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).
Standard allowances for fitting pistons to prevent piston knocks.
| Identifier | ExFiles\Box 35\2\ scan 106 | |
| Date | 27th August 1919 | |
| R R.{Sir Henry Royce} 285 m (80 T) (S.F. 674 23.6.19) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 1376 To EH from R.{Sir Henry Royce} c. to CJ. c. to Bn.{W.O. Bentley / Mr Barrington} c. to EP.{G. Eric Platford - Chief Quality Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to EFC. R6/G27.8.19. RE PISTONS. - X.2748 I would like it to be thoroughly understood that I have never recommended the fitting of pistons tighter than our usual standard allowances with the object of preventing piston knocks. These allowances are difficult to describe in a letter as they vary with different parts of the piston, and different types of pistons. Generally speaking, however, it is an average of .004 or .005" clear for cast iron or steel and double this amount for aluminium, for a 4 1/2" diameter piston. | ||