Thursday, March 26, 2009

Tailgate fabrication

Now that I have the jig made, I bought the steel then cut and fitted the parts for the tailgate. For the side rails, I opted to use 1 and 1/2-inch by 1/4-inch steel strap. After cutting and trimming them to exact length, I drilled two 3/8-inch holes for the mounting bolts into both side rails, into which will be inserted 5/16-inch machine bolts to mount the tailgate into the mirror box. The heads of these bolts will be countersunk below the surface of the mirror box's sides. This will prevent the bolt heads from scuffing the inside of the rocker box and allow for smooth and easy motion.

For the top, middle and side rails, I opted to use one inch square steel tubing with a wall thickness of 1/8-inch. This will provide enough metal for the collimation bolts to grip the threads without the risk of them becoming stripped. Finding the tubing has been a bit of a problem since all the steel suppliers here will only sell it in 20 foot lengths. So I bought a 20 foot piece of tubing and had them cut it in half so I can get it home. Then it was simply a matter of cutting three 16-inch long pieces then, laying out, marking with a center punch then drilling all the holes for the bolts that will be added to the tailgate at a later time. Using a center punch and steel ruler, I got the holes marked and drilled in the right spots with my small drill press.

Then it was back to the jig where all the pieces were arranged in their correct positions for tack welding. I then used a square to check that the assembly was square, which it was. After tacking, I then checked again to make sure it was square. Then I welded one side of each rung at a time until each rung was welded to the side rails all the way around. After touching up the welds where the bead was undersized I partially filed away one spot with a little porosity and re-welded it. The metal was fairly clean so the voltage at the arc may have been too high for the welds I was making. I turned up the wire feed speed to compensate. The welding wire I am using seems to be on the troublesome side for porosity effects, or my machine generates higher amperage and voltage at the arc than expected. Then I filed down the butt welds where the top of the gate will fit into the mirror box.

I'll probably dress the welds with a grinder later, but both diagonals are identical and that can only mean the tailgate is square. All that's left to do now is to thread the holes for the collimation bolts then prime and paint the tailgate with flat black rust preventing paint.

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