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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 discussing the performance and production of A.C.6 and A.C.9 bearing alloys with hard and soft shafts.

Identifier  ExFiles\Box 115\5\  scan0026
Date  6th May 1938
  
1020a ?

Rml/R.{Sir Henry Royce}

6th May, 1938.

J.{Mr Johnson W.M.} Howlett, Esq.,
Managing Director,
Wellworthy Piston Rings Ltd.,
Lymington, HANTS:

Dear Mr. Howlett,

From what you say it would evidently be an exceedingly good thing to have a general talk round the bearing situation in the immediate future.

Briefly, the situation we have arrived at here is as follows:-

With hard shafts A.C.6 bearing alloy will run satisfactorily as both a big-end and a main bearing. We have been using it in production for about two years. We have, however, had constant trouble with excessive scrap in the production of bearings in this alloy. Recently a modification was made to the alloy to facilitate production, and we completed a test on it yesterday. The strip was entirely satisfactory. We now, therefore, have an alloy which is simple to produce and satisfactory on hard shafts.

Our experience on soft shafts has been limited to one engine which we ran on the road and which did about 20,000 miles with A.C.6. big-end bearings. During the road running it was not subject to anything except average English conditions which we know are not nearly so severe as commercial or Continental conditions.

During the next 10 days, we shall run a severe endurance test on A.C.9 alloy on a soft shaft, which should settle this issue, but we do not propose to run it as a main bearing on a soft shaft. The reason for this is that we have succeeded in re-designing our engines so that Babbit can be used for main bearings and give the life we require.
  
  


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