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).
Engine component testing, including cylinder and bearing performance, and fuel types.
| Identifier | ExFiles\Box 173\1\ img104 | |
| Date | 26th January 1934 | |
| -2- 5. The period of running to produce failure, using 3 c.c's is about 7 hrs., when rate of attack is rapid, but trouble commences after 3 hrs. running with 6 c.c. lead. 6. Oily cylinders reduce trouble particularly if supplied through super-charger. 7. Fighting grade fuel is 87 octane. With regard to lead bronze bearings, these are used on air-cooled as well as water cooled engines and give very satisfactory results. Bearings from 2 suppliers are used, viz: Allison's and Bohn's, in both cases bearings are made from solid and not from bent strip. Allison's bearings, however, give best results. All bearings are supplied finished, allowance being made for final reaming in position, adopted clearances are in line with A.A. practice, being .001 - .00125 per inch dia, oil pressure 6 -7 lbs. sq. in., inlet temperature 90°C. The bearing experience on Conquerors has been obtained with balance weight crankshafts, semi-balanced type, similar to a Kestrel type, which was introduced in the days of white metal bearings owing to repeated failures of crankcase center bearing panels. Test conditions under which R.R. bearings fail are much more severe than in the case of the Conqueror. For latter, test conditions stipulate that engines should be run up to normal power and speed, throttle being fixed and 3% overspeed & 4% r.p.m. run in stages of 20 seconds duration. After each period normal speed and power conditions are restored for two minutes and repeated until five minutes total running has been completed. Grooveless bearings are used with six feed holes for lubrication, holes being equally spaced in top and bottom halves with annular groove externally for oil supply. It would appear that this arrangement provides greater oil pressure at bearing, with grooves, oil, particularly under extremely high temperature conditions, can readily flow out of bearings. | ||