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).
The stiffening effects of a wide axle pad and inclined shackle on springs.
| Identifier | ExFiles\Box 43\2\ Scan140 | |
| Date | 8th May 1926 | |
| Oy1-E-5826 -2- May 8th, 1926. I. Stiffening effect of wide axle pad, inclined shackle etc. a.{Mr Adams} Our note that the Phantom springs were 13% stiffer than our own referred to the fact that the Phantom like the front-brake Silver Ghost has springs with 2.6 inches free camber, run .5 negative, or 3.1 inches total deflection, while we still have springs with 3.5 inches camber run flat. This is the 12-1/2% increase to which Mr. Royce refers. b. Wide axle pad. We find that whereas the flat load is slightly reduced with the wide axle pad, the stiffness, or rate of change of load, is increased especially in the range of negative camber. We suggest that since the frequency of oscillation depends on the stiffness (or rather on the ratio of stiffness to load), the "attitude" of the spring on the loaded car (which will be practically the same with a wide or narrow pad) is not an indication of the riding quality to be expected. By clamping down to the wide axle pad the free camber of the spring is reduced actually about 3/8". c. Inclined shackle. In the same way the inclination of the shackle, while it does not affect the load which the spring will carry when flat, increases the stiffness of the spring at all deflections after the first two inches (approx.). Taking as an example a spring of 3-1/2 inches initial deflection, 310 lbs. per inch, and 40" working length, supported one end on a shackle inclined 20° to the vertical. (Shackle assumed long so that change in angle is neglected and only the effect of horizontal tension is considered):- Deflection from unloaded position. 1" 2" 3" Flat 4" 5" 6" Spring Change in load for this deflection. (a) Spring on rollers both ends. 310 310 310 310 310 310 lbs. (b) Spring shackled as above. 296 308 320 326 343 357 lbs. | ||