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 determine the effect of the amount and position of balance weights on flywheel vibration.
| Identifier | ExFiles\Box 181\M13\M13.2\ img086 | |
| Date | 27th August 1931 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} c. Sg.{Arthur F. Sidgreaves - MD} c. Mor. E.{Mr Elliott - Chief Engineer} c. Ds. EV.{Ivan Evernden - coachwork} Hs{Lord Ernest Hives - Chair}/Gry{Shadwell Grylls}/1/AD27.8.31. ORIGINAL. 25 HP. BALANCE WEIGHTS. 85010. X634. We have carried out tests to find out the effect on the flywheel vibration at 3100 R.P.M. or 42 M.P.H. in 3rd. gear of the amount and position of balance weights. The experiments were done on 18-GIV car, the engine being diamond mounted and fitted with a 2" pin crankshaft. We estimate the out of balance per crank of this shaft as 6.20 lbs.ins. and of the big end 2.88 lbs.ins. giving a total of 9.08 lbs.ins. Subsequent calculations on our full balance weights show them to be about 5% too small. The car fitted with no weights had a distinct flywheel vibration and when 12 full weights were fitted (which reduced the half torsional speed from 51 to 40 M.P.H.) the flywheel vibration could only just be detected when the engine was very hot. One would say that a customer would not notice it. We then took off 6 weights, the remaining 6 being equivalent to R's eight weight, 6 unit scheme. These 6 weights were tried in 3 positions, namely on webs 1, 3, 6, 7, 10 and 12; then 2, 4, 6, 7, 9 and 11, and lastly 1, 4, 6, 7, 9 and 11. In all the positions the half torsional period was at 44 - 45 M.P.H. In the first position with a weight immediately next to the flywheel, the engine was still very smooth, the flywheel vibration being very little worse than with all 12 weights. In the second position with no weight near the flywheel and also the weight on No.5 crank remote from the flywheel, the vibration had returned and was as bad as with no weights at all. We therefore carried out the test in the third position i.e. with a weight next to the flywheel but with no weight helping No.6 journal. This we found to be as good as the first position, showing that to eliminate the flywheel period the important fact is to have a balance weight next to the flywheel on No.12 web. We next reduced the 6 weights in the third position to balance the crankshaft only and a certain amount of vibration became apparent. Therefore, either R's eight weight scheme or the Chrysler scheme balancing crankshaft and big end should overcome the flywheel vibration, the latter being better for the bearings but necessarily being of greater inertia than R's scheme. Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} | ||