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 with Phantom III hydraulic tappets and proposing changes to clearance tolerances.
| Identifier | ExFiles\Box 96\2\ scan0208 | |
| Date | 22th January 1937 | |
| To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} c. c. to E.{Mr Elliott - Chief Engineer} 3524 Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}4/AP.22.1.37. PHANTOM III. HYDRAULIC TAPPETS. Trouble is being experienced, mainly with cars in service, of the valves sticking open due to binding of the hydraulic plungers in their casings. Likewise, valves are also held off their seats when a car is started after being left out in the open during very cold weather, due to the leakage factor past the plun ger being inadequate to deal with the thick cold oil. The latter can be overcome by the use of thin oil, Mobiloil Arctic in place of the standard Castrol XL. oil. This, however, does not help us with the former trouble which occurs when the engine is hot. The plungers actually show hard marks where the binding has taken place, and this we think is due to minute particles of carbon etc. which get past the filter being sufficient to render the existing clearance of .001 to .0012 insufficient and cause the plunger to bind. Several cars have been cured of this trouble by increasing the diametrical clearance up to .002, which at the same time helps considerably the cold starting difficulties. As the tappets are not noisy with a plunger clearance of .002, we should like you to alter the clearance details henceforth from .001-.0012 to .0015-.002. Giving a little extra tolerance of clearance will no doubt help in the production of these parts. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} | ||