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).
Technical memo discussing methods for measuring spring rates and the effects of various components on wheel rate.
| Identifier | ExFiles\Box 154a\2\ scan0303 | |
| Date | 17th May 1940 | |
| -2- Oy.7/D/May,17.40. I have passed on your remainder method for finding distortion effects to Henry Fuchs who thinks it is a very good idea and one which will give very good approximations without analysis. He is going to use it as a check on analysis at the next opportunity. In order to avoid as many sources of error as possible, the rate should be measured at the outer wishbone pin either on the car or on a rig, and compared to the calculated rate for this position. From there on out to the tire contact the calculations are straight-forward and admit of little error. It does not appear satisfactory to Henry or me to set up empirical "ground rules" for rate at the wheel which ignore the effect of load. Your remark that you have no means of actually measuring spring rates is almost unbelievable. Surely, you have an Avery or Olsen machine for load testing leaf springs? Incidentally, what wheel rate changes do you get from turning the spring around on its seat? We have found as much as 12-15 lbs. per inch variation on springs which were not pushing coaxially. Which is one reason for preferring the Chevrolet cheaper spring construction with the chopped off bottom coil and corresponding lower pan which will not allow the spring to turn. I do not think you will find much change in rate from deterioration of the rubber bushings. 15-25 lbs. per inch at the outer wishbone pin for all the rubber bushings including those on the stabilizer links is reasonable. Oy. | ||