Subject: Automobile Engineering

Topic: Suspension, Wheels & Tires

Difficulty: Medium

Helper spring:
Helper spring are provided on many commercial vehicles in addition to main leaf spring. They allow for a wedge range of loading. When the vehicles is only lightly loaded, there helper springs do not come into operations. But as the load is increased they take their share of load. Generally helper spring are used on rear suspension only. Fig 2.1 shows the use of helper spring. When the load on the road wheel increases so much so as to deflect the main spring to such an amount that ends of the helper string touch the special brackets fixed to the side member, the helper spring comes into operation.

Coil Springs:
The coil springs are used mainly with independent suspension, through they have also been used in conventional rigid axle suspension as they can be well accommodated in restricted spaces. The energy stored per unit volume is almost double in the case of coil spring than leaf spring. Coil spring do not have noise problems , nor do they have static friction causing harshness of ride as in case of leaf spring The spring takes the shear as well as bending stress. The coil springs cannot take torque reaction & side thrust, for which alternative arrangement have to be provided. Fig:2.2 shows coil spring.