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#11
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"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.) -- Risto Varanka | http://www.helsinki.fi/~rvaranka/hpv/hpv.html varis at no spam please iki fi |
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#12
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"Liquid Drive" bike prototype at auction
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. -- Risto Varanka | http://www.helsinki.fi/~rvaranka/hpv/hpv.html varis at no spam please iki fi |
#14
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"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
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"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 -- Rick Onanian |
#16
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"Liquid Drive" bike prototype at auction
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
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"Liquid Drive" bike prototype at auction
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... -- Risto Varanka | http://www.helsinki.fi/~rvaranka/hpv/hpv.html varis at no spam please iki fi |
#18
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"Liquid Drive" bike prototype at auction
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? |
#19
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"Liquid Drive" bike prototype at auction
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#20
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"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.) -- Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971 |
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