In the process of building a boat I ran into a problem which required the fabrication of a new tool. The rub rails for the boat are schedule 40 aluminum pipe 2 1/2" in diameter. They require significant bending along a radius of approximately 14'. I tried numerous ways to bend the pipe without a roller and wound up kinking the pipe every time. After consulting some commercial boat builders the general consensus was that a ring roller was needed. Heavy duty commercial ring rollers are extremely expensive so I decided to build one. My design utilizes 7/8" plate sides (that just happened to be the thickness I could find used). The shafts are a little less than 2" in diameter, riding on huge tapered roller bearings that are adjusted for end play using castle nuts and cotter pins. The roller shafts are driven with #80 chain and a huge gear box. I've use a VFD to control the speed and direction of the rollers. All the dies for the roller were made from a piece of 6" diameter steel repurposed from a sewage treatment plant in Michigan. The roller has worked very well, bending huge pipes without any kinking. The pipes are bent then compared to a full-size template of the radius. After the pipes are bent they are split on a band saw. Sorry for some of the pictures, the downloading software rotates them and I can't fix the problem. If anyone knows how to fix this problem let me know, I have more tools to post.