An arc welder


As a child I was forever dismantling anything I could get my hands on and trying (usually unsuccessfully) to make build new, better things. As I've grown up, my access to tools and knowledge of physics has improved; this has however had the result of increasing the frequency of both successful creations and disasters.

Earlier in the year, I decided that an arc welder would be a useful thing to own and would increase that number of other unwise things I could build. Now any sensible person would at this point would have checked out ebay or screwfix; in case it was not already obvious, I'm not that sensible. I logged into freecycle and posted, offering to save people a trip to the tip by taking their old broken microwaves off their hands.

There are lots of fun bits & bobs inside an old microwave, but for this particular project I was after the transformers; I salvaged 2 transformers and with the aid of an angle grinder, an oven, a variety of odd bits of wood and a mallet removed the original secondary windings then replaced them with some nice thick copper that I bought online.

Now that I had two transformers, I bought some car battery cable, a huge crocodile clip and a welding rod holder and wired it all up. I plugged both the transformers into a multi-gang extension lead and I turned the mains on. There was a nice satisfying buzzing sound, but as soon as I touched the welding rod to the scrap of steel I was using for the test the fuse blew. This was obviously drawing more than the 13A that the sockets in the garage can supply. Now clearly at this point the correct course of action would be to consult an electrician in order to install a dedicated 30A circuit for the welder; I didn't have an electrician handy, but I did have two 13A sockets in front of me. A little test proved that while 13A wasn't enough, 26A was plenty.

Once I had a working welder I set about welding every piece of scrap steel I had to hand together; this kept me occupied for a few hours, but suddenly the welder stopped working properly - it would not strike an arc and was making a much louder buzzing noise. I casually lifted my mask to see what was going on, and instantly knew what the problem was: the 3" flames coming from the top of each transformer.

After much swearing and fumbling with the power switch with welding glove clad hands, I disconnected the electricity and put the fires out. While the primaries were ruined, luckily enough the secondaries I'd wound survived. I went back to freecycle and managed to find a couple of replacement transformers, with which I rebuilt the welder. This time I left the thermal safety cutouts in place.

It has proved useful for building a variety of other things, the most useful is probably my wood stove thingie:

and the least useful is probably the swiss army teapot:

the welder was too powerful and made lots of holes; it's useless as a teapot and most of the other tools are impossible to use without having a teapot in the way.

Shameless link to my blog with more details
(madsporkmurderer, Thu 11 Oct 2012, 18:21, 7 replies)

Awesome(ly stupid).
Can you make me a plasma cutter?
( ousgg is not seeking approval, Thu 11 Oct 2012, 19:03, closed)

A plasma cutter is on my todo list, there are other things that are currently taking priority (the jet engine is taking the most time at the moment). My attention span is barely long enough to finish projects once, the chance of ever getting around to making another for someone else is vanishingly small...
(madsporkmurderer, Mon 15 Oct 2012, 21:45, closed)

I like the bit where you managed not to die horribly.

( Dr. Shambolic je suis charlie, Thu 11 Oct 2012, 19:09, closed)

That bit was worryingly close to not happening

( ousgg is not seeking approval, Thu 11 Oct 2012, 20:58, closed)

Big click for the swiss army teapot!

( skeltonator Needs some new daps., Sat 13 Oct 2012, 16:00, closed)

I like the wood burner
How is it holding up? I've read they they don't last too long (with heavy use).
(RJWEcology is just sharpening his axe on, Mon 15 Oct 2012, 16:09, closed)

I'm yet to find out; it's currently sat in my basement and has only been out once since I arrived back at uni. Time will tell I suppose, it may well end up as a patchwork mess of bits of old steel welded over the holes as they appear
(madsporkmurderer, Mon 15 Oct 2012, 21:48, closed)