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).
Engine knocking issues and theorising that cold weather expansion of a single aluminium piston could cause major failures.
| Identifier | ExFiles\Box 35\2\ scan 008 | |
| Date | 25th November 1915 | |
| COPY. R.R. 255 a (400 T) (S C. 836 18-2-16) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 1546 To Wor.{Arthur Wormald - General Works Manager} for EH from R.{Sir Henry Royce} c. to J.{Mr Johnson W.M.} c. to EY. c. to E.{Mr Elliott - Chief Engineer} c. to Na.{Mr Nadin} R6/B251115. November 25th 1915. RE - ALUMINIUM PISTONS. Referring to yours of November 23rd, I have not been at all distressed with the knocking of the pistons in 49 GB, but on one occasion during the cold weather the engine pulled up on the first hill just within a minute of the garage. As far as I can tell, it was a combination of the cylinders being fairly free from lubrication and the sudden expansion of the piston in a cylinder which had not heated up. No damage was done, and the engine was re-started as usual within a minute or two. It appeared to be just the same as if there had been no water in the cooling system. Now I suggest that it was probably only one piston which pulled up the whole engine, and it is just possible in, say a 12 cylinder engine, that one tight piston might be subject to the whole torque generated by the 12 cylinders. The connecting rod, therefore might get an excessively heavy tension at the ends of the stroke, and this may possibly have accounted for two of the serious break-downs which have lately occurred. In one case the piston head was pulled off, which at the time was thought to be due to want of strength, but which may have been due, as we pointed out at the time, to the expansion of the top part of the piston. 2748 | ||