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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).
Recording the experiences and results of testing steel versus bronze bushes in synchromesh gearboxes.

Identifier  ExFiles\Box 136\4\  scan0203
Date  19th January 1938
  
1183

Sg.{Arthur F. Sidgreaves - MD} from Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}
c. Hs.{Lord Ernest Hives - Chair}
c. By.{R.W. Bailey - Chief Engineer}
c. Hdy.{William Hardy}
c. RHC.{R. H. Coverley - Production Engineer}
c. Da.{Bernard Day - Chassis Design} Mx.{John H Maddocks - Chief Proving Officer}

Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}2/AP.19.1.38.

GEARBOX BUSHES.

The object of this memo is to record the experiences we have had with steel bushes and thrust faces in the free pinions of synchromesh gearboxes.

During the original dynamometer testing in April, 1937 of the mock-up Ph.III. overdrive, the brass overdrive bushes had worn to such an extent after 63 hours that the gear would no longer stay in mesh. Steel bushes were therefore tried at the usual bronze clearances and were satisfactory on dynamometer. On the road the first pukkha box seized after a very few miles. The clearances were increased to 1 1/2 - 2 1/2 thou. inside and outside and .003 end float.

At these clearances the following results on Ph.III. have been obtained:-

32-EX. - Box.15.HS.{Lord Ernest Hives - Chair} 18255 miles - no trouble.
35-EX. - Box.16.HS.{Lord Ernest Hives - Chair} 7477 miles - " "
37-EX. - Box.17.HS.{Lord Ernest Hives - Chair} 1000 miles - bushes seized.
39-EX. - Box.7.HS.{Lord Ernest Hives - Chair} (mock-up) 4229 miles - no trouble at bronze clearances.

On the first Bentley overdrive, steel bushes at P.3. clearances seized after 2150 miles, wrecking the gears and casting.

On Wraith we have done a total mileage of 47800 miles with steel thrust faces, including three cars of over 10,000 miles and have now had a seizure after a few hundred miles on a new box on 26.G.Vl.{V. Lewis / Mr Valentine}

On all cars we are reverting to bronze bushes and thrust faces. We justify this by the following results -

36-EX. - Box.12.HS.{Lord Ernest Hives - Chair} (mock-up overdrive) 18,000 miles. No measure-able wear of bushes.

5.B.lV. 15,000 miles and 100 hours on 3rd.gear. No measurable wear of bushes.

In spite of 81000 miles spread over 9 cars we are forced to the conclusion that steel is not a reliable material
continued
  
  


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