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).
Abandoning cast iron pistons due to seizure risk, comparing them with aluminium pistons on weight, expansion and engine silence.
| Identifier | ExFiles\Box 35\2\ scan 172 | |
| Date | 12th December 1919 | |
| Contd. -3- Hs{Lord Ernest Hives - Chair}3/LG12.12.19. The most definite argument for abandoning the cast iron pistons to was because the risk of seizure was so very great, owing to the fact that in order to avoid piston knocks, they were run with a very fine clearance. We suggest that the risk of seizure can be eliminated with the cast iron piston if we used a split cast iron piston. The split cast iron piston should work very much better than a split aluminium piston (1) because of the less expansion (2) because the cast iron is a more suitable materialto stand deflection when it is heated. If we accept, that the split cast iron piston will overcome the seizing difficulty, the other main objections to the cast iron is the fact of its weight and the fact that we shall not get such a cool working piston - asregards weight we should not add so very much - The present aluminium piston weighs.-------- 3 lbs 3 ozs complete The ram type aluminium piston weighs.------ 3 lbs 6 ozs " The cast iron pistons we used on pre-war cars weighs. ----------- 3 lbs10 ozs. The biggest advantage we should lose would be tge cool piston which we get with the aluminium. Thism of course, would be very serious if the engine was running full power continuously but as on a car engine, such a small percentage of its life is run full power, it is not quite so serious. In any case, we are told by Sales Dept. that the silence of the car is the first consideration, and no matter what advantage we gain in any other direction, it will not be entertained if it is obtained by sacrificing silence. We are not suggesting for one moment that we should abandon work on the aluminium pistons. We feel confident that we shall Contd. | ||