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).
Issues and proposed improvements for Ph.II self-adjusting direct-acting hydraulic tappets, focusing on air lock problems.
| Identifier | ExFiles\Box 158\5\ scan0085 | |
| Date | 25th April 1934 | |
| C O P Y. Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}2/KW.25.4.34. Ph.II Self Adjusting Tappets (Direct Acting). ------------------------------------------ With reference to our previous report, Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}5/KT.14.9.33 on this type of hydraulic tappet, LEC.3501, it was stated that our chief trouble was the trapping of air in the oil compression space and the inability of the oil feed, even with pressures as high as 50 lbs./sq.in. to move this air lock. This condition occurred after stopping the engine, the oil being squeezed past the plunger clearance by the valve spring loading and then on restarting any air in the oil feed line was forced along by the incoming flow of oil past the ball valve and into the oil compression space. As arranged in the original scheme (LEC.3501) the oil compression space is above the ball valve and the latter above the oil feed passage, so that there is little chance of preventing air from entering the mechanism. From the various experiments carried out on this scheme it was shown that to improve on this arrangement the following features must be incorporated - (1) That the oil compression space be below the ball valve, there being no desire for any air intermixed with the oil feed to flow in a downward direction. (2) That the non-return ball valve be below its seat to prevent any air being trapped when the engine is turned by the starter, before the oil pressure has reached the mechanism. (3) That an oil reservoir be arranged above the ball valve to allow time for air separation as the oil is fed past the valve. (4) Provision of an air release for the oil feed and above the passage of the latter. These details are included in two schemes Hs.{Lord Ernest Hives - Chair}1206 & Hs.{Lord Ernest Hives - Chair}1210, the plunger mechanism being identical. The difference is that in the former, the plunger is housed in the rocker above the push rod, whereas in the latter the plunger is above the valve spring. Of these two schemes, Hs.{Lord Ernest Hives - Chair}1210 is the most satisfactory, noticeably at low speeds where the time limit of load on the plunger is greatest, and the advantage can be attributed to the following reasons:- | ||