Rock / Print Tumbler

This is my rendition of a simple rock tumbler. Inspired by onkelgeorg's [Affordable Rock Tumbler](http://www.thingiverse.com/thing:935252). The following axle can be located in one of several positions to accommodate a wider variety of tumbler sizes. I have been using an empty paint can with a few ribs glued inside to encourage tumbling. Wrapping the can with some grippy draw liner material keeps the can from slipping on the tumbler's rollers. While I scavanged rollers from an old printer/scanne