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).
Damping chassis motion, rebound, and front axle control, referencing road test data.
| Identifier | WestWitteringFiles\V\October1930-February1931\ Scan382 | |
| Date | 29th October 1928 | |
| (2) DAMPING OF SLOW CHASSIS MOTION AT HIGH SPEED. It appears to us that with a damper of the uniform load type whenever the velocity of the axle vibrations is greater than that of the chassis on its springs the damping of the chassis is to some extent destroyed. The attached print shews curves illustrating this which are based on road tests of suspension and dampers given in HS{Lord Ernest Hives - Chair}/RM{William Robotham - Chief Engineer}2/29.10.28. We also give chronograph curves (HS{Lord Ernest Hives - Chair}/RM{William Robotham - Chief Engineer} 29.10.28. sheet 2.) which appear to support the theory. Assuming that the axle vibration is maintained continuously it can be seen that the higher velocity of the axle predominates and the resulting damping alternates between opposing and assisting the motion of the chassis. We can see no satisfactory cure for this apparent loss of damping. Velocity pressure would be beneficial but has serious disadvantages in other respects. More tyre flexibility might help but there are of course practical limits to this already set. CONTROL OF REBOUND. With regard to the control of the rebound we suggest that rather than use the damper as the final check the spring shackle should be shortened slightly so that it straightens out at say 2" before the free position of the spring. Or the shackle could be left unaltered and a substantial stop (adjustable by Works to provide for chassis tolerances) could be fitted on the underside of the dumb iron. All the pieces affected are very strong and the rear end of frame has considerable spring. FRONT AXLE CONTROL. The placing of the damper on the outside of the frame for the axle control makes an A.{Mr Adams} symmetrical bracket essential and even then there will be difficulty in getting a lever as long as 7.5". At 4.5" rebound (free position with new springs) there is a discrepancy of .575" between the axle and damper. We have not yet investigated the possibility of giving way to the springs without spoiling the control. We are hoping that the sliding joint may only rarely need to If much work is required from it some scheme with a link seems DA{Bernard Day - Chassis Design}/HDY.{William Hardy} | ||