Torsion beam suspension
Encyclopedia
Torsion spring
A torsion spring is a spring that works by torsion or twisting; that is, a flexible elastic object that stores mechanical energy when it is twisted. The amount of force it exerts is proportional to the amount it is twisted. There are two types...
suspension or torsion beam suspension, is a general term for any vehicle
Vehicle
A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....
suspension
Suspension (vehicle)
Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose — contributing to the car's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants...
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
Torsion (mechanics)
In solid mechanics, torsion is the twisting of an object due to an applied torque. In sections perpendicular to the torque axis, the resultant shear stress in this section is perpendicular to the radius....
resistance. The effective spring rate of the bar is determined by its length, cross section, shape and material.
Usage
Torsion bar suspensions are used on combat vehicles or tanks like the T-72T-72
The T-72 is a Soviet-designed main battle tank that entered production in 1970. It is developed directly from Obyekt-172, and shares parallel features with the T-64A...
(many tanks from late in World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
used this suspension), and on trucks and SUVs from Ford, Dodge
Dodge
Dodge is a United States-based brand of automobiles, minivans, and sport utility vehicles, manufactured and marketed by Chrysler Group LLC in more than 60 different countries and territories worldwide....
, GM, Mitsubishi, Mazda
Mazda
is a Japanese automotive manufacturer based in Fuchū, Aki District, Hiroshima Prefecture, Japan.In 2007, Mazda produced almost 1.3 million vehicles for global sales...
, Nissan and Toyota. Manufacturers change the torsion bar or key to adjust the ride height, usually to compensate for heavier or lighter engines. 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 (more importantly) 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 compared to coil springCoil spring
A Coil spring, also known as a helical spring, is a mechanical device, which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces...
s. A disadvantage is that torsion bars, unlike coil springs, usually cannot provide a progressive spring rate. In most torsion bar systems, ride height
Ride height
Ride height is the amount of space between the base of an automobile tire and the underside of the chassis; or, more properly, to the shortest distance between a flat, level surface, and any part of a vehicle other than those parts designed to contact the ground...
(and therefore many handling features) may be changed by simply adjusting bolts that connect the torsion bars to the steering knuckle
Steering knuckle
-Introduction:In automotive suspension, a steering knuckle is that part which contains the wheel hub or spindle, and attaches to the suspension components...
s. In most cars with this type of suspension, swapping torsion bars for a different spring rate is usually an easy task.
Leveling
Some vehicles use torsion bars to provide automatic levellingSelf-levelling suspension
Self-levelling refers to an automobile suspension system that maintains a constant ride height of the vehicle above the road, regardless of load....
, using a motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
to pre-stress the bars to provide greater resistance to load and, in some cases (depending on the speed with which the motors can act), to respond to changes in road conditions. Height adjustable suspension
Height adjustable suspension
Height adjustable suspension is a feature of certain automobile suspension systems that allow the motorist to vary the ride height or ground clearance. This can be done for various reasons including giving better ground clearance over rough terrain, a lower ground clearance to improve fuel economy...
has been used to implement a wheel-change mode where the vehicle is raised on three wheels so that the remaining wheel is lifted off the ground without the aid of a jack.
History
Before World War II, the front wheel drive Citroen Traction AvantCitroën Traction Avant
The Citroën Traction Avant is an automobile which was produced by the French manufacturer Citroën from 1934 to 1957. About 760,000 units were produced.-Impact on the world:...
(1934) had independent front torsion bar suspension and a flexible trailing dead axle, also sprung by torsion bars. The flexibility of the axle beam provided wheel location features like a twist beam axle. The Czechoslovakia
Czechoslovakia
Czechoslovakia or Czecho-Slovakia was a sovereign state in Central Europe which existed from October 1918, when it declared its independence from the Austro-Hungarian Empire, until 1992...
n Tatra
Tatra (car)
Tatra is a vehicle manufacturer in Kopřivnice, Czech Republic. The company was founded in 1850 as Schustala & Company later renamed Nesselsdorfer Wagenbau-Fabriksgesellschaft, a wagon and carriage manufacturer, and in 1897 produced the first motor car in central Europe, the Präsident. In 1918, it...
cars designed by Professor Hans Ledwinka
Hans Ledwinka
Hans Ledwinka was an Austrian automobile designer.- Youth :Ledwinka was born was born in Klosterneuburg , near Vienna, then part of the Austro-Hungarian Empire....
in the mid-1930s used all round independent torsion bar suspension, along with air cooled rear engines. Also in the 1930s, prototypes of the first Volkswagen Beetle
Volkswagen Beetle
The Volkswagen Type 1, widely known as the Volkswagen Beetle or Volkswagen Bug, is an economy car produced by the German auto maker Volkswagen from 1938 until 2003...
incorporated torsion bars—especially its transverse mounting style. Ledwinka's concept had been copied by Ferdinand Porsche
Ferdinand Porsche
Ferdinand Porsche was an Austrian automotive engineer and honorary Doctor of Engineering. He is best known for creating the first hybrid vehicle , the Volkswagen Beetle, and the Mercedes-Benz SS/SSK, as well as the first of many Porsche automobiles...
