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).
Seized piston in a Bentley chassis, discussing potential causes, scuffing on other pistons, and recommendations for running-in procedures post-rebore.
Identifier | ExFiles\Box 114\3\ scan0181 | |
Date | 15th July 1938 | |
HQ. C. GWH.{George W. Hancock - Head Chateauroux} C. K.{Mr Kilner} BY.8/G.15.7.38. BENTLEY CHASSIS. B.3-EJ. COL. HANCOCK. Referring to the seized piston on the above car, whilst it is seizure on the upper land which has ultimately caused failure, it is very evident that we only just missed a seizure due to pure running conditions on the skirt of the piston by the skin of our teeth. Five pistons out of the six showed 'scuffing' on the skirt, undoubtedly due to the fact that we have so far on repair work not arranged for a method of running in. In the future this is being met by tin plating, but at the same time it is desirable that customers should be warned after a rebore that the engine revs. should be kept below 3000 r.p.m. until 200 or 300 miles have been accomplished. I am aware that this may cause an outcry, but it is better that the customer should be told to do this than we should have to run the risk of replacing pistons which have seized, as the result of being leaded heavily at high speeds immediately after a rebore, when we have abstained from running in the piston due to the cost incurred and unnecessary wear and tear on the car. In this case we will have to face the cost of the replacement. I am inclined to think that the car may have been run with the carburetter needle in the starting position causing excessive petrol to reach No.6 cylinder. It is difficult, however, to establish this, and to accept the scuffed pistons resulting from running under load immediately following the rebore would spoil our case. BY.{R.W. Bailey - Chief Engineer} By | ||