The pulsing of the blower torque from the load changing constantly is brutal on belts. V belts take it better. There was a manufacturer who tried a chain but it didn't work out. Something's have already been worked out and aren't worth changing.
Gene
Indeed, been there and done that,.... under protest.
At Steam Genie, our owner suggested that we give it a go (synchronous belt). He had just finished putting together a street rod, and thought the belt looked so impressive on his supercharger, that for aesthetic reasons we should put it on our lineup of slide-ins. I insisted that it would NEVER work. The rotational vibration of a two cylinder, combined with the same, with the straight-lobe blower would knock the teeth off in short order. I was accused of being pessimistic, and not a team-player for having sound engineering reasons to forgo the attempt. Alas, we did it anyway. We produced about two dozen units before it became apparent that our custmers were dissatisfied with an average belt life measured in a few dozen hours.
Two cylinder 4-stroke horizontally opposed engines produce a sinusoidal torque with a period equal to the RPM. A v-twin is actually worse, inasmuch as the sine wave becomes offset and irregular. The straight lobe blower traditionally used also has a cyclical torque resistance that varies though a rotation. This induces a vibration that varies by speed, When the sine wave crests intersect, it is called a "critical speed", where the destructive vibration is at its most extreme. Running the engine anywhere near this speed is very hard on the coupling device. Fortunately, v-belts "soak" up these vibrations with little fatigue. Timing or synchronous belts do not. Synchronous belts are designed specifically to be very stiff, so they can assure zero slip and be used for timing applications. With a helical lobe blower, and a well harmonically balanced V-8, they work actually well for an automotive supercharger. On a slide-in TM, the best you could hope for is a few dozen hours, if you can steer clear of critical speeds (no linear throttle).
