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).
Analysis of gear lubricant, spark plug performance, and a potential engine failure due to pre-ignition.
| Identifier | ExFiles\Box 179\2\ img108 | |
| Date | 31th December 1931 | |
| Hs{Lord Ernest Hives - Chair}/Yng.S/KK.31.12.31. -5- the gears were not scrapped it appears that the lubricant is not capable of the duty imposed on it by the gears. PLUGS. Lodge A.55. All the central electrodes showed signs of having been very hot and the mica insulation round the electrode had started to burn. It is evident that these plugs are incapable of withstanding the heat conditions of the sleeve valve engine. They had run 16 mins. at F.T. (155 lbs/sq.in. MEP.) and 45 mins. on endurance tests at 145 lbs/sq.in. MEP. K.L.G.633. These plugs ran only 5 mins. at F.T. (156 lbs/sq.in. MEP.) and their best value was not fully explored. The trouble with these plugs originated in the extension pieces supplied with the plugs, jamming on the threads, with the result that in several instances the cap nut turned with the extension on disconnecting the plug lead and allowed the mica laminations above the gland nut to become slack. In one instance an attempt to retighten the cap nut drew the central electrode up through the mica. These plugs were returned to Messrs K.L.G. Cause of Failure. In reviewing the failure we must consider the possibility of pre-ignition. The burning of A.6 piston may have originated from some form of pre-ignition. There was, however, none of the symptoms associated with pre-ignition viz. sudden and violent fluctuations in lift and in extreme cases a backfire which results in stopping the engine. The lift fell off gradually and steadily after 2 - 3 mins. running. The cylinder head of A.6. bore does not bear any signs of burning and all remaining heads and pistons do not appear to have been subjected to more than the usual quantity of heat. The plug electrodes however, show signs of having been very hot and the trouble may have possibly arisen from this source. It is of interest to note that at full throttle 2250 R.P.M. with the same ignition advance, there was no audible detonation. Hs{Lord Ernest Hives - Chair}/H.R.Young. | ||