Torsion bar suspension

A torsion bar suspension, also known as a torsion spring suspension, is any vehicle

The main advantages of a torsion bar suspension are soft ride due to elasticity of the bar, 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 unitary 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) may be changed by simply adjusting bolts that connect the torsion bars to the frame cross member. In most cars with this type of suspension, swapping torsion bars for a different spring rate is usually an easy task. Longitudinal torsion bars extend under the passenger compartment, cutting into interior space by raising the floor, while in transverse systems, torsion bar length is limited by vehicle width.

Leveling

Some vehicles use torsion bars to provide

The first vehicle to use torsion bars was Leyland Eight designed by J. G. Parry-Thomas and produced from 1920 to 1923, however its rear suspension, patented in 1919,^[1] was retrospectively named "torsion bar assisted" by Leyland in a 1966 publication^[2] because the bars only complemented the leaf springs. Less than two dozen cars (including racing variants) were produced, and the suspension was only ever used again on Marlborough-Thomas racing cars few years later.

In 1923 Parry-Thomas patented an updated design featuring a true torsion bar design with no leaf springs,

It was used extensively in European cars like Renault, Citroën and Porsche/Volkswagen, by less known producers like Mathis and Röhr in the 1930s, as well as by American Packard in the 1950s. The Packard used torsion bars at both front and rear, and interconnected the front and rear systems to improve ride quality. Morris Minor and Oxford from the late 1940s onwards used a front torsion bar system very similar to the Citroën, as did the Riley RM models. The revolutionary Jaguar E-Type introduced in 1961 had a torsion bar front suspension very similar to the Citroën and Morris Minor, and an independent coil spring rear suspension using four shock absorbers with concentric springs (coilover).

An early application of a torsion bar in an American car was by

The most famous American passenger car application of the torsion bar, was the Chrysler system used beginning with all Chrysler products starting with the 1957 model year in cars such as the Imperial Crown series, Chrysler Windsor, DeSoto Firedome, Dodge Coronet and Plymouth Belevedere although Chrysler's "Torsion-Air" suspension was only for the front axle; the same basic system (longitudinal mounting) was maintained until the 1981 introduction of the K-car. A reengineered torsion bar suspension, introduced with the 1976 Dodge Aspen, introduced transverse-mounted torsion bars (possibly based on the Volkswagen Type 3 passenger car) until production ended in 1989 (with Chrysler's M platform). Some generations of the Dodge Dakota and Durango used torsion bars on the front suspension.

General Motors first used torsion bars on their light-duty pickup trucks in 1960 until it was phased out in 1963 where traditional coil springs are used up front for their 2WD trucks. Its first use in a passenger car was in 1966, starting with the E-platform vehicles (Oldsmobile Toronado, Cadillac Eldorado), 4WD S-10 pickups and Astro vans with optional AWD, and since 1988, full size trucks and SUVs with 4WD (GMT400, GMT800, and GMT900 series).

Porsche used four-wheel torsion bar suspension for their

Variations

The German World War II Panther tank had double torsion bars.^{[citation needed]} Needing bars longer than the width of the tank to get the required spring rate and maximum elastic bend angle from available steel alloys, designer Ernst Lehr created a suspension that effectively folded the bars in half. For each wheel, one rod was attached to the suspension arm, while another was mounted to a nearby point on the frame. On the opposite side of the tank, the two rods were attached to each other and fitted into a pivot.^{[citation needed]} Deflection of the suspension arm caused both halves of the double torsion bar to twist. A disadvantage of the torsion bar suspension used in Tiger and Panther tanks (and many other WWII-era tanks and other AFVs) was the inability to incorporate an escape hatch through the bottom of the hull, a common feature of WWII-era tanks, as the torsion bar arrangement would have blocked crew access to such a hatch; however, the absence of leaf, coil or volute springs often left a large expanse of the side of the hull clear to include a side-escape hatch, and it was rare for a tank to be flipped over in such a way that all top-side hatches were unable to open, which is the purpose of ventral hatches.

Many contemporary main battle tanks use torsion bar suspension, including the American M1 Abrams,^[13] German Leopard 2,^[14] and Chinese MBT-3000,^{[citation needed]} though the newest generation of tanks such as the Russian T-14 Armata utilize an adjustable hydraulic suspension.^{[citation needed]} Due to their small size, tremendous load capacity, and relative ease of service, torsion bar suspension has been ideal for tanks, though it is not without disadvantage. The large travel and high elasticity of the torsion bars results in a "rocking" motion when the tank is moving or coming to a sudden stop. A gun stabilizer must be used to compensate for the rocking motion. Due to the massive weight of a main battle tank, compared to an automobile, there is a much greater risk of breaking a torsion bar on sudden bumps or maneuvers, and if it is not replaced in short order the reduced suspension can affect the maneuverability of the vehicle, and in extreme cases risk immobilizing the vehicle as the reduced capacity of the suspension causes additional torsion bars to break.

Other uses

Torsion bars were sometimes used instead of conventional coil valve springs in some older motorcycles, such as the Honda CB450, and also on the Panhard Dyna X and Panhard Dyna Z cars of the 1950s. They were also used in the door mechanism of the DMC DeLorean automobile and trunk lids of some Toyota Corolla (E30) models.

References