What is a PIV Drive?

A PIV is a variable ratio mechanical transmission. This allows you to alter the draws/speeds/tension of one section with respect to another. It is usually done with a pair of cone pulleys or belts or the like. PIV is an acronym that stands for Positively Infinitely Variable. Seriously, this drive is stone age crude. Anyone still using them could consider donating them to some industrial museum. If we need precision control of a mechanical transmission ratio, we would use a harmonic drive instead such as some older printing presses did. However, now days we simply put individual drives on each section because we can control them to around 1/1,000 electrically (or a bit better with some servos).