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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Epicyclic third gear schemes for the Phantom II gearbox.

Identifier  ExFiles\Box 15\5\  Scan176
Date  11th November 1930
  
X7310.
BY9/G.11.11.30.

PHANTOM 11 GEAR BOX - EPICYCLIC THIRD SCHEMES.

At the Conference I expressed the view that R's latest scheme only provided four gear ratios, but there was a general impression that this idea was wrong and that the scheme arranged for six ratios.

The facts of the case are as expressed by me at the Conference, the latest gear only provides four gear ratios as at present.

The misconception arose from the fact that six ratios could be provided with the arrangement of gears, but such six gears would not be easily utilized in sequence. R.{Sir Henry Royce} has selected the four ratios out of the six which are in sequence for the purpose of easy and simple control.

The fault with R's original proposal for a simple epicyclic third combined with one sliding change, apart from the reverse, was precisely the same as he would encounter in trying to utilize all the six changes possible in his present scheme, and is explained as follows :-

Epicyclic 3rd. Original Scheme.

a/- First speed is obtained by combining the epicyclic third and sliding change in series.

b/- Second speed is obtained by combining direct drive and the sliding change in series.

c/- Third speed is by epicyclic reduction as simple train direct to third motion shaft.

d/- Fourth or direct speed by locking the epicyclic and driving direct.

It will be observed that the direct drive and the epicyclic train are used alternately in the sequence of gears, but in the new train the selection of the six possible gears is such
  
  


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