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).
Tests on a Big Bentley crankshaft damper and spring drive to eliminate gear rattle.
| Identifier | ExFiles\Box 136\1\ scan0295 | |
| Date | 13th December 1933 | |
| COPY. To E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/FJH.{Fred J. Hardy - Chief Dev. Engineer} c. By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/FJH.{Fred J. Hardy - Chief Dev. Engineer}3/KT.13.12.33. BIG BENTLEY CRANKSHAFT DAMPER & SPRING DRIVE. TO LBC.3602. In this damper the spring drive of the crankshaft pinion is independent of the damping of the slipper flywheel. The pinion has very little inertia as it is not connected to the flywheel. One object of this arrangement is the elimination of gear rattles either in conjunction with the balancing cam or, if possible, without the latter. As first received the driving springs were as on the present standard damper and the pinion damping spring was to B.1019. The calibration was as follows :- Pinion Driving Load (either direction) 17.5 lbs at 17.5 ins. Pinion Damping. 0.5 lbs at 17.5 ins. Slipper Damping. 14.75 lbs. at 17.5 ins. The damper was fitted to an engine (Unit B.7) which, with the standard damper and balancing cam, had a bad gear rattle period at between 700 and 800 r.p.m. The gears had between 0.004" and 0.006" of backlash between the crank pinion and camwheel and the camwheel and dynamo pinion. It is certain that a very large proportion of this rattle occurred between the dynamo and camwheel. Whether there was any rattle between the camwheel and crank pinion is not certain. The rattle occurred only with the engine under load and was much less severe with the ignition fully retarded. With the new damper as received and run with the balancing cam the gear rattle period at 750 r.p.m. was entirely absent. There was less general noise from the gears at speeds over 2000 r.p.m. There was a slight insipient rattle at all speeds up to 1500 r.p.m. under load and with the ignition fully advanced. This noise was not at all serious as a rattle but was taken as an indication that one gear wheel was over running another. | ||