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 design and ring configuration for aluminium pistons in car engines.
| Identifier | ExFiles\Box 77\3\ scan0156 | |
| Date | 29th March 1920 | |
| R.R. 235 A (100 T) (S.F. 346. 6-8-19) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2460. X.3757. To Oy. From R.{Sir Henry Royce} Copy to CJ. " " JCR. " " NA.{Mr Nadin} " " Bn.{W.O. Bentley / Mr Barrington} " " Hs.{Lord Ernest Hives - Chair} " " EP.{G. Eric Platford - Chief Quality Engineer} " " HM.{Capt. W. Hallam - Head Repairs} R5/G29.3.20. X.2748. RE PISTONS FOR CAR ENGINES. X.3757. We have recently concluded that aluminium pistons must have a ring at the very top, otherwise carbon deposits there, and heavy running causes piston to expand and get very tight, causing dangerous condition with knocking noise. We have just adopted six narrow rings, top one unpinned, second, fourth and sixth on power side, thrid and fifth on compressing side. The best pistons we have found so far are split, (Mr. Hives' scheme) they are thicker at the sides (cast oval inside). Be sure your patterns are correct, and all is right before going ahead, because pistons are not a long job, and can wait until we are as sure as possible of our ground as to the best thing to do. R.{Sir Henry Royce} In the hard form, said to be due to the use of castor oil, but this will be proved. | ||