CMP tail gate hinges

[Grant Bowker]

I was working to make hinges for the 15 cwt trailer rescued from the Smiths Falls scrapyard as pretty much the complete box needed rebuild. Some of the hinges made are shown. There were variations in stock size and length depending on location and use but all were made the same way.

[Grant Bowker]

The jig used to bend the hinges was made from scrap bits of angle, rod and plate welded (crudely) together. The photos show the jig and the bending sequence scribbled on some wood that has probably since been fed to Lucifer. The bending had to take place in phases as I couldn't work fast enough the do the full bend in one heating of the stock. I was using an oxy-acetylene torch for the heating. If you have access to a forge, it might work better.

[Grant Bowker]

When I was looking for heavy gauge tube/pipe for the stationary part of the hinge on the trailer body I realized there is an alternate approximation of the hinge possible. You could weld a suitable length of pipe to your flat strap, dress the weld and not have a terrible representation without any bending. The pipe I found suitable was 1/2" schedule 80. The schedule 80 has heavier walls than the common schedule 40 so is both stiffer and a better fit on 1/2" rod. I haven't made any hinges this way but photos show the idea and the fit of rod within pipe.

[Jordan Baker]

Awesome, thanks for the pictures. That is something I can easily rig up.

Im just curious on the actual process. Do you fix the jig in a vice, then insert the metal strap in from the top and flush with the bottom edge of the angle iron? Heat and bend as you until the strap is now against the long side of the angle iron?

Is the diameter of the rod on the jig the same diameter as the finished inside diameter of the hinge?

[Grant Bowker]

The jig was in the vice. I preheated the hinge stock before inserting it as you described. My thought was that I would limit the heat getting into the jig to reduce distortions. Most hinges took a second heating.
The jig rod was the same size as the hinge rods but to ensure a bit of clearance I did run a 33/64" drill down the barrel of the freshly made hinges. some didn't need any material removed, some did.

[Jordan Baker]

Ok thanks. Ill come up with my own jig. Looks to be simple enough.

I also found this link for hand forging this type of strap hinge. I know for our use, all the hammering marks would not be correct.

http://www.fao.org/docrep/009/ah637e/AH637E21.htm

[Jordan Baker]

I found some time this afternoon to make up my hinge jig. Thanks for the pictures.