RELATION OF SPRING-SUSPENSION TO RIDING-QUALITIES ¹ 260045

This is an analysis of spring action such as occurs on an automobile driven on a highway having bumps and depressions, a discussion of the requirements of spring-recoil checking devices, and an account of experiments made with a car on which different combinations of springs of various lengths and flexibilities were used and the distribution of weight on the frame was varied. Spring action was analyzed previously by means of small models that simulated the suspension and weight distribution of a motor-car. The compression and recoil action of springs and their relation to the travel of the car as represented by the time element are discussed. Although the more-flexible springs absorb the bumps better, it is shown that their recoil is greater unless it is damped by a shock-absorbing device.

The limitations of shock-absorber or recoil-check design are pointed out and the author asserts that a device that never allows the springs to reach their normal position stiffens the springs and increases the riding-discomfort. Obviously, the more the springs are tied-down the stiffer they become and the less capable of depression when striking a bump. That interleaf friction can be a satisfactory means of taking-up spring recoil is an erroneous belief that must be discarded, is asserted, and the greatest improvement in riding-comfort that can be made in the average car by the owner at reasonable expense is to grease the springs well, put on spring covers and automatic lubricators, and fit shock-absorbers that resist the spring recoil but do not make the springs stiffer on the bumps.

To check conclusions arrived at from analysis and casual observations, experiments were made with a car on the road. These are illustrated and described. As a result of the study and the limited number of road experiments made up to the time of writing, the author concludes that

1. (1)
   Front springs must be shackled at the front end or so mounted that full spring-travel can occur without changing the direction of the front wheels; heavier master leaves may be required for safety, and one or two rather heavy leaves above them will make the axle stable under application of four-wheel brakes
2. (2)
   Longer front springs must be used and room for spring action must be increased to at least 4 in.
3. (3)
   Internal friction of the springs must not exceed 10 per cent of the normal weight they support, and if leaf springs are used they must be lubricated
4. (4)
   Efficient devices that will check the spring recoil at the proper time and not restrict the yield of the springs on bumps or when the wheels drop into road depressions must be fitted
5. (5)
   The procedure in developing the spring-suspension of a car should be changed; the tests with new models prior to production should be made with springs of various lengths and flexibilities and with various distributions of weight on the frame. With different body-models it may be necessary to use springs of different characteristics
6. (6)
   Every effort should be made, under present limitations of passenger-car design, to locate the weight over the axles rather than between them