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 spring stiffness, horizontal tension, and twisting effects on vehicle ride comfort.
| Identifier | ExFiles\Box 43\2\ Scan137 | |
| Date | 28th April 1926 | |
| -2- The horizontal tension from the original inclined shackle is about 250 to 300 lbs. This produces an appreciable change in the spring stiffness, but it would seem that 20 lbs. horizontal thrust could not make any noticeable change. We have found that even a slight twisting effort applied to the front axle in such a direction as to produce an S-bend in the front springs, will produce an uncomfortable joggle in the rear seats. With front tires removed (to eliminate their "bounce") a twist of about 60 lbs.feet applied with a frequency of 250 per minute (approx.) will produce a noticeable joggle in the rear. But there is no such twisting effect on the car. The hubs are practically in line with the top-plate of the springs, and the resistance of the tires (assuming frictionless bearings in the hubs) can only appear, therefore, in the top plate of the spring as a horizontal force of say 20 lbs. (i.e. there can be no S-bending effect in the springs till the brakes are applied.) With even slight road irregularities this average force of 20 lbs. may vary enormously from say minus 180 lbs. to plus 220 lbs., and when the spring has negative camber these varying horizontal tensions and compressions would cause rapid variations in the apparent stiffness of the half of the spring which was not shackled. These variations in stiffness might be in the order of plus or minus 6%. This might give rapid variations of plus or minus 6% in the rate of change of acceleration on a bounce. But I cannot see that there should be any appreciable difference in these effects from shackling at the front or the rear. Unless possibly the rigid attachment to the frame at the rear, compared with the relative flexibility of the front horns, has something to do with it. Oy. MO/E | ||