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"Liquid Drive" bike prototype at auction



 
 
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  #11  
Old November 26th 03, 09:18 PM
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Default "Liquid Drive" bike prototype at auction

In rec.bicycles.misc Chalo wrote:
: 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

So besides the obvious issue of whether it can be made to work in
practice, there is the issue whether the efficiency can be
improved. Even with some serious advantages, I'd guess many
serious cyclists stay away from a system that loses them 5% or so
of efficiency.

: 2) Two-wheel drive, which this bike does not have

: This is another feature that some have tried to provide, while others
: wonder why. The benefits of four-wheel-drive in cars look similarly
: esoteric to me, yet many people opt to pay a premium for 4WD or AWD
: cars. If such a thing were available for bikes (and without glaring
: shortcomings), I wonder whether there would be any noteworthy handling
: benefits. I don't ride my bikes in the muck, but perhaps those who do
: would appreciate 2WD?

A drive on both rear wheels of a delta trike would be preferable.
With just one wheel driving they can have a tendency to turn one
way when going uphill. If you have two wheels driving the traction
is also better as one wheel slipping won't matter much then.

It would make drive design easier on trikes (and recumbents in
general). In an effort to eliminate the long chain, some people
currently create forward-driven designs. This introduces some
issues such as whether the chain needs to twist etc. The long
chain would be eliminated with a hydraulic system but also you
could probably easily make interesting designs such as a tadpole
trike with the drive in both of the front wheels. (Of course such
exist already but they might just become trivial.)

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  #12  
Old November 26th 03, 09:35 PM
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In rec.bicycles.misc Phil wrote:

: In a bike? That is an interesting idea, but I don't think we could
: pedal fast enough to get good clamping force on the belt. The
: hydraulic CVT would be fun to try.

Would uneven pedalling forces also be an issue?

AFAIR there are some - very few - recumbents that are belt-driven.
It's not the most popular chainfree drivetrain option. I think the
Thys rowingbikes use a wire instead of a chain, for example.

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  #13  
Old November 26th 03, 10:26 PM
Rick Onanian
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On 25 Nov 2003 23:43:18 -0800, (Chalo)
wrote:
It looks like the fella behind this CVT hydraulic bike is trying to


It says that it's a constant 1:2 ratio in the description. Where
did you see CVT?

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

Some people insist we want CVT, but hydraulically driven vehicles have
always had it available and are still rather uncommon. For instance,

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


Probably a similar answer as to my question: Why do we have 10 speed
cassettes with sprockets that are one or two teeth different from
the next? Apparently, tolerance != efficiency (probably not enough
so to make the drivetrain efficiency loss worth it, though).

This is another feature that some have tried to provide, while others
wonder why. The benefits of four-wheel-drive in cars look similarly
esoteric to me, yet many people opt to pay a premium for 4WD or AWD


In cars, there are these effects:
1. In slippery conditions, you're less likely to get stuck
2. In slippery conditions, with only one axle driving, with a
steady amount of throttle (enough only to maintain a speed), hitting
a low-traction spot can result in loss of lateral traction for the
tires on that axle. This is not a big deal for FWD but easily causes
spinouts with RWD.
3. An AWD sportscar can produce a great powerslide (I think). I
imagine that it combines a classic RWD powerslide with the FWD
powerslide that I practiced (which, I believe, most people don't
know is possible, but is really easy). If the front lacks lateral
traction, and you're steering the way you want to go, and you give
it gas, the tires rotation will pull you in the direction they're
pointed. If the rear is loose, then the rear wheels give the
classic RWD powerslide.

AFAIK, a RWD powerslide is damn near impossible to do on clean, dry
pavement. FWD powerslides work fine with such traction.

Disclaimer: Don't try it! The "FWD powerslide", as I call it, is
extremely dangerous and requires a commitment to keeping full
throttle through the whole curve. As soon as you let go of the
throttle, the front wheels will let go and you will plow straight
ahead regardless of where you steer. Additionally, front traction
may exceed rear traction, in which case you have nearly impossible
to correct oversteer. If you brake, you will absolutely unweight
the rear tires and spin out.

cars. If such a thing were available for bikes (and without glaring
shortcomings), I wonder whether there would be any noteworthy handling
benefits. I don't ride my bikes in the muck, but perhaps those who do
would appreciate 2WD?


Handling benefits would only show up in very low traction situations
(snow, mud, deep sand). Actually, it would be useful in deep sand.

However, the point would be for steep, loose hills. You get to
concentrate on pedalling instead of having to devote attention to
maintaining traction. There is a hill I can't get up; I even have
super low gears on my MTB, but in the end, I can't seem to throw my
weight around for proper traction. The only person who I've seen
make it up the hill went in with loads of speed and was strong
enough to _never_ slow down at all. He was in a pretty high gear,
too.

Technique can make it work, but it sure would be nice to have
technology to help.

3) Integral braking, which the inventor's website mentions, but which
does not appear to be incorporated into this bike

I think that having a bike's drive and braking functions integrated
into the same apparatus is the most desirable potential feature of a
hydraulic drivetrain. Check valves could be adjusted to match
available maximum braking torque to the load, and the force required
to close the braking valves would be miniscule compared to that
required to actuate normal rim or hub brakes.


