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).
Technical memorandum discussing the performance and characteristics of Phantom double valve springs.
| Identifier | ExFiles\Box 17\6\ Scan040 | |
| Date | 11th May 1928 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Tsn. c. to BJ. Wor.{Arthur Wormald - General Works Manager} c. to HG. E.{Mr Elliott - Chief Engineer} c. to BY.{R.W. Bailey - Chief Engineer} DA.{Bernard Day - Chassis Design} PHANTOM DOUBLE VALVE SPRINGS. Referring to E3/M9.5.28. the double valve springs to Lec.2479 designed for and fitted to EAC.14 bounce at a slightly lower speed than the std. single spring. The loads, valve closed, are : Double springs 57.5 lbs., and single spring E.70442 60 lbs. and the bouncing speeds are 2700 and 2900 r.p.m. respectively. The 2700 figure was found by ear, and verified by watching them bouncing with an Ashdown Rotoscope; it is rather lower than would be expected, which may be due to Surging phenomena. From the type of acceleration diagram that is used for all RR. cams, we would suggest that it is more important to increase the spring force with the valve closed than with the valve open. There is always an ample margin of spring force at full lift. A suitable type would appear to be a low rate spring or springs with a load, valve open, of about the same as standard, which is 88 lbs. We have no definite data as to where the valves first leave the cam, but we think that when floating is so far advanced as to cause observable bounce that they are leaving at the first 'changeover' point on the lift side. The outer springs when detailed to Lec.2479 were found to have insufficient clearance between full lift and contd :- | ||