, whose successors later had to acknowledge the influence of Ledwinka's sophisticated Tatra models on the Porsche-designed Kdf-Wagen of 1938 (later renamed the VW Beetle), a post-war lawsuit resulting in a DM3,000,000 settlement paid by Volkswagen to Ringhoffer-Tatra in 1961.
The system was applied to many new combat vehicle
Combat vehicle
A combat vehicle, also known as a ground combat vehicle, is a self-propelled, weaponized military vehicle used for combat operations. Combat vehicles can be wheeled or tracked.- Automation :...
designs during the Second World War. It was used extensively in European cars Renault
Renault
Renault S.A. is a French automaker producing cars, vans, and in the past, autorail vehicles, trucks, tractors, vans and also buses/coaches. Its alliance with Nissan makes it the world's third largest automaker...
, Citroën
Citroën
Citroën is a major French automobile manufacturer, part of the PSA Peugeot Citroën group.Founded in 1919 by French industrialist André-Gustave Citroën , Citroën was the first mass-production car company outside the USA and pioneered the modern concept of creating a sales and services network that...
and Volkswagen
Volkswagen
Volkswagen is a German automobile manufacturer and is the original and biggest-selling marque of the Volkswagen Group, which now also owns the Audi, Bentley, Bugatti, Lamborghini, SEAT, and Škoda marques and the truck manufacturer Scania.Volkswagen means "people's car" in German, where it is...
, as well as by Packard
Packard
Packard was an American luxury-type automobile marque built by the Packard Motor Car Company of Detroit, Michigan, and later by the Studebaker-Packard Corporation of South Bend, Indiana...
in the 1950s. The Packard used torsion bars at both front and rear, and interconnected the front and rear systems to improve ride quality. The then revolutionary Jaguar E-Type
Jaguar E-type
The Jaguar E-Type or XK-E is a British automobile, manufactured by Jaguar between 1961 and 1975. Its combination of good looks, high performance, and competitive pricing established the marque as an icon of 1960s motoring...
introduced in 1961 had a unique torsion bar front suspension and an independent coil spring rear suspension using four shock absorbers with concentric springs.
The most famous American passenger car application was the Chrysler system used beginning with the 1957 model year, although Chrysler's "Torsion-Aire" suspension was only for the front; the same basic system (longitudinal mounting) was maintained until the 1981 introduction of the K-car
K-car
K-car may refer to:*Chevrolet C/K, Chevrolet and GMC's full-size pickup truck line from 1962 until 1998*Chrysler K platform, an automobile platform...
. A reengineered torsion bar suspension, introduced with the 1976 Dodge Aspen
Dodge Aspen
The Dodge Aspen, produced from 1976 to 1980, was a compact car from Chrysler Corporation's Dodge division; its Plymouth-branded counterpart was the Volaré . It was launched as a two-door coupe, a four-door sedan, and a unique-for-the-segment station wagon...
, introduced transverse-mounted torsion bars (possibly based on the Volkswagen Type 3
Volkswagen Type 3
The Volkswagen Type 3 was a range of small cars from German manufacturer Volkswagen , introduced at the 1961 Frankfurt Motor Show, Internationale Automobil-Ausstellung ....
passenger car) until production ended in 1989 (with Chrysler's M platform). Light duty Dodge trucks however continue to use torsion bars on their front suspension.
General Motors has used torsion bars since 1966, starting with the E-platform vehicles (Oldsmobile Toronado
Oldsmobile Toronado
The original Toronado began as a design painting by Oldsmobile stylist David North in 1962. His design, dubbed the "Flame Red Car," was for a compact sports/personal car never intended for production...
, Cadillac Eldorado
Cadillac Eldorado
The 1953 Eldorado was a special-bodied, low-production convertible . It was the production version of the 1952 El Dorado "Golden Anniversary" concept car, and borrowed bumper bullets from the 1951 GM Le Sabre show car...
