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).
The causes of troubles with aluminium pistons versus cast iron pistons, focusing on gas leakage.
| Identifier | ExFiles\Box 16\1\ Scan154 | |
| Date | 7th November 1923 guessed | |
| -2- The reason why I think the troubles we have had with these various parts enumerated is due to the aluminium piston, is that it is admitted there is greater leakage of gas past this type of piston, although more rings are used than there used to be with the cast iron piston. It is also agreed by EP.{G. Eric Platford - Chief Quality Engineer}, his assistant, Mr. Maddocks and Hm.{Capt. W. Hallam - Head Repairs}, that the crankcase is hotter as a result of this increased leakage; eft it is agreed that the increased leakage is due to the increased side clearance demanded on the aluminium piston, it being generally thought that the cast iron piston fitted the cylinder more closely all over and that when a slight amount of oil was present the skirt of the piston acted as a deterrent to gas leakage, so that it will be seen that it is not argued that the six narrow rings are not as effective as the lesser number of wide rings, but rather that the better fitting skirt of the cast iron piston was a better seal. We have not, at the moment, an aluminium piston which is suitable for the pre-war engine, as the pre-war connecting rod was shorter than the post-war. This, however, could soon be remedied. EY. | ||