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).
Technical bulletin establishing a standardized routine for oil flow tests on Bentley models.
| Identifier | ExFiles\Box 114\3\ scan0002 | |
| Date | 23th February 1939 | |
| To: Hd.{Mr Hayward/Mr Huddy} R.{Sir Henry Royce} Levallois Rm{William Robotham - Chief Engineer}/GWH{George W. Hancock - Head Chateauroux} (K) BY/SB{Mr Bull/Mr Bannister}6/MG.23.2.39 OIL FLOW TESTS - BENTLEY Oil flow figures taken at different Depots vary to some extent, also there is variation when using the same machine under different conditions. This has been found to be due to engine temperature variation, because although the crankcase temperature is taken as a basis for comparison, this does not necessarily indicate the crankshaft temperature, which is really the factor controlling the viscosity of the oil passing through the bearings. The crankshaft temperature only approaches the crankcase temperature after a period of running, i.e. when the heat "soaks" through to the crankshaft. In order to make the test as stable and consistent as possible, the following routine has been established: (a) When the Owner or tester reports low oil pressure or thump, the oil flow test is applied as soon as the temperature has fallen to 45°C. (Crankcase temperature measured inside the oil filler). (b) If cold, the car is taken on the road for approximately 20 miles, so that the crankshaft absorbs the maximum heat. The engine is then allowed to rest until the crankcase temperature reads 45°C. (c) Consequent upon this temperature revision, the time basis has been amended to 3 mins. 30 secs., below which bearings are in need of attention. The bearing sinkage is determined by measuring the "lift" of the crankshaft after the engine has been removed from the frame and the lower half crankcase removed. A dial gauge is fastened to the crankcase with the needle pointer resting on the turned flange of No.7 Journal bearing. A lever is then placed between the crankcase and the flywheel, and reasonable leverage used to take up the slack, this being recorded on the gauge. The remaining bearings are checked if necessary, after removal of the crank, by a known gauge, the bearing and housing being replaced and tightened up. BY/SB.{Mr Bull/Mr Bannister} | ||