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).
Copy of a letter from Dennis Bros. to Wellworthy Piston Rings regarding a failed test of centre main bearings.
| Identifier | ExFiles\Box 115\5\ scan0100 | |
| Date | 20th August 1938 | |
| Copy of letter received from Dennis Bros.Limited., Guildford, Surrey. Messrs. Wellworthy Piston Rings Limited. Lymington, Hants. 20th August,1938. Dear Sirs, Attention of Mr. Blackith. Rolls-Royce Bearings. Confirming our telephone conversation of this morning, we regret to have to advise you that we are still in trouble with the centre main bearings 35559 made in RR.AC9 alloy. We have run one of these bearings with .0035" diametral clearance and .009" end clearance for two days at light loads and speeds. On the third day the load was applied gradually, and the initial running was concluded with five minutes at 3,000 r.p.m. under full load. The engine was then stripped, and the bearing examined. Everything was found to be in a satisfactory conditions, and it was then decided that we should today make a full power 6-hours run at 3,000 r.p.m. A start was made at 6.a.m., and the engine was gradually warmed up until full speed and full load had been obtained at 6.30. At 6.45 the engine showed signs of distress, and the test was immediately stopped. On examining the centre main bearing we found that it had scored in the same manner that we had seen previously on the journal faces, while on the thrust faces there was evidence of heavy loading. The bearing used in this test was one with a reduced outside diameter, but it is quite evident that this has had no real beneficial effect. We also carried an oil groove on the trailing edge of the bearing on each joint line, so that oil would be spread over the full surface of the bearing. This also has made very little improvement. We had considered the proposition of milling or machining a flat on the centre journal of the crankshaft, but in view of the type of failure of the bearing under the last test we do not think that even this would be sufficient to give us a bearing which we could fit and forget. Under the circumstances, we have decided t | ||