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).
Phantom II piston complaints and proposing an increase in piston length.
| Identifier | ExFiles\Box 182\M19\ img099 | |
| Date | 5th January 1931 | |
| Hs.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} Wor.{Arthur Wormald - General Works Manager} From Mx.{John H Maddocks - Chief Proving Officer} COPY. Mx.{John H Maddocks - Chief Proving Officer}8/T5.1.31 PHANTOM 11 PISTON - QUARTERLY COMPLAINTS. While we have considerably reduced the number of complaints due to piston trouble, and with the introduction of extra cylinder lubrication, we hope to reduce them still more - I consider that we can improve the Phantom piston by increasing its length. The first 50 Phantom 11 Chassis were much shorter on the bearing area than those fitted to Phantom 1. As a result of experience on test these were increased in length by .4" with beneficial results. By comparison with the 20/25HP. piston which gives no trouble on test and practically none in service with piston knocks, the Phantom 11 piston is still deficient in bearing area. The ratio of length to diameter is - Length. dia. 20/25 HP. 3.250 2.600 Phan.11. 4.250 2.600 Therefore the Phantom 11 piston should be .800 longer to put it on the same basis as the 20/25 HP. piston. This may mean an increase in piston weight of approximately 2 ozs. It is a matter for design and experimental work. to go into. Incidentally RRAI. have always been in favour of a long piston, and use a piston .600 longer than our present standard, and they claim with beneficial results for absence of piston knocks and long life. MX.{John H Maddocks - Chief Proving Officer} | ||