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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).
Excessive wear on Bentley 60 oil pump and distributor drive gears, with proposed modifications.

Identifier  ExFiles\Box 123\5\  scan0141
Date  31th October 1938
  
Typed Content:
TO RM{William Robotham - Chief Engineer},
BY/NS{Norman Scott}
c. Rm.{William Robotham - Chief Engineer}
c. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}
BENTLEY 60 OIL PUMP AND DISTRIBUTOR DRIVE GEARS.

With regard to the excessive wear of the gears of the oil pump and distributor drive on the cast iron engine, the high wearing point would be relieved by reducing the outside diameter of the gear on the camshaft and increasing the outside diameter of the driven gear by corresponding amounts, retaining the standard depth and form of teeth.

The present gears, although having no interference are just on the verge, and any slight variations or deflections would probably cause an interference.

The maximum diameter to which the gear on the oil pump driving shaft can be increased is governed by the bore through which it has to pass in assembly viz. 1.1875", so that it is only possible to increase the gear blank by .032" making it 1.181 diameter, and the wheel on the camshaft will be reduced to 1.707 diameter blank, the pitch diameter of the gears remain unaltered although their chordal thickness will be altered to agree with the revised addendums.

Will BY/NS.{Norman Scott} please issue the necessary details for the above gears to be tried as soon as possible. In the meantime, a step in this direction should be made by merely reducing the outside diameter of the existing gear on the camshaft by .020" making the diameter 1.720, nothing else being altered.

Will Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} please have this alteration made at the earliest opportunity on the experimental engine now running with the steel camshaft and the bronze driven gear.

Handwritten Content:
[Top left corner, crossed out] JNR.{Charles L. Jenner}
[Top left corner] ANY OTHER SUGGESTIONS? Run
[Bottom of page] To RM.{William Robotham - Chief Engineer} I agree to the above. but we ought to try a steel wormwheel mating with a steel camshaft. like our competition / DA.{Bernard Day - Chassis Design} when we get the oil pumps back from W. Bell we shall see if there is excessive loading. JNR{Charles L. Jenner}
  
  


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