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).
Comparison of the performance and reliability of Studebaker and B.80 dampers.
| Identifier | ExFiles\Box 124\1\ scan0221 | |
| Date | 24th July 1939 | |
| -3- Rm{William Robotham - Chief Engineer}/JRS.8/MH.{M. Huckerby}24.7.39. In order to compare the Studebaker and B.80 dampers, the best results obtained with each, i.e. Studebaker damper .0240 slug ft.² inertia and 55-60 rubbers and B.80 damper .0485 slug ft.² inertia with a stiffness of 318 lbs.ft.degree are plotted on Fig. 7. At the higher speeds, especially above 3500, there is very little difference between the two dampers, but below this speed the amplitudes are larger with the Studebaker, at some places considerably larger. The peak at 2000 r.p.m. in the Studebaker resonance curve is a first order vibration of the low frequency mode and quite apart from the fact that this frequency would be at a much lower speed in practice, the accelerations involved are much less than those for a similar amplitude occurring at resonance with the higher frequency vibration. This follows from the fact that the amplitude of acceleration due to vibration is w²a, where 'w' is the angular velocity of the vibration and equals 2 x vibration frequency and 'a' is the vibration amplitude. Thus one degree amplitude due to the low frequency vibration produces only the same acceleration as 1 x 2000²/12000² i.e. as .028 degree amplitude at the higher frequency, assuming 2000 and 12000 vibrations per minute as the approximate natural frequencies of the two modes of vibration. As the Studebaker damper is very little inferior to the B.80 which has a moment of inertia of .0485 slug ft² and a weight of 11 lbs. 10 ozs. On the score of reliability the advantage is heavily with the Studebaker which has successfully completed an endurance run of 50 hours when the B.80 damper was found to have seized and many springs broken after 18 hours running. Also, at that time the Studebaker damper had not been tuned to the B.80 and therefore, the best setting could not be given, and when the actual rubbers used were afterwards tested they gave results similar to the 75-80 rubbers in Fig.6. | ||