Colt Case Ingersoll Garden Tractors

Like I needed another project. Yet, for a few reasons I am taking a stab at converting the AC stick welder to DC. For one, the latest welds I did on the 644 with the AC welder, using 6011 electrodes, were pretty ugly. I'm pretty sure it's not the welder's fault, but mine, lacking technique. Still, I feel that it would be nice to switch the welder to DC.

As I said, I already have a rectifier bridge apparently capable of doing 400A and up to 1600V. I take that with a big grain of salt. The size of the device is about 3.5x2.5 inches, and maybe 3/4 inches thick. Looking at some data sheet found on the internet for this China made device, the power dissipation vs mean current:
Gotta love the lack of numbers on the graph. I'm assuming each line is 100 amps on the x axis, and 100 watts on the y axis. I doubt I'd weld at 200 amps, but let's just pretend I do. According to the graph the power dissipation would be a little less than 200 watts. To dissipate 200 watts you need a pretty good size heat sink, and air flow. There isn't enough room in the case of the welder for a proper size heat sink. I could use a heatsink on the outside of the case with a 12V fan attached to it, but that just complicates everything. More thinking needed.

200 Watts does seem too much, less than 1/3 HP. Motors that size don't have fans. And, unless you're working on a pipeline, you won't be welding too long. Put the biggest heat sink you have, and give it a try, see how hot it gets. I think I have some aluminum extrusion somewhere.

I have some pretty big aluminum heat sinks, about 8 in wide by 12 in long. You're welcome to have one if you want to pay shipping.

FUTZ wrote: ↑Mon Oct 24, 2022 3:53 pm 200 Watts does seem too much, less than 1/3 HP. Motors that size don't have fans. And, unless you're working on a pipeline, you won't be welding too long. Put the biggest heat sink you have, and give it a try, see how hot it gets. I think I have some aluminum extrusion somewhere.

Thanks, I got some heat sinks, I'll see what fits. Just pulled off the fan cover which was taking a lot of room. Will post pictures soon.

200 watts may not be much, but the max junction temperature is 150C and solid state devices have a very sharp fry turning point. I'll test it with what I have and if not good enough I'll try with a bigger heat sink.

I had certain fun making 4 awg cable lugs from 1/2" copper pipe. Found a transformer with a thick secondary to use as output choke, but it needs a core gap so I wasn't looking forward to cut a gap in the core.

That's why you need a metal cutting band saw.

But a narrow cutting disc in an angle grinder will do the trick.

Well now, my welding technique still sucks but now it sucks DC


This is what I cobbled up

I am amazed how well it works. And the heat sink doesn’t even get warm to touch on 110 amps and continuous welding for a couple of 1/8 6011.

In the second picture is a transformer sitting on the floor. Is that the choke? Is it connected only to the primary side and open on the secondary side?

Spike188 wrote: ↑Mon Oct 24, 2022 11:52 pm In the second picture is a transformer sitting on the floor. Is that the choke? Is it connected only to the primary side and open on the secondary side?

Yes, except it's connected only on the secondary. This is not finished, I want to take it out and gap the core, and add thermal paste between the heat sink and diode bridge.

wait 'till you try 7018 on DC. You'll feel like you just graduated welding school.

The difference between 6011 and 7018 is amazing.

Bob