MacPherson strut

The MacPherson strut is a type of automotive suspension system that uses the top of a telescopic damper as the upper steering pivot. It is widely used in the front suspension of modern vehicles and is named for American automotive engineer Earle S. MacPherson, who originally invented and developed the design. A simple MacPherson strut suspension on the left front wheel of a rear-wheel drive vehicle. The front of the vehicle is at bottom right of the image. Upper green: Vehicle body/strut interface Red: Steering knuckle or hub carrier Blue: Lower control arm or track control arm Light blue: Steering gear tie rod or track rod Lower purple: Radius rod Upper purple: Coil spring Yellow: Tubular housing containing shock absorber or damper Lower green: Vehicle frame or unibody member History Earle S. MacPherson was appointed the chief engineer of Chevrolet's Light Car project in 1945, to develop new smaller cars for the immediate post-war market. This gave rise to the Chevrolet Cadet. By 1946 three prototypes of the Cadet design had been produced. These incorporated the first MacPherson strut independent suspension both in front and rear. The Cadet project was cancelled in 1947 and the disgruntled MacPherson was enticed to join Ford. Patents were filed in 1947 (U.S. Patent 2,624,592 for GM) and in 1949 (U.S. Patent 2,660,449 for Ford), the 1949 patent citing designs by Guido Fornaca of FIAT in the mid-1920s. The strut suspension of the pre-war Stout Scarab could have been an influence and long-travel struts in aircraft landing gear were well-known by this time. French Cottin-Desgouttes utilized a similar design, albeit with less sophisticated leaf springs, however the Cottin-Desgouttes front suspension was in turn inspired by American engineer J. Walter Christie's 1904 design. MacPherson designed the strut for all four wheels, but it is normally used for the front suspension only, where it provides a steering pivot as well as a suspension mounting for the wheel. The first production car to use McPherson struts is often listed incorrectly as the French 1949 Ford Vedette, but it was developed before MacPherson with an independent front suspension based on wishbones and an upper coil spring. Only in 1954, after the Vedette factory had been purchased by Simca, did the revised Simca Vedette switch to using front struts. Following MacPherson's arrival at Ford, the first production car to feature MacPherson struts was the British-built 1950 Ford Consul and later Zephyr. Design A MacPherson strut uses a wishbone, or a substantial compression link stabilized by a secondary link, which provides a mounting point for the hub carrier or axle of the wheel. This lower arm system provides both lateral and longitudinal location of the wheel. The upper part of the hub carrier is rigidly fixed to the bottom of the outer part of the strut proper;...

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Multi-link suspension

A multi-link suspension is a type of vehicle suspension design typically used in independent suspensions, using three or more lateral arms, and one or more longitudinal arms. A wider definition considers any independent suspensions having three control links or more multi-link suspensions. These arms do not have to be of equal length, and may be angled away from their "obvious" direction. It was first introduced in the late 1960s on the Mercedes-Benz C111 and later on their W201 and W124series. Typically each arm has a spherical joint (ball joint) or rubber bushing at each end. Consequently, they react to loads along their own length, in tension and compression, but not in bending. Some multi-links do use a trailing arm, control arm or wishbone, which has two bushings at one end. On a front suspension one of the lateral arms is replaced by the tie-rod, which connects the rack or steering box to the wheel hub. In order to simplify understanding, it is usual to consider the function of the arms in each of three orthogonal planes. 5-link rear suspension Rear view Top view Solid axle configuration For a solid axle vehicle the multi link suspension provides control of the axle during suspension cycling and to locate the axle under the vehicle. The most common is the four link with panhard bar. This is found in many cars and pickup trucks. The four link is also used heavily in off-road racing and drag racing. The four link for a solid axle has a few variations such as the triangulated four link and double triangulated four link. Although common in off-road vehicles these are not commonly found on the street. Plan view The arms have to control toe/steer and lateral compliance. This needs a pair of arms longitudinally separated. Front view Independent suspension The arms have to control camber, particularly the way that the camber changes as the wheel moves up (into jounce, or bump) and down into rebound or droop. Solid axle suspension In a solid axle suspension the upper arms may have an angle of at least 45 degrees between them, to prevent the axle from moving from side to side while allowing the axle to articulate and move freely up and down. Side view Independent suspension The arms have to transmit traction and braking loads, usually accomplished via a longitudinal link. They also have to control caster. Note that brake torques also have to be reacted - either by a second longitudinal link, or by rotating the hub, which forces the lateral arms out of plane, so allowing them to react 'spin'...

