Q. I need to make extra-wide wheeltubs for the rear wheels on my truck. I know that some companies have these readymade, but I want to make them to my own design. The simplest wheeltubs have a square edge, but I want mine to have a nice, rounded edge, which I think will look more finished.
I have a good idea about how to shape the flat inner part of the tub, and how to curve the metal for the outer part, but I'm not sure what the best way is to make the rounded edges. I have considered using a hammer and dolly to curve the edges freehand, or making a hammer-form. Also, I don't know if it's best to do all the forming on one part, or half the forming on each part. How would you recommend doing this?
Via the Internet
This is a beading machine being used to curl the edge of a sheetmetal panel over to 45 deg
A. While you certainly could form the edges freehand with a hammer and dolly, you'll get a much nicer job if you use a hammer-form. You could also use a beading machine to curl the edges of both parts.
Starting with the hammer-form approach, you can make a good form from plywood. You may want to glue together two or more thicknesses of ¾-inch plywood, depending on the size of the radius you want to make. Once the glue has dried, you can cut an arc the same diameter as your wheeltub. This can be cut with a saber saw, and the edge can be smoothed with a disc sander. Next, you can round off the edge of the form. A great way to do this is with a rounding-over bit on a router, but it can be done by careful work with rasps and sanders, too.
To form the flat portion of the tub, the metal blank is cut so that the edge will be the correct size after it is formed to 45 degrees. A little experimentation will tell you how to size the curved edge of the blank, but it will be very close to the size of the hammer-form. A clamping block is used to sandwich the metal being formed, and this needs to be trimmed back to the point where the edge radius starts.
With everything clamped together, the edge of the metal is worked carefully down to match the shape of the form. As long as everything is tightly clamped, this should go quickly and leave you with a beautifully formed blank with no distortion.
The outer panel is formed in a similar manner, but clamping it to the form will be more difficult. A straightforward way to do this is to use a few drywall screws to hold the metal to the form. Although it would be beneficial to use a clamping block for this, it's so difficult to make and hold a curved block that I'd dispense with it for this part of the job. The screws alone should work pretty well, and the only downside is that you'll have to fill some screw holes, and perhaps do a little touchup work with a hammer and dolly.
A beading machine can be used to do this job, too, with special dies. I have a new YouTube channel (youtube.com/user/covellron) and if you look at the “Beading Machine Basics” video, you'll see how these dies work. Although I'm making a different part in the video, the process would be just the same for a wheeltub.
However the parts are formed, the last step is to weld them together, and metal-finish the joint. With a bead roller, you could put some stiffening ribs into the panels, too. It's a great way to personalize your truck!
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