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 steering and suspension systems, focusing on issues like wheel fight, wobble, and vibration frequencies.
| Identifier | ExFiles\Box 173\4\ img239 | |
| Date | 9th March 1936 guessed | |
| (sheet 2) Dubonnet jobs for example all show the first type but practically none of the second. The moment of inertia about the kingpin is doubled on these jobs. All Dubonnet jobs are free from high frequency wheel fight on the road though they will wobble if the steering friction is inadequate. (3) The chief advantage of bell crank steering on wishbone jobs is the difficulty of making a stiff bell crank. One can actually see the bell crank performing its function as a spring in the steering mechanism by lying under the car while it is running with the wheels hopping on the drums. The wishbone steerings which are freest from wheel-fight all show low speed fight on the drums, though not on the road. (4) Toe in errors as the wheels go up and down have no effect whatever on wheel fight. The most perfect geometry we have ever produced was the worst for flight. Steerings with toe in errors three times as great as we now use may be made free of wheel fight by "tuning" them till the wheel flap frequency is below 500 cycles a minute. (5) The steering boxes with straddle mounted rocker shafts are about twice as stiff for loads at the end of the pitmar arm as our older steerings with overhung rocker shaft. They appear to promote wheel-flight for this reason. They are too rigid. I can see that our information is incomplete, and because you say that you have escaped wheelfight by stiffening the rocker shaft, I am appealing to you for help. I can see that it might be possible to so stiffen a steering hook-up that the natural frequency of wheel flap was actually raised to 800 a minute or more and I imagine (although I have never seen such a steering) that it would be free of both kinds of wheel fight. I should immensely appreciate it if you or Rm{William Robotham - Chief Engineer} would write or even cable me exactly what you have done by stiffening the rocker shaft. Have you previously suffered from a 400 a minute fight and lifted up the wheel flap frequency into the quiet zone between 400 and 550, or have you previously suffered from a 550 | ||