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).
Main bearing, oil pressure, and connecting rod failures for a Bentley engine, chassis No. B.117.JY.
Identifier | ExFiles\Box 131\2\ scan0063 | |
Date | 30th September 1937 | |
Handwritten: Peiles to 1113. Handwritten: SWDL{Len H. Swindell} By.{R.W. Bailey - Chief Engineer} Rm.{William Robotham - Chief Engineer} ✓ Mx.{John H Maddocks - Chief Proving Officer} Sr. KINGSBURY. Rm{William Robotham - Chief Engineer}/GWH{George W. Hancock - Head Chateauroux}/DPB/30.9.37. BENTLEY. REPORT UPON MAIN BEARINGS IN RELATION TO OIL PRESSURE AND CON.ROD FAILURES. --------------------- We have dismantled Lp{Mr Lappin}'s engine, removed from chassis No.B.117.JY at the request of By, the mileage being 13,101. The sequence of events in so far as the running of this engine is concerned is as under:- 1. Car sent to this Depot for a plain R.10, no complaint of any description. 2. Owner coming under category of hard drivers, it was decided to fit a modified oil pump. 3. To carry out this modification it necessitated the lifting of the cylinder block, wh ch in turn disclosed to us the state of the big end bearings, numbers 4 & 5 of which were replaced, and in due course returned to By for examination, the engine in the meantime being reassembled and delivered, passing off test in a normal manner. It was at this junction that after the examination of the big end shells by By that instructions were issued by him for the chassis to be recalled to the Depot in order that the engine could be removed for extensive bearing examination. The result of this examination disclosed the following facts which are clearly shewn in the attached chart. From this chart it will be seen that the main bearings have a clearance above the nominal clearance of .003". No.1 - .0022, 2nd - .0029, 3rd - .0056, centre .0084, 5th .0029, 6th .005", Rear No.7 - .0056. I would then draw your attention to the figures of the main bearing sinkages and their relation to the clearances given, bearing in mind that this engine did not disclose in the slightest degree that there was anything abnormal with it. I have the following observations to make in the light of my experience here with the 4 1/4-litre under service conditions in so far as bearing troubles and low oil pressures are concerned. -contd- | ||