Cause and proposed cure for an 'elusive knock' in an engine, traced to faulty big end bearing assembly and poor gudgeon pin lubrication.
| Identifier | ExFiles\Box 48\1\ Scan118 | |
| Date | 25th March 1920 | |
| R.R. 235 a (100 T.) (S.F. 846. 6-8-19) G. {Mr Griffiths - Chief Accountant / Mr Gnapp} 2460. X737 X4190 Hs. {Lord Ernest Hives - Chair} from EP. {G. Eric Platford - Chief Quality Engineer} c. to Bn. {W.O. Bentley / Mr Barrington} c. to By. {R.W. Bailey - Chief Engineer} c. to Da. {Bernard Day - Chassis Design} c. to Ck. {Mr Clark} EP {G. Eric Platford - Chief Quality Engineer} 11/F25.3.20. X.2748. X.3429. RE. ELUSIVE KNOCKS? - X.737 An engine was condemned on test the other day owing to it having a decidedly bad knock which we considered was a bad sample of elusive knock, and which was demonstrated to you by Mr. Maddocks. Although we have our usual attention to the pistons, the knock was not cured and could not be passed, but after further investigation, it was discovered that there was a shortage of oil supply to the gudgeon pin, due to the faulty fixing of the big end bearings, the top bearing instead of bottom bearing being fixed in the cap, and fice versa, hence no oil-way ti the gudgeon pin. On fixing the rod correctly, we found that the trouble disappeared. I bring this to your notice as I feel it may guide us in obtaining some cure for the elusive knock, as we feel that this knock is certainly one which takes place from the gudgeon pin, it having the same general characteristics as a black gudgeon pin. This also proves to us the fact that we might increase the lubrication of our gudgeon pins to advantage, and it has been suggested the the hole in the connecting rod could be extended or made into an annulus so that the oil feed to the gudgeon pin is increased more than ti is atmpresent. The holes in the bearing are even now note central, and do not therefore get the full bore of oil from the crankshaft. I should be glad if you will give this matter your serious consideration, as we are anxious to avoid anynfurther cars going out on which the elusive knock we feel is sure to sooner or later develop. Is thereany reason why the holes in the big ends should not be in the centre of the bearing? EP. {G. Eric Platford - Chief Quality Engineer} | ||
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).