[Barlea]

A 1/2" wide strip of paper can be wrapped around the pulley so that it overlaps and cut across the overlap. This will give an accurate circumference, fold it exactly in half for 180*, fold the end in to the crease for 90* and again for 45*. Next fold is 22.5* and if you have folded and creased carefully it will be at least good enough to work out the diameter for Richard's strip. ..B.