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).
Manufacturing and design difficulties with lash adjusters and associated components.
| Identifier | ExFiles\Box 125\1\ scan0122 | |
| Date | 29th October 1934 guessed | |
| -2- 3. Removal of too much stock on top face of cap #881229 to obtain a smooth and square face. This surface must be hard inasmuch as it is subjected to sliding action of the eccentric arm under considerable load. 4. Failure to obtain low leakage rate past plunger valve seat. This has been due to difficulty in grinding in the small valves #883195 and the inability to obtain true seats in the plunger body #882927. At the present time, it seems entirely feasible to use the plungers without cyaniding and obtain the seat by striking the valve head, which is sufficiently hard to form its own impression. Wear of the plunger is negligible if the body is left soft, and supplied with clean oil. B.P. #881232 Spring-Hydraulic Lash Adjuster Plunger. This spring must be maintained within very close limits for load as specified, and changes in design would require experimental work to determine allowable tolerance in load at actual operating length of spring. Insufficient spring load slows up the plunger action at low speeds with cold oil, and at high speeds with hot oil either of which will create noise in the valve gear. Excessive spring load increases the tendency of the valves to ride and burn. The use of two concentric springs wound right and left hand is being tried experimentally at this time to reduce the spring stress and so obtain a longer life on this part. Useful life has not been sufficiently long, due to springs taking a permanent set and spring load dropping below the required minimum (See redesign X885318). B.P. X885313 RH{R. Hollingworth} Eccentric Lash Adjuster X885314 LH{Mr Haworth} Manufacturing difficulties with these parts have been as follows :- 1. When iron is sufficiently hard to obtain good wearing qualities at contact point with the plunger cap, machining is difficult. Eccentrics are cast in pairs to obtain uniformity of hardness in the castings. 2. The rocker shaft hole .718" - .719" diameter must be a smooth finish. The oscillating movement of the eccentric is so small that it tends to press out the oil film between the eccentric and rocker arm shaft, resulting in galling of the parts. As a preventative of this galling action, the rocker shaft is copper plated quite heavily. Clearance limits between the shaft and eccentric are .001" to .003" after copper plating. | ||