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 high-frequency vibration, wheel fight, and steering mechanisms.
| Identifier | ExFiles\Box 170\3\ img018 | |
| Date | 25th February 1936 guessed | |
| -6- (b) High Frequency. We now find on the Chrysler 6 an engine mount which is tuned so that the max. engine movement occurs at 530-550 cycles/min. It appears that in this car the engine is actually making a half-hearted attempt to balance out the high frequency wheel fight. We have not seen an engine which went so completely "crazy" at wheel-hop frequency since the earliest days of wishbone development work. After considerable testing on the drums we have the impression that the attempt to use the engine to balance out high frequency fight is not successful, but this is new to us and requires further investigation. (8) Two and Three Link Steering Mechanism. If, as we believe, the steering mechanism must have a certain degree of flexibility to escape wheel fight on wishbone jobs, then the two-link steering systems like Chrysler uses are at a disadvantage. On these cars there is no drag link and bell crank, which by their flexibility might reduce wheel fight, or in which we can put opposed springs to tune out the wheel fight. Although we introduced the bell crank steering on the S.L.A. jobs with wishbone suspension early in 1933, we never really understood why it gave us such a good steering, even with a solid drag link. By observing T.W., Chrysler, Cadillac 60 and Olds cars on the bump rig, the advantage of the bell crank is now quite clear - namely, that it is very difficult to make a bell crank stiff. Lying under the car one observes that when the T. end of the bell crank is shaking sideways 1/16" or more, at 560 cycles/min., the lower end of the pitman arm is not moving at all. We know from S.L.A. experience that springs in the tie rods, though they reduce wheel fight, have fatal disadvantages in causing the wheels to toe out when brakes are applied. This causes dangerous steering. The only softening effects which can be obtained in a two-link steering are flexibility in the pitman arm or rocker shaft. It appears that Chrysler have some flexibility in both these parts, and we are making tests to find out. | ||