Torsion bar suspension

A torsion bar suspension, also known as a torsion spring suspension (not to be confused with a torsion beam rear suspension), is a general term for any vehicle suspension that uses a torsion bar as its main weight-bearing spring. One end of a long metal bar is attached firmly to the vehicle chassis; the opposite end terminates in a lever, the torsion key, mounted perpendicular to the bar, that is attached to a suspension arm, a spindle, or the axle. Vertical motion of the wheel causes the bar to twist around its axis and is resisted by the bar's torsion resistance. The effective spring rate of the bar is determined by its length, cross section, shape, material, and manufacturing process. A torsion bar with no load applied A torsion bar with a load applied A front VW Beetle suspension cross-section   Usage Torsion bar suspensions are used on combat vehicles and tanks like the T-72, Leopard 1, Leopard 2, M26 Pershing, M18 Hellcat, and the M1 Abrams (many tanks from World War II used this suspension), and on modern trucks and SUVs from Ford, Chrysler, GM, Mitsubishi, Mazda, Nissan, Isuzu and Toyota. Manufacturers change the torsion bar or key to adjust the ride height, usually to compensate for engine weight. While the ride height may be adjusted by turning the adjuster bolts on the stock torsion key, rotating the stock key too far can bend the adjusting bolt and place the shock piston outside its standard travel. Over-rotating the torsion bars can also cause the suspension to hit the bump-stop prematurely, causing a harsh ride. Aftermarket forged-metal torsion key kits use relocked adjuster keys to prevent over-rotation, and shock brackets to keep the piston travel in the stock range. Advantages and disadvantages The main advantages of a torsion bar suspension are durability, easy adjustability of ride height, and small profile along the width of the vehicle. It takes up less of the vehicle's interior volume than coil springs. Torsion bars reached the height of their popularity on mass-production road cars in the middle of the 20th century at the same time that unitary construction was being adopted. At a time when the mechanics of stress and metal fatigue in monocoque body frames was poorly understood, torsion bars were very attractive to vehicle designers as the bars could be mounted to reinforced parts of the central structure, typically the bulkhead. Using MacPherson struts to achieve independent front suspension with coil springs meant providing strong turrets in the frontal structure of the car. A disadvantage is that torsion bars, unlike coil springs, usually cannot provide a progressive spring rate. In most torsion bar systems, ride height (and therefore many handling features)...

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Anti-roll bar

An anti-roll bar (roll bar, anti-sway bar, sway bar, stabilizer bar) is a part of many automobile suspensions that helps reduce the body rollof a vehicle during fast cornering or over road irregularities. It connects opposite (left/right) wheels together through short lever arms linked by a torsion spring. A sway bar increases the suspension's roll stiffness—its resistance to roll in turns, independent of its spring rate in the vertical direction. The first stabilizer bar patent was awarded to Canadian inventor Stephen Coleman of Fredericton, New Brunswick on April 22, 1919. Anti-roll bars were unusual on pre-war cars due to the generally much stiffer suspension and acceptance of body roll. From the 1950s on, however, production cars were more commonly fitted with anti-roll bars, especially those vehicles with softer coil spring suspension.   An anti-roll bar (in black) on the rear of a Porsche, which traverses the underside of the car. Flexible bushings attach it to the chassis. Also visible on the right is one of the links that connect the bar to the suspension (drop link). These twist the anti-roll bar when the vehicle is cornering, resisting body roll. Purpose and operation An SUV, with anti roll bars removed, shows how one wheel can be much lower than the opposite side, as the body rolls (tilts) more without anti roll bars. Photo of 2 front-wheel springs, with the tires removed. Each suspension spring is connected to the central sway bar assembly. File highlighted to show anti-roll bar. An anti-sway or anti-roll bar is intended to force each side of the vehicle to lower, or rise, to similar heights, to reduce the sideways tilting (roll) of the vehicle on curves, sharp corners or large bumps, essentially counteracting the centrifugal forces of the vehicle rounding the curve. With the bar removed, a vehicle's wheels can tilt away by much larger distances (as shown by the SUV image at right). Although there are many variations in design, a common function is to force the opposite wheel's shock absorber, spring or suspension rod to lower, or rise, to a similar level as the other wheel. In a fast turn, a vehicle tends to drop closer onto the outer wheels, and the sway bar soon forces the opposite wheel to also get closer to the vehicle. As a result, the vehicle tends to "hug" the road closer in a fast turn, where all wheels are closer to the body. After the fast turn, then the downward pressure is reduced, and the paired wheels can return to their normal height against the vehicle, kept at similar levels...

