Build your own Tube BenderNext we're going to make the frame for the bender. Start by cutting a piece of the 40mm x 80mm box section at least five feet long for the base. The upright for mounting the former on wants to be offset to one side by 1" plus the thickness of its mounting plate, since I used ¼" plate that meant 1 ¼". So I used two pieces of 1 ¼"x 1 ¼" box about 5 ½" long welded to the side of the base about a 1" from one end.
Trace the shape of the stub axle out on a piece of ¼" plate and mark the holes. Cut it out and drill the holes. Then take the piece of pipe or tube that sleeves over the tube size you want to bend and cut it in half lengthways. You want this to be a pretty accurate semi circle so cut it a little on the generous side and make sure you're going to have the seam in the scrap bit. Grind or file the cut edges so that they're straight and come halfway up the tube you want to bend. Also cut about a foot of the 40mm x 80mm box. Bolt the mounting plate to the hub (you'll probably only be able to get three of the bolts in) and clamp the whole assembly to the foot of box section, then take the half section of tube and place it on the base packing it up by a ½" or so, place a piece of tube of the diameter you want to bend on top of it. Place the former on top of that so that the tube is supporting it and there is a small gap between the sides of the groove on the former and the half section of tube, mark off the length of 40mm x 80mm and trim it to suit. It's vital that the tube is in contact with the face of the drum AND the half section of tube that forms the guide, so check this carefully, then you can reposition everything for welding.
Once that's all welded, the next step is to make the guide and add the stirrup to the former. Cut off about a 1 ½" of the guide to make the stirrup for the former. Using a piece of tube to align everything make a packer for the bottom of the guide, and cut a 40mm x 25mm piece of ¼" plate. The packer for the bottom of the guide ought to be sized so that it positions the tube parallel to the base of the bender. Weld the guide to the packer, and then weld the 40mm x 25mm piece of ¼" to the base to act as a stop to prevent the guide from sliding along the base during bending. IMPORTANT BIT, the end of the guide should be positioned directly under the stub axle of the former. Once that's done, I used a couple of pieces of 1" angle to provide a location for a single 6mm bolt at the rear of the guide, but you could make a couple of tags out of the ¼" plate. The idea here is that the bolt only provides a location for the guide and the stop is what actually, well, stops it. This means you can change guides and formers for different diameters of tube, which is almost certainly something you'll want to do at some point. The next thing to do is the stirrup that pulls the tube round with the former. The positioning of the stirrup is another IMPORTANT BIT. The back edge of the stirrup needs to be between 1" and 1 ¼" from the front edge of the guide. Less than this and it will be bloody hard to bend decent wall tube with it, more and it will tend to collapse the tube. With the guide and the piece of tube in position, mark the scythes handles along the centre line of the tube and cut them off. The stirrup should slide along the tube and meet up with them afterward. Once it's all fettled to your satisfaction, then weld the stirrup to the scythe handles, vee-ing the joint out first as this point is going to be under a lot of load and we don't want it flying off do we?
All that remains is to make a handle and add some feet to the base. The handle bolts to the drum so you can move it round for another bite if you need a 180 degree bend, so another piece of the ¼" plate is drilled to fit over the wheel studs on the former and then welded to a six foot piece of tube for the handle. I used some water pipe for this, but scaffold tube would be better. Cause the water pipe bent.... |