The starter motor parts and how ...

...a starter motor works. Full instructions on the internal starter motor wiring and the brilliant engineering involved to make the mechanism work .

We never think of the starter moter until we have a problem!

The brilliant engineering that’s involved in starter motor parts are never really appreciated — but if you want to make a repair you will be amazed at both the simplicity and genius in a design that has remained pretty much unchanged since the device was first perfected.

You have seen the old black and white pictures of people swinging a starter handle that was inserted into the centre of the crank case in the pioneering days of motoring — well the starter motor does the same thing but uses the mechanical advantage of a large cogged gear driven by a small gear - the small cogged gear being driven by the starter motor.

The engine crank shaft has a large cogged gear coming out of the crankcase — as you know this needs to be turned over to get the motor running BUT the small gear on the starter assembly does not need to be permanently attached to the engine when it is turning at high revs because the bearings would wear out pretty fast.

You therefore need to engage the starter gears before the starter motor rotates — if the small gear engaged while it was turning you would be the proud owner of a bunch of iron filings pretty quickly!

Right. The electric starter motor is at rest.

An electro magnet is activated which pulls a lever engaging the starter motor gear to the large crankcase gear .

When the electro magnet piston is at its limit of travel an electrical contact is made activating the electric starter motor.

OK — the engine is now running and will rev as high as you want it by stepping on the gas. But we do not want the cars engine now driving the starter motor, do we?

Or we will manufacture more of those iron filings!

Well the small drive shaft is both sprung loaded to return to its rest position — waiting for the next time you need it to start your car — but more importantly it is called a bendix!

This bendix act like a clutch that only drives the large cog on the engines crankshaft — if the engine starts driving the bendix it simply free wheels — this is important as the starter motor is designed for low revs and high torque

This is another brilliant explanation from Davidsfarm on You Tube... take a look, he's very entertaining.

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