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Hydrostatic Hybrid Bicycle

pedals on a pump, hydraulic motors in-hub
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Several designs have been proposed on the 'bakery to power a hybrid bicycle with stored energy from batteries, springs, flywheels, or compressed air. I believe the ideal way to make a hybrid bicycle would be to use hydraulic pumps, reservoirs, hoses, valves, and motors to store and manage the power of pedaling.

A small fluid pump would fit between the pedals and provide power to a reservoir integrated into the frame. A system of valves and lines could carry the power to in-hub hydraulic motors for one or two wheel drive. During normal operation, the valves would effectively allow for different gearing for hills and level ground. Going downhill, one could use regenerative braking to store potential energy as hydraulic pressure for later use.

Adding a small moped motor with another hydraulic pump would allow for higher speeds and better hill-climbing ability. With pedalling and the motor combined, it would be possible to store up enough energy for brief runs at highway speeds, or quick bursts of power, depending on how big of a tank was used.

Hydrostatic drive systems have been widely baked on many kinds of construction equipment, so I think it would be relatively easy to scale down to a bicycle. Like construction equipment, you could even run power take-off hoses from your bike to power hydraulic tools and jacks. The system might loose some energy to heat, but this would be made up by the regenerative braking system.

discontinuuity, Feb 18 2007

Nahum Goldenberg www.hydrocad.blogsp..., www.hydrocad.com
[Hydrocad, Nov 22 2009]

Wikipedia's Hydraulic Bicycle entry http://en.wikipedia...i/Hydraulic_bicycle
[goldbb, Nov 22 2009]

[link]






       I think I remember a compressed-air bike as an April-Fool's article in a bike magazine. [+]
baconbrain, Feb 19 2007
  

       Wouldn't this weigh a ton?
jhomrighaus, Feb 19 2007
  

       It would probably weigh more than a regular bike, but probably about the same as electric bicycles currently sold. The extra weight would be offset by the hill-climbing ability.
discontinuuity, Feb 19 2007
  

       Would this ability also offset the loss in efficiency? My contention is no, but I'm not going to back that up with numbers so feel free not to listen.   

       The regenerative braking thing holds some merit, however there is generally not a great deal of braking energy wasted on bicycles in normal situations. I commute on a bike daily and I can't recall the last time I actually braked heavily. Even if I did, the relative lightness of bike and rider (compared to say, car and driver) would mean that there is not a great deal of braking energy there for the harvesting.   

       All in all, I don't think that the system proposed here would be truly worth it. I estimate that the disadvantages of increased weight and decreased efficiency would not be offset by the potential advantages proposed.
Texticle, Feb 19 2007
  

       I think the other issue is that there is relatively little energy stored in a pressurized fluid, Hydraulics are efficient but only with a constant pressure supply.
jhomrighaus, Feb 20 2007
  

       [Texticle], I ride my bike up and down a large hill several times a week, so this idea would help out people like me, or those who might normally buy an electric bicycle. As for efficiency, I don't have any numbers, but I imagine that it wouldn't be much less than a conventional chain drive. It would definately be a lot smoother, since you would be able to pedal at a more or less constant speed, with the valves acting as different gear ratios.   

       If anyone knows more about hydraulics than me, please feel free to set me straight. The main idea is simply to find another way to store potential energy in a hybrid transmission. It might be better to just use batteries like most hybrid cars today.
discontinuuity, Feb 20 2007
  
      
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