Continued with the rear frame raise project today. I started making the combination rear bumper/rear frame cross-member. I cut the bumper tube (2" x 4" x .188") 60" long. It'll be a bit wider than the body with corner armor. I figured it will keep that rear radiused corner a little more protected. The design uses four recovery points and a hitch receiver that go through the rear bumper, welded on both sides, and then get welded to the front cross-member. So I had five through-holes to cut (both sides of the bumper). I had SendCutSend make some templates to make the cutting easier. Situations like this are where plasma cutters really shine. I didn't take pictures cutting the hitch receiver hole, but I did take pictures cutting the oval holes for the recovery points. Because the body has that sheet metal flange that hangs down, I needed about 1" clearance from the top of the bumper to the top of the recovery points and hitch, so all through-holes are lower than centered.
In this first picture, you can see the hitch receiver hole has been cut, and the template is in place to cut the oval holes with the plasma torch:
And after cutting:
Unfortunately, I didn't quite get the templates right. I accounted for the torch diameter and kerf, and even added some space, but the added space wasn't quite enough with the inexactness of holding the torch perpendicular to the workpiece. It's less than .010" too small. I'll have to use a carbide burr or mini-belt sander to clean things up so that the pieces fit in the holes. Better too small than too big, though! Much easier to remove 10 thou than put it back!
So the day ended with these parts mocked up (the hitch receiver was pickling, so it's not in the picture):
I haven't discussed the body mount plates, yet. You can see those in the picture above. I went with .188" thick, which is very close to the thickness of the double .090" sheet used on the factory rear cross-member. I'm going to have to machine .090" off the top of the bumper and rear frame pieces where that plate is sitting to keep the same geometry, though, because there's only one .090" sheet on top the factory frame beams.
An additional issue with replacing the rear cross-member with a bumper that has the same rear vertical plane as the cross-member is the body mount centerlines fall inside the front plane of the rear bumper. To accommodate the body mounts, I got some 2.5" OD x .188" wall DOM tubing, and I'll weld those into cuts in the bumper, and then add some gussets. This picture shows a bit of that (the DOM pieces were also pickling, so they're not in the picture, but you can see the round cutout for it in the bottom of the bumper):
To be continued...
