1300 Amp MOT Spotwelder - Fail

Experimental spotwelder with an old MOT and single turn secondary winding.
Plenty of heat but no metallic fusion.
The quality of the welds is not good. Soldering was marginal.
The current was exceeding my expectations.

0:06 Current readings
0:30 Preparations
1:16 Removing the HV windings
3:19 Fitting the Cu busbat
4:44 Testrun on Copper
5:32 Trying with solder
8:45 Rough weld

[ElectricExperimentsRobert]

Even if you say that it is unsuccessful, it is always a nice video.

[RetroSwim]

Ah, the Australian Safety Boots, glad you have the appropriate PPE for the job! :D

[pirate]

HINT: use drill to free-up winding after you cut it with metal saw, secure primary winding with thick tape so you don't damage it. Lastly don't forget to remove magnetron current limiter protection plates between primary and secondary.

[TehMG]

I think part of the problem is that you are using a steel bolt as one of the electrodes. Instead of heat being generated at the interface between the two work pieces, most of the heat is being generated in the tip of the steel bolt due to its resistance being much higher than that of the copper you're trying to weld.

The material of the electrodes should have either a much higher melting point than the work piece, or a much lower resistance. Copper electrodes work well for spot welding steel, but for spot welding copper, something like graphite might work.

[GrantE]

I had the same performance when I was using a single turn on the MOT core. About 1200-1400A when shorted together, but it was difficult to get a solid contact. Switching to 2 turns of 0AWG cable resulted in 700A, and the higher open-circuit voltage of ~1.8V helped with the issue of poor contact. But it was still hopeless when spot welding anything larger than a battery tab, which needed several attempts. I had better luck heating up a section of copper pipe for soldering, but the copper pipe was only marginally hotter than the MOT itself by the end of the procedure, haha

[diecksl]

Try 2 or 3 turns of thick copper wire. This produces around 3 - 5 volts, this is needed for welding (I guess your setup produces under 1 volt). My welder works well with 400 - 600 amps. And use copper electrodes as another viewer recommended (lower resistance than steel)

[ideafromkurdistan]

Thanks but this Transformer 220V, by whst ampe or watt ?

[koningbolo]

probably the bar heated up mostly because the brass bolt transferred its heat to the bar.
Maybe try again with 35 or 50mm2 battery cable and make 1 full turn inside the MOT which should give you 1, 5-1, 7 V open terminal voltage and 600-700A...which should be enough to spotweld steel.

[A_Aron]

I really enjoy your content so I subscribed to your channel. I watched your vids for hours.

[highvoltagerules]

Hey Ray,

I think if you managed to get 2 windings of copper around it' it would of been more effective. But good try thier mate,
that copper bar was a good fit lol. And that transformer him was epic mate. 👍 😜 great video

Thanks for sharing mate,

👍 👍 👍 👍 👍THUMBS 🆙 👍 👍 👍 👍 👍

[kimkaphwan]

I think you must make a tip on that screw, this will ensures that the current flows in a minor section of conductor heating it and the point of contact with the parts to weld. (Sorry for my bad english, hope you understand it)

[rakselectric]

That is a nice meter and cool Dutch socket to the left

[antoineblanchard]

0:54 i see a lot, but you r first person how recorder the meter current, nice concept.

[WaynesElectrical]

*_Private Message sent._*

Haha, look at the size of the busbar. :D

Just out of interest, what exactly was the open circuit voltage on the ends of that busbar?

It couldn't have been much as the bar didn't make a full turn around the core.

That L&G CF6 which you show at 1.07.... that has a 1965 cert badge on it.
Was that an ex. Electric board meter from the UK?

At Haha. Just a random S301 floating about in shot of the camera. :D

Aaaah, it seems that it cannot seem to do the soldering. As others have said, a few more volts and a bit less amps might have done the job. Afterall, anyone can have stacks of Amps, but if the voltage isn't there to push the not much happens.

It would however be very handy to get a plastic-fantastic electronic meter on that busbar and slowly teeaase up the current until something inside its little cheap plasticky box lets loose. :D

Would be funny to see the pulse light going at it like a disco strobe with the display throwing funny shapes, and being a sealed unit, there would be nowhere for the pressure to escape, so would be funny to see it expand like a rugby ball. :D

Thanxx for showing,

-Wayne's Electrical.

_10th September 2017, 20.23_

[julianschafer]

Please decide if you want to weld or to sold

[peterc]

What you need is more turns of secondary . One turn = 1volt, you have about 1volt less or more on the secondary that will make a lot of current because of the thick copper but it surely won't be able to weld.

[juceliomendesmendes]

Olá irmão boa tarde eu gostei muito desse trabalho Qual é o material que colocou dentro do tráfico de microondas

[riiwind]

I thought we were M.O.Ting cars in this vid :D

[CPUTests]

The fail point is that bolt at the point of contact should be copper. If it was copper you would be able to solder anything pretty much.

[koningbolo]

your setup should work if: 1. you use copper electrodes. 2. weld higher resistance metals like steel...
You bend busbar constitutes a half turn but should make for less then 1 V open terminal voltage but a crazy amount of current... 1300A short circuit current sounds about right (though welding steel results in a higher resistance so maybe a 750-800A current should be reachable...
Spot welding is a form of resistance welding whereby a current flows through a relative small area of a relative resitive metal causing it to melt locally and fuse. Same goes for Butt welding (of rings and larger diameter wire or tubes even). As far as I know it is not possible to weld copper and certainly not with a brass electrode...maybe with electrodes fashioned from the carbon rods from a AA or AAA battery !?? Keep in mind the welding (high heat production) happens where the resistance is greatest... in you setup that would be in the brass bolt... Brass being 20 times more resistive then pure copper (which comes within 10-25% to that of steel)
The only electrode material capable of (theoratically) wleding copper would be silver but then you run into the problem of erroding the electrodes very fast because silver melt at a lower temp then copper...
I have build a ring welder (for chainmail) form parts salvaged from a 1300W microwave oven and some random parts laying around the workshop... I have a short video about it with a lengthy description on my channel... @your service...
BTW: I left the metal plates in the transformer. I have understood those limit (tame down) the magnetic flux inside the core and prevent the transformer from saturating and drawing crazy high currents from the mains power supply...