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).
Potential causes and solutions for piston knocks, including lubricants, ignition timing, and piston design.
| Identifier | ExFiles\Box 35\2\ scan 037 | |
| Date | 25th August 1919 | |
| H.R. 235a (500/T) (S.D. 40s. 26-4-17.) Hm.{Capt. W. Hallam - Head Repairs} 2/156/13. To EH. from R.{Sir Henry Royce} Copy to CJ. " " BN.{W.O. Bentley / Mr Barrington} " " DA.{Bernard Day - Chassis Design} " " EFC. X. 2748 RE PISTON KNOCKS. I believe the lubricant will have an enormous effect on the knocking of the pistons, when we get to the bottom of it. It has occurred to me that the reason why our engine shows a tendency to piston knocks over some other types of engines may be due to the ignition commencing in the pocket, and it has occurred to me that some advantage might be gained by keeping the pocket ignition later than the magneto ignition, and also temporarily arranging the ignition plug centrally over the piston. From my own experiments I cannot detect any support of this suggestion so give it for what it is worth. One has noticed that a possible explanation of the variation from one car to the other might be due to the relative time of firing of the two ignitions, or to the differnece in quantity of lubrication retained or supplied to the cylinder walls, by splash or otherwise. A further suggestion is to use bevel or slowly tapered lower edges, and a number of annular rings for retaining and distributing the oil. | ||