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).
Report received from the U.S.A. detailing issues and observations regarding hydraulic silent tappets.
| Identifier | ExFiles\Box 173\2\ img294 | |
| Date | 23th March 1934 | |
| COPY OF REPORT RECEIVED FROM Rm.{William Robotham - Chief Engineer} IN U.S.A. DATED 12.3.34 To eg. From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to Rg.{Mr Rowledge} c. to A.{Mr Adams} c. to By.{R.W. Bailey - Chief Engineer} SILENT TAPPETS. I saw G.M. about our Hydraulic Tappet difficulties to-day. (1) They have never been able to make this work with a ball valve. They tried before adopting the poppet valve type and went back to the ball again after succeeding with the poppet valve, but the result still unsatisfactory. Symptoms occasional breathing, such as ours, attributed to lack of damping of the ball which lets it fidget on its seat. Also ball not coming down squarely. If they guided the ball they found it liable to jam in the guide. (2) The hydraulic tappet has forced them to make better valve gear because it shews up valve spring surge or incipient bouncing by holding the valve off its seat as in our case. (3) Dirt in the oil has been a prolific source of trouble. (4) They agree with us that most of the noise in the valve gear comes when the valve is closing. They attribute some of this to loss of effective camshaft toe due to deflection in the valve mechanism. (5) They use a constant velocity toe having a vel. of 1/2 thou. per camshaft degree. The length of toe necessary depends on the amount of deflection in the valve gear, but is usually between .010 and .015. If the valve gear is very rigid, it can be less. (6) If we have further trouble with the eccentric fully floating bush they suggest needle bearings here. | ||