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).
Valve gear rocker geometry for the RAC.10, Phantom and 20 HP models to reduce noise when seating.
| Identifier | ExFiles\Box 17\6\ Scan019 | |
| Date | 3rd March 1928 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/ACL. c. to BJ. Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} c. to BY.{R.W. Bailey - Chief Engineer} OY. X7060 Hs{Lord Ernest Hives - Chair}/ACL2/LG13.3.28. VALVE GEAR ROCKERS FOR RAC.10. X8060 Y5060 With regard to the geometry of the valve rockers on the Phantom and 20 HP. The practice is now to place the pivot of the rockers level with the valve tips, as stated in your memo E5/M7.3.28., so that there is the minimum of side thrust when the valve is at the point of seating. This practice we have proved to possess considerable advantage over the previous standard practice in eliminating the noise caused by the valve meeting the valve seat out of line. [Diagram showing rocker arm pivot and valve stem alignment] This is confirmed on production chassis by the Test Dept. and they inform us they now have very little trouble with noise from the valves when seating. The only trouble they have experienced in this respect - and this only occasionally - has been due to local 'high spots' on either the valve tip or the rocker pad which resulted in an eccentric thrust on the valve and resulted in noise as the valve seated. This of course has been corrected by ensuring accurate contact of the valve tip and rocker pad. As the result of this experience we should therefore recommend the scheme we are at present using - i.e. contd :- | ||