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).
Expansion of aluminium pistons and the potential for engine damage from a tight piston.
| Identifier | ExFiles\Box 180\M3\M3.6\ img029 | |
| Date | 8th July 1919 | |
| To EH. from R.{Sir Henry Royce} Copy to CJ. " " DA.{Bernard Day - Chassis Design} ORIGINAL D R16/G30/6/19. [STAMP: 8 JUL 1919] X.2448 RE PISTONS. Thank you for your memo (EH2/LG27/6/19) with reference to the expansion of pistons. It seems quite as well to know what the expansion is, and from the table given it would appear that the piston, even at the top surface, does not exceed an average temperature of more than about 150°C. I am so much in favour of the aluminium pistons because they do not hopelessly stop the engine, should they get over-heated and bind, which it appears all pistons are liable to do, unless the clearance is greater than the piston knocks will allow. It occurred to me sometime ago that with an engine of 12 or more cylinders, a tight piston might cause a breakage of a rod or piston itself, due to the whole horse power of the rest of the engine falling on to this particular tight rod. Mr. Day might ask one of his assistants like Mr. Evernden, to make the necessary calculations to tell us at what number of cylinders a tight piston would result in a disaster to the rod or piston, with various assumed factors of safety. R.{Sir Henry Royce} | ||