Spring Suspension System in Automobile | Leaf Spring Suspension System | Leaf, Coil and Torsion Springs in Suspension System

INTRODUCTION TO LEAF SPRINGS

Leaf springs also denoted to as semi-elliptical springs are one of the ancient form of suspension used in vehicles, particularly heavy vehicles. A leaf spring appears like a bow minus the string. It contains of a stack of curved narrow plates of the same width and varied length clamped together with shorter plates at the center to form a semi-elliptical shape. The center of the arc delivers location for the axle, tie holes are made available at either end for getting attached to the body.

LEAF SPRINGS IN SUSPENSION SYSTEM

Any spring, maybe it’s a leaf, torsion or coil spring, must compensate for irregularities in the road surface, keep the suspension system at a fixed height and support added weight without excessive sagging.
Each of those works is very significant in providing comfort, specific handling and load-bearing ability in the modern vehicle – three key areas that will raise customer concerns.

01 - LEAF SPRING IN SUSPENSION SYSTEM - SUSPENSION SYSTEM LEAF SPINGS

In ancient times the steel multi-leaf spring is one of the first-born and most widely used spring designs in suspension systems. The leaf spring have many advantages, not only it acts as a spring, but also because it attaches the axle straight to the chassis.

TYPES OF LEAF SPRINGS

There are two varieties of leaf springs. They are the mono-leaf springs and the multi-leaf springs.
As the name proposes, the mono-leaf suspension involves of a single link. They are thick in the middle and narrowing out at the end. It does not offer much strength and suspension to dragged vehicles.

01 - LEAF SPRING IN SUSPENSION SYSTEM - MONO TYPE LEAF SPRINGS

Multi-leaf springs are mainly used for heavier vehicles which offer increased strength and suspension. The recent development in design is the parabolic leaf spring. It can contain a mono-leaf or multi-leaf configuration. It has less leaves in comparison to the semi-elliptical multi-leaf springs whose thickness differs from center to the end and it follows a parabolic path. This shape not only saves weight but also provides greater flexibility which improves ride quality. A trade-off of using parabolic leaf spring is reduced load carrying capability.

01 - multi type leaf spring - leaf spring suspension system.

TORSION SPRINGS IN SUSPENSION SYSTEM

Torsion-bar suspensions have been used for many years on vehicles provided with short-long-arm (SLA) suspension systems. As the name implies, the torsion bar is basically a round bar, about four feet long, that’s designed to twist as weight is applied to the suspension system. Since a torsion bar is usually preloaded by a clockwise or counterclockwise coil constructed into it, a torsion bar will fit on the side of the vehicle for which it was de­signed.

01 - TORSION SPRING IN SUSPENSION SYSTEM - SUSPENSION SYSTEM TORSION SPRINGS

The benefits of the torsion bar suspension system inc­lude compactness and light weight. Since the torsion bar tension is measured by a threaded screw adjustment, torsion bars can be used to tune suspension height. Besides, torsion bars can be attached either to the upper or lower control arms, aggregating the versatility of the design.

COIL SPRINGS IN SUSPENSION SYSTEM

The function of a coil spring can be well understood if we imagine it as a long, thin, torsion bar twisted into a coil shape. Because the coiled wire twists through the spring’s compression/extension cycles, the coil spring essentially functions on the same principle as a torsion bar.

01 - COIL SPRING IN SUSPENSION SYSTEM - COIL SPRING APPLICATIONS

As a coil spring occupies a relatively small space, it can be used in a most types of suspension designs including MacPher­son strut, solid axle with trailing arms, independently sprung rear axle, or any SLA suspension system using a spring or coil-over shock absorber configuration.
Most recent imports use the coil spring in differences of the MacPherson strut design. In common, wire gauge, length, overall diameter and numbers of coils control the characteristics of the coil spring.

Sometimes a coil spring can be considered as a variable rate spring that increases load-bearing capability as it’s compressed. Flexible rate coil springs are often used in chassis configurations that rarely carry heavy loads.

ADVANTAGES OF SPRINGS IN SUSPENSION SYSTEM
1) The manufacture of the suspension is simple and strong as it performances as a linkage for holding the axle in place and thus a separate linkage isn’t necessary.
2) As they detect the rear axle, the need for trailing arms and panhard rod is removed, thus saving cost and weight.
3) It provisions the weight of the chassis.
4) It controls chassis roll more proficiently by utilizing a higher rear moment center and a wider spring base.

