Originally Posted by onehundred80
My humble thoughts, always offered, sometimes ignored. Take your pick.
Looking at tighed1's photos the error appears to be about .140" (the pitch between the ribs) with this much error then the stresses on the belt will not be equal across its width which I guesstimate at 8 x .140" = 1.12". Maybe someone will let me know how much this figure wrong, I would like to know. Standard pitch is .140, hence my 1.12" figure.
This stress will go all around the belt as the belt is being stretched on the front face and compressed on the rear face at the crank pulley. This will lead to the belt being pulled back into alignment at the various grooved pulleys, while at the plain pulleys the tension will be eased by the belt pulling back into a less stressed state. Pulled and pushed the belt will start`Hunting'. This phenomena I believe can be seen in the first movie clip in this thread with the belt moving forward and backward.
`Hunting' in the old days of flat machine belts was used to keep the belt on the pulley by crowning the pulley, the belt had equal stress each side of the belt when it stayed on the center of the crown. Move the belt too much of center and the belt slipped off.
I agree with the hunting issue. It is clear as day in the video, but a bad tensioner would have a similar problem too.