welding sheet metal to 1" square tube frame

[Pat's 49]

Has anyone built a teardrop with 1" square tube and welded the sheet metal to the tube?

[kennyrayandersen]

Has anyone built a teardrop with 1" square tube and welded the sheet metal to the tube?

It's kind of hard to do that since the 1 inch square stock is probably thicker -- it acts like a heat sink so the sheet stock wants to melt first [naturally]. It may be possible though -- I've seen some metal frames, but don't remember it the skins were welded on.

If you have some special equipment, you could possibly electrically tack weld it (I'm not sure though). The easiest to do is mechanically fasten using squeeze (pop) rivets, which can be steel with a steel shank.

If you are going to mechanically fasten the sheet you could also use aluminum sheet, which is what the Lotus 7 clone builders do (steel welded frame with aluminum skins).

[toypusher]

I would think that 1" square would be way 'overkill' for a teardrop. Half that when you get a skin on it should be plenty strong.

[kennyrayandersen]

I would think that 1" square would be way 'overkill' for a teardrop. Half that when you get a skin on it should be plenty strong.

No disagreement from me, but most of the ones I've seen framed in metal appear to use the 1 inch stock (more readily available?). If you framed it out right, the skin could carry all of the shear loads and the frame the axial loads; still, it's not particularly easy to weld the thin sheet stock to the square stock (though I've seen some car guys so it -- I think the best is to mechanically fasten the sheet to the square stock.

One thing to remember is that stuff might seem kind of flimsy before the skin gets fastened on (and that's OK). Kind of like those cheesy shelves you buy that you think there is no way this thing will hold up anything, but after you bolt it all together it ain't so bad.

[hugh]

one method that might work would be to pre-drill holes in the sheet metal and use your welder to "spot weld" the holes to the 1" tube, that way the tube gets most of the heat and if the holes are only say 1/4 or less the weld should still overlap onto the sheet.

[chorizon]

Combining what Kerry and Kennyray mentioned I think there is a simple solution.

I'd go for 1/2" sq. .060 wall tubing, with 16 ga. (~.060) steel sheet. That way, you'll eliminate any dissimilarities between the different metal thicknesses.

Maybe go thinner on the sheetmetal if you want to cut down on weight. It really all depends on the weldor and what type of machine he/she will be using.

With my limited welding skills i'd choose the TIG first, the MIG second, and the Stick-Welder "somewhere behind J-B weld".

[kennyrayandersen]

I'd go for 1/2" sq. .060 wall tubing, with 16 ga. (~.060) steel sheet. That way, you'll eliminate any dissimilarities between the different metal thicknesses.

Maybe go thinner on the sheetmetal if you want to cut down on weight.

.o6 sheet steel would be pretty heavy. .032 steel would be plenty thick for the sheet.

[chorizon]

True. The problem amateur weldors such as myself run into is concentrating the heat on the thicker metal and then "dragging" it over to the thinner material. You have to linger on the thinner metal long enough to get penetration, but not long enough to blow a hole through it. I find it kinda tricky.

I suppose if I were doing this I would try the .060 wall tubing, and the .032 sheet. I'd definitely run a few test pieces first to get the method down. I'd probably try it using a MIG first, and maybe use an aluminum bar behind the sheet as a heatsink.

[Pat's 49]

Thanks for the input, not sure I can find tube any smaller than 1" and 14 gauge locally, but will see---I have a mig and I extented the cab on the tow vehicle, a 49 Chevy pickup--I spot welded every few inches then went back and put them closer--cooling the metal with wet rag - took forever- I want a smooth outside w/o screws or rivits

[tech]

Panel bonding adhesives used in the auto industry are crash rated so we know the shear strength should be high enough.

Thinking this would be an appropriate application for those adhesives.

It is possible that an aluminum skin could be bonded to the steel framework as the bond line would prevent the dissimilar metals corrosion issues.

Semi trailers are beginning to make use of the bonding adhesives as well with very good results.

Research the different adhesives and their application.

JMH input which won't even buy a stick of gum

[PanelDeland]

Look around for a spot welder.They should work well for this.The jaw lengthMay be too short but the heat and such is controled and should be up to the task.I do think the welds may show if you are wanting bare steel but with a little filler or some glaze you could paint over it and never see them.
Any welding supply should be able to give you a demonstration of a spot welder.

[Larwyn]

Whatever approach you take to weld the sheet to the tube, by the time you complete the job, you would be expert at it. Since I own a good mig welder, my approach would probably be to plug weld it with the mig.

I do not think there are that many steel skined TD's out there but if you were to do a less than perfect job of skinning it you could always name it "Rumpledsteelskin".....................

[kennyrayandersen]

Look around for a spot welder.They should work well for this. The jaw length may be too short but the heat and such is controlled and should be up to the task.I do think the welds may show if you are wanting bare steel but with a little filler or some glaze you could paint over it and never see them.
Any welding supply should be able to give you a demonstration of a spot welder.

If you keep the spot welds toward the edge, you could cover them with the trim (you could also use countersunk rivets, but that would be a lot of work. Too bad Al is such a pain to weld.

The bonding really might not be such a bad idea if you can get pressure to the bond (that may be the real challenge with that approach!).

If you can do it, the spot welder with the trim covering the spot-weld would be the quickest and most painless as you wouldn't have to drill all the holes and spend so much time on every hole once you get the level of the spot-welder set.

[tech]

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[switterstx]

Spot welding won't work well (HF has a cheap spot welder which I looked at for my build) because it is mostly used where you can get to the front and backside of the seam. With a square tube frame you'll never get to the backside. The suggestion of drilling a hole will probably be your best bet and won't be too hard to pull off. Just use something like a 1/4 metal bit. It will eat into the tube a bit but you should be fine. My dad did this with a stick welder but a mig will do it much easier. Just use a small wire gauge and keep the amperage and feed speed down. If you get it down it will be a hell of a lot quicker than anything else you could do, even screws or adhesive. Shouldn't take more than a second or two for each plug.

Good luck,
Tom