handcrank

A handcrank is a device or mechanism that converts manual rotary motion into mechanical work or electrical energy through a crank handle attached to a shaft. The operator turns the handle by hand, causing the connected mechanism to rotate or to wind a spring or generate electricity in a small generator.

Historically, handcrank starting devices were used to start internal combustion engines in many early automobiles, aircraft, and farm machinery before electric starters became common. In modern times, handcranks appear in emergency radios, flashlights, and other portable devices that rely on human power when batteries or power sources are unavailable.

Mechanically, a handcrank typically consists of a handle affixed to a crank pin on a shaft connected to gears, a flywheel, or a generator. In wind-up devices, the crank winds a mainspring that stores energy; in generators, turning the crank drives a dynamo or alternator to produce electrical current. Some systems use a reduction gear to increase torque, allowing the operator to turn a high-load shaft with less effort.

Applications include starting engines, hand-crank generators, wind-up clocks and music boxes, and camping or emergency equipment. The handcrank design varies from simple direct-drive handles to compact, foldable units for portability.

Safety and maintenance considerations include the potential for injuries from kickback or pinching, especially in engines or high-torce applications. Cranks can slip or cause blisters if used improperly. Users should apply steady, smooth motion, avoid overexertion, and perform regular lubrication and inspection of moving parts.