Half a croissant, on a plate, with a sign in front of it saying '50c'
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tandem recumbent hydraulic

Hydraulic transmission, different gear per rider
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Each rider's pedals are directly connected to a variable displacement hydraulic pump. The displacement of each pump is adjusted by the individual pedalling to power it, to produce the most comfortable amount of torque at his pedals.

The driven axle is driven by a variable displacement hydraulic motor. The displacement is controlled by a computer, which works to keep the hydraulic pressure optimal.

goldbb, May 22 2009

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       It's both for adjustable resistance, and to avoid having a long and potentially dangerous chain going the length of the bicycle.   

       Also, as a result of dirt and weather, a chain and sproket's mechanical efficiency can be as low as 80%, while a hydraulic system will have about 95% efficiency in all conditions.   

       As for weight... if the bicycle could be designed so that the hydraulic pipes double as structural elements, it wouldn't necessarily be heavier than a chain driven bicycle.
goldbb, May 27 2009
  

       I love it. Weight be damned, hydraulics are among the most complex and least practical ways that a Halfbakery idea can be achieved, and I'm all for them for that reason.   

       Still working on a hydraulic cellphone.
normzone, May 27 2009
  

       Not bad, but a tandem recumbent would be very long.
If you don't like chains and want independent tandem drive, use drive shafts and a differential at the back ('inside-out' relative to a car - input through the two sides and output from the 'body'). Each rider can pedal as they please, and both supply power.
neutrinos_shadow, May 27 2009
  

       I think the most appealing thing about a hydraulic bicycle (for me, anyway) is the possibility of front wheel drive.
lurch, May 27 2009
  

       neutrinos_shadow, how do you propose that the power from the front pair of pedals (which are above and in front of the front wheel) go around / under / over the front passenger? lurch, Why front wheel drive? Surely all wheel drive would be more useful?
goldbb, May 28 2009
  

       Nope, I disagree with all-wheel drive. More complicated, heavier, less efficient, and for what? So you won't get stuck? Unlike a car, you can get off and pick it up. I like front wheel drive because there would be no tendency to "wheelie" going up a hill; because it can pull your front end around a corner with more authority, rather than pushing out and sliding; and because you can turn up to and past the perpendicular position of the front wheel while still riding.
lurch, May 29 2009
  
      
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