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).
Analysing the causes of transmission and other engine vibrations.
| Identifier | ExFiles\Box 178\3\ img154 | |
| Date | 5th May 1932 | |
| HS.{Lord Ernest Hives - Chair} E.{Mr Elliott - Chief Engineer}) FROM R.{Sir Henry Royce} DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer}) (At Le CanadelHenry Royce's French residence.) C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} RG.{Mr Rowledge} EP.{G. Eric Platford - Chief Quality Engineer} x5310. x634. TRANSMISSION, & OTHER VIBRATIONS. ("HEREIN LIES A TALE".) I thank HS.{Lord Ernest Hives - Chair} and EP.{G. Eric Platford - Chief Quality Engineer} for their memos. I regret I did not remember the whole history. HS{Lord Ernest Hives - Chair}/GRY.{Shadwell Grylls} did extremely well, and we may get a little deeper by further study, and obtain something very useful out of the trouble. The first thing that struck me was that it occurs at about half period 6 per rev., roughly 6 times 2400 - say 12/14000. Now if this is so it suggests that the swing (torsional) of the crankshaft may be 100 times its ordinary deflection due to the variation of kinetic energy in the pistons (i.e. when not on any period octave or harmonic.) This should be measurable (Mr.Lovesey did something 3 or 4 yrs. back.) It will be realised that this vibration is heard on cars with engines - (1) worn free, (2) in which the oil has become thin through heat, etc. shewing decreased damping, especially in the engine, and may tell us two very important things which have been only partly appreciated: (a) Our dampers (crankshaft) are not nearly effective enough at this half period, and can be made much more so probably if dry friction and heavier damper wheel are used, or centrifugal loading. (b) Except for the torque reaction at slow speed and the flywheel wobble at its speed, much of our engine roughness (P.2.) is probably due to these periods, and has forced us back, and beyond, our soft mounting of P. 1. to the softer and more effective mounting of P. 2. In other words we may do much to make a better car if we can keep the crankshaft within a smaller range of torsional swing, which swing must result in a variation of angular velocity of the flywheels and a reaction upon the engine mass, causing the whole car and frame to vibrate, as was experienced with P. 2., when it had sandwiched feet. It also results in a tendency to put the transmission in a state of torsional vibration and rattle, as experienced on the 25HP. R.{Sir Henry Royce} | ||