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).
Diagnosing 'elusive knocks' as gudgeon pin knock and discussing potential solutions with Mr. Royce.
| Identifier | ExFiles\Box 35\2\ scan 217 | |
| Date | 27th March 1920 | |
| X.2748 To EP.{G. Eric Platford - Chief Quality Engineer} from Hs.{Lord Ernest Hives - Chair} c. to Bn.{W.O. Bentley / Mr Barrington} c. to By.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} Hs{Lord Ernest Hives - Chair}3/LG27.3.20. X.2748. RE ELUSIVE KNOCKS. X.3715. X.3751. From tests on experimental cars, we confirm the results obtained on test that the elusive knock is nothing to do with the pistons but is really a gudgeon pin knock. In our case, we have come to the conclusion that the knock is from the gudgeon pin in the piston. We find that when the piston is at 150°C, the gudgeon pin is .002" slack in the piston. When I was last with Mr. Royce we spoke to him about elusive knocks and mentioned to him what we thought was undoubtedly the cause of them. We had a long discussion on this point and he suggested means of overcoming them which are to be tried experimentally. The conclusion we came to was that the best way to overcome it was to use on oil film. It is a thing which will need considerable testing because we know the risks we run with excess of oil on the pistons. When we have been testing the oil plunger pistons, we found that the fact of having an annulus in the big end bearing caused over-oiling. At the moment we think that elusive knocks are the least of the evils. Hs.{Lord Ernest Hives - Chair} | ||