Piston

engines · machines · movement · mechanics

What it does. A piston is a moving part that lives inside a cylinder and slides back and forth. Its job is to catch the force from hot, expanding gases and pass that energy along to make wheels spin, pumps work, or compressors squeeze.

In car engines. When fuel burns in an engine, it creates a tiny explosion that pushes the piston down really fast. That downward push gets transferred through connecting rods to the crankshaft, which is what actually spins your car's wheels.

Piston rings seal it. Pistons have special rings around them that keep gases from escaping past the sides. These rings are like tiny rubber bands that help the piston stay gas-tight so all that explosive force actually does work instead of leaking away.

In pumps, backwards. In water pumps and hydraulic systems, the piston works in reverse. Instead of gas pushing the piston, a motor or hand crank pushes the piston to compress or squirt out liquids like water, oil, or hydraulic fluid.

Multiple jobs. Some pistons are extra clever and also act as valves, opening and closing little doorways in the cylinder to let new fuel in or let burned gases out at just the right times.