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).
Conclusions on car engine valve gear, including drilled valves, manufacturing improvements, and hydraulic tappet adjustments.
| Identifier | ExFiles\Box 17\6\ Scan293 | |
| Date | 27th July 1934 | |
| X7060 To E.{Mr Elliott - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} c. to Lr.{Mr Ellor} c. to Sft.{Mr Swift} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}18/KW. 27.7.34. Car Engine Valve Gear. We have as you know been collecting data on valve gear for some little time. We appreciate that until we get our optical apparatus for measuring valve gear movement our information is incomplete, but attached is a certain amount of data which has so far been collected. Our own conclusions at present are as follows :- (1) Drilled Valves. We think that all our valves should be drilled for lightness. In the case of engines where we are not running on the fringe of valve bounce when the maximum speed is obtained, this means that we can use a lighter valve spring and so get quieter valve operation and less chance of timing gear rattles. We are of course forced into drilled valves with the hydraulic tappet adjustment on the Phantom and Bentley, but wish also to have them on the 20/25. (2) Valve Gear Manufacture. We have got to improve the technique of our camshaft manufacture. At the moment progress seems slow on this particular feature. Our tests have indicated that it is not sufficient to deal with the camshaft only, we have got to be more accurate in our spring manufacture, and in the limits which dictate the length of the spring in the valve closed position. We have already issued a report which shows that improvement can be made. (3) Hydraulic Tappet Adjustment. We have now a fair experience of both the Cadillac and Halford hydraulic lash compensators. For a given plunger clearance the Cadillac arrangement is sixteen times as sensitive as the Halford, in addition it adds no inertia to the valve mechanism. It is particularly suited to line O.H.V. engines of the Rolls-Royce type. It is less noisy than its competitors when the engine is first started up. | ||