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).
Letter addressing various vehicle performance issues including piston failures, oil consumption, and engine detonation.
| Identifier | ExFiles\Box 83\4\ scan0020 | |
| Date | 29th October 1935 | |
| x200a G.W. Hancock Esq., Hotel de France, Chateauroux, Indre, France. Thank you for your notes. We shall be interested to hear what caused the failure on the SpectreCodename for Phantom III. We recommend that you examine the pistons on the Bentley fairly soon to make sure that these are not cracking up. We expect them to run about 35,000 miles, however, before any trouble occurs. We are going to send you some better scraper rings for the 3½" bore pistons. Since we put the oil hole in the connecting rod through the pistons the oil consumption seems generally to have become high. We are still waiting for a report on the increase in comfort obtained from the 16" tyres. We observe that you say they hold the road. We should like to know whether you can appreciate the difference between the block with the silent tappet plungers having reduced clearance and the block with the silent tappet plungers having normal clearance. We note your eccentric failure. The 8 to 1 ratio throws an increased load on this but we think your bits may be undersize; we are investigating this. With regard to oil, herewith is a copy of a letter from Messrs. Wakefield, Please act accordingly. I am glad to note the improvement obtained in engine smoothness. Clearly we do not want to lower the compression ratio unless you consider it would make a better motor car from the sports point of view. We think the ignition advance characteristic on the governor may not be quite right for this engine. We should like you to put in some bad petrol and see whether your detonation decreases with speed, or whether you get a period round 60 to 70 m.p.h. where detonation comes up again. We have found this on a car here. Will you also please check the ignition timing on all 6 cylinders, as a small variation can increase detonation on the Bentley. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||