Rolls-Royce Phantom III - dynamo drive & idler gear


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R-R PIII - dynamo drive

Having removed the outer notch nut and spring drive disk one can see the rebated notch nut and ball race sitting in front of the pinion.  This second notch nut is threaded onto the fixed tube that locates the ball race; the pinion  spins on a separate axle on phosphor-bronze bushes.  The dynamo drive shaft is now free to be withdrawn - see below.

I had to make a castellated box spanner to release the rebated nut.  Once removed the ball race support tube can be extracted and the pinion will slide off its axle which is bolted to the block.

A photograph of all of the components is shown further down the page.

R-R PIII - dynamo drive shaft

With the outer nut removed the dynamo drive shaft is free and can be pulled out towards the rear of the engine.  The large nut in the centre is the end of the  tube supporting the ball race, the other end of which is shown above.

The four small nuts hold the pinion axle in place.

R-R PIII - dynamo drive assembly

In all their grimy glory!

On the left is the dynamo drive shaft which is only located at its forward end by the taper and Woodruff key into the spring drive disk.  Any radial displacement of the dynamo is accommodated by the spring disk.

R-R PIII - Idler retaining nut The idler gear retaining nut - conveniently located in the front corner of the engine casting adjacent to number 1 main bearing.  This nut has a left hand thread and is split-pinned in place; it locks against the shoulder of the idler gear shaft.  End float is dependant on the wear in the bushes.
R-R PIII - Idler gear bar

A cunningly devised jamming bar to stop the gear rotating whilst the nut is released.   The gear is made of fibre so its teeth should be treated with appropriate deference.

The bar is cranked to fit into the rebate and was cut to fit snugly between the nuts in order to allow its use in both directions.

R-R PIII - Idler bush Idler gear removed to expose the axle support block and bushes.
R-R PIII - Idler assembly

Gear and spindle bracket.

Note the two parallel sections on the spindle and the oiling grooves on the bush faces.

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