Automotive Suspension System

Figure 1 The three-wheeled automobile of Benz and the Stahlaradwagen of Daimler, both of the early cars are powered by gasoline and with a combustion engine in it .

Automotive suspension system history

When the car was just invented in the late 19^th century, axles and springs are from carriages. Karl Benz, a very famous German engine expert, made the first vehicle powered by gasoline in the world, the car was three-wheeled and called “motorwagen” at that time, because it looked very much like a wagen, frankly speaking, there hadn’t been a so-called suspension under the car by then, Karl Benz himself therefore became the patent holder on January 29^th, 1886{1}.

Figure 2 Early suspension made of vertical tubes in 1898

However, with the improvement of the speed, that simple axles can not satisfy the request of safety, undesirable shaking may even take cars apart. Taking safety and comfort into consideration, the first modern automotive suspension was worked out in the 1900s, which was dependent suspension system at that time{2}. William Brush suffered a motorcycle accident when he was driving his brother’s car and making a turn, a slight shaking rolled the car into a meadow, this horrible memory made him think deeply about the vehicle safety, he realized that the old springs cannot follow the increasing speed, in 1904, he invented the first modern dependent suspension system, and in 1906, followed by two significant innovations: shock absorbers and flexible axles.

Figure 3 Front suspension of Lancia Lambda (Automotive museum of Turin)

The next several decades witnessed tremendous changes in terms of the car suspension, independent front suspension was first installed in a Lancia car in 1922. Around the year of 1930, independent suspension systems began to be widely accepted by carmakers. Both of General Motors and Chrysler made big changes in the same year 1934, they imported coil spring front suspensions to replace the leaf suspensions, which is fixed directly to the axles and frame,(American car manufacturers liked it better at that time due to its     simple){3}, above all, the wheels were able to turn around and spring independently this time. Meanwhile, hydraulic shock absorbers and balloon tires were applied to majority of the new cars, the design of combining solid axles with balloon tires actually induced the front end vibration, but it will decrease the influence of the shake if the wheels move and spring separately.

Figure 4 Early Double wishbone suspension system

Double wishbone suspension system is also called A-arm suspension, is a widely used independent suspension system, it was brought about by a French carmaker named Citroen in 1934. The independent suspension is called in this way because it has arms look like wishbone to fix the position of the wheels, each arm has two install base to the frame and one mount point to the wheel, carrying a coil spring and a shock absorber to reduce shimmy. A-arm suspension system is aim to handle the camber angle well, which is a parameter revealing how the wheels lean, another advantage of this type of suspension is that it reduces the rotation and gives better steering feelings. As a result of these strong points, double wishbone suspensions are preferred by the large cars{3}.

Figure 5 Macpherson suspension strut

After the 1930s, variety of updated suspension systems come out based on a single concept of the combination of springs and shock absorbers. Another classical suspension system has to be mentioned in this field, it is well known as the Macpherson suspension system. Earle S. Macpherson designed the Macpherson strut when he was in General Motors 1947, right after the independent suspension system being accepted, until then, Macpherson suspension system has become the most popular front wheel suspension in the world. The Macpherson strut couples a coil spring and a shock absorber into a single element, this means that the suspension system is modified more tight and lighter, for this reason, it is typically suitable for front-wheel drive automobiles{3}.

Figure 6 Multi-link suspension system

Multi-link scientific achievements are emerging constantly in recent years, Lee D M A et al. derive the velocity equation of knuckle and they also find a way to solve location problems by means of Gradually Linearization in 1993{4}. Two years later in 1995 Mohamed and Attia used the constraint equation between rigid link and knuckle to obtain the suspension kinetic characteristics{5}. Almost the same year in 1995, Knapczyk and Dzierzek put forward “Release method”{6}.

In conclusion, the early cars in the 19^th century did not have suspension system, in consideration of safety and comfort, automotive suspension system appears around 1900s. 30 years later, carmakers realized the trend of changing this dependent suspension system with independent one. From then on, different kinds of suspension systems are invented and eliminated, several typical types are preferred by the carmakers nowadays, for instance, Double wishbone suspension system, Macpherson suspension strut and Multilink suspension system etc.

[1] Giancarlo Genta, Lorenzo Morello (2009): The Automotive Chassis Volume 1, Springer. ISBN: 978-1-4020-8674-8

[2] Dennis Hartman. About Car Suspension.

[3] Kevin Craig. Automotive Suspension Systems.

[4] Lee D M A, Pascoe D M, Maragy W H EI. An analysis of multi link independent

suspension systems. International Journal of Vehicle Design 1993, 14: 44-58.

[5] Mohamed M G, Attia, H A. Numerical kinematic analysis of the motor-vehicle multilink suspension system[C]. ASME Design Engineering Technical Conferences, 1995: 883-889.

[6] Knapczyk J, Dzierzek S. Displacement and force analysis of five-rod suspension with flexible joints [J]. Journal of Mechanical Design 1995, 117: 532-538