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 notes on rocker arm assembly components, including clearances, materials, and part-specific considerations.
| Identifier | ExFiles\Box 125\1\ scan0123 | |
| Date | 29th October 1934 guessed | |
| -3- 3. The width of bearing on the eccentric, for the rocker arm must be such that the rocker arm is always free endwise. End clearance should be from .001" to .005". Diametral clearance between eccentric and rocker arm should be .003" to .0045" when using a bushing pressed into the rocker arm. When a floating bushing is used, the same total clearance is necessary, but limits are specified to divide this clearance between inside and outside of bushing. The floating bushing must have sufficient strength to maintain its true shape under load. 4. A minimum of friction between all parts of the eccentric and rocker arm is desirable, hence the floating bushing construction is preferable, but considerably more expensive from the manufacturing standpoint. The use of a pressed-in bushing is entirely feasible, but is apt to result in a "grunting" noise in the assembly. This noise was removed in the Cadillac by substitution of steel for duralumin tubing in the valve lifter rods. B.P. #881252 Washer-Thrust B.P. #881237 Pin The manufacturing tolerances of these parts were determined as a result of numerous difficulties in assembly of the washers on the eccentrics. The pin must be sufficiently tight to withstand rather severe usage but must not distort the washer when pressed into place. If sufficient space is available in the eccentric, it would improve the design to move the pin center further away from the hole thru the thrust washer. B.P. #881250, 881249 and 881248 Springs-Rocker Arm Shaft. The most desirable condition for these springs is to reduce the loading to the minimum possible without allowing the rocker arms to "walk off" the eccentrics. Any increase in loading over the minimum increases the frictional load on the eccentrics, which is undesirable. | ||