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Strut bar

A strut bar, strut brace, or strut tower brace (STB) is an automotive suspension accessory usually used in conjunction with MacPherson struts on monocoque or unibody chassis to provide extra stiffness between the strut towers. With a MacPherson strut suspension system where the spring and shock absorber are combined in the one suspension unit which also replaces the upper control arm, the entire vertical suspension load is transmitted to the top of the vehicle's strut tower, unlike a double wishbone suspension where the spring and shock absorber may share the load separately. In general terms, a strut tower in a monocoque chassis is a reinforced portion of the inner wheel well and is not necessarily directly connected to the main chassis rails. For this reason there is inherent flex within the strut towers relative to the chassis rails. A strut bar is designed to reduce this strut tower flex by tying the two strut towers together. This transmits the load off each strut tower during cornering which ties the two towers together and reduces chassis flex. To accomplish this effectively (especially on MacPherson strut suspensions), the bar must be rigid throughout its length. Many manufacturers have fitted strut braces to performance models as standard or optional equipment, including the Acura CL Type-S, Acura TSX, Audi S3 8l (2000-2003), BMW M3, BMW 3 Series, Buick Regal, Ford Mustang Bullitt, Holden VY II Commodore, Honda Crosstour, Honda Integra Type R, Hyundai Genesis Coupe, Mazda Protege 5, Mazda RX-8, Mitsubishi Colt Ralliart, Mitsubishi Lancer Evolution, Mitsubishi Outlander, Mitsubishi Eclipse, Nissan Altima, Nissan Skyline, Nissan 350Z, Pontiac GTO, Pontiac Bonneville GXP, Saab 900 NG, Toyota MR2, Toyota Solara, Toyota Camry SE, Volvo S60 and the Subaru Legacy mounted strut bar Combined strut bar and overflow container in an mk2 Saab Sonett. GM vehicles Many GM front wheel drive vehicles in the 1990s and later came factory equipped with strut tower braces as standard equipment. For example, the H body Buick Lesabre, C body Buick Park Avenue, their Olds and Pontiac brethren, E-body cars such as the Buick Riviera, Buick Reatta, Oldsmobile Toronado, Cadillac Eldorado and Cadillac Seville, and so on. The W-body '91 to '95 Oldsmobile Cutlass Supremeconvertibles and Buick Regal came with a STB, whereas most W-body coupes and sedans did not. Oldsmobile Regency (H-Body) Factory STB

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Dual ball joint suspension

A dual ball joint suspension uses a pair of arms, one in tension, one in compression, to replace a wishbone, in a MacPherson or SLA suspension. The outer end of each arm terminates in a ball joint, hence the name. General description The two arms, the spindle, and the body, form a four-bar link. Use of the linkage at the lower suspension connection of either a MacPherson strut or a short long arms suspensionreadily gives an effective virtual ball joint outboard of the spindle, which is very useful for a suspension designer, allowing negative scrub radius whilst allowing the ball joints to move in and thus out of the way of the brakes. Some manufacturers use a double ball joint arm to replace both wishbones on a short long arms suspension. This provides further opportunity for optimising the geometry. Examples It is used on large cars such as the Lexus LS 460, BMW X5, Ford Territory, and General Motors' Zeta-derived models. Disadvantages The extra ball joint adds weight and cost. It also increases steering friction, and the parasitic friction in the suspension. The geometry has some undesirable characteristics that need careful management, such as returnability from full lock when parking. References The Automotive Chassis Engineering Principles, J. Reimpell, H. Stoll, J. W. Betzler, ISBN 978-0-7680-0657-5

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Corvette leaf spring

Corvette leaf spring commonly refers to a type of independent suspension that utilizes a fiber-reinforced plastic (FRP) mono-leaf spring instead of more conventional coil springs. It is named after the Chevrolet Corvette, the American sports car for which it was originally developed and first utilized. A notable characteristic of this suspension configuration is the mounting of the mono-leaf spring such that it can serve as both ride spring and anti-roll spring. In contrast to many applications of leaf springs in automotive suspension designs, this type does not use the spring as a locating link. While this suspension type is most notably associated with several generations of the Chevrolet Corvette the design has been used in other production General Motors cars, as well as vehicles from Volvo Cars and Mercedes-Benz. Fiat produced cars with a similar configuration, using a multi-leaf steel spring in place of the FRP mono-leaf spring. Design The C5 Corvette's rear suspension The leaf-spring suspension configuration is independent, because the movement of one wheel is not determined by the position of the other. Control arms are utilized to define the motion of the wheel as the suspension is compressed. The usual coil springs are replaced with a single FRP spring, which spans the width of the car. As in independent suspension systems using coil springs, and unlike the common leaf-spring supported Hotchkiss rear axle, the suspension kinematics are defined only by the control arms. As in a coil-spring suspension design, the FRP mono-leaf spring supports the weight of the vehicle. However, the FRP leaf springs differ from steel coils and traditional steel multi-leaf springs in a number of significant ways. The FRP plastic springs have 4.3–5.5 times the strain energy storage per weight, compared to steel. This results in a lighter spring for a given application. The single FRP mono-leaf front spring used on the fourth-generation Corvette is 33 percent of the weight of an equivalent set of coil springs. Comparing FRP to conventional steel leaf springs in similar applications, the weight saved is even greater. The third-generation Corvette offered an optional FRP mono-leaf spring as an alternative to the standard multi-leaf steel spring, the 22-kilogram (48 lb) steel spring being replaced by a 3-kilogram (7 lb) FRP spring. Volvo claims a weight savings of 5 kilograms (10 lb) by using a FRP spring in the rear suspension of its second-generation XC90, compared to designs using coil springs.In addition to the reduction in vehicle weight, the weight of the spring is partly unsprung mass. The relative sliding movement of the leaves of a multi-leaf steel spring results in stiction-based hysteresis with respect to spring compression. This...

