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).
New type test requirements, piston and piston ring issues, and sparking plug performance.
| Identifier | ExFiles\Box 27\3\ Scan220 | |
| Date | 15th May 1939 guessed | |
| 14. A new type test requirement, stated variously to be due to the Army and to the Civil Authorities, calls for a type test to be carried out with an oil inlet temperature of 120°C. In spite of the larger amount of heat to oil Wrights say that a 12" diameter cooler over-cools a 1200 HP.engine. Piston and Piston Rings One heard many rumours of piston ring troubles which were stated by the engine people not to exist on current types, but Mr.Meeter of the Perfect Circle Piston Ring Company said that the trouble was due to wear which caused feathering of the rings at high B.M.E.Ps., of the order of 225 lbs/sq.in. for take-off, and 175 to 190 lbs/sq.in. for cruising on 100 octane fuel. He was not decided yet as to the advisability of pressure pattern, and he personally was putting his faith in the development of alloy irons. He said that little was known about the mechanism of failure, but that at a certain B.M.E.P. the side pressure on the ring became too great for it to be able to spring, and this caused high oil consumption and blow by.{R.W. Bailey - Chief Engineer} Pratt & Whitney have tested rings as made by and used in England and said they had found them no better than their own, but it must be remembered that they are operating at lower piston speeds and higher pressures than we are. Regarding pistons, Pratt & Whitney consider that the waffle pattern under the cylinder head and the circumferential fins in the skirt are absolutely essential. Wrights have copies Pratt & Whitney in circumferential fins, and Pratt & Whitney are now going to fingers under the cylinder head instead of a closed waffle, in other words, the pattern of the waffle instead of the mould. With both Pratt & Whitney, and Wrights, gudgeon pin cracking has been a serious trouble. Sparking Plugs Ceramic platinum pointed plugs obtained from England have created a favourable impression in the States. With Hurley Townsend (now Bendix) and B.G. plugs the useful life was quoted variously at from 60 to 100 hours before cleaning. | ||