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).
High oil consumption issues, piston ring performance, and the need for re-boring cylinders.
| Identifier | ExFiles\Box 144\3\ scan0052 | |
| Date | 5th June 1936 | |
| -3- This was under high average speed conditions, and towards the end of the test the bearings became very badly scored. This test indicates the point we have previously made, which is that since recently the cyl. bores have been more highly polished, the piston rings take some little time to bed down and until then the oil consumption is poor. In nine endurance runs in France we have not finished up with an oil consumption worse than 1000 M.P.G. The only cars which we have had the opportunity of investigating so far which have a high oil consumption have been some fitted with lead bronze big end bearings. We know that these are likely to overoil, but dealing with them does not help us appreciably in finding out what is wrong with the standard cars. We must have the opportunity of tackling one of these complaint cases, more particularly where the car has not covered any great mileage. We shall be no longer effecting a cure than a Depot. We have heard from K.{Mr Kilner} that B-60-FB was re-bored after a mileage of 3,105, and that Chassis No. B-5-EJ was re-bored after 10,959 miles. There is something extraordinary about a car that has to be re-bored after covering such a small distance, and we should like to know whether the figures are correct and if so, whether anything peculiar was found out. Surely the block and pistons from B-60-FB might have been submitted to us for examination. From our end of the job we have developed some piston rings which settle down in less than a third of the time of the ordinary ring. If, however, in certain cases the present standard car has to be re-bored after 3,000 miles, we know that the new ring is not going to get over the trouble. Briefly, therefore, we should like full information on - (1) The number of the 43 complaints last quarter where new pistons and rings had to be fitted, or where the oil consumption was definitely found to be due to oil passing the piston. How many were cured by the rocker shaft modification ? (2) Whether service confirms our experience that oil consumptions take 2,000 to 3,000 miles to settle down. | ||