraulically driven vehicles have
always had it available and are still rather uncommon. For instance,
Hondamatic motorcycles never caught on, though their system seemed to
work as intended. I'm unconvinced that it's really as desirable as
its proponents say.

The original CB750A and CM450A Hondamatics were not CVTs. They used
fluid torque converters instead of a plate clutch (just like any
automatic car), and 2-speed transmissions. I'm not even sure if they had
automatic shifting.

http://100megsfree4.com/honda/h0700/amatic.htm

You mean this Hondamatic?

http://he.honda.ca/motorcycles/model...RX500FA_pf.asp

It's not a motorcycle, but it is interesting. A hydraulic CVT on an ATV.

I think the argument for a hydraulic CVT on a utility ATV is much
stronger than the one for the same drivetrain on a motorcycle, and much,
much stronger than the argument for a bike.

How did CVT become associated with the HPV community, when human power
seems to tolerate a wide range of RPM?

It's a logical extension: like all underpowered engines, humans benefit
from lots of gearing choices. This led people to believe that continuous
gearing would be even better than a mere 18 or 27 or 30 speeds.

4) Possibly less regular maintenance and system wear

Many hydraulically powered machines work around the clock for years
between breakdowns in the hydraulic systems. (I am reminded of
various forklifts I've worked with, whose batteries always seemed to
be troublesome but whose hydraulics were seemingly invincible.)
Hydraulic systems by their nature run in a lubricant bath, and much of
the mechanical wear in them occurs to the fluid.

I am sure that not every cyclist would be willing to give up a
noticeable amount of efficiency to have a service interval measured in
years, but some certainly would if the cost were not offensive.

I think the problem is that you can get similar durability and better
efficiency and weight by going to a shaft drive. That's why most
performance-oriented applications (cars) use shafts as a compromise
system when chain or gear drive setups don't have what it takes.

The possibilities outrun my ability to imagine good uses for them-- so
much about the bikes we know is just corollary to the chain drive,
that it's difficult to imagine what a "normal" bike would be like in
the absence of one. The high wheeler is what you get when you assume
that a bike's cranks will drive its axle directly, and the diamond
frame with derailleurs is what you get when you assume the use of a
chain drive. If you don't assume either of those things, then what?

I suppose the answer to that will have to await another feasible
alternative, if there is one.

Chalo Colina

That's just the trick. Chain is so good, it defeats all other options.
You use belts or enclosures if the filth bothers you, but that's it.
Maybe some recumbents would benefit from a long, stiff shaft drive,
given their ludicrous chain issues.


--
Ryan Cousineau, http://www.sfu.ca/~rcousine
President, Fabrizio Mazzoleni Fan Club