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).
Effects of shackle inclination on suspension stiffness and potential modifications.
| Identifier | ExFiles\Box 43\2\ Scan120 | |
| Date | 5th April 1926 | |
| Oy2-E-4526 -2- April 5, 1926. (2) b. The shackle inclined at 21.1° (as on the Phantom) we find increases the stiffness in the first inch a further 10-1/2%. Of this we find 1-1/4% due to the drop in the front shackle pin from the swinging of the shackle and 9-1/4% due to the horizontal tension in the spring. The total stiffening effect from the above two causes is 18% in the range from flat to 1" negative and 34% in the range from 1" negative to 2" negative. Taking the initially stiffer Phantom spring as against the present Springfield standard the increased stiffness in the first 1" is 35-1/2%. In the second 1" it is over 50%. (3) The effect on the full range of suspension from 2" positive to 2" negative is shown on the attached chart which is taken from tests on the Olsen spring test machine. The figures from the tests and confirming calculations for the drop in centre and for the horizontal tension effects are given in attached supplement. (4) We are wondering whether the front shackle is inclined forward on the Phantom in order to reduce a forward thrust tending to resist tire friction and braking effects, and keep the rear shackle pin pulled forward to avoid rattles. If so it would seem desirable to modify the front spring so that even under the horizontal tension and with the wide clip it would have a stiffness corresponding to 3-1/2" or 4" deflection under normal load. Yours very truly, MO/E | ||