Hydraulic bicycle

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A hydraulic bicycle is a chainless bicycle that transfers power to the pedals by means of a liquid passing through tubes from hydraulic pump to hydraulic motor and back.

Advantages include:

Shifting, through valves and displacement, provides either continuously variable gearing or more steps.

Shifts smoothly under full power.

Drive transmits power while pedaling forward and backward. Thus racers can power bicycle through turns by alternating short forward and backward pedal strokes. No slack or backlash occurs, in either direction. Ability to coast is maintained.

Mechanism is clean and operates silently.

Far fewer moving parts (about 10 vs over 70), all of which are continuously bathed in clean lubricating fluid, require far less maintenance.

Sealed systems maintain constant efficiency upwards of 95% in all conditions (see Hydristor). In contrast, a chain-and-sprocket system loses efficiency in bad weather and dirt – from 97% in lab conditions down to less than 80%.

Sealed systems require much less maintenance than open chain system.

Front or two-wheel drive systems now possible.

ABS braking: drive doubles as hydraulic brake, eliminating the weight, cost, and maintenance of regular brakes.

Production models of some designs would be comparable in weight and cost to chain-and-sprocket designs.

The hydraulic (hydrostatic) transmission could be very useful for recumbent bicycles because the hoses are much easier to fit on than the long chain.

Energy recuperation, storage and power assist could be added easily.

Disadvantages include:

Implementations to date are heavier than those of bicycle chain and sprocket designs. These comparisons, however, are based on laboratory prototypes, which also provide a special means of measuring performance (a feature unnecessary in production).