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 to eliminate timing gear rattles on a 25 HP engine.
| Identifier | ExFiles\Box 181\M13\M13.2\ img140 | |
| Date | 30th November 1931 | |
| To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} c. to Sg.{Arthur F. Sidgreaves - MD} Mor. c. to E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} c. to BY.{R.W. Bailey - Chief Engineer} TIMING GEAR RATTLES X634. X5070. With the new high lift camshaft on the 25 HP and the stronger valve springs to bounce at 3900 R.P.M., we have encountered difficulties due to rattles in the timing gears. With the low inertia type of spring drive we have only two variables for eliminating the rattle; namely the rating of the spring drive and the damping of the slipper flywheel. Previous tests had shewn that at least 14 lbs. damping at 17¼" radius is necessary to overcome the half torsional period. With this amount of damping we have tried various driving loads. All loads are reckoned at 17¼" radius to bring the drive on to the stops. With 8 lbs. there was a very bad rattle at 250 R.P.M. and another at 800 R.P.M. With 11 lbs. driving load, both rattles were less bad. With 19 lbs. the low speed rattle had vanished and the one at 800 is very slight. With 22 lbs. the rattle was worse. The optimum condition is therefore :- Driving load on the stops of 19 lbs. at 17¼" radius. Damping load of 15 lbs. at 17¼" radius. We also tried lower damping loads which decreased the rattles but not by a method we can employ, owing to the torsional period. Nor was a solid drive an improvement as this caused a bad rattle at 1600 R.P.M. Since this trouble has only arisen with the advent of the new camshaft, we are sending you these results in case you wish to modify the camshaft drive on J.111 by incorporating a spring drive. Hs{Lord Ernest Hives - Chair}/H.Grylls. | ||