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/diy/ - Do It Yourself

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250702 No.250702 [Reply] [Original]

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

>> No.251011
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251011

>> No.251221
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251221

Bumping for love of MOT welders.

>> No.251364

I'd stick with the transformer oil...
Pump the coolant through a radiator and use a high CFM fan.

>> No.251447

>>251364
>radiator

hmm.... This reminds me, I have an old dehumidfier I have no use for that still works perfectly. The side of the coils that drip the water get extremely cold. I may look into turning that into a cooler for the transformer oil.

>> No.252257
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252257

Today I decided to really stress test my first and smallest MOT welder, a spot welder. It worked and surprisingly did not get too hot inside the coils; in fact they weren't even warm. The tips heated up so much they fell out though, which was expected.

I decided to make a "chuck" for an old angle grinder I found. the angle grinder has 2 discs on it that screws onto the shaft. So, instead of running to the hardware store to replace a part on the grinder, I decided to use the disc to clamp tighten the abrasive disc. I'm not familiar with this model of angle grinder so I don't know what tool or nut it used before. I needed to make a chuck that could slip into the holes on the disc and wrench it tight.

Here's pics of the tool making and how welds look.

Here's a video of the last weld being done (too much background noise and slightly out of focus. I only have two hands),

>DIY Stereo Transformer Spot Welder - Welding cold forged nail stock together.
>0:44sec
http://www.youtube.com/watch?v=wlr9YdOD5gM

Check that video's descriptions for technical info about the spot welder.

>> No.252258

>>252257
>smallest MOT welder,

Er, it is not a MOT, it is a transformer from a stereo. I'm just so used to typing out MOT since I have 5-7 MOTs and only 1 stereo transformer.

>> No.252643

>>251364
Active pumping defeats the idea of thermosiphon flow. If the case is designed correctly, it'll flow fast and free so long as heat is being applied on one end and it's being cooled properly on the other.

>> No.253030
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253030

This isn't a MOT welder, but I thought someone might really like this information since this is a pretty quick way to weld, with the least amount of items needed, the least amount of electrical aptitude needed, and the video is actually pretty good,

>Welding with jumper cables and a pair of batteries
http://www.youtube.com/watch?v=PV5oLPLUzrM

This might as well be a welding general thread.

>> No.253072

>>252643
Thermosiphon... brilliant!
No really, that's pretty clever. I didn't think of that.

>> No.253219

>>253072
Well, the idea is to have as little moving parts inside the case of transformer oil as possible. This reduces added heat and there's once less thing to monitor and break down. Fans on the outside of the transformer oil case are easy to monitor and replace.

>> No.254254
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254254

I thought there was another welding thread. lol