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).
The design, function, and testing of a self-adjusting tappet mechanism for the Phantom II model.
| Identifier | ExFiles\Box 17\6\ Scan154 | |
| Date | 14th September 1933 | |
| X7860 To E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Bwdl. C. Wor.{Arthur Wormald - General Works Manager} C. HY.{Tom Haldenby - Plant Engineer} C. RG.{Mr Rowledge} Hs{Lord Ernest Hives - Chair}/Bwdl.S/KT.14.9.33. SELF ADJUSTING TAPPETS (PHANTOM II) (Loc.3501). This scheme is in the form of a plunger incorporated in the rocker arm, the push rod operating upon the ball base of the plunger. The oil cushioning takes place between the top of the plunger and its housing which is formed by the rocker. The plunger takes the direct valve spring loading (75 - 125 lbs.) so that the oil is squeezed out during every valve operation and has thus to be replenished. Oil is pressure fed via a non return ball valve which has a .005" lift into the cushioning space, so returning the plunger and taking up all the tappet clearance. It is then ready for the next valve opening, the clearance between the plunger and its housing with the resultant oil leak providing the cushioning effect. As received for test the diametral clearance was .001" and under this condition we could not get the plunger to operate. After reducing the clearance and relapping to .0005 the mechanism functioned with a certain amount of success. The oil feed was transferred to the main pressure from the intermediate rocker pressure, as there is a condition in the latter even when boosted up when there is no oil pressure. This condition is when the oil is 70°C or over and the engine run dead slow. If the pressure is reduced below 5 lbs/sq.in. the mechanism is unreliable in that the plunger does not return quick enough. When running with the reduced plunger clearance and under main bearing pressure, the mechanism does produce silent valve operation, either idling or high speeds, and up to an oil temperature of 90°C. It works equally well with initial clearance of either .010, .020, or .030". Its failing is that if the engine is stopped with the valve spring load on the plunger and then restarted, | ||