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).
Responding to Mr. Hives, discussing engine tappet noise, cam form design, and valve timing.
| Identifier | ExFiles\Box 138\1\ scan0034 | |
| Date | 11th May 1932 | |
| COPY. X634. HS{Lord Ernest Hives - Chair}/RM.{William Robotham - Chief Engineer} } FROM R.{Sir Henry Royce} E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} } (At Le CanadelHenry Royce's French residence.) RL/M.11.5.32. Rec'd & despatched from WW. 20.5.32. X5770. X5090. C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} C. to BY.{R.W. Bailey - Chief Engineer} RHC.{R. H. Coverley - Production Engineer} re. J.{Mr Johnson W.M.} Z. MR. Hives' memo of 4.5.32. to hand. Much seems to be wrong, but I believe it is not so largely due to changes in design, as to the exact proportions needed in production, for great perfection. For instance: ENGINE. Tappets seems to be noisy under all conditions, and therefore not entirely due to difference of temperature, and to me it suggests that the cam form is not good for silence. Possibly some little mistake in the toe, (I believe the tappets are offset). We intended at one time to have a long toe to the cam so that the timing might vary with difference in temperature between push rod and crankcase, but not the noise to any great extent. I have always felt nervous of high lift cams because of valve spring requirements, and noise. (1) Long duration. } I agree these (2) Reasonably fast acceleration } are good if new cam forms are made. (3) 112º. E.O. rather late, I.C. also later than past practice. (4) Two cams alike - 225º CS. with .020 clear: Rapid accelerations - i.e. .020 tappet clearance. [Diagram: A circle with radial lines indicating angles of 50° and 40°. Labeled "E.O." and "Change over 5º"] I had the impressions that MR. Lovesey got good HP. without high lift. It will be understood that no lift, no noise, and therefore the higher the lift the greater the noise. | ||