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Originally Posted by ram It would help to use a diagram to explain the terms: lateral-links, watt-linkage, panhard-rod, etc.
Many of our budding auto-buff friends may be clueless about the engineering of the automobile.
Lack of a good sketch-scanner, is a temporary handicap, else I would post my sketches to explain some of these terms as they crop up. |
I would like to help you here since you are not able to scan and upload a sketch due to unavailability of a good sketch scanner. I have very little or no knowledge as compared to you but still I am trying to explain these terms with whatever information I could gather from the internet. Please feel free to correct me.
Lets start with Suspension itself.
Suspension -
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 handling and braking for good active safety and driving pleasure, and keeping vehicle occupants comfortable and reasonably well isolated from road noise, bumps, and vibrations.
Suspension system can be broadly classified into -
(a) Dependent Suspension
(b) Independent Suspension
(c) Semi-dependent Suspension
Panhard Rod -
A Panhard rod or track bar is a component of a car suspension system that provides lateral location of the axle. Originally invented by the Panhard automobile company of France in the early twentieth century, this device has been widely used ever since.
While the purpose of the rear suspension of an automobile is to allow the wheels to move vertically with respect to the body, it is undesirable to allow them to move forward and backwards, or from side to side. It is this latter movement that the Panhard rod is designed to prevent. It is a simple device, consisting of a rigid bar running sideways in the same plane as the rear axle, connecting one end of the axle to the car body or chassis on the opposite side of the vehicle. The bar is attached on either end with pivots that permit it to swivel upwards and downwards only, so that the axle is in turn allowed to move in the vertical plane only. This does not effectively locate the axle longitudinally, therefore it is usually used in conjunction with trailing arms which locate the axle in the longitudinal direction. This arrangement is not usually used with a leaf spring rear suspension, where the springs themselves supply enough lateral rigidity, but only with coil spring suspensions.
The advantage of the Panhard rod is its simplicity. Its major disadvantage is that the axle must necessarily move in an arc, relative to the body, with the radius equal to the length of the Panhard rod. If the rod is too short, there will be excessive sideways movement between the axle and the body at the ends of the spring travel; therefore the Panhard rod is less desirable on smaller cars than larger.
Watt's Linkage -
Watt's linkage was invented by James Watt (19 January 1736 – 19 August 1819) to constrain the movement of a steam engine piston in a straight line.
The Watt's linkage is also used in the rear axle of a car suspension as an
improvement over the Panhard rod, which was designed in the early twentieth century. Both methods intend to prevent relative sideway motion between the axle and body of the car. The Watt’s linkage however approximates a vertical straight line motion more closely.
It consists of two horizontal rods of equal length mounted at each side of the chassis. In between these two rods, a short vertical bar is connected. The center of this short vertical rod – the point which is constraint in a straight line motion - is mounted to the center of the axle. All pivoting points are free to rotate in a vertical plane.
In a way, the Watt’s linkage can be seen as two Panhard rods mounted opposite of each other. In Watt’s arrangement however, the opposing curved movements introduced by the pivoting Panhard rods are compensated by the short vertical rotating bar.
Torsion Bar -
A torsion bar is a solid bar of steel which is connected to the car chassis at one end, and free to move at the other end. They are almost always mounted across the car, one for each side of the suspension. The springing motion is provided by the metal bar's resistance to twisting.
Torsion bars are normally locked to the chassis and the suspension parts with splined ends. This allows them to be removed, twisted round a few splines and re-inserted, which can be used to raise or lower a car, or to compensate for the natural 'sag' of a suspension system over time. They can be connected to just about any type of suspension system listed on this page but are commonly found on trailing arm suspension.
Live Axle -
A live axle is a type of beam axle suspension system that uses the drive shafts that transmit power to the wheels to connect the wheels laterally so that they move together as a unit.
A live axle consists of a central differential in a single housing that also contains the drive shafts that connect the differential to the driven wheels. The differential is connected to the engine via a swinging propeller shaft and a universal joint. The complete assembly is suspended on coil springs or leaf springs.
Some live axles use trailing arms, semi-trailing arms, Panhard rod, or Watt's linkage to control the vertical and lateral movements of the axle. Others, particularly older vehicles, use Hotchkiss drive, in which the leaf springs provide axle location as well as suspension.
As with any beam axle, the advantages of the live axle are relative simplicity, lower manufacturing costs, lighter overall vehicle weight, and the fact that the axle and suspension systems take up little or no interior volume. Because the axle assembly is a fairly simple and rigid arrangement, it can easily be made stronger and more robust, which is an advantage for vehicles with substantial power or that are intended for rugged or off-road usage.
The principal disadvantage is the negative effect on ride quality and handling. The wheels cannot move independently in response to bumps.
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All the information and pics has been taken from wikipedia, car bibles, griggsracing.