Bushing (isolator)From Wikipedia, the free encyclopedia

"Rubber bushing" redirects here. For the plant species, see rubber bush.

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A bushing or rubber bushing is a type of vibration isolator. It provides an interface between two parts, damping the energytransmitted through the bushing. A common application is in vehicle suspension systems, where a bushing made of rubber(or, more often, synthetic rubber or polyurethane) separates the faces of two metal objects while allowing a certain amount ofmovement. This movement allows the suspension parts to move freely, for example, when traveling over a large bump, whileminimizing transmission of noise and small vibrations through to the chassis of the vehicle. A rubber bushing may also bedescribed as a flexible mounting or antivibration mounting.

These bushings often take the form of an annular cylinder of flexible material inside a metallic casing or outer tube. Theymight also feature an internal crush tube which protects the bushing from being crushed by the fixings which hold it onto athreaded spigot. Many different types of bushing designs exist. An important difference compared with plain bearings is thatthe relative motion between the two connected parts is accommodated by strain in the rubber, rather than by shear or frictionat the interface. Some rubber bushings, such as the D block for a sway bar, do allow sliding at the interface between one partand the rubber.

Contents [hide]

1 Advantages and disadvantages2 Applications3 History4 See also5 References6 Bibliography

Advantages and disadvantages [edit]

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The main advantage of a bushing, as compared to a solid connection, is less noise and vibration are transmitted. Anotheradvantage is that they require little to no lubrication.

Disadvantages include:

Rubber bushings can deteriorate quickly in the presence of oils (e.g., motor oil, mineral oil) and extreme heat and cold.The flexibility of rubber also introduces an element of play in the suspension system. This may result in camber, caster, ortoe changes in the wheels of the vehicle during high-load conditions (cornering and braking), adversely affecting thevehicle's handling. For this reason, a popular aftermarket performance upgrade is the replacement of rubber suspensionbushings with bushings made of more rigid materials, such as polyurethane. Polyurethane bushings are also available formany vehicles with approximately the same characteristics[citation needed] as the manufacturers original bushings, but withgreatly increased durability.[citation needed] This is useful on vehicles that have a reputation for wearing out standard rubberbushings, but for which harder bushings with increased harshness of ride are not wanted.

Applications [edit]

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As shock mountsIn vehicles:

Anti-roll bar (US Sway bar) links and mountingsShock absorber mountings

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Double wishbone suspension assembliesGear stick for vehicles with a manual transmissionMost high-speed inline internal combustion engines are prone to torsional vibration of their crankshafts; the straight sixand straight eight engines being particularly prone to this problem due to their long crankshaft length. Althoughstraight eight engines faded from the marketplace in the 1950s, many straight six engines have and still do featurecrankshaft vibration damping utilizing rubber bushes. The 3,442 cc Jaguar XK 6-cylinder engine of 1948 and mostsubsequent versions of the ubiquitous Jaguar XK engine used a proprietary Metalastik vibration damper to protecttheir crankshafts from potentially damaging torsional vibrations. To quote William Heynes,[1] "The Metalastik damperconsists of a steel plate to which is bonded, through a thick rubber disk, a malleable iron floating weight. Variations ofthe weight, rubber volume and mix, give these dampers a very wide field over which they can operate."

In skateboards, bushings enable the tilting of the trucks, thus allowing the board to turn.In fastening, bushings are also used to transfer loads from a fastening to a much larger area in the underlying structure,the object being to reduce the strain on individual fibers within the underlying structure. (See also grommet.)

History [edit]

Charles E. Sorensen credits Walter Chrysler as being a leader in encouraging the adoption of rubber vibration-isolatingmounts. In his memoir (1956), he says that, on March 10, 1932, Chrysler called at Ford headquarters to show off a newPlymouth model.

"The most radical feature of his car was the novel suspension of its six-cylinder engine so as to cut down vibration. Theengine was supported on three points and rested on rubber mounts. Noise and vibration were much less. There was still alot of movement of the engine when idling, but under a load it settled down. Although it was a great success in thePlymouth, Henry Ford did not like it. For no given reason, he just didn't like it, and that was that. I told Walter that I felt itwas a step in the right direction, that it would smooth out all noises and would adapt itself to axles and springs andsteering-gear mounts, which would stop the transfer of road noises into the body. Today rubber mounts are used on allcars. They are also found on electric-motor mounts, in refrigerators, radios, television sets—wherever mechanical noisesare apparent, rubber is used to eliminate them. We can thank Walter Chrysler for a quieter way of life. Mr. Ford couldhave installed this new mount at once in the V 8, but he missed the value of it. Later Edsel and I persuaded him. Rubbermounts are now found also in doors, hinges, windshields, fenders, spring hangers, shackles, and lamps—all with the ideaof eliminating squeaks and rattles."[2]

Lee Iacocca credits Chrysler's chief of engineering during that era, Frederick Zeder, with leading the effort.[3] Iacocca saidthat Zeder "was the first man to figure out how to get the vibrations out of cars. His solution? He mounted their engines on arubber base."[3]

Chrysler's novel engine-mounting method was marketed as "Floating Power". Its basic idea soon became the conventionalmethod throughout the automotive industry.

See also [edit]

AN-VIShock mount

References [edit]

1. ^ Heynes, WM. The Jaguar Engine, a paper presented to the Institution of Mechanical Engineers on 27 February 1953.2. ^ Sorensen 1956, pp. 226–227.3. ̂a b Iacocca 1984, p. 149.

Bibliography [edit]

Iacocca, Lido A. (1984), William Novak, ed., Iacocca: An Autobiography, Bantam Books, ISBN 978-0553051025,LCCN 84045174 .

Sorensen, Charles E.; with Williamson, Samuel T. (1956), My Forty Years with Ford, New York, New York, USA: Norton,LCCN 56010854 . Various republications, including ISBN 9780814332795.

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