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 performance data, bearing issues, and combustion chamber clearances.
| Identifier | ExFiles\Box 116\1\ scan0006 | |
| Date | 10th November 1937 | |
| -2- (c) Rpm = 1800. (d) Engine is of open combustion chamber type with sunk head pistons and is supercharged by an exhaust driven centrifugal blower. (e) The maximum BMEP. is 140 lbs square inch. (b) Maximum explosion pressure = 1200 lbs square inch. (g) The full consumption is, approx. .34 pts/BHP/Hr. They are at present using lead bronze connecting rod bearings having .006 to .007 clearance on 3.125 dia. crankpin and white metal main bearings. Their troubles apparently have been:- (1) Inability of leady bronze to run satisfactorily with compounded oils. (2) Excessive oil consumption, they are at present trying to reduce clearance of the connecting rod bearings to overcome this trouble. (3) Failure of white metal main bearings. Their lead bronze bearings are at present costing them 27/9 per complete bearing of two halves. They have tried "Satco", and the first set gave remarkably good results, but they admit that they have since had trouble with bad adhesion on later sets. OTHER INFORMATION OBTAINED. Combustion Chamber. They find that clearance between piston crown and cylinder head is very critical, and, in consequence, they limit the maximum tolerance on the dimension from connecting rod big end centre to piston crown to .004. The limit on the dimension between connecting rod big end to small end is .001. They further state that a variation of .010 in the clearance between piston crown and cylinder head has a marked result on the performance. We saw this engine running, and for an oil engine was remarkably free from "thump" | ||