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).
Investigation into piston seizures on the upper lands of the 25/30 HP chassis.
Identifier | ExFiles\Box 107\3\ scan0131 | |
Date | 27th June 1938 | |
Rm.{William Robotham - Chief Engineer} O.Mr. BY.10/G.27.6.38. 25/30 HP. CHASSIS - RE: PISTON SEIZURES ON UPPER LANDS. I attach hereto copy of Hd{Mr Hayward/Mr Huddy}/SB.{Mr Bull/Mr Bannister}10/HR.17.6.38. which represents the history of the three cars which have had piston seizure on the upper land, from which you will see that in each case a top decarboning had taken place. GXM-54. HARPER. This was the car where the piston was broken up. It had been twice top decarboned, and failed in 737 miles after the second de-carboning. GXM-18. HOLLOWAY. Part of the top land was completely torn away. Two top decarboning had taken place, and failure occurred in 3,204 miles after the last decarboning. GWN-56. MILLS. This car had one top decaburisation. Failure took place in 4,600 miles later. We have never had a failure of this type on either the 20 HP. or 20/25 pistons. The following are the facts as I see them :- (a). In each case the piston which seized was No.6. (b). 20 HP. had a top land .125 deep. ) With a .075 Radius 20/25 HP. had a top land .200 deep.) at top corner. 25/30 HP. with which we are dealing - top land .250 deep, with .025 radius at top corner. It is clear from an examination, which I made personally of the cylinders and pistons on all three of the above chassis that the seizure had started with a top land. (c). An examination of individual pistons, other than the one seized, from each of the engines showed no signs of 'scuffing' on the bearing surfaces but a tendency to pick up on the axis of the gudgeon pin. If this picking up became more serious, its first action would be to lock the top ring which would be sufficient to account for the rest of the failure. The failure is similar in its origin and results as | ||