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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).
Failure of AC7 Bentley Bearings and proposing changes to the casting process to prevent future issues.

Identifier  ExFiles\Box 115\1\  scan0063
Date  16th September 1936
  
To Wor.{Arthur Wormald - General Works Manager}
Hs.{Lord Ernest Hives - Chair}
F.{Mr Friese}
BT.{Capt. J. S. Burt - Engineer}
Sft.{Mr Swift}

Rm{William Robotham - Chief Engineer} X1070

HL1/AG.16.9.36.

Laboratory.

Re: AC7 Bentley Bearings.

I understand that two big end bearings have failed in France. It appears from examination of the pots from which the bearings are made in the works, that the strength of the alloy close to the top or feed end is not so great as that about halfway down, also the grain size is different as indicated by micro or macro test.

In consideration of this we anticipate that parts of the two failed bearings will be found to correspond in structure with that found close to the top of the casting in which region there is also a greater liability to porosity at minute internal cracks.

In consideration of the above it is suggested that about 20% of each pot casting should be discarded in order to eliminate the trouble (at present discard is not always as great as this). The 20% rejects can be remelted for production.

Also if desired an etching test could be done on bearings in the rough machined condition - as part of inspection.

Hl.
  
  


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