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).
Analysis of engine and crankshaft vibrations, their causes, and potential solutions for various car models.
| Identifier | ExFiles\Box 137\4\ scan0188 | |
| Date | 29th January 1931 guessed | |
| (2) The Japan3. designs did not seem to be shaping well, and other troubles of P. 2. made me think that the directors would like me to return, but I am glad they do not because I can still do a little to help, and might not be any more use if I returned because I have so much pain in the cold weather. I am more satisfied that we shall be doing some good to the engine (Japan) now we are putting the gears back and doing away with the spring drive, but we shall still need the damper which now being separate from the half time drive is much simpler. It has only lately been discovered by Derby that the flywheels are not steady at a certain high speed, and naturally it follows they will cause vibrations. Calculations shew that they would not whirl in the ordinary way (like the propeller shaft) but having the disturbing force effect of the crankshaft they seem to get into a state of vibration, which we anticipated in our single cyl. unit had we designed it with two bearings only and a very large overhanging flywheel. Now it strikes me very forcibly that we have lately run into this more often than formerly because of the increase in engine revs. due to more powerful engine, lower gear, and better roads. I am sure that our P. 2. is better than P. 1. or Silver Ghost, but the engine revs. are often 20% higher than formerly and this is the real reason this particular trouble is so much more often met: in other words the modern cars - (1) more often have the engine revs. low giving torque reaction vibration. (2) more often have the engine revs. very high, resulting in crankshaft vibrations. Since we now know that the crankshaft sets the flywheel vibrating we can cure it at least to some extent, but previously these vibrations were thought to be from other sources, or causes, which were difficult to treat. We cannot hope to get a crank-chamber that will not deflect sufficiently to set the flywheel vibrating providing we reach its natural period, but we think that we can fairly easily increase the periodicity, and we have done so on 'China' (late last Autumn - also needed through increased engine revs.) If however we are not careful we shall get transmission vibrations due to the uneven turning moment of the 6 cyl. engine so that we have to do a little to many things, all of which contribute. They are :- | ||