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 crankshaft vibrations on the 20 HP engine.
| Identifier | WestWitteringFiles\P\2July1926-September1926\ Scan128 | |
| Date | 4th September 1926 | |
| To R.{Sir Henry Royce} from HS{Lord Ernest Hives - Chair}/ACL. c.c. to BJ. Wor.{Arthur Wormald - General Works Manager} ✓ c.c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} ✓ c.c. to DA.{Bernard Day - Chassis Design} EY. ✓ c.c. to Oy ✓ ORIGINAL Hs{Lord Ernest Hives - Chair}/ACL1/LG4.9.26. X634 X4221 X5010 20 HP. CRANKSHAFT VIBRATIONS. Crankshaft vibrations at high speeds have always been manifest on the 20 HP. and it will be remembered considerable investigation has been conducted with regard to this at one time and another but no definite conclusions were arrived at as to the cause of the trouble. Although the vibration when at its worst on the critical speed is very severe, and if dwelt upon can result in breakage of the crankshaft - as demonstrated in previous tests - it was considered at the time that the danger of this happening in service was remote due to the critical speed occurring just above the speed of maximum output - in fact just after the valves started to bounce or about 70 m.p.h. Increase of speed resulting from higher compression or other improvements naturally accentuates the trouble, and even at the present time we occasionally experience erosion of the taper at the end of the crankshaft carrying the slipper drive which we have associated with this vibration. Again, increased pressures would be expected to augment 'roughness' of the engine at lower speed periods due to the lower harmonics. From consideration of this and profiting by the previous work, we have started upon a careful investigation with the aim of elucidating the cause and finding means of eliminating the trouble experienced. contd :- | ||