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 big end bearing failure and subsequent modifications to the oiling system.
| Identifier | ExFiles\Box 115\1\ scan0127 | |
| Date | 13th November 1936 | |
| -2- Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}10/AP.13.11.36. Further, the chief failure being Nos.2 & 5 big ends indicates that the grooving and consequent oil feeding from the intermediate main bearings which are each side of Nos. 2 & 5 big ends is inadequate. Following a seizure on one particular engine of Nos.2 & 5 big ends after 2 hours running, these two bearings were renewed in similar metal and in conjunction the oiling system modified as follows:- 1. Grooves in the intermediate main bearing modified to Rm.{William Robotham - Chief Engineer}244 thus increasing the groove area ( 2 sections) from .005" sq.in. to .0125" sq.in. the area of the jet feed hole in the caps being .015" sq.in. The front, centre and rear already having an area of .015 sq.in. and were left standard. 2. Extra hole, opposite to existing and making 2 in all drilled in each crankshaft journal and crankpin. Following the above modifications a run of 15 hours was carried out without any sign of big end seizure and the condition of the bearings at the end of the run was very good and in conjunction with new main bearings are to be given a further endurance. Naturally with the freed lubrication it was necessary to increase the relief valve spring pressure in order to maintain a standard of 30 lbs.sq.in. pressure and consequently the increased oil flow from the big ends raised the oil consumption from 1.625pts/hr. to 2 pts/hr. One of our next jobs is to get a separate value for each modification. Although this shews the improvement that can be carried out on one particular type of bearing by improved lubrication we have up to the present had some successful runs with RR.56 big ends with the standard lubrication. This report must not be regarded as a complete one on bearings but as a comparative test with modified oiling to the bearings. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} | ||