DISADVANTAGES OF SPRINGS IN SUSPENSION SYSTEM
1) The leaf-spring systems are difficult to install.
2) The inter-leaf friction between the leaf springs decreases the ride comfort.
3) The leaf springs may be apt to to lose shape and sag over time. 4) Acceleration and braking torque roots wind-up and vibration. Also wind-up causes rear-end squat and nose-diving.

Suspension System of an Automobile | Needs of Suspension System in an Automobile | Broad Classification of suspension system of a vehicle

Introduction

For several years vehicle dynamics engineers have struggled to accomplish a compromise between vehicle handling, ride comfort and stability. The outcomes of this are vibrant in the vehicles we see today. In common, at one extreme are large sedan and luxury cars with excellent ride qualities but only satisfactory handling behavior. On the last end of the spectrum are sports cars with very good handling but very firm ride quality. In between is any number of variations dictated by the vehicle manufacturer and target customer needs.

Every automotive suspension has two objectives: passenger comfort and vehicle control. Comfort is delivered by isolating the vehicle’s passengers from road disturbances like bumps or holes. Control is attained by maintaining the car body from rolling and pitching extremely and maintaining good contact stuck between the tire and the road. By and large, today’s vehicle suspensions use hydraulic dampers and springs that are charged with the tasks of absorbing bumps, decreasing the car’s body motions during accelerating, braking and turning and keeping the tires in contact with the road surface.

History of suspension systems

1903 – Mors from Germany fixed a car using shock absorbers.

1920 – Leyland used torsion bars in their suspension system.

1922 – Unitary constructions and independent front suspension were initiated on the Lancia Lambda.

1932 – By this year ,the independent front suspension became common in standard cars.

1948 – Triumph Mayflower presented the combined coil spring/damper unit.

1950 – Ford implemented the McPherson strut independent front suspension on MK 1 consul.

1959 – Usage of independent rubber suspension started.

1962 – Introduction of the hydrostatic suspension.

Why do vehicles have suspension?

The purpose of a suspension system is to isolate the body and its residents from the irregularities of the road surface. In an ideal world the body should ride level and lacking vertical motion however bumpy the road surface. Another significant feature of suspension is that it should retain the tires on the ground all the time. If there were not at all suspension the tires would incline to lift off the ground every time they passed over a bump at the same time, the shock as the wheels left the ground’ and then came down another time, would be transferred precise to the passengers.

01 - NEEDS OF A SUSPENSION SYSTEM - SUSPENSION SYSTEM OF AN AUTOMOBILE

What does a suspension system do?

Preferably the suspension should allow the wheels to move up and down so that they follow the undulations in the road during the body rides level. The first necessity therefore is that the wheels should be capable of moving vertically relative to the body. All suspension has this wheel travel, which must be housed by some means.

01 - WORKING OF A SUSPENSION SYSTEM - SUSPENSION SYSTEM OF AN AUTOMOBILE

Functions of suspension system

The vehicle suspension system is mainly responsible for driving comfort and safety as the suspension carries the vehicle body and transmits all forces between the body and the road.

In order to completely influence these properties, semi-active and active components are introduced. These aid the suspension system to adapt to various driving conditions.

By addition of a variable damper and spring, driving comfort and safety are considerably improved related to suspension setups with fixed properties.

To prevent the road shocks from existence transmitted to the vehicle frame. To preserve the stability of the vehicle in pitching or rolling. To maintain the occupants from road shocks. To provide good road holding while driving, cornering and braking.

Broad Classification of suspension system

Suspension systems can be generally classified into two subgroups: dependent and independent. These terms denote to the ability of opposite wheels to move independently of each other.

A dependent suspension usually has a beam  or live axle that holds wheels parallel to each other and perpendicular to the axle. When the camber of one wheel differs the camber of the opposite wheel changes in the same way (by convention on one side this is a positive change in camber and on the other side this a negative change).

An independent suspension permits wheels to rise and fall on their own without disturbing the opposite wheel. Suspensions with other devices like sway bars that link the wheels in some way are still classed as independent.

A third type is a semidependent suspension. In this type, the motion of one wheel does disturb the position of the other but they are not firmly attached to each other. A twist beam rear suspension is such a kind of system.