Ok, I can give it a go. Just so you know if I were to go back to the same materials I would make some things different. That said here you go:
The entire top is welded together with some scraps I found laying around my buddies fab shop. The whole thing is really a chop shop job we did in a Sunday afternoon and is totally eyeballed. The frame is 3/4 inch steel square tubing, and we just rolled it into a circle to match the trough. But since the trough isn't perfectly round we had to cut smaller straight pieces of the square tubing and weld those in where the trough is flat and not round ie the front and back in those pictures. Then we made two of these pieces one would be the bottom and the other the top frame. The top has extra "bars" with tabs on them so I could just sit top panels "in the grove" and they would not move around and close the top off.
Next we cut out small square tabs to fit the bolt holes that are already formed on the inside of the trough, drilled holes in them and tack welded them to one of the bottom frame piece so they match up with the trough. Hence the top will only fit one way on there, and the trough top now goes on with just six bolts. So the way it looked at this point was a trough with a steel "circle" frame bolted to the top.
Then we just cut a few 18" square tube strait pieces and welded them a right angles (well sort of, this is where the eyeballing becomes apparent) so we could attach the top frame.
The sides are just some sheet metal I found in the yard, cut to size and tack welded on. The rest is just polycarbonate and some wood paneling on top. Some rust treatment and painted.
Here is a pic from the inside and you can see the frame and one of the bolts just above the date in the photo. You can also see my shotty caulking where there was a pretty big gap between pieces of sheet metal.
If you have any other questions just ask.

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"Relax, Don't Worry, Have a Homebrew!" Charlie Papazian