Fluid Automatic Bicycle Transmissions
 This concept has been rejected for decades by engineers due to the "heat loss argument", which points out that at high step down values there is a lot of energy loss to heating the fluid in shear in this type of transmission. However, whenever you take a typical bicycle ride, rarely will the transmission be used this way, so, the overall efficiency is quite high, above 98% for most riding conditions. Then there's cost, you can built a cheap fluid automatic transmission. <<click for a powerpoint presentation>>

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