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【正文】 oach itself was sometimes called a thoroughbrace)AutomobilesAutomobiles were initially developed as selfpropelled versions of horse drawn vehicles. However, horse drawn vehicles had been designed for relatively slow speeds and their suspension was not well suited to the higher speeds permitted by the internal bustion engine.In 1903 Mors of Germany first fitted an automobile with shock absorbers. In 1920 Leyland used torsion bars in a suspension system. In 1922 independent front suspension was pioneered on the Lancia Lambda and became more mon in mass market cars from 1932.[2]Important propertiesSpring rateThe spring rate (or suspension rate) is a ponent in setting the vehicle39。s weight. This allows the vehicle to perform properly under a heavy load when control is limited by the inertia of the load. Riding in an empty truck used for carrying loads can be unfortable for passengers because of its high spring rate relative to the weight of the vehicle. A race car would also be described as having heavy springs and would also be unfortably bumpy. However, even though we say they both have heavy springs, the actual spring rates for a 2000lb truck are very different. A luxury car, taxi, or passenger bus would be described as having soft springs. Vehicles with worn out or damaged springs ride lower to the ground which reduces the overall amount of pression available to the suspension and increases the amount of body lean. Performance vehicles can sometimes have spring rate requirements other than vehicle weight and load.Mathematics of the spring rateSpring rate is a ratio used to measure how resistant a spring is to being pressed or expanded during the spring39。s Law. Briefly, this can be stated aswhereF is the force the spring exerts k is the spring rate of the spring. x is the displacement from equilibrium length . the length at which the spring is neither pressed or stretched. Spring rate is confined to a narrow interval by the weight of the vehicle,load the vehicle will carry, and to a lesser extent by suspension geometry and performance desires.Spring rates typically have units of N/mm (or lbf/in). An example of a linear spring rate is 500lbf. A nonlinear spring rate is one for which the relation between the spring39。lbf force, the second inch exerts an additional 550lbf), the third inch exerts another 600lbf). In contrast a 500inches will only exert 1500s shear modulus (., about 12,000,000 lbf/in178。lbs/inch, if you were to move the wheel 1inches, the lever arm ratio would be to 1. The wheel rate is calculated by taking the square of the ratio () times the spring rate. Squaring the ratio is because the ratio has two effects on the wheel rate. The ratio applies to both the force and distance traveled.Wheel rate on independent suspension is fairly straightforward. However, special consideration must be taken with some nonindependent suspension designs. Take the case of the straight axle. When viewed from the front or rear, the wheel rate can be measured by the means above. Y
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