I'm trying to find the correct name for a type of drum or spool which is used to drive a cable. The one I'm thinking of is not a straight cylindrical type, it tapers in on a radius at one end and then reached the middle of the drum and then tapers back out again (radiused, not a v type). It is a variable diameter drum designed to cause the cable to bind and not slip. I would like to know the name of the type and a link to where I might buy one. I am thinking about that method as a drive for a flame cutter.