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).
Insufficient bearing clearance, connecting rod fitting procedures for Phantom III engines, and engine maintenance recommendations.
| Identifier | ExFiles\Box 146\1\ scan0248 | |
| Date | 9th May 1938 | |
| Sr/VA2/ET.9.5.38 - 2 - INSUFFICIENT CLEARANCE. We quote below the 2nd paragraph of your HPS.{Horace Percy Smith - Experimental Factory Mgr}I/VS.{J. Vickers} 30.10.37: "These bearings have been diamond bored allowing ".0025 clearance on diameter to a standard shaft, "and it should be understood that any slight tight-"ness apparent when rods are looseley assembled is "due to spring in the shell, not incorrect clearance, "and will gradually disappear as nuts are tightened" Your memo was translated into French for the bene-fit of our shop foreman who, like the undersigned, gathered from the above (especially in view of the fact that the new rods had been sent specially to us for this car) that the clearances were correct and that we should not have to resort to any hand fitting. This is the reason why we did not check for clearance, although, as stated in our Sr/VAI/ET.29.4.38, the rods were free for side play on the crankpins. We note that the crankpins on this car are .0005" above standard. We were not aware of this when we fitted the new rods and we did not possess records, at this end, that would in-dicate it. In view of this seizure we will naturally, in fu-ture, when fitting new connecting rods to Phantom III engines, measure up the crankpins and make sure that the bearings have correct working clearance. Concerning the last paragraph of your memo, we should like to have a ruling from the Works (apart from whether a failure of a bearing has occurred or not) at what mileage it is considered advisable that an engine should be removed from the frame and stripped for cleaning purposes, prior to fitting a set of new connecting rods incorporating Hall's metal bearings. Judging from the condition of the engine of the above chassis, from the point of view of cleanliness after stripping, we should say that it would be advisable to strip for cleaning after 30,000 miles or more, especially as you state that Hall's alloy bearings are definitely more sensitive than white metal to the presence of dirt particals between the surfaces. Sr/VA. /d/ | ||