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"Liquid Drive" bike prototype at auction



 
 
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  #1  
Old November 26th 03, 08:43 AM
Chalo
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Default "Liquid Drive" bike prototype at auction

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.

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

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?

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.

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.

5) No intrinsic configuration constraints

This seems most relevant to suspension bikes, where chain drive and
suspension components compete for space and exert forces upon each
other, and to recumbents, where the rider's behind often interrupts
the straight line between drive sprocket and driven sprocket. But the
hydraulic "driveline" is just a pair of hoses, and can be fitted
around (or through) other mechanisms. It could be routed under the
cargo bed of a carrier bike, for instance, or within a frame tube to a
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.

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
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  #2  
Old November 26th 03, 08:51 AM
Hugh Fenton
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Default "Liquid Drive" bike prototype at auction


"Chalo" wrote in message
om...
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.

snip
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.

snip

Chalo Colina


Thanks Chalo,
I really find these things fun - wish I had time to have a go at building
such impracticalities....

Theoretically instead of dispersing the braking energy through turbulence in
the hydraulic fluid you COULD use the pressure (via an accumulator) to store
the energy for future use.

Not suggesting its at all practical, but makes an interesting mind project.
Hugh Fenton



  #3  
Old November 26th 03, 11:35 AM
Simon Brooke
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Default "Liquid Drive" bike prototype at auction

(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. I'm unconvinced that it's really as desirable as
its proponents say.

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


Many years ago my father drove a little DAF car which had a CVT system
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.

I'd like to *try* a CVT bike, particularly off road, but I suspect
losses in the system would outweigh any advantage.

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?


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. Again, I'd be most
interested to try an AWD off-road bike, but, once again, I suspect
losses in the system would outweigh any advantage.

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.


Now, for off-road use, that strikes me as being one *substantial*
advantage.

There's a final potential advantage to hydraulic drive which you
haven't mentioned, which is power buffering or capacitance. When you
stand up and stomp on the pedals going up hill, the power delivery to
the back wheel is anything but smooth and off-road this unsmooth power
delivery tends to break traction. With a hydro-pneumatic accumulator
you could buffer the transmission and smooth out the stomping, and
that would probably be at least as useful as AWD in marginal traction
situations.

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!

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

For office use only. Please do not write or type below this line.
  #4  
Old November 26th 03, 12:42 PM
Ed Chait
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Default "Liquid Drive" bike prototype at auction


"Chalo" wrote in message
om...
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


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 750cc Honda with the CVT transmission was a dog. If I recall correctly,
it produced about half the horsepower at the rear wheel that the regular
model did.

Not many people are willing to buy a 750cc bike that performs like a 250.
Another issue against it was that the motorcycle community, with it's higher
than average level of machismo posturing, did not warm up to the
introduction of something as un-manly as a full-sized automatic motorcycle.

Ed Chait


  #5  
Old November 26th 03, 01:05 PM
Simon Brooke
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Posts: n/a
Default "Liquid Drive" bike prototype at auction

(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/

For office use only. Please do not write or type below this line.
  #7  
Old November 26th 03, 04:32 PM
Buck
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Default "Liquid Drive" bike prototype at auction

"Simon Brooke" wrote in message
. uk...

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. Again, I'd be most
interested to try an AWD off-road bike, but, once again, I suspect
losses in the system would outweigh any advantage.


Find a dealer to test out this all-wheel-drive bike:
http://www.christini.com/

AWD is a great addition to a car in slippery conditions. The Audi Quattro
was banned from European touring car racing because they were deemed to have
an unfair advantage.
http://www.audiworld.com/news/02/unf.../content.shtml

While this is great press for cars, I doubt all wheel drive would make much
difference in bicycle racing.

-Buck


  #8  
Old November 26th 03, 06:25 PM
Phil
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Default "Liquid Drive" bike prototype at auction

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.

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


Many years ago my father drove a little DAF car which had a CVT system
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.

CVTs like you are describing on the DAF have been used successfully in
snowmobiles for about 50 years. 186,000 snowmobiles, all with CVTs,
were sold last year so I would say they are quite widespread. The
biggest snowmobiles are currently putting out 170+ HP, made possible
by advances in belt and clutch technology. The CVT is a simple,
effective, and efficient transmission. The biggest hurdle to clear
for automotive use has been building a belt that can handle high
loads. Snowmobilers think nothing of putting a new belt on every 2000
miles or so, as 2000 miles is a long way by snowmobile. That is not
acceptable in a car, I believe all current automotive applications are
using some form of steel link belt.

Polaris also uses a CVT in most of their ATVs. I'm not sure exactly
what they are, as I don't ATV, but I think they are belt driven. They
sell a ton of them.

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.
  #9  
Old November 26th 03, 06:47 PM
Carl Fogel
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Default "Liquid Drive" bike prototype at auction

(Chalo) wrote in message . com...

[snip]

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


[snip]

Dear Chalo,

Do we really tolerate a wide range of RPM?

I'm open to correction, but my impression is that
we actually have a fairly narrow, low RPM power
band and that this is why only bicycles use the
peculiar derailleur system. (Jobst Brandt may
have said something like this somewhere.)

That is, many bikes now offer 20-30 front-rear gear
arrangements (some duplicates) for an effective
speed range from about 8 to 40 mph (the upper limit
being theoretical for most of us in terms of level
pedalling). Most engines with a wide range of RPM
use only four or five speeds to handle 8 to 100+ mph.

Most of what I see here suggests a cadence ranging
from about 80 to 120 RPM, with my glacial 50-60 RPM
being beneath contempt. So our fastest effective RPM
seems to be only about twice our lowest RPM, while
most cars and motorcycles happily idle along at
around 800-1,200 RPM and reach 3,000 to 10,000 RPM,
depending on how close they are to racing.

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. I wouldn't want to ride one on my daily ride,
since much of it is level (fixed-gearing too low),
there's a long trudge up a ride at about 10 mph
(fixed-gearing too high), and then there's the 40 mph
coast back down the hill (God bless freewheel ratcheting).

Of course, my understanding of the matter may be as
limited as my pedalling RPM. Oh, yes, how did continuously
variable transmissions become associated with the human
powered vehicle bunch? I imagine that it's because they're
even more gadget-crazy than we are--until they try something,
they can't be absolutely sure that they don't like it, and
a few more experiments might be even more fun.

Carl Fogel
  #10  
Old November 26th 03, 09:02 PM
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Default "Liquid Drive" bike prototype at auction

In rec.bicycles.misc Simon Brooke wrote:
: 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.

Stepless means also that you can make very small adjustments, and
have the exact gain ratio you require for a given riding
situation.

Another exciting possibility would be a very wide gear range. At
least recumbent trikes can use a very wide gear range as they can
reach high speeds going downhill but can also be ridden very
slowly uphill.

Not to mention racing vehicles with a 16" rear wheel - you
wouldn't need the large chainrings for those.

--
Risto Varanka | http://www.helsinki.fi/~rvaranka/hpv/hpv.html
varis at no spam please iki fi
 




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