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What is the best way to tack the tubing?
Do you tack only in one side of the tubing?
Do you tack at the 4 corners?
or 2 sides?
How did you guys do it?
pics would be great.

Thanks it advance

Randy

I tack on either side of the joint usually since one side is usually clamped to the table and I want the heat shrinkage to be balanced.

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

Tack diagonal corners initially, and clamp everything down like a tornado's coming if you want to minimize distortion. Even then, it'll warp some when you release it, but it'll be pretty close....

and as i found, if you can swing it...let the clamped portion cool overnight (or at least for several hours). i'm sure it's overkill but i got a lot less distortion when i took my time and left it clamped for an extended period of time after the welding. and what i have done is fully welded the bottom and top rails while securely clamped and the rest of the tubes i just tacked during the build and once it is all together i'll fully weld it while taking my time and not getting it too hot.

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**Build diary**

Sound advice - that's the way we did it, too, and the finished diagonal measurements on the frame were less than 1/8" total distortion...closer than a brand new factory car.

By the way, I've got photos of my build at http://www.freewebs.com/zetec7/ if anyone's interested....

Zetec7
Nice frame pics.....I like the Colin Chapman I can lift my whole frame shot.

Good Job so far....

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I'll keep an eye out for you!

To err is human...
I am more human than most.

Just an FYI to those starting a frame. Welding distortion works in funny ways. When hot it will warp very very slightly in one direction, when it cools it will retract in the other direction quite a bit. I've heard this phenomenon referred to as "heat shrinkage". If you would like to see an illustration of this, then grab a three foot section of straight tubing and put a 3" weld bead up one side near the middle of the tube. After it cools check it out. It will have a bend in it toward the side you welded on.

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

Do you think alot of that distortion has to do with using 16 gauge steel? I'm betting a thicker metal would resist distortion, good penetration or not. Of course, I wouldn't use that thick of metal for the frame, so it's kind of a pointless point :p

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The trouble with having an open mind, of course, is that people will insist on coming along and trying to put things in it.

-Terry Pratchett

I don't think thickness plays a huge factor. I saw in Herb Adam's book where he show how to add negative camber to a solid rear axle by heating the housing along the top with an acetalyne (sp?) torch. That housing is usually pretty thick stuff.

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

Yup, I remember reading that now. Hmm, science, good stuff.

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The trouble with having an open mind, of course, is that people will insist on coming along and trying to put things in it.

-Terry Pratchett

thicker steel would distort much less given the same amount of heat. but if you put enough heat into it to actuwally weld it might come close. it is amzing what heat can do to a chunk of steel. it takes years of experince to master this. the best advice for welding a frame, always weld oposite sides of your tubing back to back and jump around as much as you can. welding the opostie sides helps cancel out the pull caused while welding. jumping around helps to keep weld zones cooler and keeps the heat soak down.