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).
Technical letter to G.W. Hancock discussing crankshaft periods, flywheel inertia, and timing gear noise reduction.
| Identifier | ExFiles\Box 82\3\ scan0256 | |
| Date | 10th May 1935 | |
| G.W. Hancock, Esq., Hotel de France, Chateauroux, Indre, FRANCE. /200n Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}14/KW.10.5.35. Many thanks for your notes. The elimination of your crankshaft periods by raising the damper load is embarrassing because we believe that you did this earlier in the test and did not get rid of the period at 3750 r.p.m. Our view at present is as follows. As we stiffen up the crankshafts we reduce the amplitude of the period and increase its frequency. This means that there is less total movement at the damper end over which the damper can operate. Therefore more damping has to be supplied in the same time. We are at present working at about the limit, and really want a bigger damper having more flywheel inertia and more cotton duck with a larger radius. The high compression head of course contributes to the trouble because it increases the punch which produces the period. Another point we have discovered is that if we lighten the flywheel too much, on a crankshaft period it begins to move as well as the slipper wheel. In the extreme of course the slipper wheel might remain stationary and the flywheel move entirely, in which case the slipper wheel will be rendered quite useless. We have therefore got to have a minimum inertia on the flywheel, and we are finding out what this is. Actually we think your flywheel is O.K. if we only get the right crankshaft damper. We are finding that we can cut a lot of timing gear noise out by putting an asbestos cover over the timing case. We did some experiments on Peregrine which showed that the timing case had very little effect on the oil temperature. We should, however, like you to confirm this on 5-B-IV. You could use ordinary pulped asbestos of the type employed for covering steam pipes. P.T.O. | ||