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  1. #1
    Bicyclochondriac.
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    Hydraulic drivetrain?

    Anyone know if the idea of a hydraulic drivetrain (as opposed to chain-driven) has been explored much for bikes?

  2. #2
    bi-winning
    Reputation: rkj__'s Avatar
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    I don't think it has been done, AFAIK.

    Could you give me an example of a vehicle that has a hydraulic drivetrain?
    When under pressure, your level of performance will sink to your level of preparation.


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  3. #3
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    Quote Originally Posted by rkj__
    I don't think it has been done, AFAIK.

    Could you give me an example of a vehicle that has a hydraulic drivetrain?
    I think some tractors use it. I've driven a Bobcat, and it used hydraulics for the drivetrain, and my uncle had a tractor that did. I don't know how it works (think I'll look it up).

  4. #4
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    Just answered my own question...

    Quote Originally Posted by kapusta
    Anyone know if the idea of a hydraulic drivetrain (as opposed to chain-driven) has been explored much for bikes?
    Just answered my own question, a least partially....


    http://www.powerengine.com/aitx000liquidbik.htm

  5. #5
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    Quote Originally Posted by kapusta
    Anyone know if the idea of a hydraulic drivetrain (as opposed to chain-driven) has been explored much for bikes?
    A friend made one for a college project. Didn't really work, but it looked cool.

  6. #6
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    Quote Originally Posted by kapusta
    Just answered my own question, a least partially....


    http://www.powerengine.com/aitx000liquidbik.htm
    Hydraulic Transmissions will have a maz efficiency around 80% or lower.

    Well maintained bike will be 95% efficiecy.

    Ouch!

  7. #7
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    I was thinking hydraulic shifter/der combo...but it looks like Shimano and Campy have put there money in the electronic boat.
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  8. #8
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    Quote Originally Posted by havnmonkey
    I was thinking hydraulic shifter/der combo...but it looks like Shimano and Campy have put there money in the electronic boat.

    Safe Products made a hydraulic conversion for Shimano in the mid-90's.

  9. #9
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    Quote Originally Posted by rkj__
    I don't think it has been done, AFAIK.

    Could you give me an example of a vehicle that has a hydraulic drivetrain?
    Loaders, many dozers, bobcats, many modern tractors.

    However they have them for a purpose, in that they can be controlled to provide varying pressure on the wheels under varying loads at varying speeds, with a "torque converter", rather having to slip a clutch or continually change gears to get enough revs to be in the engine's power band.

    For instance if you drive a loader on the flat with the engine at constant speed and constant throttle, then start up a hill, the engine maintains speed, but the loader slows down more with steepness. It has not actually changed gears. Same goes if you start pushing a load.

    They are also set up very nicely to "shuttle" from forward to reverse without a clutch. Not really much use on a bike....unless you are a trials freak!

    They are not efficient. They are heavy. Some sort of automatic gearing on a bike would be nice, but these are not the way to go.

    The other hydraulic alternative (and this is what, IMO, is used on the bike that a link in this thread leads to) is a direct drive system: "positive displacement" I think they are called. That is where a pump drives a motor, and both completely block the passage of fluid unless they are moving, as would a piston system. These are more efficient, but still lose a lot to friction, compared to a chain or even gear drive. They have to, in order to be sealed so tightly. You simply cannot turn a good hydraulic motor by hand. They also need very high pressures (heavy components) or high fluid flow (loss due to friction in pipes etc)

    I remember seeing an attempt at auto-gearing on a bike, which actually changed the length of the spokes on the rear wheel....no.... ....it changed the length of the "spokes" on the chainring as the pressure on the pedal changed. I heard no more about it

    Nick

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