[Destroyer]

A harmonic balancer is, basically, a vibration damper. When an engine (any engine) runs it vibrates. The crankshaft harmonic balancer is a device connected to the front of an engine's crankshaft, usually built into the crankshaft pulley. It's usually made of rubber and metal, which easily absorbs any harmonic vibrations that could harm the engine otherwise. Look closely at most balancers and you'll see that they are made of an inner metal mass, then a rubber ring, and then another metal mass with groves in it (the pulley). To further explain in far better language then I could muster here is a quote from Wkipedia on how they work.

"Each time a cylinder fires, the force of the combustion is imparted to the crankshaft rod journal. The rod journal deflects in a torsional motion to some degree under this force. Harmonic vibrations result from the torsional motion imparted on the crankshaft. These harmonics are a function of many factors including frequencies created by the actual combustion and the natural frequencies the metals make under the stresses of combustion and flexing. In some engines, the torsional motion of the crankshaft at certain speeds can synchronize with the harmonic vibrations, causing a resonance. In some cases the resonance may stress the crankshaft to the point of cracking or complete failure. The harmonic balancer helps minimize torsional crankshaft harmonics and resonance. The damper is composed of two elements: an inertia mass and an energy dissipating element. Most often made of rubber, this element may be composed of a synthetic elastomer, a clutch, a spring or fluid. The mass counteracts the torsional crank motions and in concert with the energy dissipating element absorbs the harmonics vibrations".

So you see, by absorbing most of the harmonic vibrations being imparted to the crankshaft by the detonation of the air/fuel mixture in the cylinder the balancer extends the life of your engine. Pretty smart these engineer type people. <grin>