Vibration Damper
The power impulses of an engine tend to set up torsional vibration in the crankshaft. If this torsional vibration were not controlled, the crankshaft might actually break at certain speeds; a vibration damper mounted on the front of the crankshaft controls this vibration.

There are a few variations of the vibration damper (fig. 3-44), but they all accomplish their task basically in the same manner. They all use a two-piece design The differences in design are in how the two pieces are linked together. One type of damper links the pieces together by an adjustable friction clutch. Whenever a suddenchange in crankshaft speed occurs, it causes the friction clutch to slip. This is because the outer section of the damper tends to continue at the same speed. The slippage of the clutch acts to absorb the torsional vibration. Another type of damper links the two pieces together with rubber. As the crankshaft speeds up, the rubber compresses, storing energy. This minimizes the effect of crankshaft speed increase. As the crankshaft unwinds, the damper releases energy stored in the compressed rubber to cushion the speed change in the other direction.