An Introduction to Multi leaf and Parabolic Road Springs
A leaf spring, commonly referred to as ‘laminated/carriage spring’ is a simple type of spring, which is usually put into practice for suspension purposes in wheeled vehicles. It is one of oldest springing types, and is sometimes known as cart spring or semi-elliptical spring. Leaf springs aquire the shape of slightly curved lengths of carbon spring steel of rectangular cross section. The central point of the arch is fitted to the axel while tie-holes fitted at either ends are used for fastening to vehicle’s body structure. For heavy vehicles, the leaf springs can be manufactured from many leaves loaded up on the topside of each other in many layers, usually with increasingly smaller leaves. Besides the locating action, a leaf spring to a certain extent also performs springing as well as damping functions.
There are two ways to attach spring leaves to a vehicle; they can either be secured directly to the structure at both ends, or simply fastened at one end, normally the front with the other end attached via a bolt or pin, to a a small swinging arm. This arm is ideal for soft springiness, as it takes-up the ability of leaf springs to stretch when compressed.
History
Dating back to previous times, there were so many varieties of leaf springs, widely known as full elliptical springs with two eyes to hold the bushings attached at their ends. They were actually fastened to the structure at the top central point of the upper curve, while the center at the bottom was connected to live suspension modules such as a solid font-axle. Other suspension modules like trailing arms would be required for the layout, but not for semi-elliptical leaf springs that used a lower arc. As far as Quarter Elliptic springs were concerned, they carried the thickest parts of leaves stack attached to the rear tends of shorter leaf framework with the other free end fixed to the differential. The Ford Model T, as an instance of non elliptic leaf spring, carried more than one springs over its gap area that were arched in the shape of yoke. As an alterative to shock absorbers or dampers, several manufacturers started laying non-metallic sheets in the middle of metal-leaves such as wood.
Leaf-springs were widely employed on automobiles up to the year of 1970, but after that when a move to front-wheel drive occurred, manufacturers started using Coil springs instead on more classic suspension designs. However, leaf-springs are still utilized in HCVs (heavy commercial vehicles) like railway carriages, SUVs and trucks and vans, just because they have the capability to spread out the force more widely on the chassis of vehicle, whereas coil-springs transmit it to single point. Contrasting to coil springs, leaf-springs can also locate rear-axles, doing away with the need for attaching trailing arms and Panhard rod (a component of car’s suspension system which gives lateral position of the axle), and thus saving cost as well as weight in simple live-axle rear suspension system.
Parabolic Leaf Springs are another contemporary implementation, and comes with a design featured by fewer leaves, each having a varying thickness from central points to ends, following a ‘parabolic arc’. There is no need of “inter leaf friction pads” in this design, so there is contact only between springs at the central point (where the axle is attached) and at the ends. In addition to weight-saving, the key benefit of parabolic leaf spring is its huge flexibility that improves the vehicle’s ride quality, approaching to that of coil-springs.
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About Multi-leaf & Parabolic Road Springs
