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).
Results and conclusions of various piston tests, noting scoring issues and proposing further investigation.
| Identifier | ExFiles\Box 178\4\ img087 | |
| Date | 2nd May 1932 | |
| -2- HS{Lord Ernest Hives - Chair}/Yng.1/ANL2.5.32 contd. to settle this point. No improvement resulted from the modification and the remaining tests were of various piston profiles and clearances. RESULTS. None of the types of piston tried were a satisfactory job and although K.39 Type Test profile was the best effort it definitely was not good enough to start 100 hours. After running, the same characteristics were evident with every type of piston i.e. scoring of the thrust face, particularly on B. side. Corresponding score marks showed up on the cylinder liners, whilst the piston thrust faces on B. block seemed to be drier than those of A.{Mr Adams} block although the cylinders appeared to be well lubricated as a whole. CONCLUSIONS. Test No.7 (being run at a lower power) enables the increase in the rating to be ruled out as even a contributory cause of the trouble. Test No.2 - increase in piston ring gaps - proves that butting of the rings was not the cause of the scoring of either the pistons or the rings. The evidence points to a breakdown of the lubrication since :- (a) The worst scoring is on the thrust faces of B. side pistons and this part of the cylindersis the least lubricated of any. (b) Buzzard pistons run water cooled on P.4 oil show the same scoring characteristics in a milder form and are only just a passable job from this point of view. (c) 1929 "R" engine pistons which are of exactly the same profile with slightly increased clearances, function perfectly under a greater load running water cooled on Castor oil. In view of the foregoing we now propose to start tests with standard Buzzard pistons, running water cooled on castor oil in order to prove the point and then to investigate the conditions when running evaporatively cooled. HS{Lord Ernest Hives - Chair}/Yng. | ||