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De Dion tube

A de Dion tube is an automobile suspension technology. It is a sophisticated form of non-independent suspension and is a considerable improvement over the swing axle, Hotchkiss drive, or live axle. Because it plays no part in transmitting power to the drive wheels, it is sometimes called a "dead axle". De Dion suspension uses universal joints at both the wheel hubs and differential, and uses a solid tubular beam to hold the opposite wheels in parallel. Unlike an anti-roll bar, a de Dion tube is not directly connected to the chassis nor is it intended to flex. In suspension geometry it is a beam axle suspension. de Dion suspension characteristics: Camber change on one sided bumps, none on rebound. de Dion tube is shown in blue. The differential (yellow) is connected directly to the chassis (orange). De Dion rear axle History The de Dion tube was named after Comte Jules-Albert de Dion, founder of French automobile manufacturer De Dion-Bouton. The tube, however, was invented around 1894 by co-founder Charles Trépardoux for use on the company's steam tricycles. Advantages and disadvantages Advantages: Reduced unsprung weight compared to the Hotchkiss drive (live axle), since the differential and half-shafts are connected to the chassis. Unlike most fully independent suspension there are no camber changes on axle loading and unloading (or rebound). Fixing the camber of both wheels at 0° assists in obtaining good traction from wide tires and also tends to reduce wheel hop under high power operations compared to an independent suspension. The choice of shock absorbers and springs is made easier. The two wheels may be individually aligned, allowing for independent camber (vertical) and track (horizontal) alignment. Disadvantages: A pair of CV or universal joints is required for each wheel, adding complexity, cost, and weight. If coil springs are used, then a lateral location link (usually either a Panhard rod or Watt's linkage) is required, plus additional torque links on each side (five link suspension) or a combination of lower trailing links and an upper transverse wishbone. None of these additional links are required if leaf springs are used, but ride can be compromised due to the leaves having to do double duty as both locating links and springs. The torque links are not required if the setup uses inboard brakes, like in the Pegaso 1502, Rover P6, all Iso cars and Alfa Romeo type 116 (and derivatives), as the wheels do not transmit torque to the suspension. Sympathetic camber changes on opposite wheels are seen on single-wheel suspension compression, just as in a Hotchkiss drive or live axle. This is not important for operation on improved surfaces but is more critical for rough road or off road...

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Twist-beam rear suspension

The twist-beam rear suspension (also torsion-beam axle or deformable torsion beam) is a type of automobile suspension based on a large H or C shaped member. The front of the H attaches to the body via rubber bushings, and the rear of the H carries each stub-axle assembly, on each side of the car. The cross beam of the H holds the two trailing arms together, and provides the roll stiffness of the suspension, by twisting as the two trailing arms move vertically, relative to each other. Twist-beam rear suspension of a Volkswagen Golf Mk3 About The coil springs usually bear on a pad alongside the stub-axle. Often the shock is colinear with the spring, to form a coilover. In many cases the damper is also used as a restraint strap to stop the arm descending so far that the coil spring falls out through being completely unloaded. This location gives them a very high motion ratio compared with most suspensions, which improves their performance, and reduces their weight. The longitudinal location of the cross beam controls important parameters of the suspension's behaviour, such as the roll steer curve and toe and camber compliance. The closer the cross beam to the axle stubs the more the camber and toe changes under deflection. A key difference between the camber and toe changes of a twist beam vs independent suspension is the change in camber and toe is dependent on the position of the other wheel, not the car's chassis. In a traditional independent suspension the camber and toe are based on the position of the wheel relative to the body. If both wheels compress together their camber and toe will not change. Thus if both wheels started perpendicular to the road and car compressed together they will stay perpendicular to the road. The camber and toe changes are the result of one wheel being compressed relative to the other. Conceptual model of a twist beam suspension. The green segments illustrate the axle stub centerlines. At rest the axles are in line and the wheels are vertical (Camber = 0 degrees) The twist beam suspension with the left axle deflected upwards. The deflected wheel now has negative camber. The left and right axles are no longer aligned. The right wheel's camber has changed to positive due to the deflection of the left wheel. Single wheel deflection (deflection due to roll) vs both wheels up (deflection in bump). Note that when both wheels are deflected the axles remain in line and the...

