Re: V belt, How buy?
Nehmo, Goog mentions about adjustable pulleys and I think they have them at Grainger, but I thought I was going to at first be able to adjust length with the section belts where links of the belt can be removed or added to adjust length. Only thing is that the tension I needed and that the belt stretched so adjustment that way did not snug up enough. The belt slipped on the smaller of the two pulleys. The regular v-belt that I got at the auto parts store Kragen was a Gates belt and does have very little stretch. I made a slotted adjustment and move the whole bottom jack shaft up or down, which for my dual stacked jack shaft allows the tension between top an bottom jack shaft pulleys to be set just right without slipping.
I will look to see what kind of cost there is involved in adjustable diameter pulleys, as it may be in the future for me if in the big picture it is easier.