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).
Lead bronze big end bearings, shims, liners, clearances and crankshaft lubrication.
| Identifier | ExFiles\Box 146\3\ scan0191 | |
| Date | 30th November 1936 | |
| -2- Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}3/AP.30.11.36. We assume from your remarks that the lead bronze big end bearings which have been lightly scored can be cleaned up without having to take anything material off the lead bronze surface. If the lead bronze has come off one of the shims it is reasonable to expect that the others would not be long in going if re-fitted. In view of this we suggest that you fit a set of RR.56. liners which we will send out, also a set of W/M.{Mr Moon / Mr Moore} main bearings .030" undersize for the regrind. The RR.56. shims should be made to exactly the same thickness as the ones taken out. ---------- With regard to the RR.56. big ends we recently sent out for your trials car which is fitted with Hall's metal bearings, it would be advisable to have a minimum clearance of .002" and not .00175" We have found that by improving the lubrication in the crankshaft there is much less risk of any big end failure. This comprises increasing the grooves in the intermediate main bearings to the attached drawing Rm.{William Robotham - Chief Engineer}244 and drilling an extra and opposite hole in each crankshaft journal. We think that this might be carried out in conjunction with the fitting of the RR.56. big ends. It should be noted that the oil pressure be a minimum of 30 lbs/sq.in. at high speeds. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} Drg. Rm.{William Robotham - Chief Engineer}244 attached | ||