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).
Design propositions for valve rockers and rocker bar centres.
| Identifier | ExFiles\Box 43\3\ Scan122 | |
| Date | 15th January 1927 | |
| To R.{Sir Henry Royce} from E.{Mr Elliott - Chief Engineer} c. to B.J. c. to Hs.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} X4003. E1/M15.1.27. RR. F.10. VALVE ROCKERS X.3822 WITHOUT ROLLERS. X.4003 X.3866 Regarding your memo. of the 11th.inst. there appears no reason why we cannot have interchangeable rockers with the existing cyl. block. There will be minor alterations to the intermediate and rear camshaft bracket dies, and a new bracket will be required at the front end. Regarding the rocker bar centres we have the choice of two propositions - (1) 2.2" centres as shewn on LeC.2363 which allows us to use 1.3 dia. valve springs with plain rocker bosses, or 1.4 valve springs with rocker bosses cut away. (2) Still further reducing the centres by using cut away bosses with 1.3 valve springs to save weight and avoid adding to the width of the engine. This scheme would render unnecessary any alteration to the outline of the valve gear cover. We are finishing off the scheme to proposition No.2. as we feel that we may yet require, now, or in the future, the 1.4 spring. Moreover we see that by slight extra machining we may yet avoid adding .8" to the overall width of the engine with No.1. We are sending you herewith a copy of tracing of LeC.2363 shewing a lever arranged with two inch dia. equivalent rollers, and a print of LeC.2350 for comparison, shewing a 1.5 equivalent roller. The cam forms have been drawn to an existing valve lift curve. With the 2" roller the rocker bar is loaded 50% more than at present vertically and with the 1.5 roller the extra vertical load is 25%. This is of course due to the smaller leverage brought about by the geometry with the existing position of camshaft. The lateral thrust remains about the same as will be seen by the force diagrams which are to the same scale. We should like to know which rocker you would like us to use. At the moment the design is made for LeC.2350. E.{Mr Elliott - Chief Engineer} | ||