The new suspension system called "CLASS" (Compressible Liquid Adaptive Suspension System) is a hydraulic suspension that replaces vehicle springs, shock absorbers, and stabilizers with a complete system whereby the fluid itself is the spring/damping/stabilizer medium. With the aid of an onboard computer, spring stiffness automatically and instantaneously changes according to road conditions and driver technique, over a broad range while the vehicle is being driven.

The use of a compressible fluid as a spring and damping medium is not new, according to Richard Meyer, President of LST, which began using compressible fluid on heavy-duty mining trucks in the 1980s. The system includes a microprocessor located in the onboard control module, which processes thousands of signals transmitted from sensors each second. The system detects variations in steering to predict vehicle yaw and signals from each wheel to control body roll. Also, brake and speed sensors are used to reduce dive and increase control during emergency situations. Each of these sensors contributes to the overall system.

According to LST, CLASS is the first new commercial suspension system designed for the transportation industry since the introduction of air springs. The system's design reduces resonant vibrations and eliminates the undesirable handling characteristics of conventional suspension systems. CLASS is said by the company to be the only suspension system that can instantaneously change the spring rate at each wheel by several thousand percent, independent of load or deflection. This results in a suspension that can handle the required load capacity, while simultaneously providing a soft ride and superior handling than that found in other systems. The company claims that if the system were installed on over-the-highway trailers, the tires would remain on the ground when traveling with an empty load. With current suspension systems, the tires often leave the ground, causing instability and safety problems, not to mention excessive tire wear and frame stress.

LST's goal was not simply to design another conventional suspension system, but a totally new system that used advancements in hydraulics and computer controls. To bring this type of new technology to the industry, LST assembled a team of engineering professionals in such fields as hydraulics, mechanical engineering, electrical systems design, simulation development, and overall suspension design.

Jean L. Broge

AEI September 2000
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