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).
Investigation into camshaft oscillations on the Wraith III engine.
| Identifier | ExFiles\Box 136\1\ scan0300 | |
| Date | 1st July 1938 | |
| To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} c. Sg.{Arthur F. Sidgreaves - MD} c. Hs.{Lord Ernest Hives - Chair} c. Da.{Bernard Day - Chassis Design} c. RRC. c. Nx. c. Da{Bernard Day - Chassis Design}/Jnr.{Charles L. Jenner} Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}2/BR.{T. E. Bellringer - Repair Manager}(1.7.38. WRAITH III CAMSHAFT OSCILLATIONS. Since the Fabroil camwheel off 26.G.VI after the 20,000 miles test revealed uneven wear and excessive on six peaks, we have investigated this trouble by means of our torsional indicator. Full details will be given in a later report but the summary of the results obtained is as follows. With the standard spring driven crankshaft damper, no crankshaft oscillations get through to the crank pinion, as proved by checking the latter with the indicator, therefore the six peak wear on the camwheel cannot be due to the effect of crankshaft oscillations. Taking diagrams on the actual camshaft, the amplitude of the torsional oscillations with normal backlash in the gears of .001 - .002 is very small but sufficient to show us that a six peak diagram existed. By increasing the gear backlash to .015 - .020 thus cutting out the damping effect of the gears, a definite six peak diagram is registered which reaches a maximum amplitude of .4° at 3800 r.p.m., this speed incidentally approximates to the road speed at which a period of vibration has been complained of. Our tests lead us to regard the camshaft as the exciting force and the dynamo and pump inertia as responsible for the resonance of the oscillation as if the dynamo and pump be disconnected the amplitude of the oscillation is considerably reduced. The best combination we have found to effectively reduce the amplitude is to increase appreciably the flexibility of the dynamo drive rubbers and increase the inertia of the camwheel. | ||