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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).
Results of testing ground versus unground gears in Bentley gearboxes.

Identifier  ExFiles\Box 112\2\  scan0046
Date  13th January 1938
  
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Da{Bernard Day - Chassis Design}/Hdy.{William Hardy}15/G.13.1.38.

As regards the question whether we need grinding at all on this gear, the car we took for the journey (56-BN{W.O. Bentley / Mr Barrington}) had unground 1st. speed gears, and on our return we tried two Bentleys (3-B-4 and 23-AE) with the standard ground gears. The result of this test was the confirmation of the remarks given in Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}2/AP.14.12.37. that there is not much to choose between the unground and the ground gears.

The B.50 box is likely to be more noisy on 1st. and R.{Sir Henry Royce} than the present Wraith, as the latter has ground helical gears, and as mentioned in Gry{Shadwell Grylls}'s memo is more silent than the Bentley.

We recommend that we proceed with both ground and unground gears in parallel, so that a comparison can be made over a number of cars, and in the event of difficulties with unground gears we can instantly change them to ground gears.

We left the Gear Grinding Co. under the impression that they would soon be required to grind a few gears for this gearbox for experimental purposes, and they asked that they might be sent a layshaft or two as soon as possible, in order to determine whether any difficulties had been overlooked.

DA{Bernard Day - Chassis Design}/Hdy.{William Hardy}
  
  


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