EVOLUTION OF SUSPENSION SYSTEMS
The Early Days
The suspension system is used in a vehicle to maximize the friction between tires and the road surface, provide steering stability and provide comfort to the passengers. First suspension systems were used in old ox-drawn carts. They had iron chains attached to the wheeled frame of the carriage. These were limited to slow speed carriages.
Things you need to know before we dive in
Before going to all the suspension systems here’s a look at what axle articulation means. Its the vertical wheel travel that says, how far the wheels can travel with respect to the chassis. Good articulation means that all wheels can stay on the ground while traversing obstacles without losing traction.
The Leaf Spring Suspensions
The Leaf spring suspension is several layers of durable metal stacked together to act as a single unit. These suspensions are directly attached to the frame. In heavy vehicles, they have the advantage of spreading the load more widely over the vehicle’s chassis. In difficult terrain, a leaf spring does not offer good articulation.
The Torsion Bar Suspensions
A Torsion Bar suspension uses a torsion bar as its main weight-bearing spring. One side of the torsion bar is attached firmly to the chassis and the other side terminates at the wheel spindle. The torsion bar suspension has soft ride quality due to the elasticity of the bars. The problem was that they take up more space in order to provide more elasticity to the bar.
The Coil Spring Suspensions
Coil springs are very good energy-absorbing devices and occupy a lot less space compared to leaf spring and torsion bar. Coil springs absorb energy and release them at the same rate which causes pitching. Shock absorbers are used to control the speed of the retraction of the coil springs and eliminate pitching.
The MacPherson Strut Suspensions
The MacPherson Strut is known for its simple geometry due to which it is widely used in the front suspension of cars. Here the telescopic damper itself is used as a rotating linkage between the knuckle and the chassis. when the suspension is in action there is some degree of wheel angle change due to which it is not considered to have good handling compared to other independent suspension geometries.
The Double Wishbone Suspensions
The Double wishbone has two wishbones or A-arms at the top and the bottom to hold the wheel in place. Both the wishbones have two mounting points to mount to the chassis and one joint to the knuckle. Even though it has a complex design and is expensive this geometry allows the engineers to accurately control the motion of the wheel throughout the suspension travel.
The Multi-Link Suspensions
A multi-link suspension has three or more lateral arms and one or more longitudinal arms and at each end, they have a ball joint or rubber bushing. It was first introduced in the Mercedes-Benz C111 in the late 1960s. This suspension geometry allows the designers to incorporate both good ride quality and good handling. The design is expensive and complex. It is very difficult to tune the system without computer-aided design analysis.
The Air Suspensions
An Air suspension system has an electrical or engine driven air compressor that pumps compressed air to the flexible bellows, usually made from textile-reinforced rubber. Luxury cars such as Rolls-Royce phantom and Volvo XC 60 comes with these. The air pressure inflates the bellow and raises the chassis from the axle. This system provides a smooth and constant ride quality. This system calls for frequent maintenance due to these external systems.
The Hydro-Pneumatic Suspensions
The hydro-pneumatic suspension uses a combination of hydraulic fluid and compressed nitrogen gas. The hydraulic system uses the same hydraulic pump used for power steering and brakes. This system has a very high load-bearing capacity and is used in heavy earth-movers. The maintenance of this type of suspension system needs specially fitted power tools in the workshops.
The Bose Suspensions
Bose suspension is an electromagnetic suspension system that was developed by bose in 2004. It was a scaled version of the loudspeaker driver and electromagnetic motor which was based on a control algorithm and microprocessor. They showed off their suspension on a modified Lexus LS400 and Porsche 911. The suspension not just damps the roadway pump but actively contradicts them. Bose Eventually sold this technology to Clear Motion which will be developing the system for production.
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