/diy/ - Do It Yourself

I've been slowly gathering parts to build both a MOT spot welder (1800-2000amps) and a MOT arc welder (100-250amps). I have the MOTs and they seem to work well for what I need to do. However, I want to use as few MOTs as possible in order to keep the weight down. I want 100% duty cycle too. So, liquid cooling, via mineral oil is my best, cheapest bet.

I have tons of old CPU/GPU aliminum heat sinks and I plan to use thermal past and strap them to the MOTs in several places including right on the primary wiring. Then I'll submerse them into a metal container of mineral oil. The outside of the container will have more heatsinks attached to it everywhere I can place them. These will be air cooled. I want to make a container that is "0" shaped so there will be a thermosiphon flow inside. The entire welder unit will be placed in what you can describe as an air tunnel with a high CFM fan blowing up from the bottom.

I have 1 gallon of transformer-grade mineral oil, but I think I may need to buy some of the cheap stuff too (baby oil).

Any tips or tricks I should know about for cooling?

>pic related, from an old test run

>>159543
Here's a couple test vids of mine,

Stereo Transformer Spot Welder
http://www.mediafire.com/?bgpv5onjgmwqy62

MOT Spot Welder
http://www.mediafire.com/?k71cj181w7v78a3

I'm making a 3rd one that will be an arc/stick welder. I'm currently waiting for my shipment of transformer oil for it. To make a stick welder you really need serious cooling. Otherwise, the duty cycle will be so low that you won't be able to use it much and if the stick gets stuck it'll fry the transformer before you can get it unstuck or shut off.

If you know some electronics you can use a thermal switch on the transformer to shut it off in case it gets too hot. You can get those from toasters and overhead projectors. Basically, it's a solenoid that trips when it's too hot.

Some vids of the 2 other spot welders I have been testing theories with,

MOT Spot Welder m4v (10.72MB) uses 8-strand 10AWG and 1 winding
http://www.mediafire.com/?k71cj181w7v78a3

Stereo Transformer Spot Welder m4v (12MB) uses 8-strand 12AWG 3 windings.
http://www.mediafire.com/?bgpv5onjgmwqy62

For the OP transformer, I'm planing on using something far larger than 10AWG wire. This time, I'm going to try to use a copper grounding rod for the secondary winding. It's 5/8 inch thick and from my calculations should be able to fit into the MOT for one complete winding. However, it is not insulated. I plan to buy some tool-dip (Plasti-dip Synthetic Rubber Coating) and once I get the coil made I'll dip it in. This should give it enough insulation to keep it fro grounding.shorting out on itself or the E-I frame. If that fails to squeeze in, I'll try the same thing with a few pieces of 4AWG wire twisted together, tinned, then tool-dipped.

The test was a success! This makes me wish I had a clamp meter. I really want to see which transformer has more amps and how many there is.

Here's a video of the test weld. There was an upload error at 99% so I don't know if the video will work right. Let me know if it won't play properly,

>10.72megs
http://www.mediafire.com/?k71cj181w7v78a3