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).
Investigating the high oil consumption on the 25/30 Chassis, comparing piston and ring arrangements with other models.
| Identifier | ExFiles\Box 144\3\ scan0080 | |
| Date | 9th July 1936 | |
| To Sg.{Arthur F. Sidgreaves - MD} from Hy.{Tom Haldenby - Plant Engineer} Copy to W/S. H.{Arthur M. Hanbury - Head Complaints} Copy to BY.{R.W. Bailey - Chief Engineer} DA.{Bernard Day - Chassis Design} Rm.{William Robotham - Chief Engineer} MX.{John H Maddocks - Chief Proving Officer} OWR. Re Oil Consumption on 25/30 Chassis. I am in receipt of your SG{Arthur F. Sidgreaves - MD}2/E8.7.36 and have investigated the matter thoroughly in conference with BY.{R.W. Bailey - Chief Engineer} DA.{Bernard Day - Chassis Design} Rm.{William Robotham - Chief Engineer} and MX.{John H Maddocks - Chief Proving Officer} (E.{Mr Elliott - Chief Engineer} and Hs.{Lord Ernest Hives - Chair} being away from the works today). I have also now seen LA{L. A. Archer}2/T6.6.36 and am of the opinion that such a note should not have been written, as it is likely to be misleading. The high oil consumption has nothing whatever to do with the method or quality of production. The method is the same as it has been for years and we are all agreed that the cause of the trouble is not to be found there. The production is precisely the same as on the 20/25 and Bentley, and yet the results are quite different. The real reason is that we have gone in to production of the 25/30 with an arrangement of piston and rings different from anything we have produced before, and although it may eventually be found that the 25/30 piston and rings can be made to give satisfactory oil consumption, nobody knows how to do it today, and the problem is still being investigated by the Experimental Department. The 20/25 piston which has always been satisfactory from this point of view and is still satisfactory as produced today, is of the RR. split skirt type fitted with four rings all pinned. The 25/30 has a similar type of RR. split skirt piston but has only three rings and these are not pinned. The Bentley has a similar ring arrangement to the 25/30 (i.e. three rings not pinned) but they are fitted to the Aerolite piston and it was because this ring arrangement was considered to be satisfactory on Bentley that it was adopted on the 25/30. Experience has proved however that this ring arrangement is not good when fitted to the RR. type of piston, the oil consumption being actually doubled. It is plain to see that to effect improvement in the oil consumption, some modification must be made to piston or rings, or both. contd | ||