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Author: Subject: Ghetto Vacuum Chamber Ideas
battoussai114
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Ghetto Vacuum Chamber Ideas

I've just received a 1Kg pack of 13x molecular sieves and a piece of aluminum to machine myself a cryogenic adsorption vacuum pump. But I still trying to decide what I'll use as the vacuum chamber (considering bell jars are impossible to find here).
So far I've though of getting a pressure cooker and drilling it to add the connections, which wouldn't allow me to se inside (which sucks). Or risking a bit and getting a tempered glass bowl and using it as a bell-ish jar, but I'm a little worried about the stress on the flat bottom of these bowls and I don't think I'd want to discover if I should be worried through the empirical route..... and it will be a real pain trying to get measurements of the bowl shape and trying to use some FEA to check if the stress would go beyond what glass can withstand.

[Edited on 19-6-2015 by battoussai114]
Zombie
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Look on Fleabay for corning ware. You can drill your fittings into it.

Quick look...

They tried to have me "put to sleep" so I came back to return the favor.
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Sulaiman
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could plastic bowls work? e.g. http://www.ebay.co.uk/itm/DANSK-DENMARK-LARGE-CLEAR-PLASTIC-...
get a new un-scratched/stressed one though.

definitely build a wire mesh cage for testing;
evacuate it, tap it with a hammer, if it survives then they are probably ok
keep the mesh always there just in case
and of course .. always wear safety goggles etc.

some glass bowls look strong enough to hold a vacuum ... same precautions
http://www.ebay.co.uk/itm/Lovely-Vintage-Arc-Large-Clear-Gla...

[Edited on 20-6-2015 by Sulaiman]
jock88
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AHHHH the need to see inside!!!!

You could try adding a sight glass to a large gas cylindar with the bottom removed. It would not be that hard to add a sight glass. Thick perspex would do.
You could even add a light inside to see even better. Big, cheap and getto. WHAT MORE DO YOU WANT???
zed
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Well, An old TV tube might do. Or, maybe not.

This vacuum stuff is tricky. You got yer Corning Ware, which looks to have a flat bottom, about 6inx6in. So 6x6=36 square inches. Times ~15LBs/sq.in. So 36x15.....Oh, about 500 LBs of pressure/ 6inx6in area. I like Corning Ware, but maybe not fer this.

Could use a bell jar myself. Sadly, in these troubled time, they are too damned expensive. Could try used jewelry gear. Folks doing investment casting often utilizes a bell jar, and high vacuum, to boil bubbles out of their castings.

Got a stainless type chamber, with a poly carbonate top, fairly inexpensive on ebay. Might at least, generate ideas.

http://www.ebay.com/itm/Degassing-Vacuum-Chamber-2qt-Capacit...

[Edited on 20-6-2015 by zed]
Zombie
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Those de-gass'rs are great. I have a 5 gallon one for de gassing epxoy.

For the corning ware I was only referring to the the Pyrex lid. Set it on a gasket made from a silicone cookie sheet. I've seen a few on Utube.

Here's a plastic one.

They tried to have me "put to sleep" so I came back to return the favor.
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battoussai114
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Hey guys, thanks for the ideas.
I think I might risk using a flat botom mixing bowl, if it doesn't implode right in my face I'd have the aditional benefit of having an all glass chamber pretty much ready for me to play around with sputtering and other PVD stuff.

@zombie and sulaguy, note that the tube video of the guy with a plastic one and your relate is what gave me confidence to use the glass one.... if it blows up I'll send you post cards with pictures of me in the ER.

@zed, I guess I'm not brave & bold enough to tear a TV appart for the vacuum tube. And I've heard you need ninja skills to work with those tubes without breaking them.

@jock88, I think everyone can relate to this need
Long time ago (aka last year) a fellow maker sugested taking advantage of (the now disposable) fire extinguishers people have to use in their cars around here as makeshift gas storage tanks. Can't beleive neither of us took the idea forward... but I'll probably postpone this again as I don't have any machining tools other than a (not)dremel multi-tool thingy, and the dudes who do the machining for me at the university are currently on a stryke.

By the byes, if any of you is currently in need of a decent vacuum meter check this out: http://www.ebay.com/itm/Capacitance-manometer-hi-vacuum-gaug...

Based on the description its seem prety simple to interface with it's analog output and it's really cheap. Too bad I've blown my budget by a whole lot this month by getting a little too excited at the scrapyard I got the aluminum and buying some stepper motors for what may come to be a 3D printer.
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For your test run on the glass mixing bowl you could always cover the outside with duct tape. Then if it does fail, the glass does not hurt you. If it does not fail then you know you are onto a winner.
Zombie
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There you go L-sum.

How about those clear silicone mixes they use for mold making?

battoussai114 , Keep the ER Pictures but if you can send samples of brain matter... Zombies like brain matter.

They tried to have me "put to sleep" so I came back to return the favor.
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zed
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Keep in mind, the "Pyrex Lid" on that cassarole dish, is not Borosilicate glass. When I discovered this anomally, I was very disappointed.

The Pyrex sold in cookware, is a tempered glass of ordinary composition.
careysub
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I would go with an aluminum pressure cooker. Seals tight easily, and you have an access port already in the lid. If necessary aluminum is easy to drill and tap to attach other fittings. Operating temperature is 118 C so even with a polymer gasket you should be able to push it higher (130 C?).

And no risk of implosion.

If you get an all aluminum pressure cooker (see the All-American* brand) then they are good to whatever aluminum can take before warping.

The All-Americans are the Mercedes of pressure cookers, and so are not as cheap, the smallest model (model 910, 10.5 qt) is about $190. Vintage All-Americans are listed right now on eBay for under$100. A horribly tarnished, banged up unit should be fine for this use.

Do you really need to see your moly sieves as they are desiccating?

*They sell to the scientific market with a line of autoclaves based on the same design.

[Edited on 20-7-2015 by careysub]
battoussai114
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