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Soldering/Brazing of Cu/W alloy sheet

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Proud Mary

Sun Oct 04 2009, 08:27PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Bored Chemist wrote ...

Just a thought; if this runs hot enough to need tungsten then I don't see the mica standing up to the heat.
Mica can stand about 900C. Plain copper will survive nearly 1100 and it's easy to solder, has a low resistance and is cheaper.

An excellent point, which I should have clarified earlier. The reason for the use of tungsten in the low energy initialization gap is to protect the mica from the heat flash and shock of the main discharge, which should approach 1MW peak pulse power according to theory. If necessary, the mica/Cu-W sandwich ignitors can be replaced after every shot, in which case I would agree that the use of wolfram was totally unnecessary, if the trigger gap is to be trashed after each shot.

This is not a TC type of gap, which must endure tens of thousands of operations, but one which I hope can be made to last for between 10 and 50 shots, without opening the module, with the loss of its 5 bar nitrogen every time it is fired, but as it is an experiment, I'm not in a position to tell you the outcome!

doctor electrons

Sun Oct 04 2009, 09:17PM

Registered Member #2390 Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381

Harry!
Well i kicked the idea around a little bit and i believe the gas cylinder is going to be your best bet. You can get one relatively cheap and they are a piece of cake to work with. Just make sure it's from an inert gas! I personally have chopped a few up in my time. Any decent horizontal band saw can take a slice out of a cylinder. Should also be no problem to have an individual with a lathe thread the inside for you. A "T" cylinder has a wall just under an inch thick so pressure is no problem. I really can't think of any readily available "garage mechanic" solutions. A stainless steel pressure cooker maby? Boy grandma may get a bit upset come thanksgiving time

Though i personally wouldn't trust a pressure cooker past 80psi without wearing the ol standby catchers mask and chest protector!! Hey you never know, try taking a stroll around a junk yard and something may grab your attention! One thing you shouldn't do is have a welded "tank" or "vessel" without heat treating it. That could be bad and nobody wants to see anybody subjected to that!

Proud Mary

Sun Oct 04 2009, 11:18PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Doc, I know you have to be a bit off your head to spend as much time as I do dreaming about gigantic electric discharges, but no way would I put 5 bars in a pressure cooker, though I think it would be great - a really good idea with lots of space and easy access- if it should turn out that the whole gizmo will run well at say 2 atmospheres. I'll give it serious thought for the 'one shot devices' because it won't matter if the pressure cooker blows so long as the switching occurs in the low nanosecond range.

Pressure cookers have lost the popularity they once had in England, so a regular hunt in thrift shops will turn out a regulat trickle of the grey and ugly with wobbly handles for a few dollars each, but the seal can replaced with glass rope. It might be a very good idea for all the learning part of the experiment I have to do, since the easy access, and big open top will make it a cinch compared with the final development of a module to slide inside the "T" cylinder with one inch walls which you suggest, and sounds good to me. If that blows it will be boo-koo big bang, so it sounds like something to be tried under a pile of sandbags out in the open a deal away from anyone, or any livestock that might take fright.

Have you got any thoughts or suggestions about the annealing of the "T" cylinder, Doc?

doctor electrons

Sun Oct 04 2009, 11:55PM

Registered Member #2390 Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381

You don't have to worry about the "T", they're ready to go! A scuba tank may work just as well and they are really cheap on ebay! As long as you don't make any changes to the metal with heat. When you machine (or have someone machine it) tell them to "keep it cool" They should understand. Pressure cookers have a let off valve on them. You could change the valve to suit your needs. Say a better one that would pop off at a safe level? Numerous things come to mind like air compressor tanks (too thin) Pressure pots for large industrial paint guns (aluminum) but the gas cylinder surely seems to be the best. I spent a few years fabricating motorcycles from a pile of metal so the junkyard mechanic in me comes out when i hear of such cool projects!
Now a more accurate answer. If you do end up doing some welding or other such things to the "T", you should be able to find a factory or specific heat treating business somewhere near you. They would have to heat the part to a high temperature then gradually, over the course of a day or two, bring the temp back down to a normal temp, say 80f before the annealing process is complete. This however would pretty much trash any machining, like threads or a machined fit / "O" ring seal

So if you go that route do the machining last! I will look at some of my old reference books to see if you could accomplish this in a regular house hold oven. I have had spring steel heat treated and it only cost me $25 us. Its not real pricey!

Proud Mary

Mon Oct 05 2009, 05:57AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Thanks for all your enthusiasm and help for my project, Doc. Pity we can't chill out together over some cold beers, so you'll just have to imagine a Virtual Beer until some final catastrophic upheaval of the tectonic plates crashes the New World into the Old, and we can just walk across the smoking volcanic debris field and shake hands!

You think I'm making all this hogwash up? Not according to the members of the Evangelical Church of the Final Judgment just down the road, where they keep putting up huge posters telling everyone that "we are in the last days" and that the Apocalypse is just round the corner, though they can't say exactly when. Their Pastor is called Brother Noah, and his followers will accompany him in his arc over the thrashing waves as it boils up at the end of the world. It's very imaginative stuff, I guess, like something out of a horror flick, but their clear-eyed certainty is scary when it isn't ridiculous. "We are in the last days, my friends!"

doctor electrons

Mon Oct 05 2009, 09:44PM

Registered Member #2390 Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381

I think they'll be ok as long as they don't drink the koolaid! Speaking of beers, i better stock up if the world is going to end. I can almost be sure that i will be parched when that happens

Either way don't sweat it, just glad i could help. When i first came here to 4hv i was almost afraid to post anything in fear of being ridiculed for not knowing what i was talking about. However, thanks to kind individuals like yourself i have been feeling a tad more welcome, possibly even useful. No matter what, i am glad to be here. I am happy to lend some good advice when i can. As for the spark gap, i can't wait! I am excited to see it! 99.9% of good ideas come from a dream and a bar napkin if you know what i mean. Happy fabricating Harry!!

jpsmith123

Tue Oct 06 2009, 03:19AM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Spark gap design is an interest of mine as well.

I plan on building a pressurized trigatron type unit as soon as I get this PITA transformer done (which may be never, at the rate I'm going).

In any case, it sounds like you're after a very fast rise time or low impedance or something?

I have some literature that goes into some detail in calculating things like rise time, gap length, power loss/efficiency, etc., if that may be of use.

Proud Mary

Tue Oct 06 2009, 03:36AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

jpsmith123 wrote ...

Spark gap design is an interest of mine as well.

I plan on building a pressurized trigatron type unit as soon as I get this PITA transformer done (which may be never, at the rate I'm going).

In any case, it sounds like you're after a very fast rise time or low impedance or something?

I have some literature that goes into some detail in calculating things like rise time, gap length, power loss/efficiency, etc., if that may be of use.

Fast rise time is where it's at!

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