Leaf spring


Leaf spring

Originally called "laminated" or "carriage spring", a leaf spring is a simple form of spring, commonly used for the suspension in wheeled vehicles. It is also one of the oldest forms of springing, dating back to medieval times.

Sometimes referred to as a semi-elliptical spring or cart spring, it takes the form of a slender arc-shaped length of spring steel of rectangular cross-section. The center of the arc provides location for the axle, while tie holes are provided at either end for attaching to the vehicle body. For very heavy vehicles, a leaf spring can be made from several leaves stacked on top of each other in several layers, often with progressively shorter leaves. Leaf springs can serve locating and to some extent damping as well as springing functions.

A leaf spring can either be attached directly to the frame at both ends or attached directly at one end, usually the front, with the other end attached through a shackle, a short swinging arm. The shackle takes up the tendency of the leaf spring to elongate when compressed and thus makes for softer springiness.

History

There were a variety of leaf springs, usually employing the word "elliptical". "Elliptical" or "full elliptical" leaf springs referred to two circular arcs linked at their tips. This was joined to the frame at the top center of the upper arc, the bottom center was joined to the "live" suspension components, such as a solid front axle. Additional suspension components, such as trailing arms, would be needed for this design, but not for "semi-elliptical" leaf springs as used in the Hotchkiss drive. That employed the lower arc, hence its name. "Quarter-elliptic" springs often had the thickest part of the stack of leaves stuck into the rear end of the side pieces of a short ladder frame, with the free end attached to the differential, as in the Austin Seven of the 1920s. As an example of non-elliptic leaf springs, the Ford Model T had multiple leaf springs over its differential that were curved in the shape of a yoke. As a substitute for dampers (shock absorbers), some manufacturers laid non-metallic sheets in between the metal leaves, such as wood.

Leaf springs were very common on automobiles, right up to the 1970s, when the move to front wheel drive, and more sophisticated suspension designs saw automobile manufacturers use coil springs instead. However, leaf springs are still used in heavy commercial vehicles such as vans and trucks, SUVs, and railway carriages. For heavy vehicles, they have the advantage of spreading the load more widely over the vehicle's chassis, whereas coil springs transfer it to a single point. Unlike coil springs, leaf springs also locate the rear axle, eliminating the need for trailing arms and a Panhard rod, thereby saving cost and weight in a simple live axle rear suspension.

A more modern implementation is the parabolic leaf spring. This design is characterised by fewer leaves whose thickness varies from centre to ends following a parabolic curve. In this design, inter-leaf friction is unwanted, and therefore there is only contact between the springs at the ends and at the centre where the axle is connected. Spacers prevent contact at other points. Aside from a weight saving, the main advantage of parabolic springs is their greater flexibility, which translates into vehicle ride quality that approaches that of coil springs. There is a trade-off in the form of reduced load carrying capability, however.

ee also

* Corvette leaf springs
* Coil spring


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Look at other dictionaries:

  • leaf spring — leaf′ spring n. mac a long, narrow, multiple spring composed of several layers of spring metal • Etymology: 1890–95 …   From formal English to slang

  • leaf spring — ☆ leaf spring n. a spring built up of strips of metal: see SPRING …   English World dictionary

  • leaf spring — A length of flat spring steel plates bent in an arch usually with curled ends to allow mounting to the frame. Two holes are drilled in the center to mount a u bolt shackle which surrounds the axle. Some applications need only one leaf spring; but …   Dictionary of automotive terms

  • leaf spring — noun long narrow spring consisting of several layers of metal springs bracketed together • Hypernyms: ↑spring * * * noun : a spring made of superposed strips, plates, or leaves * * * a long, narrow, multiple spring composed of several layers of… …   Useful english dictionary

  • leaf spring — noun A spring in the form of a curved length of steel, used in the suspension of wheeled vehicles. Syn: carriage spring, cart spring, laminated spring, semi elliptical spring …   Wiktionary

  • leaf spring — a long, narrow, multiple spring composed of several layers of spring metal bracketed together: used in some suspension systems of carriages and automobiles. See illus. under spring. [1890 95] * * * …   Universalium

  • leaf spring — /ˈlif sprɪŋ / (say leef spring) noun a spring made from a long piece of spring steel or several layers bracketed together and attached at each end with the axle located in the centre; traditionally used for carriages …   Australian English dictionary

  • leaf spring — noun Date: circa 1893 a spring made of superposed strips or leaves …   New Collegiate Dictionary

  • leaf spring — noun a spring made of a number of strips of metal curved slightly upwards and clamped together one above the other …   English new terms dictionary

  • Corvette leaf spring — Since 1963, transverse leaf springs have been an integral part of the suspension of GM s Chevrolet Corvette. This article concerns the practical differences between leafs and coils, popular misconceptions, and the design considerations that led… …   Wikipedia


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