The Moving Parts of an Engine

by Thomas James
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Hemera Technologies/ Images

The internal combustion engine is of huge importance to industrial civilization. It is what powers virtually every vehicle on the roads all over the world. As the name suggests, this type of engine works by burning fuel inside the engine and converting the energy produced into motion. The fuel is usually either gasoline or diesel. There are several different types of internal combustion engine, but they all work on the same basic principles and share similar basic components.


The piston is a cylindrical device that sits flush within the cylindrical combustion chamber. When fuel is injected into the combustion chamber in an internal combustion engine, the piston rises up and squeezes the fuel-and-air mixture. The spark plug ignites the fuel; the ensuing explosion forces the piston down, turning the crankshaft and forcing another piston up to compress the fuel-air mix in another combustion chamber. It is in this way that the heat energy released when the fuel is burned is converted into work.

Connecting Rod

The connecting rod is attached to bottom of the piston. The connecting rod is attached to the piston by a mechanism that allows is to rotate in a flat plane. The other end of the connecting rod is attached to the crankshaft. When the piston goes down, the connecting rod moves in a motion that forces the crankshaft to turn.


The crankshaft consists of a rotating shaft with several "crank pins" coming off it at different angles. The axis of a crank pin is offset from the axis of the rotating shaft. The crankshaft turns the up-and-down motion of the pistons into rotating motion that ultimately turns the car wheels.


The valves control the entry of fuel and air into the combustion chamber. They also control the exit of exhaust gases from the combustion chamber. Exit and entry must be carefully timed to ensure that the entry of the fuel, the burning of the fuel, the movement of the piston and the exit of the exhaust all happen in the right order.

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