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Beam axle

A beam axle, rigid axle or solid axle is a dependent suspension design, in which a set of wheels is connected laterally by a single beam or shaft. Beam axles were once commonly used at the rear wheels of a vehicle, but historically they have also been used as front axles in rear-wheel-drive vehicles. In most automobiles, beam axles have been replaced by front and rear independent suspensions. Beam axle and Panhard rod on a 2002 Mazda MPV Implementation Solid axle suspension characteristics: Camber change on bumps, none on rebound, large unsprung weight With a beam axle the camber angle between the wheels is the same no matter where it is in the travel of the suspension. A beam axle's fore & aft location is constrained by either: trailing arms, semi-trailing arms, radius rods, or leaf springs. The lateral location is constrained by either: a Panhard rod, a Scott Russell linkage or a Watt's linkage. While shock absorbers and either leaf springs, coil springs, or air bags are used to control vertical movement. The Twist-beam rear suspension is a similar suspension design, however its beam axle is able to twist thereby functioning as an anti-roll bar to control the roll motion of the body and is considered to be a semi-independent suspension design. Live axle vs dead axle A live axle in a Jeep. This is the front suspension, using coil springs. A live axle is a type of beam axle in which the shaft (or, commonly, shafts connected to move as a single unit) also transmits power to the wheels; a beam axle that does not also transmit power is sometimes called a dead axle. While typically used in vehicles with Hotchkiss drive, this suspension system can also be used with other types of power transmission. Advantages The principal advantage of the beam axle is its simplicity. This simplicity makes it very space-efficient and relatively cheap to manufacture. They are nearly universally used in buses and heavy-duty trucks. Most light and medium duty pickup trucks, SUVs, and vans also use a beam axle, at least in the rear. Beam axles have an important advantage for off-road applications, as they provide better vehicle articulationand durability in a high load environment. Disadvantages The drawbacks are that it does not allow each wheel to move independently in response to bumps, and the mass of the beam is part of the unsprung weight of the vehicle, which can further reduce ride quality. Also the cornering ability is typically worse than other suspension designs because the wheels have zero camber angle gain during body roll. Front beam axle suspension is also unusually sensitive to any lack of concentricity in the hub and wheel assembly which can cause a side-to-side oscillation ("shimmy") of the steering at certain speeds...

