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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).
Engine performance issues, specifically piston ring blow-by, oil loss, and crankshaft vibration at high speed.

Identifier  ExFiles\Box 5a\3\  03-page136
Date  28th November 1931
  
85840

Hotel de France,
Chateauroux,
FRANCE.

To Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}
From G.W.H.
28/11/31.

18.G.IV.

We have received your memo Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}2/AD.26.11.31.

re. piston rings.

There was, when the engine was first built up, piston ring blows on 18.G.IV. There is no definite blow past the rings, at the moment, when the engine is idling. We are, however, using a lot of oil, and the consumption is no doubt due to the oil being blown past the rings at high speed, hence the very pronounced detonations we are now having. The 20 & 25 H.P. car has always suffered from crankcase pressure as I have continually reported, after approx 5000 miles, oil being forced out of the front end, and to release it we have run with the cap off the crankcase filler. We therefore quite agree with you that our design of piston ring requires alteration.

We are losing quite a lot of oil from No.7 bearing into the clutch case, also having removed the gauze from the breather on the carburetter which we found choked up, we are now having quite a lot of oil forced into the carburetter.

Re. Crankshaft Period.

You will see in today's report that we have reached the speed of the crankshaft period. There was a high wind blowing behind the car and a speed of 87 M.P.H. was reached. We reckon that the speedometer is approx 4 M.P.H. fast. The speed was immediately dropped and the actual period of time was only a few moments on the period. Roberts, who was driving, says there was no doubt about it. It did not require any listening to or feeling, for the whole engine was vibrating. It is quite possible for an owner having the same conditions to repeat it, therefore, do you think it would be the best policy to fit the smaller balance weights?

G.W.H.
G.W.Hancock.
  
  


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