Recently I've been puzzling over how to recreate the bars supporting the fenders of the 15 cwt trailer. The bars are made of solid 2"x1/2" material, beyond what we've normally formed at the barn. Some of the bends are clearly made on a press brake as seen on the stubs left on the frame by a previous owner. Other bends are about 1-1/2" radius, similar to the fender edge. With few remaining to study, this has been an exercise in making something that looks like what is found in photos.
To create the radius bends, I had a choice - either pay the local steel supplier/fabricator or think of a way to bend the bars. Being cheap and stubborn by nature, and not being wise enough to know I'm not supposed to be able to figure out how to make something we decided to have a go. Heat seemed unlikely to work nicely so it became how to press form the bend.
The male (round) former was made from a section of 3" OD pipe (probably nominal 2-1/2") found in the barn's spare parts bin. It was reinforced with steel discs set every inch along its length and welded in place. A piece of 2" channel was added along one side for the press to bear on. In retrospect, I should have trimmed the legs of the channel a bit more so it bore on the pipe at its centerline as well as at the legs (for better support under pressure). The support for bending was made from more rusty scrap - two pieces of angle welded to a plate. I don't think there's any special magic in the spacing of the angles except that they need to be close enough to each other that the bar being bent will reach the full 90 degrees (if too widely spaced, 90 will not be possible) and far enough apart to permit solid welding. the worst of the rust was polished off the corners of the angles for smoother sliding of the bar stock and the corner radiused a bit for the same reason. Trials were performed with thinner and narrower bars to confirm the tools would work, then moved to the actual size. I was pleasantly surprised how well the 20 ton press worked to do the job. To overcome the springback in the bent bars, I did need to press far enough that the inner legs of the angles bent a bit to allow a bit of overbend in the bar stock.
As shown, all 4 bars came out very much the same for radius and also very close to the 90 degees of the framing square.
|