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).
Procedure to prevent No.6 piston seizure on 25/30 HP engines during decarboning.
| Identifier | ExFiles\Box 107\3\ scan0129 | |
| Date | 29th June 1938 | |
| Hd.{Mr Hayward/Mr Huddy} c. Rm.{William Robotham - Chief Engineer} c. CKH.(R) 561 EY.14/G.29.6.38. 25/30 HP. ENGINE - RE: DECARBONING. In view of the fact that we have had No.6 piston seize up on the engine in three different chassis (GXM-54 Harper, GXM-18 Holloway, and GWN-56 Mills) following a decarboning operation, it is evident that in the interests of the customer, as well as the Company, we must avoid the possibility of this recurring in the future. In order to achieve this end it will be necessary to adopt the following procedure :- (a). In decarboning the pistons the cylinder block must be lifted from the crankcase, so that the piston can be completely decarboned round the upper band. (b). A chamfer of .100 must be produced on the upper land of the piston to reduce the depth over which the carbon can collect between the upper face of the top ring and the upper edge of the piston. I attach hereto copy of EA/SB.{Mr Bull/Mr Bannister}10/HR.17.6.38. which represents the history of the three cars mentioned above. The matter is being investigated, and if and when we have information which will modify the above instruction a further note will be issued. In the meantime the Depots can not act upon these instructions. The variation from the 20 HP. and 20/25 HP. piston is an increased depth of land above the top ring. BY.{R.W. Bailey - Chief Engineer} | ||