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squirrelbait
11-08-2012, 06:18 PM
Recently i've purchased a Miller 220A TIG welder and have been chopping bikes, trying to gain some experience. One problem i've been having is serious distortion in attaching the more sensitive tubes (head tube, bottom bracket) looking on other websites i see people using brass and bronze heat sinks to help with this. ....however i dont have $160 to buy just ONE size for a couple projects. has anyone had much success building their own out of found or fabricated materials? I'm fairly resourceful but am at a loss for new ideas.

sandman
11-08-2012, 07:05 PM
Recently i've purchased a Miller 220A TIG welder and have been chopping bikes, trying to gain some experience. One problem i've been having is serious distortion in attaching the more sensitive tubes (head tube, bottom bracket) looking on other websites i see people using brass and bronze heat sinks to help with this. ....however i dont have $160 to buy just ONE size for a couple projects. has anyone had much success building their own out of found or fabricated materials? I'm fairly resourceful but am at a loss for new ideas.

A simple fact is that welding causes distortion, even a good butt welded joint can give a 0.5mm (0.020" contraction although if its an angled joint tacked up as Brad reccomends will contract but not induce angular change,I normaly clamp then tack strips as bracing straps prior to welding and let the weld go cold before breaking the straps away, then you could get into the realms of sequential welding so each weld pulls the metal in the opposite direction to the previous weld, harder than it sounds,but just logical keeping track of the weld placement.You dont need heat sinks , sounds like lower amps and solid jigging needed, just my thoughts , every success with your project
John

sandman
11-08-2012, 07:08 PM
Addendum , deletete harder than sounds, read " easier than sounds "

Radical Brad
11-08-2012, 09:39 PM
Just pondering...

Seems most of the distortion will be due to the heat affected zone right at the bead, so I wonder what effect a heat sink would have on the integrity of the weld? If one side of the joint was to cool at a more rapid rate than the other, would this cause a micro fracture along the welded area? I see this a lot when working with harder steel using 6013. When I welded my car axles, it took a great deal of care during the cooling of the welded area to avoid these cracks. As for distortion, I just plan ahead and assume it will always happen. These days I can set a 90 degree joint off kilter, weld it, watch it warp, and end up less than .5 degrees out after distortion pulls.

Brad

darnthedog
11-09-2012, 07:06 AM
In Welding tips and trick they talk about flooding back side of material with Argon to prevent oxidation on backside while tig welding. But only for Filling holes do they recommend using a heat sink of Copper as the hole filling is not a stressed joint. Tig is a very localized heat. So if your experiencing lots of distortion you amperage may be too high as you have the heat spreading too far across the metal from what I have read. Tig welding is supposed to be the least distorting of welding. And as mention before if you weld a small bit and then let it cool then weld opposite sides a small bit and let them cool. the distortion is reduced as well. Brad instructions in his plans discuss this. Tack cool tack cool till all sides are tacked. Distortion can be kept to a minimum. Sandman's suggestion is also valid with insuring your material is held in place as you tack it. Rapid cooling will only cause more distortion so only natural air to cooling between tacks. Hope that helps

Tradetek
11-09-2012, 12:38 PM
Back purging is only necessary for Stainless Steel.

Are you doing your welds in one continuous weld or are you doing them in short sections working at opposite points in a staggered approach after competing 4 small tacks?

Also, post some pictures of your welds.

sandman
11-09-2012, 05:57 PM
a last thought to add to the wealth of good information offered, a second layer of weld can pull a a joint back too and be dressed back but as has been said just let it cool naturally.
john

Trike Lover
11-10-2012, 07:22 PM
..... just logical keeping track of the weld placement.You dont need heat sinks , sounds like lower amps and solid jigging needed, just my thoughts , every success with your project
John

I'll just chime in here with my two bits worth of being an "occasional" stick welder for 30+ years before getting a MIG setup.
What John has said is bang on. Many years of bodging with a Lincoln AC 225 - your basic 240 VAC buzz box - taught me several things that have helped tremendously when alignment is an issue. Even now that I'm using a MIG setup, I still follow these same points:
1) Jig or clamp where possible. It's amazing what some 2 x 4, some scrap plywood, and some deck screws will do in terms of making up a jig for a "one-off" or "two-off" job. Well worth the time it takes in terms of improving your results.

2) Start with small tack welds. Just enough to join the two pieces. If you put your thumb over a tack weld and can see weld around the edges of your thumb, your tacks are probably too big.

3) Make your tack welds at opposite sides or ends as appropriate, so that the contraction of one tends to be countered by the contraction of the other. This may involve flipping your piece in your jig, but a bit of planning ahead avoids most of that.

4) Spacing your tack welds well apart. This may sound like a no-brainer, but I've seen people putting their tack welds 1/8" apart and wondering why they get distortion. Initial tack weld spacing, when possible, should be wide - 1, 2, even 3 inches apart.

5) Use lower amps and smaller diameter rod - the less current, the less heat and the less distortion. Smaller rod will allow you to make welds with good penetration at lower current settings. With MIG, you can just dial back the current.

6) If you can't make up a jig, often times you can use large C-clamps and a couple of lengths of fairly hefty angle iron, one on either side, to keep pieces in initial alignment. By keeping your welds small, you also don't end up welding the angle iron to the pieces under construction.

7) As Brad has pointed out, figure on a certain amount of distortion due to contraction when doing your initial setup, if not using a strong jig. You can minimize the distortion by spacing your initial tack welds, alternating from side to side when doing your welds, and not running any more current than necessary. (This last also helps prevent blow-outs or holes, which are ugly as well as being a pain to fill in). Once you have your initial series of tack welds made, check the alignment. Sometime a few licks with a lump hammer will correct a small distortion without creasing the metal. After making your first series of tack welds, make your next set halfway between the initial tacks, again keeping the welds small. Check for distortion - if you're getting a lot of distortion due to contraction, you may have to grind away the welds and reset the pieces in an initial alignment that's "out of true", but that will get a lot closer to correct alignment as the welds contract. Once you've got a series of tack welds, maybe having made two or three passes of tacks on a big piece, then start filling in the spaces, again alternating sides and/or ends. Check your alignment as you go - don't be in a rush.

Some of my friends have used colorful language to describe my stick welds - "bird poop" is probably the most complimentary, but putting pieces together using the points above, and that John, Brad, and DTD have made, I've managed to make welds that keep the pieces pretty much in the alignment I want when I'm finished, and even if they're not very pretty, they're good and strong. A few minutes after doing the final welds with the grinder or a flapwheel will improve the overall appearance amazingly, LOL.

My biggest mistake, when I first got my buzz box and started welding, was to use thick rod, high amps, and make long passes (because having had so much trouble striking an arc in the first place, the tendency was to just keep going). Experience has taught me the error of my ways - my welded parts are a lot straighter, even if not pretty, and the extra time involved in fabricating a clamping jig pays huge dividends.

As usual, I've run on here, but unless you're welding all the time, it's _hard_ to get good, even, well aligned welds with good penetration. The guys who do it all day every day know all these tricks, and they also get a really good feel for how a particular shape or thickness of material will respond or contract. "Occasional" welders like me pretty much have to "re-calibrate" every time, if not welding on a regular basis.

Good luck with it.
TL