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).
Connecting rod materials, bearing block design, and oil pressure issues.
| Identifier | ExFiles\Box 179b\3\ img190 | |
| Date | 14th February 1931 | |
| -2- Cont'd.{John DeLooze - Company Secretary} Another important factor in connection with connecting rods is that it has been proved that we can apply the lead bronze and get good adhesion on to C.R.N.S. material. The bearing blocks on the present standard rods have had to be made in mild steel because of the difficulty with white metal. If we make these blocks in C.R.N.S. and also add the modifications to get rid of the sharp corners we shall expect to overcome the breaking of the big end bearing blocks, which is one of the weakest points on the present rod. Our reason for saying this is that the engine which has run eleven hours at 900 HP. has the mild steel blocks without the sharp corners and this showed no signs of fracture. With the further modification of C.R.N.S. we should increase the margin of safety. One other important point in connection with oil grooves in bearings is that at the present time it is possible for a big end bearing to run out and this makes no difference to the oil pressure (which is direct evidence that very little oil gets to the big end). There have been cases where the big end bearing has run out and it has only been found by examination of the filters and finding white metal. Except for that the engine would have been flown again until the rod had been destroyed. When we have grooves in the bearings if any oil runs out there is an immediate drop in oil pressure which will give the pilot a clear indication that something is wrong and should save the engine being smashed up. With the lead bronze bearings we have to give increased clearance and it is certain that we shall have to increase the capacity of the oil pump. The tests of measuring the pressure in the crank pins has taken longer than we thought. It is not due to the fact that we have not been working on it. We have got a number of results but they are not sufficiently reliable to report. There is no doubt that the pressure in the crank pins is quite low. Hs.{Lord Ernest Hives - Chair} | ||