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).
Investigation into the cause of failures on supercharged engines, focusing on oil pressure and connecting rods.
| Identifier | ExFiles\Box 179b\3\ img078 | |
| Date | 30th January 1933 | |
| -2- Cont'd.{John DeLooze - Company Secretary} As it is shewn that the fault is very much worse on the supercharged engine, we have to look for some special conditions on that engine. The first point is that this engine is capable of delivering more horse-power. We think this can be dismissed as the cause of the trouble because on the test bench we have run these bearings full throttle, maximum speeds, with only the usual wear and tear. The next point is that most of the supercharged engines are in single seater machines which do more aerobatics and we know that when rolling they lose oil pressure for some time. Our tests on the bench have shown that the engine will only run for a very limited time with loss of oil pressure, therefore it is safe to assume that this is one of the chief causes of the failure. It is impossible to say that it is the entire cause of the failures because of the recent eight failures two of them (25%) we are certain were not due to aerobatics. In one case the engine failed in our own machine at Tollerton and we are positive that nothing abnormal was done with this machine. The failure was characteristic of all the other failures No.2 rod failing. The other failure occurred on an engine running on the test bed at Farnborough and this engine was only doing normal duties. Every one of our connecting rod failures occur on the front end of the engine, and the majority are numbers 1 and 2. There have been isolated cases of No.3 but no failures whatever on 4, 5, and 6. We have therefore to find a reason why the front connecting rods should suffer worse. We have run with pressure gauges on the oil manifold and find that the pressure under all conditions is absolutely uniform. We are collecting considerable evidence from the test bed running to show that under normal conditions No.1 connecting rod bearing seems to suffer worse and it gets better as we go down the engine to No.6. As the primary cause of the failure is due to lack of lubrication this is the first point to tackle. It is reported that the engines vary considerably in the time taken for the oil pressure to return after a roll. This we are investigating to see whether it is variation in oil pumps or some variation in the installation. | ||