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Fabricating the front and rear uprights for the center spar posed an interesting challenge. Each is about 18 inches long. One has a thickness of .063 inches. Which if that were all I had to deal with, I could bend it in my regular leaf brake and be done one with. However the other pair is 1/8" thick and I think would be a little too much to bend for the leaf brake.
Fortunately I have a hydraulic press and also a 26" press brake to go along with it.The problem with the press brake though is that it can not bend beyond 90 degrees because of the press die. Also the nose of the press brake was too narrow and not rounded to the required 1/4" nose radius. Time for some modifications.
First step is to modify the nose base to give it 1/4" radius.
Which turned out quite well.
I also needed to modify the base of the press brake. Originally there was a solid 90 degree vee die, which does me no good since I need to bend to 85 degrees. This was replaced by a couple of pieces of 2"x2"/3/16" wall tubing so I could do an "air bend".
The above picture also shows the start of the bend. The piece of aluminum stuck to the nose bar is a site line guide. Since I can not see the center line of the bend, I draw a site line offset by 1/2" from the center that I could use to make sure blank was lined up properly.
The picture below shows the bend in progess and provides a better view of modifcations made to the original brake. The upside down dial indicator is so I could return the press to its last known position when I release the part to check the angle.
The finished blank ready to be trimmed to size.
This process was quite a bit of work to make a couple of parts. It took several days of my vacation from work to complete. However I did learn a lot from the process in terms of machining techniques and parts fabrication. For someone that does not have a bunch of machine tools, it might be possible to form the 1/8" parts using the hammer method. These parts can also be had very cheaply from Zenith. They are about 12.50 apiece when I looked at the parts catalog.