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jimboflying
11-21-2010, 06:20 PM
I am having trouble welding the 3/8 channel used in the bird cage and other places. I am using a TIG welder with the pulser on. I frequently melt the edge back. It seems like the energy wants to go to the edge instead of where I am trying to direct the arc. Does anyone have tricks or suggestions?

jrussl
11-21-2010, 06:35 PM
You need to have a foot pedal and back way off as you approach the edge. Of all the welding I have done on my airframe, this has to be the hardest.

What kind of welder do you have? I started with a Miller Econotig and it gave me fits. The "on" current was somewhere between 25-30 amps so when it lit up, it was already at too high of current. I came up with a technique where I would dance on the pedal, turning the arc on and off. Sounds goofy but it worked. My new Dynasty works much better. Advertised "on" current is 2 amps. No need to use the pulser but still will burn the edge of the Piper channel if not careful.

Other Jeff

cubdriver2
11-21-2010, 06:40 PM
Our grandmothers made B29s with a oxy- acetylene torch, might even work on a Super Cub :lol:

Glenn

jrussl
11-21-2010, 06:41 PM
Another trick I use is to change the angle of the torch to direct more heat into the thicker section that I am welding the Piper channel to. I keep the weld puddle centered more on the thicker section and then kind of "wave" it up on the channel for a brief moment. I remove or lower the heat as soon as the puddle wets the Piper channel. This is of course if you are not welding channel to channel.

Hope this helps.

Other Jeff

mike mcs repair
11-21-2010, 07:04 PM
use a smaller diameter tungsten....

what size are you using?

Skip
11-21-2010, 07:23 PM
I agree with jrussel you need to have a rheostat (foot control) on your machine. You can use either a 1/16th or 3/32 tungsten but don`t sharpen it to a needle point. Use some sort of belt sander or really fine grinding wheel and sharpen it to a point then blunt the end of the tungsten just a little, this will prevent the arc from wandering and give you a nice even halo to your arc. Whas gas are you using straight argon or argon co2 mix. I have a Lincoln Idealarc with a foot control, I set the max amps at 75 and use a 1/16th filler wire and go from there.

jrussl
11-21-2010, 07:34 PM
Ditto what the other guys have said......

I use a 1/16th tungsten, small flat on end, straight argon, 75 amps max, #9 torch with 6mm gas cup.

I also find that when I am trying to work with a very small weld puddle that using 0.045 wire is easier. If I use 1/16th rod, it seems to cool off the puddle too much when I dab it in. I just run off and straighten some 0.045 MIG wire.

behindpropellers
11-21-2010, 07:52 PM
Is brazing an option for attaching this type of channel?

Not sure what kind of welder you have but if you can set the amperage to where it will get the puddle formed. This works great for when you are in odd spots and working the peddle with something other than your foot.

Tim

cubdriver2
11-21-2010, 08:02 PM
Why are you guy's so afraid of a gas torch, you can push the heat where ever you need it and vary the temp in a split second, no peddles, no fuss, no quessing, light it and go.

Glenn

Bushwhacker Air
11-21-2010, 08:05 PM
We're using .035 wire with low amps (25) and foot pedal.(using a Lincoln precision TIG 225) When attaching to the heavy tubes and think parts (rear wing fittings come to mind) it's important to get the base metal heated (need more amps here) up and bring it into the channel - the .035 wire will blend in nicely.

mike mcs repair
11-21-2010, 09:23 PM
Is brazing an option for attaching this type of channel?


no brazing around chromoly the book says....

planenut
11-21-2010, 09:27 PM
Some good advise here! But what i would do is get a thumb control for your tig torch. Wheather it's a slide or a rotory knob and practice with it. Foot controls are fine for bench welding, but when you have to get out of postion to weld something your never going to have good amp control with the foot pedal. Start the puddle on the thicker metal and let it flow to the thinner piece. Use a small 1/16 tungsten and small gas cup in order to get in close.

Gordon Misch
11-21-2010, 09:45 PM
You can braze the channel - it's mild steel. But you have to weld the channel to the 4130 primary structure.

The TIG torch orientation matters on these corners, and I'm trying to remember for sure what Steve, a true expert, told me. I THINK he said to point the torch into the joint from the open part of the joint, into the vee formed by the joint. That way the arc can't wander to the work metal from behind and overheat it. Also, he taught me to start a tack on the thin, then pull it to the thick. Making kind of a wire-shaped tack between the two. Then repeat until there's enough weld metal bridged to complete the bead.

My biggest trouble is being able to see well enough, and relatively poor hand-eye coordination, so I tend to contaminate the tungsten WAY too frequently. But start at the corner where it tends to blow away, and start on the thin, to build up some mass. BTW, Steve uses 3/32 tungsten sharpened to a medium-long needle point, and about 85 amps at full foot-pedal depression.

behindpropellers
11-21-2010, 09:57 PM
A tig torch with a flexible head is another thing that has helped me.
Tim

petez
11-21-2010, 11:08 PM
The gods say that as long as it isnt a structual componet it can be brazed.

mike mcs repair
11-21-2010, 11:23 PM
... to start .... on the thin, then pull it to the thick.....

you sure you arn't saying that backwords??.... thats kinda backwards of what works... would just be cold weld on top of the thick area..

like jrussl above described is what I have always found works best for joining the channel to the structure....


I keep the weld puddle centered more on the thicker section and then kind of "wave" it up on the channel for a brief moment. I remove or lower the heat as soon as the puddle wets the Piper channel. This is of course if you are not welding channel to channel.

Gordon Misch
11-22-2010, 01:24 AM
Mike - - The way I wrote it works best for me - been doing it that way for 40 years or so, but that doesn't necessarily make it the best!!??? The idea is to build up some thermal mass and an increased conduction cross-section on the thin stuff. Seems to make it easier for the thin material to dissipate any excess heat while the arc is directed at the thick stuff to get it hot. I've seemed to get the best results this way whether with gas, stick, wire, or TIG.

When fixing a blow-thru, this sequence seems to be necessary - at least in my experience. Sure wish I could see like I used to though; there wouldn't be nearly as many blow-thru's!!

swoeric
11-22-2010, 10:05 PM
i'd let this guy do it if you are having troubles. http://www.youtube.com/watch?v=rLnN-hqgfxY

mike mcs repair
11-23-2010, 01:05 AM
i'd let this guy do it if you are having troubles. http://www.youtube.com/watch?v=rLnN-hqgfxY

:D :D :D

ewww.. mirrors.. ick....

Skip
11-23-2010, 07:53 PM
I used to say if you can step across the gap I can weld it. If it will hold shelled corn it`s good to go.