To be useful, it would need two-wheel-drive, and separate drives for
front and rear, else you wouldn't be able to proportion it. Sounds
cool.

5) No intrinsic configuration constraints
drive wheel far removed from the crank. Even a crank is not a given;
it could just as well be treadles or something else yet.


That would be cool, some different form of interface. What are
treadles? Maybe foot and hand pedalling could be combined.

chain drive. If you don't assume either of those things, then what?


How about a bike shaped like a cow? That would be cool.

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


There probably is one, and probably nobody will come up with it till
long after we're all dead. I hope that statement is wrong.

Chalo Colina

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Rick Onanian
  #14  
Old November 26th 03, 10:50 PM
Eric M
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Default "Liquid Drive" bike prototype at auction

In article ,
Simon Brooke wrote:
(Chalo) writes:

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.


The Hondamatics didn't catch on because motorcyclists in the US
are interested in sport, and not solely in practical commuting.

The Rokon and Husqvarna automatic dirt bikes were moderately
sucessful but failed because of reliability issues.
(Rokons would lose drive if the belt got wet, and the Husky
transmissions would blow up and give you four automatic neutrals).

OTOH, there are a lot of new Audis running around with "six speed"
computer-controlled CVTs.

which operated through pairs of opposed cones with a belt linking
them; the belt was automatically moved from one end of the cones to
the other to vary the ratio. The system was remarkably effective and
seemed quite a good thing, but as you say hasn't been widely adopted
(I think there were limitations on how much power it could
transmit). Similarly, hydraulic CVT gearboxes were around on farm
tractors when I was a boy, but the vast majority of tractors continue
to have mechanical gearboxes.


Most newer small diesel and garden tractors in the US are hydrostatic.
Essentially zero maintenance, and MUCH easier to use for mowing
or front-end loader work... or anything except plowing straight lines.


All wheel drive on an off-road vehicle is generally a good thing,
provided that you have limited-slip differentials or the
equivalent. If one wheel spinning brings the whole vehicle to a halt
there isn't a lot of point. However, a pushbike is much lighter than
other off road vehicles. If you do get into a situation where the back
wheel just can't grip the usual solution is to put the bike on your
shoulder and walk a bit. So AWD isn't that big an issue, although it
might be useful on loose, gravelly climbs.


The front wheel doens't have much traction on climbs since
all the weight is transfered to the rear.


Yamaha have done some experimental 2wd off-road motorcycles, and
have even run them in rally raids (similar to the Paris-Dakar).
The hydraulic 2wd WR450 is supposed to go on sale to the general public
in the 2004 model year, although I'll beleive it when I see it.

The description I read sounds like it's very different from
a normal rwd dirt bike to ride.


However, the inventor of this creation claims only 90% efficiency. Am
I not right in believing that deraileur systems achieve about 93%? I
know 3% isn't much, but then bicycles are not exactly high
powered. Still, an interesting system - would definitely be fun to
play with!


I think bicycles are more like 98% efficient, if that's the
case 90% would really suck.


Eric

  #15  
Old November 26th 03, 11:54 PM
Rick Onanian
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Default "Liquid Drive" bike prototype at auction

On Wed, 26 Nov 2003 21:50:19 GMT, "Eric M" wrote:
The front wheel doens't have much traction on climbs since
all the weight is transfered to the rear.


Well, AWD would be welcome when the rear wheel loses traction.
Consider that on steep, loose hills, riders tend to lean [sometimes
excessively] far forward to balance and pedal.

Eric

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Rick Onanian
  #16  
Old November 27th 03, 06:35 AM
Tom Sherman
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Rick Onanian wrote:

... How about a bike shaped like a cow? That would be cool....


See http://www.chicagotraveler.com/cows/235.jpg

Tom Sherman - Planet Earth
  #17  
Old November 27th 03, 01:24 PM
[email protected]
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In rec.bicycles.misc Eric M wrote:

: I think bicycles are more like 98% efficient, if that's the
: case 90% would really suck.

AFAIK chain efficiency depends on whether you run it in laboratory
conditions (maybe a bottom fairing or casing it all in an oil bath
would do the trick too) or if the chain is dirty from all the
real-world stuff flying around on roads...

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varis at no spam please iki fi
  #18  
Old November 27th 03, 06:20 PM
Adam Rush
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The best argument against my sissified view of our
narrow RPM is probably the fixed-gear crowd, who
use a single speed to run around. I suspect that they
start off noticeably slower and top out much sooner,
much like a four-speed car stuck in second gear all
day.


Hey buddy, how can I get this car out of second gear?
  #20  
Old November 28th 03, 04:09 AM
A Muzi
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Default "Liquid Drive" bike prototype at auction

Carl Fogel wrote:

-snip-
Here's a stray question to emphasize the depth of my
ignorance: are there fixed-gear tandems? If so, do
they use a different gear--higher or lower--than
either rider would normally use?

-snip-

Traditionally, the only competitive tandem event is on the
track. Gearing used to be 46x16. (I haven't kept up with that.)

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www.yellowjersey.org
Open every day since 1 April, 1971

 




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