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Independent suspension

Independent suspension is a broad term for any automobile suspension system that allows each wheel on the same axle to move vertically (i.e. reacting to a bump in the road) independently of the others. This is contrasted with a beam axle or deDion axle system in which the wheels are linked – movement on one side affects the wheel on the other side. "Independent" refers to the motion or path of movement of the wheels or suspension. It is common for the left and right sides of the suspension to be connected with anti-roll bars or other such mechanisms. The anti-roll bar ties the left and right suspension spring rates together but does not tie their motion together. Most modern vehicles have independent front suspension (IFS). Many vehicles also have an independent rear suspension (IRS). IRS, as the name implies, has the rear wheels independently sprung. A fully independent suspension has an independent suspension on all wheels. Some early independent systems used swing axles, but modern systems use Chapman or MacPherson struts, trailing arms, multilink, or wishbones. Independent suspension typically offers better ride quality and handling characteristics, due to lower unsprung weight and the ability of each wheel to address the road undisturbed by activities of the other wheel on the vehicle. Independent suspension requires additional engineering effort and expense in development versus a beam or live axle arrangement. A very complex IRS solution can also result in higher manufacturing costs. The key reason for lower unsprung weight relative to a live axle design is that, for driven wheels, the differential unit does not form part of the unsprung elements of the suspension system. Instead, it is either bolted directly to the vehicle's chassis or more commonly to a subframe. The relative movement between the wheels and the differential is achieved through the use of swinging driveshafts connected via universal joints (U joints), analogous to the constant-velocity (CV) joints used in front-wheel-drive vehicles. A multi-link type rear independent suspension on an AWD car. The anti-roll bar has some yellow paint on it. Independent suspension Suspension Suspension is the only component that separates the driver and/or passenger from the ground. The suspension in a vehicle helps absorb harshness in the road. There are many systems and designs that do this, such as independent suspension. (Longhurst 1). Advantages This system provides many advantages over other suspension systems. For example, in solid axle suspension systems, when one wheel hits a bump, it affects both wheels. This will compromise traction, smoothness of the ride, and could also cause a dangerous wheel shimmy when moving at high speeds. With independent suspension systems, the bump primarily affects only the contacted wheel. This offers many advantages such as greater ride comfort, better...

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Electromagnetic suspension

Electromagnetic suspension (EMS) is the magnetic levitation of an object achieved by constantly altering the strength of a magnetic field produced by electromagnets using a feedback loop. In most cases the levitation effect is mostly due to permanent magnets as they don't have any power dissipation, with electromagnets only used to stabilize the effect. According to Earnshaw's Theorem a paramagnetically magnetised body cannot rest in stable equilibrium when placed in any combination of gravitational and magnetostatic fields. In these kinds of fields an unstable equilibrium condition exists. Although static fields cannot give stability, EMS works by continually altering the current sent to electromagnets to change the strength of the magnetic field and allows a stable levitation to occur. In EMS a feedback loop which continuously adjusts one or more electromagnets to correct the object's motion is used to cancel the instability. Many systems use magnetic attraction pulling upwards against gravity for these kinds of systems as this gives some inherent lateral stability, but some use a combination of magnetic attraction and magnetic repulsion to push upwards. Magnetic levitation technology is important because it reduces energy consumption, largely obviating friction. It also avoids wear and has very low maintenance requirements. The application of magnetic levitation is most commonly known for its role in Maglev trains. Floating globe. Magnetic levitation with a feedback loop. History Samuel Earnshaw was the one to discover in 1839 that “a charged body placed in an electrostatic field cannot levitate at stable equilibrium under the influence of electric forces alone”. Likewise, due to limitations on permittivity, stable suspension or levitation cannot be achieved in a static magnetic field with a system of permanent magnets or fixed current electromagnets. Braunbeck’s extension (1939) states that a system of permanent magnets must also contain diamagnetic material or a superconductor in order to obtain stable, static magnetic levitation or suspension. Emile Bachelet applied Earnshaw's theorem and the Braunbeck extension and stabilized magnetic force by controlling current intensity and turning on and off power to the electromagnets at desired frequencies. He was awarded a patent in March 1912 for his “levitating transmitting apparatus” (patent no. 1,020,942). His invention was first intended to be applied to smaller mail carrying systems but the potential application to larger train-like vehicles is certainly apparent. In 1934 Hermann Kemper applied Bachelet’s concept to the large scale, calling it “monorail vehicle with no wheels attached.” He obtained Reich Patent number 643316 for his invention and is also considered by many to be the inventor of maglev. In 1979 the Transrapid electromagnetically suspended train carried passengers for a few months as a demonstration on a 908 m track in Hamburg for the first International Transportation Exhibition (IVA 79). The first commercial Maglev...

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