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).
Letter to G.W. Hancock concerning Autoflux pumps and an analysis of piston failures.
| Identifier | ExFiles\Box 82\1\ scan0211 | |
| Date | 22th August 1933 | |
| G.W.Hancock Esq., Hotel de France, Chateauroux, Indre, FRANCE. From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}2/MA.22.8.33. We note that you have obtained one of the Autoflux pumps for trial. You will appreciate that there is not much chance of us fitting this pump as it is American, but we should like you to let us have it as soon as you have completed your tests thereon. With regard to the piston failures, we believe that this may have been accentuated by the reduction in diameter of the top lands of the piston. We find that when Mx.{John H Maddocks - Chief Proving Officer} was carrying out his experiments with piston bedding in order to facilitate production he agreed to an alteration in the diameter of the top portion of the piston, which we show on the attached sketch. (coming later). This means that the skirt can collapse .010 before the land starts to touch the cylinder walls. We can see that at high speeds this bottom land might materially support the skirt, therefore on the piston we have sent out we have got Mx{John H Maddocks - Chief Proving Officer}'s dimensions for the skirt and the old 20HP. dimensions for the crown and lands. We think that the gumming up of the top two rings may be ascribed to the unnecessary clearance which has been incorporated on this point. We also believe that the oil temperature has a large bearing on the piston failure. The reason we say this is because the strength of the aluminium is falling very rapidly with temperature. The piston is cooled entirely by oil and heat loss through the rings. | ||