LO 8-10 Identify and describe the types of crankshaft vibration

1.3. Rotating Pendulum Vibration Absorber

Rotating Pendulum Vibration Absorber

Unlike regular balancers, a pendulum vibration absorber provides torsional control by producing forces that directly cancel forces that produce torsional vibration. Steel rollers, called centrifugal pendulums , fit loosely into a specific number of holes in either a harmonic balancer or an overhead cam drive gear. The rollers store and release energy back into the crankshaft rather than converting the mechanical energy into heat energy the way dampers do Figure 70. A patented mathematical algorithm is used to calculate roller, hole, and gear size in order to control how the rollers move forward during compression strokes when the crank slows and rolls backward during the power stroke. Movement of the rollers back and forth minimizes engine speed changes, keeping torsional vibration low. Manufacturers claim that the pendulum damper provides a smoother-running engine, increased valve train stability, and more accurate injection timing. Pendulum dampers have the advantage of being lighter than conventional dampers.

FIGURE 08-70: A rotating pendulum vibration damper is used by Caterpillar in overhead camshaft Advanced Combustion Emissions Reduction Technology (ACERT) engines.