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).
Type test of a Bentley engine unit, analysing main bearing wear and test results.
| Identifier | ExFiles\Box 3\6\ 06-page274 | |
| Date | 24th October 1934 | |
| X453 To E.{Mr Elliott - Chief Engineer} from Dm{D. Munro}/Rm.{William Robotham - Chief Engineer} c. to Mar. c. to Ry. c. to Elt. c. to Hx. c. to Isl. TYPE TEST OF BENTLEY UNIT. With a view to ascertaining the mechanical reliability of the present standard Bentley unit, we subjected one to a Type Test. Attached are full particulars of the power developed, the type of running, and the condition of the engine after test. We are very satisfied with everything except the main bearing wear. We have of course less balance on the Bentley than on the 20/25 owing to the necessity for keeping the critical crankshaft speed out of the running range. Nevertheless, with nitrided crankshafts we hoped for better results. The recent 10,000 miles test on the Bentley has confirmed the rather excessive main bearing wear. After examining the last engine which ran in France we concluded that probably foreign matter in the oil and dust in the atmosphere contributed materially towards the wear of the parts in question. After this run on the test bed, however, where little dust is encountered, and where special filtering apparatus is used for the oil, we have come to the conclusion that we do not suffer badly from either of these factors in our normal road running. The wear on the bearings with the continuous oil feed always appears to be worse than the bearings without this feature but actually, as will be seen from the chart, this is not so. We think that these results indicate the high wear factor which is likely to be encountered at modern speeds, and show the desirability of having as near 100% balance as possible on the "Wraith" and also being as generous as possible with the journal bearings. | ||