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Friday, April 23, 2021

Understanding Torsional Vibrations… by Ken Cooke

The basic function of the clutch on modern heavy-duty diesel engines is to stop torsional vibrations from reaching the transmission and other drivetrain components. In fact 90% of the clutches work cycle is dampening vibrations from the engine to the driveline. This is accomplished with spring dampers in the clutch disc. These coil springs compress with the application of torque and transmit force to the spring covers which are attached to the disc hub, thus transferring vibration free torque to the transmission input shaft.

There are three basic categories of torsional rates for clutch dampers: rigid, standard and soft damper.

Rigid Dampers have no springs and act as a direct link from the engine to the transmission providing no protection against torsional vibration. Rigid clutch discs are never used in new OEM applications.

Standard Dampers include all 10-spring and most 8-spring types. The springs used in these dampers are approximately 1.5″ long and do not offer a large amount of protection. While these dampers were completely adequate for most heavy-duty applications several years ago, they are generally incapable of reducing the engine flywheel vibrations developed with modern slow speed electronically fueled engines. The use of standard dampers in heavy duty applications has virtually ceased in modern OEM applications. The trend is to use more capable soft-rate dampers.

Soft-Rate Dampers such as those found on Eaton’s new 7-spring Advantage Series® heavy-duty clutches, offer much better protection against engine flywheel induced torsional vibrations. Their springs are generally longer than springs used in standard rate dampers and offer more deflection before coil lock occurs. This larger spring deflection is equated to lower torsional spring rate. With lower torsional rate, the resonant frequency of the complete drivetrain is lowered.

Advantage Series® clutches offer the performance, reliability and protection you need to stay productive and profitable. These new industry leading clutches offer advanced features like a new bearing housing design, longer lube intervals, a protected internal adjustment mechanism with a full-round contamination baffle and square adjusting ring threads that reduce the risk of sticking and seizure. Advantage clutches also come with a 2 year warranty backed by the Roadranger® support network.

Conclusion – Older style 10-spring clutches are not capable of dampening the damaging torsional vibrations on modern electronic engines. When peak engine torque exceeds the damper capacity, the driveline will be abused. This abuse will cause faster wear and potentially damage your transmission, driveline and differentials. Since damper capacity is a product of the springs, changing the number and type of springs changes the stiffness of the entire system. Maximum drivetrain component life can be achieved by using a clutch that was designed and engineered for your engine.

When you need to replace your clutch, phone Coastline Transmission and Differentials at 604-533-4651 and ask us for a quote to install a new Advantage Series genuine Eaton 7-spring clutch.