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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).
Letter to Ford Motor Co. discussing test results for different scraper rings on the Silver Ghost engine.

Identifier  ExFiles\Box 27\2\  Scan146
Date  22th December 1933
  
x177/5.

Experimental Dept.

Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} 2/KW.

22nd December, 1933.

Mr. Smith,
The Ford Motor Co.,
Dagenham,
ESSEX.

Dear Mr. Smith,

In view of your troubles I thought you might be interested to see the results of some tests we did on the Silver Ghost in 1925.

Graph 'A' shows the effect of scraper rings.

Curve 1 is a typical oil consumption curve, increasing very nearly as the square of the speed. It will be noted that it is obtained with plain rings.

Curve 2 was taken with 'L' shaped rings, which we spoke about. These are most effective scraper rings, depending for their action upon the fact that the unit pressure at the bottom of the ring is higher than at the top. The difficulty is that their efficiency falls with wear. This can be easily demonstrated because the rings are lapped. They are no good.

Curve 3 demonstrates that high unit pressure achieves the same sort of result, because all we have done here is to narrow the ring and put a relief under both.

The perfect circle type scraper ring is merely the unit pressure theory carried further.

Graph 'B' indicates that the oil consumption when plain rings are fitted to the pistons can very definitely be affected by the oil flow through the bearings.
  
  


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