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).
Letter from Cadillac discussing steering difficulties and wobble characteristics in various suspension types.
| Identifier | ExFiles\Box 170\3\ img011 | |
| Date | 26th February 1936 | |
| Og File CADILLAC MOTOR CAR COMPANY DETROIT, MICHIGAN CADILLAC AND LASALLE MOTOR CARS February 26, 1936. W. A.{Mr Adams} Robotham, Esq., Rolls-Royce, Limited, Derby, England. Dear Rm{William Robotham - Chief Engineer}: When Day and Grylls were over we discussed at length the steering difficulties of the P III and several of our own cars. A thought just occurred to me which may excite comments from you of a helpful nature. We have isolated here on the bump rig, - using various cam-shape and exciting frequencies - two very definite varities of wheel fight as produced by road bumps, the one occurring about 400 a minute and the other about 550. The low frequency fight is a close relative of low speed wobble and the high frequency of shimmy. The two above varities occur to some extent on all types of suspension but all the Dubonnet's show an emphasis on the low frequency variety and all the wishbone types, also all plain axles, show an emphasis on the high frequency. This is what one would expect from consideration of the swinging masses and natural wobble frequency of the two forms of suspension. Now I recall that about twelve years ago Hs{Lord Ernest Hives - Chair}, in investigating steering on the early 20 hp (I believe) formed the opinion that a steering mechanism should be "tuned" to give a definite low speed wobble at say 18 mph and then enough friction should be added to damp the wobble out. In such cases the steering was free from wheel fight throughout the range. Everything we have done since seems to confirm his general ruling, even with such vastly different front suspensions as we use today. | ||