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Double wishbone suspension

In automobiles, a double wishbone suspension is an independent suspension design using two (occasionally parallel) wishbone-shaped arms to locate the wheel. Each wishbone or arm has two mounting points to the chassis and one joint at the knuckle. The shock absorber and coil spring mount to the wishbones to control vertical movement. Double wishbone designs allow the engineer to carefully control the motion of the wheel throughout suspension travel, controlling such parameters as camber angle, caster angle, toe pattern, roll center height, scrub radius, scuff and more. Wishbones and upright painted yellow Implementation Double wishbone suspension (front) on a Saab Quantum IV The double-wishbone suspension can also be referred to as "double A-arms", though the arms themselves can be A-shaped, L-shaped, or even a single bar linkage. A single wishbone or A-arm can also be used in various other suspension types, such as variations of the MacPherson strut. The upper arm is usually shorter to induce negative camber as the suspension jounces (rises), and often this arrangement is titled an "SLA" or "short long arms" suspension. When the vehicle is in a turn, body roll results in positive camber gain on the lightly loaded inside wheel, while the heavily loaded outer wheel gains negative camber. Between the outboard end of the arms is a knuckle. The knuckle contains a kingpin for horizontal radial movement in older designs, and rubber or trunion bushings for vertical hinged movement. In newer designs, a ball joint at each end allow for all movement. Attached to the knuckle at its center is a bearing hub, or in many older designs, a spindle to which the wheel bearings are mounted. To resist fore-aft loads such as acceleration and braking, the arms require two bushings or ball joints at the body. Double wishbone suspension in action as on display at the Toyota Museum in Nagoya, Japan At the knuckle end, single ball joints are typically used, in which case the steering loads have to be taken via a steering arm, and the wishbones look A- or L-shaped. An L-shaped arm is generally preferred on passenger vehicles because it allows a better compromise of handling and comfort to be tuned in. The bushing in line with the wheel can be kept relatively stiff to effectively handle cornering loads while the off-line joint can be softer to allow the wheel to recess under fore-aft impact loads. For a rear suspension, a pair of joints can be used at both ends of the arm, making them more H-shaped in plan view. Alternatively, a fixed-length driveshaft can perform the function of a wishbone as long as the shape of the other wishbone provides...

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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 performance and fuel economy at high speed, or for stylistic reasons. Such a feature requires fairly sophisticated engineering. Citroën CX in high position. Height adjustment is most often achieved by air or oil compression used for the "springs" of the vehicle - when the pressure is varied - the vehicle body rises or lowers. Factory systems Height adjustable suspension from 1954 - high position An Audi A8 Multi Media Interface control screen for its Adaptive Air Suspension, which gives the vehicle clearance a range from 95 mm to 145 mm Kneeling bus in Dublin The first instance of a production vehicle with adjustable suspension was on the 1954 Citroën 15CVH. This vehicle featured a self-leveling, height adjustable hydropneumatic suspension. Since this time, these systems have appeared continuously on Citroën models, including the DS and CX. Height adjustable suspension was banned in the United States from 1974 to 1981, due to the stringent interpretation of passenger vehicle bumper height regulations by the U.S. government agency NHTSA. Subaru was one of a few manufacturers who offered the feature after the ban was lifted on the Subaru XT, the Subaru Leone wagon and the Subaru Legacy for a short time. Many modern SUVs use height adjustability as part of active suspension systems to improve the vehicle's versatility on and off-road. The Range Rover offered this feature from 1993. New models of the Ford Expedition have a computer-controlled system designed for convenience, which lowers automatically when the doors are unlocked by remote, returns to normal height when the vehicle is started, and (on 4-wheel-drive models), raises when the 4x4 system is engaged. Some cars use these systems to improve the vehicle's handling by lowering the vehicle's height during higher speeds - a current example being the Mercedes-Benz Active Body Control system. Another example is the Audi A8, which when driven at speeds of more than 120 km/h for more than 30 seconds reduces its clearance from 120 mm to 95 mm. The new 2011 Jeep Grand Cherokee also includes adjustable suspension in the 4x4 model. It automatically lowers when the Park selection is engaged, and also lowers at high speeds to improve aerodynamics. It also allows drivers to manually raise the suspension for off-road situations. Starting in 2012, the Tesla Model S offers height adjustable suspension as an option. Two goals are accomplished - the long, low slung car can be raised to avoid road obstacles - it also lowers at speed on the highway to improve aerodynamics. Height adjustable air suspensions are also equipped on...

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