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 vibration test results concerning damper settings, inertia, stiffness, and backlash on crankshafts and camshafts.
| Identifier | ExFiles\Box 124\1\ scan0220 | |
| Date | 24th July 1939 | |
| -2- Rm{William Robotham - Chief Engineer}/JRS.8/MH.{M. Huckerby}24.7.39. The best setting was found for each by trial and error and Fig. 2 shows the amplitudes occurring. These curves show up clearly the low frequency vibration mentioned in Rm{William Robotham - Chief Engineer}/JRS.1/JH.22.4.39 especially the 1 1/2 order of this mode, which remains practically constant independent of the damper inertia and setting. In future tests it is proposed to eliminate this low frequency vibration by inserting a torsionally flexible coupling between the engine and the dynamometer, or, if this is not available to eliminate the effect of the low frequency vibration by taking curves with two or more sets of clutch centre springs of different stiffness. Fig. 3 shows curves taken from the crankshaft and camshaft with the best damper conditions from Fig.2, namely B.80 damper with .0485 slug ft² inertia and a spring constant of 318 lbs.ft.degree. The camshaft amplitude curve shows peaks at the same speeds as they occur in the crankshaft curve, indicating that the camshaft is excited by the crank. At the higher speeds the camshaft amplitude exceeds those imposed upon it by the crank and the accelerations involved mean that the loading on the teeth is actually reversing and the camwheel teeth are traversing the backlash. Fig.4 gives two camshaft amplitude curves with the same damper, one with the standard camwheel and one with a special camwheel having .020 backlash. The effect of the increased backlash is only slight. Fig. 5 gives the torsional stiffness characteristics of the Studebaker damper with rubbers having a durometer hardness of 35-40, 55-60 and 75-80. The mass moment of inertia of the Studebaker damper flywheel is .0246 slug ft². Vibration amplitudes were found for the damper employing each of the three sets of rubbers, and the results are shown in Fig. 6. The best overall results for this damper are found in the case of the 55-60 durometer rubbers. | ||