I needed to do some rather demanding sheet metal work on the Mrs' mini van, and needed a decent welder. Being of little means, I set out on the great adventure of a low buck TIG set up. Hopefully some of this will help other people.
It all started with a hot deal on an old (1988) Hobart Porta-TIG power source on Craig's list ($150). It has pulsed & HF DC, 300A on three phase, and 200+ on single phase, and is very full featured.
It did all of that, and rolled around easily at about 90 pounds. The challenge was it was an industrial welder, and single phase meant 460 not 230 volts.
With the guidance from some nice folks here, I ended up buying a nice GE 25KVA standard 240/480 transformer ($150). Those work both ways, stepping up or down voltage, and soon I had 50A 230 that made 460 @ 25A in my little work shed. The start up buzz and hum of the transformer alone are cool and powerful sounding, though at 185#, it did take some of the porta out of Porta-TIG.
The next step was a little stick welding to see it all work. I was nicely impressed. It worked very well from very low to very high amps, and I was making decent beads in a couple of practice runs.
The next stop was going from stick to TIG. It was just a bare power supply. I got a used really heavy duty 180A Weldcraft compatible torch from the guy with the transformer for $20. The regulator/flow meter ($40) and hoses (25'=$26) were cheap enough on E-Bay.
The only welding supply place within 85 miles is Airgas, about an hour away each way. There I got a year lease on the 60CF tank for $60, and the first fill for about $35. Since I had no ID on the torch, I had them set me up with a set of consumables front to back, including some electrodes. That set me back about $30. The torch was an odd size and the man from Airgas had to call Weldcraft to find the right power block. Some people don't like Airgas, but they were very helpful and appreciated my business. I don't care for the idea of leasing a bottle, but at the moment money is tight. Hopefully in a year I can buy one and be done with it. For now the low cost of entry was key.
The Hobart 10 pin DIY pedal
The pedal brought the biggest challenge. I need a 409004A Hobart 10 Pin foot pedal. I searched high and low, and didn't like the price. I found good pedals in the 160-180 range, but that was more than I spent on the welder itself. No way. I have the schematic, which I posted here http://www.silvercliff.com/welder.html . There is another one from that aftermarket pedal company, with the only difference being that they run the caps across the pot leads instead of to ground. I still don't know which one is right, so the plan for now is to stick to the Hobart print.
In my earlier days I had some related tech school and a lot of work experience in various electrical and electromechanical control places. It has been a long time, but I remember a lot of it. The rest I can look up. I also have a long history of creatively fixing things using available resources. Some of us have names for that, bailing wire mechanic, or worse.. After 30+ years of creative repairs, I think I like Alternative Solutions Technologist.
So off I went to go and source some parts. I found some nice NOS high end resistors on E-Bay that fit the bill, and a few bucks bought 5 of them. The same went for the capacitors, and a roll of shielded cable. The 7W resistors were a little over spec'ed as were the caps, but I wanted reliable stuff. The potentiometer was a good quality 2W from Newark Electronics, a company I remember from the panel shop in the 80s. The shielded cable was a really good deal, I got a 100' roll of nice Belden foil shield 10conductor 22 gauge cable with a very tough exterior sheath for $25. Again I hit E-Bay for a nice extruded aluminum project box to house the whole mess ($22). I bought a hinge, washers, and springs from the local hardware store ($10). Another big score was the Aphenol 10 pin connecter, where I got both sides complete with inserts shipped for $12 on E-Bay. I am not a fan of pots that have integrated switches, so I complicated things a little with using a Cherry switch (2 for $4) and a cam set up for the trigger switch.
After a couple of nights of ciphering and scribbling on notebook paper, I came up with what should be a reliable and pretty serviceable design. I have been thinking about it all day, and haven't come up with much in the way of changes. Right now the question is how much pedal travel I want. The initial design had 3", but a minor change can put it to half of that. I like the idea of long travel for sensitivity, but too much travel could make it uncomfortable.
At the moment I am at about $105 on the pedal. I am waiting on the parts, so I don't now how it will end. As it turns out, with most of the stuff coming in lots, that $105 includes most of the stuff to build a second one. It would take another pot, connector, project box, and some minor hardware, call it $40-50. I will wait to work out the bugs in version one before worrying about building a second one or selling off the parts and plans as a kit..
I have high hopes for the pedal project. It should look cool with a nice AL box and diamond steel foot pad, all in black.
Potentiometer is a 2 Watt linear taper 25K ohm. Mine has a high actuation service life switch with a metal shaft and bushing, and strong stops ($16).
Cable and box need to be shielded from high frequency and other welding EM output.
A table top version with a knob would be a lot easier.
tank & first fill 100
torch 20, consumables 30
reg $40, hoses $26, power connector $16
To be continued....
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