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 component issues including tappet failure, oil supply problems, and crankshaft oscillations.
| Identifier | ExFiles\Box 123\5\ scan0321 | |
| Date | 23th February 1939 | |
| -7- Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}1/MH.{M. Huckerby}23.2.39. After several curves the tappets became noisy and examination revealed several tappets broken and others scuffed. The scuffing was confined to the inlet valves and the cam tips showed signs of wearing away, which we attribute to the high loaded springs coupled with the .450 lift. The trouble, however, was rather involved as at the same time the camshaft was riding forward due to the oil trap behind the rear of the camshaft thus reducing the turning moment on the tappets. Regarding the failures which occurred through the windows of the tappets, the fractures revealed "white iron" which for durability is undesirable and since fitting "grey iron" tappets no further trouble has been experienced. The oil trap mentioned in the former paragraph was reported in our memo Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}9/MH.{M. Huckerby}13.1.39. and cured by drilling a release hole. Starting with a very inadequate oil supply to the valve gear, as stated in Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}4/MH.{M. Huckerby}1.2.39, this has been corrected by an annular groove around the rocker shaft, or the bush, the latter being chosen as most suitable for production. Overflow drain holes in the tappet compartment are required as oil builds up in this chamber. Oil leaks through the joints of the sheet metal tappet doors due to their inadequate stiffness and we think die-cast alum covers would be more suitable. Similar to B.60 the valve gear is quiet up to a tappet clearance of .010. CRANKSHAFT DAMPER. The results obtained on the crankshaft oscillations have been fully reported in the memo Rm{William Robotham - Chief Engineer}/JKS.10/JH.13.2.39, the summary of which is that whilst the harmonic damper considerably reduces the amplitude to .05 degrees, the experience on the B.60 is that unless a spring drive be used, the amplitude must be reduced to negligible amount to avoid camwheel failures. However, as the max. amplitude is at a lower speed on the 8-cyl. it may be better off for gear failure. Tests will be made to prove this. | ||