), 4 wheel drive S-10
Chevrolet S-10
The first compact pickup from General Motors was the rebadged Isuzu KB sold since 1972 as the Chevrolet LUV. The 1973 Arab oil embargo forced GM to consider designing a domestically-produced compact pickup truck. As usual, parts from other GM chassis lines were incorporated. The first S-series...
pickups & Astro
Chevrolet Astro
The Chevrolet Astro was a rear-wheel drive mid-sized van introduced by Chevrolet in 1985 to rival domestic competitors the Dodge Caravan/Plymouth Voyager twins and the Japanese Toyota Van. Also sharing the Astro's platform was its sibling, the GMC Safari...
vans, and since 1988, full size trucks (GMT400, GMT800, and GMT900 series).
Porsche used torsion bar suspension for their 911
Porsche 911
The Porsche 911 is a luxury 2-door sports coupe made by Porsche AG of Stuttgart, Germany. It has a distinctive design, rear-engined and with independent rear suspension, an evolution of the swing axle on the Porsche 356. The engine was also air-cooled until the introduction of the Type 996 in 1998...
series from 1963 until 1989 with the introduction of the 964. They are also used in the rear suspension of the 924
Porsche 924
The Porsche 924 is an automobile produced by Porsche AG of Germany from 1976 to 1988. A two-door, 2+2 coupé, the 924 replaced the 914 as the company's entry-level model, and was the model that finally retired the 912. In production terms, the 924 was the first Porsche model powered by a...
, 944
Porsche 944
The Porsche 944 is a sports car built by Porsche from 1982 to 1991. It was built on the same platform as the 924, although 924 production continued through 1988. The 944 was intended to last into the 1990s, but major revisions planned for a 944 S3 model were eventually rolled into the 968 instead,...
, and 968
Porsche 968
The 968 is a sports car sold by Porsche AG from 1992 to 1995. It took over the entry-level position in Porsche's lineup from the 944, with which it shared about 20% of its parts...
.
Variations
Some front-wheel driveFront-wheel drive
Front-wheel drive is a form of engine/transmission layout used in motor vehicles, where the engine drives the front wheels only. Most modern front-wheel drive vehicles feature a transverse engine, rather than the conventional longitudinal engine arrangement generally found in rear-wheel drive and...
automobiles use a related type of torsion beam suspension, usually called a twist beam rear suspension
Twist-beam rear suspension
The twist-beam rear suspension, also known as torsion-beam axle 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...
, in which the rear wheels are carried on trailing arm
Trailing arm
thumb|220px|Trailing arm rear suspension of [[Front-engine, front-wheel drive layout|FF]] carsA trailing-arm suspension is an automobile suspension design in which one or more arms are connected between the axle and the chassis. It is usually used on rear axles...
s connected by a laterally mounted torsion beam. The torsion beam functions both as wheel locating arm and as an anti-roll bar to resist lateral motion of the wheels as the body leans in turns. Its advantages are that it is inexpensive to manufacture and install, and engages a minimum amount of interior volume, leaving more space for the carriage of passengers, cargo, and other components. Because the torsion beam acts in the lateral plane, not vertically, the twist beam axle cannot provide ride height adjustment, and it suffers, to some extent, similar car handling
Car handling
Automobile handling and vehicle handling are descriptions of the way wheeled vehicles perform transverse to their direction of motion, particularly during cornering and swerving. It also includes their stability when moving at rest. Handling and braking are the major components of a vehicle's...
limitations as other beam axle
Beam axle
A beam axle is a suspension system, also called a solid axle, in which one set of wheels is connected laterally by a single beam or shaft...
suspensions. However these limitations may not be apparent on the road, because of the trend towards firmer, more sporty suspension setups with more limited wheel travel. Twist-beam rear suspensions were pioneered on the Volkswagen Golf
Volkswagen Golf
The Volkswagen Golf is a small family car manufactured by Volkswagen since 1974 and marketed worldwide across six generations, in various body configurations and under various nameplates – as the Volkswagen Rabbit in the United States and Canada , and as the Volkswagen Caribe in Mexico .The...
in the early 1970s, and remain common on compact cars and minivan
Minivan
Minivan is a type of van designed for personal use. Minivans are typically either two-box or one box designs for maximum interior volume – and are taller than a sedan, hatchback, or a station wagon....
s.Some street trucks and suvs have that type of front end such as the ford ranger and ford explorer
Other uses
Torsion bars were sometimes used instead of conventional coil valve springs in some older motorcycles, such as the Honda CB450Honda CB450
The Honda CB450 was the first "big" Honda motorcycle with a 444cc dual overhead cam engine producing 43-45 horsepower . Appearing first in the 1965 four-speed K0 model, and progressing through a series of KX models with various improvements and styling changes, notably a redesigned gas tank and 5...
. They were also used in the door mechanism of the DeLorean DMC-12 automobile.