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 tests comparing different piston ring configurations and their effects on oil consumption and block distortion.
| Identifier | WestWitteringFiles\V\December1930-February1931\ Scan017 | |
| Date | 1st December 1930 | |
| Hs{Lord Ernest Hives - Chair}/ACLL/ADS.12.30 contd. -2- used only the plain scraper ring at the top and the oil consumption on this test amounted to only 5 1/2 pts/hour. Half the number of pistons were standard, however. There were signs of overoiling - smoky exhaust - when idling but this was not confined entirely to the pistons with the upper scraper ring. It is interesting to note that the oil consumption of the engine during the previous two hours acceptance test was 7 pts/hr. The same piston rings were used for the latter test as on the acceptance test. During the acceptance test the engine was standard with regard to the pistons, liners and blocks. The four distortion marks under the holding down bolts are still evident with any of the above schemes. We think we can safely say this is due to local crankcase distortion on the face. On the engine we ran without water in an attempt to break the block. This shewed distortion more pronounced than any other case and we think this may have been due to the extra tension put on the studs by the excessive heating of the cylinder head. We would summarise this latest test as follows :- (1) Increased clearance between liner and block combined with reduced foot and raised rubber appear a considerable improvement in reducing distortion on the present design. (2) The four distortion patches under the holding down studs are still evident and we think due to local lifting of the crankcase in the locality of the holding down studs. (3) Pistons with scraper ring raised to top of skirt give much better bedding in liner (freedom from markings) than the standard piston with bottom scraper ring. Combination of (1) and pistons with top scraper ring are very good and although with half this type of pistons the oil consumption was not excessive, we should want to do more tests and at higher speeds to test the oil consumption. Generally, we can say that all the modifications tested above shew a definite improvement. Hs{Lord Ernest Hives - Chair}/ACL. | ||