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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).
Torsional period testing on a 25HP engine with 12 balance weights.

Identifier  ExFiles\Box 137\4\  scan0332
Date  27th April 1931 guessed
  
Copy for files.
8634.
X.634.
X.5010.

TORSIONAL PERIODS ON 25HP. WITH 12 BALANCE WTS.
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We have run the cast iron unit C.9 in 18.G.IV. with no damping in the slipper wheel and have found marked torsional periods on full throttle at 28, 42, and 56 MPH. the one at 42 being present on the overrun also. The master period is therefore at 84 MPH. or 4200 RPM. with 12 balance weights, to balance the crankshaft only. The gear rattles at 39-38 MPH. is not therefore due to a crankshaft torsional period. since booms are not worse on the overrun than on the drive and are not affected by alterations to the slipper wheel we consider them in no way due to a crankshaft oscillation.

It is noticeable that the master period becomes very noticeable at 52 MPH. on 3rd. speed or 3800 RPM. This is 400 RPM. lower than we should expect.

Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}
  
  


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