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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).
Comparing engine gear quietness and slack between the 20 HP and 40/50 models, detailing tests on the 20 HP spring drive.

Identifier  ExFiles\Box 42\2\  Scan092
Date  15th December 1922
  
[Handwritten in top right corner]
(Sos. P)
E'o rattly gear design &
Hs{Lord Ernest Hives - Chair}'n tentative summary
& proposals

[Typed]
To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair}
c. to CJ.
c. to E.{Mr Elliott - Chief Engineer}
c. to Ba.
c. to BY.{R.W. Bailey - Chief Engineer}

ORIGINAL.

[Handwritten above title]
20hp
[Typed]
ENGINE GEARS.

The accumulated experience obtained from the 60 or 70 20 HP. cars made so far, shows that the engine gears are more difficult to get quiet and remain quiet than on the 40/50. We have been carrying out a number of tests in connection with this and the conclusions we have come to are as follows :-

The design of the spring drive on the 40/50 has very definite advantages compared with the 20 HP. On the 40/50 there can be no slack between the crankshaft and the spring drive. There also can be no slack between the spring drive and the damper. In the case of the 20 HP. there can be slack between the spring drive and the crankshaft - there can be slack between the damper and the spring drive - there can be slack between the damper and the crankshaft - there can also be end play in the crankshaft pinion.

We find that if there is the least slack between the spring drive and the friction damper, it sets up very bad rattles. We have carried out the following tests.

On a 20 HP. engine we removed the springs from the spring drive which left it so that the friction only took the drive of the camshaft. We set this accurately and then ran the engine to see whether it had moved. We found that it required a total spring pressure of 52 lbs. in order to ensure that the friction drive did not slip with the engine running at slow speeds. We also found it took /22 lbs. in order to prevent it

contd:-
  
  


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