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).
Test report on engine components including main bearings, oil filter, and spark plugs.
| Identifier | ExFiles\Box 97\4\ scan0174 | |
| Date | 23th November 1938 | |
| -3- Photograph III shows that whitemetal main bearings of the Wraith, 26.G.VI, after French test. It is hoped that further modifications will enable this standard to be reached on Bentley. The rear thrust ring was beginning to crack when removed for inspection at 13,454 miles. It was returned for examination although it would no doubt have covered the full mileage and more without collapsing. It compared favourably with the rear thrust face of the Wraith rear main bearing. See photographs IV and V.{VIENNA} There is room for improvement in both cases. The front thrust ring was in excellent condition. The big end bearings were good. Oil pressure was maintained throughout at a mean of 30 lbs/sq", but was inclined to fluctuate unless there was at least one gallon of oil in the sump. The present minimum mark is at 5 pints and maximum is 14 pints. We recommend that the min. mark is moved 0.5" towards the max. In this position it will indicate 8 pints, and 6 pints will be required to fill to max. A 'General' by-pass oil filter was fitted. After 7036 miles the oil was slightly dirty, and at 12,383 miles it was very dirty and a new cartridge was fitted. 1023 miles later the oil was clean, but it appears that the cartridge was over-loaded with sludge in cleaning the very dirty oil, as it again became dirty 4868 miles after fitting the new cartridge. On the next test a new cartridge should be fitted at 5,000 miles and every 10,000 miles thereafter and the results observed. No.5 sparking plug required a special spanner. This should not be necessary when the final induction pipe is available. Champion L.H.8 sparking plugs were used, set at .020" clearance, and re-set once during the mileage. The gaps opened up at the usual rate for Bentley, i.e., .010" to .013" per 5,000 miles. The plugs were in good condition at the end of the mileage, and the points appeared to be corroded less than with previous plugs tried. Traffic running on these plugs is required. The engine gears were not noticeable when idling. A thrash period at about 22 m.p.h. could be detected at the end of the running, but this was not outstanding and considered normal for the mileage. | ||