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).
Engine endurance testing, detailing piston seizure, cracking, and oil temperature trials.
| Identifier | ExFiles\Box 86\2\ scan0100 | |
| Date | 25th October 1933 guessed | |
| -3- The engine turned quite freely by hand but there was a definite loss of compression in No.4. cylinder. From the figures taken during the run we are inclined to think that the piston seized at approximately the same time that No.6. exhaust valve seized, so that loss of power was put down to exhaust valve trouble. Whilst examining the piston it was noticed that the gudgeon pin had seized, and that it had definitely moved one way, so much so in fact, that the end of the gudgeon pin was beyond the piston skirt and bearing on the cylinder wall. The piston was then forced hard to one side of the cylinder, this assumption is supported by the fact that the piston was bearing exceptionally hard on one side. Diagram I shows how the gudgeon pin had moved. Our later experience lends support to this assumption, since after fitting new piston and gudgeon pin no more trouble was experienced. After 21 hrs. endurance the test was concluded, piston knocks when hot were very slight, and when cold there was only a slight knock from No.4. piston. At the end of the 21 hrs. the pistons were removed for further examination and a slight crack had formed on No.2. piston, extending from the end of the horizontal slot immediately below the Scraper ring to the top of the longitudinal groove below. This is shewn in Diagram 2. Chalk tests failed to show any further cracks than the one mentioned above on No.2. piston. The endurance run was started with an oil inlet temperature to the bearings of 50°C but later this was increased in stages. It was decided to increase the inlet temperature in order to satisfy ourselves that the connecting rod big end failure on B.2. unit was due not to the fact that a high oil inlet temperature was used, but this unit had not the latest oil scheme fitted. The oil inlet temperature on B.2. unit was 90°C. After 1 hr. with the inlet temperature at 60°C this was increased to 70°C, for the next hour; the following hour was run at 80°C, and from then onwards the inlet temp. was maintained at 90°C and as far as we know at present without any detrimental effect. | ||