In cars, double wishbone suspension is an independent suspension design using two (sometimes parallel) wishbone-shaped arms to find the wheels. Each wishbone or arm has two fitting points on the chassis and one connection on the knuckle. Shock absorbers and coil springs are fitted to the wishbones to control vertical movement. The double wishbone design allows engineers to control the movement of the wheel carefully during suspension travel, controlling parameters such as camber angle, caster angle, toe pattern, mid-roll height, scrub radius, abrasions and more.
Video Double wishbone suspension
Implementation
The double wishbone suspension can also be referred to as "double A-arms", although the arm itself may be A, L-shaped, or even a single bar relation. One wishbone or A-arm can also be used in a variety of other suspension types, such as variations of the MacPherson strut. The upper arm is usually shorter to induce negative camber during jounces suspension (up), and often this setting is titled "SLA" or "short long arms" suspension. When the vehicle is spinning, the body roll results in a positive camber on the lightweight inner wheel, while the outer wheel weighs the negative camber load.
Between the end of the arm patch is the knuckle. The knuckles contain kingpins for horizontal radial movements in old designs, and rubber or bushing trunions for vertical hinged movement. In newer designs, the ball connections at each end allow all movement. Attached to the knuckle in the center is a bearing hub, or in many older designs, a pivot where the wheel bearing is fitted.
To hold back loads such as acceleration and braking, the arm requires two bushing or ball joints on the body.
At the tip of the knuckle, a single joint ball is usually used, in which case the steering load must be taken through the steering arm, and the wishbones look A or L shaped. The L-shaped arm is generally preferred on passenger vehicles because it allows better handling and comfort compromises to be adjusted. Busing that is in line with the wheel can be maintained relatively rigid to effectively handle the cornering load while the off-line connection can be Softer to allow the wheel to recess under the front-rear impact load. For rear suspension, a pair of joints can be used at both ends of the arm, making it more H-shaped in the plan view. Alternatively, the fixed-length driveshaft can perform the wishbone function provided that another wishbone form provides control over the upright. This setting has been successfully used in Jaguar IRS. In the elevation view, the suspension is a 4-bar link, and it is easy to look for camber gain (see camber angle) and other parameters for a specified set of bushing or ball-joint locations. Various bushing or ball joint should not be on the horizontal axis, parallel to the center line of the vehicle. If they are set at an angle, then anti-diving and anti-squat geometry can be contacted.
In many race cars, springs and silencers are relocated within the bodywork. The suspension uses bellcrank to transfer power at the end of the knuckle of the suspension to the internal springs and dampers. This is then known as a "thrust" when the travel spur "pushes" on the rod (and then the rod should join the bottom up and tilt up). As the wheel rises, the thrust pushes the internal spring through the pivot or pivot system. The opposite setting, "pull rod", will pull the rod during the trip of the bump, and the rod should be attached to the top of the strait, downward sloping. Finding springs and inboard dampers increases the total mass of the suspension, but reduces the unsprung mass, and also allows the designer to make the suspension more aerodynamic.
Short-sleeved short suspension
A short arms arms suspension (SLA) also known as double wishbone suspension is not the same. The upper arm is usually an A-arm, and shorter than the bottom link, which is an A-arm or L-arm, or sometimes a pair of tension/compression arms. In the latter case, the suspension may be called multi-link, or double joint ball suspension.
The four-row connecting mechanism formed by unequal arm length causes changes to the camber of the vehicle as it rolls, which helps keep the square contact patch on the ground, increasing the vehicle's main cornering capacity. It also reduces the outer edge wear of the tire.
The SLA can be classified as a short roller, where the top ball joints on the shaft are in the wheel, or the long spindle, where the shaft wrapped around the tires and the top of the ball is above the tires.
Weaknesses
The short spindle SLA tends to require more rigid bushings in the body, as braking and bend strength is higher. Also they tend to have a worse kingpin geometry, because of the difficulty of packing the top of the ball joint and brakes in the wheel.
Long spindle SLAs tend to have better kingpin geometry, but spindle proximity to tires limits tires that are too large, or snowchains. The top balljoint location may have styling implications in the design of metal sheets on it.
SLAs require care when setting their bump steer characteristics, as they easily end up with excessive or curved steer bump curves.
Maps Double wishbone suspension
History
The double wishbone suspension was introduced in the 1930s. French car maker CitroÃÆ'Â nn started using it in their Rosalie and Traction Avant 1934 models. Packard Motor Car Company from Detroit, Michigan used it on Packard One-Twenty from 1935, and advertised it as a security feature. During that time MacPherson strut was still in the field of aviation technology and came from the aircraft landing mechanism. Then, until 1951, Ford Company decided to use MacPherson strut on small production cars, the British Consul Ford and Ford Zephyr. Thus, double wishbone is applied at the beginning of car history and there is no genetic relationship between MacPherson strut and double wishbone suspension.
Double wishbones are usually considered to have superior dynamic characteristics as well as load-handling capabilities, and are therefore commonly found in sports cars and race cars throughout automotive history. Examples of making where double wishbones can be found include Alfa Romeo, Lancia, Maserati, Mercedes-Benz, MG, Saab, Toyota and Pontiac vehicles. Aston Martin DB7, Rover 600, Honda NSX, Honda S2000 and Honda Prelude use a rare double wishbone suspension arrangement both front and rear, informed by the Honda experience in Formula One. Short-sleeved suspension, a type of double wishbone suspension, is very common in front suspensions for medium-to-large cars like the Honda Accord (replaced by less complex and expensive strains of the MacPherson struts in the 2013 model), Peugeot 407, Citroen C5, Peugeot 508 GT or Mazda 6/Atenza (both replaced by MacPherson struts in the 2014 model). It also provides camber changes at least on bump and rebound conditions.
Benefits
Double wishbone suspension gives engineers more design options than some other types. It's easy enough to know the effect of moving each connection, so that the kinematics of the suspension can be adjusted easily and wheel motion can be optimized. It is also easy to work on the loads that will be subjected to different parts that allow the lightweight parts to be more optimized to be designed. They also provide a negative camber increase to full travel, unlike MacPherson strut, which gives negative camber's advantage only at the start of jounce journey and then turns to positive camber at high meetings.
Disadvantages
Double wishbone suspensions may consume more space and are more complex, and thus more expensive, than other systems such as MacPherson buffers. Due to the increase in the number of components in the suspension setting, it takes longer for service and is heavier than the equivalent MacPherson design. At the other end of the scale, it offers fewer design options than the more expensive and complicated multi-link suspension system.
See also
- Chapman strut
- Leaf spring Corvette
- Double ball joint suspension
- Leaf spring
- MacPherson strut
- Multi-link suspension
- Strut bar
- Torsion beam suspension
- Trailing-arm suspension
- Twin-Traction Beam
- Twist-beam rear suspension
- Weissach Axle - Double wishbone suspension variant with short link on front axle bus from A-arm bottom
References
External links
- Suspension Geometry Calculator
Source of the article : Wikipedia
0 Comments