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).
Report investigating the cause of connecting rod failures in supercharged engines.
| Identifier | ExFiles\Box 179b\3\ img077 | |
| Date | 30th January 1933 | |
| To R.{Sir Henry Royce} From Hs.{Lord Ernest Hives - Chair} c. to Jg. c. to Wox. c. to Gr.{George Ratcliffe} c. to Wp. c. to Ry. c. to Ir. c. to Lp.{Mr Lappin} ORIGINAL x4117. x3859. RN.{Mr Robinson} CONNECTING ROD FAILURES. There has not been a single case of connecting rod failure on 1 B. engines normally aspirated. In one engine where the oil pump drive failed the rods had broken, but this can be dismissed. On supercharged engines, up to December 1932 four cases were reported. Two were caused by split pins wearing through. The remaining two were attributed to white metal failures in the engines. Since December 1932 eight further cases of connecting rod failures have been reported on supercharged engines. Four have been examined and can be attributed to white metal failures. The remaining four, according to reports, are similar, but we have not yet had an opportunity of examining them at the Works. As there are many more 1 B. engines in service than supercharged engines it means that we have to look for some special condition connected with those engines. It is now certain that these failures start with the failure of the bearings on the crankshaft and the reason for the bearing failing is due to temporary failure of lubrication. If we accept that the failure is due to lubrication then none of the modifications we have in hand for improved rods or articulated rods or lead bronze bearings will overcome this trouble. The first point considered was that as the recent epidemic started in moderately cold weather it might be due to starting off with too cold an oil. We think this can be dismissed entirely. (1) There is no reason why the supercharged engine should receive any different treatment to the 1 B. engine. (2) We have for over twelve months now on our hangar test made a practice of opening up to full throttle immediately the oil pressure reads on the gauge. This means that the engine is opened up after 30 secs. to full power. Sometimes the oil has been 0oC. This treatment has been given to two or three engines and we have never had the least signs of any trouble. | ||