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).
Bearing loads and failures, comparing them to American practice and detailing improvements for Bentley and Phantom III models.
| Identifier | ExFiles\Box 115\1\ scan0343 | |
| Date | 4th June 1937 | |
| To E.{Mr Elliott - Chief Engineer} from Rm.{William Robotham - Chief Engineer} c. to Sg.{Arthur F. Sidgreaves - MD} c. to Hs.{Lord Ernest Hives - Chair} c. to By.{R.W. Bailey - Chief Engineer} c. to RHC.{R. H. Coverley - Production Engineer} c. to MX.{John H Maddocks - Chief Proving Officer} 1020 BEARINGS - ALL CHASSIS. During our recent trip to America, we ascertained from the average of cars running over there that they had established the fact that if bearing loads exceed 1500 to 1800 lbs. per square inch, babbit would not stand up. In view of this fact we have had the loads on our bearings calculated with a view to seeing how we stand relative to American practice. We attach these curves. It is quite clear from these figures why we are having difficulty in getting bearings to last. Previously, we thought that some of our failures might have been attributable to crankcase distortion, since our crankcase is less rigid than that of many American cars. It is also interesting to note that with light throttle under high speed running, which we know is the worst condition for big end bearings, the P.III. big end load is much more nearly constant than that of the Bentley. This explains why, although we have had satisfactory results with lead bronze on the Bentley, we have never been very happy with it on the P.III. We have just concluded the first 15,000 mile Continental run in the history of the Bentley car at the termination of which the bearings can be considered satisfactory. The car was equipped throughout with Aluminium Tin bearings, the composition of which is the result of the continuous development work that has been going on for the past eighteen months. We have, of course, a crankshaft that will provide greater bearing area on the Wraith, and we anticipate that this will eventually be fitted to the Bentley. We are also recommending a modification to the P.III. crank which will give an appreciable increase in bearing area on the big ends, which are the weak spot. continued | ||