pistonsreciprocating

Reciprocating pistons are mechanical components that move linearly, or back and forth, within a cylinder. In many machines, this linear motion is converted into rotary motion by a connecting rod turning a crankshaft, allowing the piston to perform useful work on the surrounding fluid or gas. Reciprocating pistons are fundamental to many engines, pumps, and actuators, and they are used in both combustion-based and non-combustion systems.

Key components include the piston itself, piston rings to seal the gap between piston and cylinder, a wrist pin (piston pin) to connect the piston to the connecting rod, the connecting rod, and the crankshaft. The cylinder walls, valves or ports, and lubrication system form the surrounding assembly. Pistons are typically made from cast or forged metals such as aluminum alloys for lightness, or cast iron for wear resistance.

Operation varies by application. In internal combustion engines, combustion pressure during the power stroke pushes the piston, which via the connecting rod rotates the crankshaft; intake, compression, power, and exhaust strokes repeat in cycles. In steam engines, high-pressure steam similarly drives the piston. In hydraulics and pneumatics, fluid pressure moves the piston to actuate a hydraulic or pneumatic cylinder. Some designs use single-acting pistons; others are double-acting to deliver force in both directions.

Limitations include friction, wear of piston rings, heat transfer, and side loads that cause piston slap. Efficiency depends on sealing, lubrication, and the stroke length relative to bore, as well as the geometry of the crank and connecting rod. Reciprocating pistons remain widely used due to their simplicity, high force at low speeds, and suitability for variable displacement and precise control in engines, compressors, and actuators.