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).
Piston troubles, comparing aluminium with cast iron pistons and discussing knock issues.
| Identifier | ExFiles\Box 35\2\ scan 223 | |
| Date | 12th April 1920 | |
| R.R. 235 a (100 T) (S.F. 816 6-6-19) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2480 -3- HS{Lord Ernest Hives - Chair}1/LG12.4.20. Contd. one /considers the labour charges of to-day. As regards piston troubles on the present standard cars fitted with aluminium pistons, the percentage of pistons which are being scrapped on test never was so low as it is at the present time. It is only a matter of 1 or 2%. Seized pistons arepractically unknown. The big trouble we have on the present piston is the elusive knock or gudgeon pin knock. If we could satisfactorily overcome that when we shall be undoubtedly in a better position as regards pistons than we have ever been before. We have cars which have run 10,000 miles and which do not suffer from pist-on knocks either when hot or cold so that as regards pistons knocks we are as well-off of not better with the aluminium pistons as we were with the cast ironl We have found that if a split aluminium piston does knock it is caused by the pistons becoming .002" to .003" less in diameter owing to the split portion closing in. By peaning them with a hammer we find that we can open them out again and the piston is equal to a new on. We are recommending this procedure because we see no reason why a piston should be thrown away because it has gone in a matter of .002" to .003". X.3881. We have lately carried out tests with the latest type split cast iron pistons. We had trouble in producing them due to the fact that if we tried to machine them in the same way as we do the aluminium, i.e. not complete the splitting until after they are ground, that when they were finally split they Contd. | ||