A starter ring gear is a part attached to an

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal comb ...

that is part of the assembly which transfers the torque from the starter motor to the engine's

crankshaft A crankshaft is a mechanical component used in a reciprocating engine, piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating Shaft (mechanical engineering), shaft containing one or more crankpins, ...

, in order to start the engine. The starter ring gear is usually made from medium carbon steel. Starter ring gears are attached to either the flywheel or the flexplate of an engine. The teeth of the ring gear are driven by the smaller gear (known as the pinion) of the starter motor. The pinion engages the starter ring only during starting and once the engine is running the pinion withdraws.

Manufacture

The starter ring gear is most commonly made by forming a length of square or rectangular steel bar into a circle and welding the ends together. This ring is then machined to create flat surfaces of the required inner and outer diameters. The gear teeth are then created using a hobbing tool, followed by processes to chamfer, deburr and clean the gear teeth.

Attachment

In cars with a

manual transmission A manual transmission (MT), also known as manual gearbox, standard transmission (in Canadian English, Canada, British English, the United Kingdom and American English, the United States), or stick shift (in the United States), is a multi-speed ...

, the starter ring gear is fitted to the outer diameter of the

flywheel A flywheel is a mechanical device that uses the conservation of angular momentum to store rotational energy, a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, a ...

. The ring gear is usually fixed to the flywheel through use of an interference fit, which is achieved by heating the ring gear and so that thermal expansion allows it to be placed around the flywheel. In cars with an

automatic transmission An automatic transmission (AT) or automatic gearbox is a multi-speed transmission (mechanics), transmission used in motor vehicles that does not require any input from the driver to change forward gears under normal driving conditions. The 1904 ...

, the starter ring gear is usually welded to the outside of the flexplate.

References

{{Internal combustion engine , state=expanded Automotive transmission technologies Engine components Gears

Manufacture

Attachment

See also

References