#11
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mark g,
Thinking about your plywood. I have found that if I define a flange around the teardrop with a beadroller then I can pretty much get any crown I want. As the teardrop warps I just beat the flange into submission. I have been advised that flanging the teardrop will cause me problems down the road in fit up and welding so I stopped that. Maybe I should revisit that method. Also about bending. Looking at my profile templates this form is like half a rolled cone with a lot of shrink in the front I think. IMG_1831.jpg
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John C |
#12
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John,
I have seen headlight buckets on Morgan & Mgs that were made by wheeling diagonally across the top to raise the bubble. If you start out with the teardrop shape wheel progressively toward the edge. A little further each time. Pulling down on your panel while wheeling helps the edges move downward. so you may not need flanging. Ron
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Ron |
#13
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mark g: Is your plywood form a single thickness of plywood? Do you screw the sheet to the plywood? I've got a single piece with the hole cut out but not sure of how to proceed. Is this a hammer form where you clamp between two sheets?
Ron: I cut some more blanks this morning and will give it a try.
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John C |
#14
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Jon,
I think flanges could work. There may be associated problems, but I'm not sure what they would be. Flanges would take away your ability to shrink edges, but they would help keep the edges flat as long as they were strong enough to resist the drawing in forces of the dishing. Drawing in could cause a misalignment, but by how by much after the flange is trimmed off? Not sure. |
#15
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You could try different things. A single piece of plywood would be one but two pieces will control the reaction to "drawing" better by keeping edge ruffles from forming. You could screw through the wood and the metal. In shaping, the metal will stretch the easiest at the center of the cutout but will fail there first too. You might try stretching a little where it's easy then work that back toward the edges in courses. Preserve the thickness at the center if you can.
Last edited by mark g; 01-22-2021 at 11:29 AM. |
#16
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Ron: I tried just wheeling the fish outline across the diagonal of the profile. It warped as much or worse than in the past. That might be because of my inexperienced wheeling patterns but I'm not real hopeful about the diagonal wheeling.
IMG_2053.jpg
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John C |
#17
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This is my new test piece for the fish project. A little more like the real thing. Got one to weld up finally.
IMG_2020.jpg IMG_2025.jpg
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John C |
#18
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Nice job, how did you do it?
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#19
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mark g,
That was done without flanges using a Kent White air power hammer. Two or three times the shape went warped and I took it to the beater bag and reshaped it. Then planish in the hammer then soft stretch on the hammer to the match the templates. But this approach is not going to work. 1) The metal halves are vertically side to side at the weld. They need to be horizontally turned edges that can be butt welded together. 2) I am not physically able to hammer for more than a few minutes a day. Thus the air powered hammer. I tried the hole in plywood thing. It works fine for getting the shape roughed. But again it is shoulder, arm, and wrist work. Maybe I can find a way to put the plywood under the hammer! Going back to the flanged method and try that all the way through. One of these ways will work for me. IMG_2047.jpg
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John C |
#20
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Hi Jon,
Nice effort. What die combinations are you using on the air hammer? Are you able to edge shrink with the air hammer? Another thing that might help is to leave an opening in your weld-seam somewhere to get something like a snarling iron inside to help shape and bring the joint together. You can do a lot of tack and shape, tack and shape, before the final weld-up- if your arms and wrists will agree to it. |
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