# Word Of Caution " Vaccum Chambers"



## WILD BILL (Jan 26, 2012)

I posted a while back that I had made my own vacuum chamber an was infusing oil into my forks. The process works extremely well and is worth the effort but there is "CAUTION"

I purchased a 3 gal glass very thick 1/4" jar that i have been using. I have infused many pieces with no issues. I was using a hand held vacuum pump used for bleeding break systems. I usually took about 60 pumps to achieve the vacuum needed. Had I been using an electric pump, I probably would not have caught the failure that was about to occur.

I would always run my pieces through three to four vacuum and re-pressure sessions to in-sure of total infusion. On the second session while infusing "Sassy" I noticed bubble rising from the rear of the tank. OOPS! I immediately released vacuum and inspected the tank. There is a small crack developing in he bottom of the tank.

I got on the computer and researched "Vacuum Chambers". I came across several forums of experts?? and read numerous reports of catastrophic failures. One was from a high school Science teacher that was running an experiment with a store bought official chamber(classroom full of students) Short story, The chamber imploded! Glass everywhere,no one hurt. (homeshopmachinist.com) offered some real good info.

Most vacuum is achieved at between 28 and 31 inch/merc. The choice of materials are very important. There are several folks that are selling pre-built vacuum chambers using 3/8,1/2" acrylic. Word of "CAUTION". Most of the experts recommend tank from steel alum and the clear see through covers to be at least 1" thick. Although thinner material might work for a awhile it is a road map to disaster.The problem is the re-repetitive use. Once a fracture begins and it will, catastrophic failure is eminent. I was lucky to catch mine in time.

This was a lesson in the forces of atmospheric pressure. Not a force to mess with

My next tank will be solid (steel, alum) and much safer.

Be smart and be safe!

Bill


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## akmslingshots (Mar 2, 2012)

holy sh!t Bill, lucky escape! and a warning duly and seriously taken! I am gonna like it not for the near miss but the information and time put into the thread. This is something i intend to dapple in and to be honest the glass cracking did not really cross my mind.


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## Charles (Aug 26, 2010)

Thanks very much for posting this timely warning.

Cheers ...... Charles


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## Shazam (Jul 2, 2012)

Not sure how well it would penetrate but i came across this to use for chicken tikka.

http://www.amazon.co.uk/Minute-Electric-Vacuum-Food-Marinator/dp/B001L2ZLZ0

There are of course larger more industrial models but it might work for forks also. Two containers, one for meat and one for wood.








You would just need to line the inside with a rubber sheet or similar to protect from bashing the fork too much.

Cheers, Frank.


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## treefork (Feb 1, 2010)

Tanks for the heads up.


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## WILD BILL (Jan 26, 2012)

Shazam said:


> Not sure how well it would penetrate but i came across this to use for chicken tikka.
> 
> http://www.amazon.co...r/dp/B001L2ZLZ0
> 
> ...


Before I bought the very thick glass jar I looked at one similar. I don't think that it is capable of creating enough vacumm.


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## jskeen (Feb 7, 2011)

I can say from years of stabilizing wood using a combination of vacuum and pressure, almost any homebuilt rig will eventually fail. The trick is not necessarily design to avoid failure, but to use in such a way as to minimize the damage the inevitable failure will cause. Ever see a truckstop where they service tires for 18 wheelers? Somewhere there is always a big steel cage that a tire can be rolled into, then the air hose connected from outside to run the pressure up and seat the bead. Next time you notice one look closely, the inside of the solid steel bars is covered in deep gouges and probably bowed out from repeated explosions of heavy steel two piece rims.

I put my half inch proof tested steel tank inside a couple of tires stacked up outside my shop before I attach the hose and stand back till it is up to pressure. An easy way to avoid messes with glass jar type vacuum tubes is to store all the associated pieces parts in a big plastic storage bin. when you go to use it, set the chamber up inside the bin, and run your cycles. that way if the jar fails, glass pieces and spilled liquids are easily hauled out and dumped in the trash. (after removing the slingshot, of course ). Wipe out, fill spare pickle jar, and Bob's your uncle!


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## LittleBear (Mar 24, 2012)

One thing to keep in mind about building a vacuum chamber or, buying one, is that the larger the surface area the more strength you need. Example hold a pencil 1 inch apart while hanging 14.7 lbs from it to represent the weight of atmosphere at sea level (14.7 psi) on a small container, one inch of pencil will support that and more. Now try it with a full 8 inches of pencil or better yet since we are talking pounds per square inch pressing on a chambers surface try it with a 1/4" x 4" (1 square inch) piece of 1/4" thick glass to support that 14.7 lbs, me I want a lot thicker piece of glass, woops scratch that I don't want anything that shatters with sharp splinters like glass or brittle plastic so metal since it bends first or not-so-brittle forms of plastic those more likely to crack and leak before shattering. The one nice thing about vacuum is that that we only have to support that 14.7 psi unlike pressure pots at 45 psi or more.

BTW most food processing vacuum equipment is not intended to support more than a fraction of total vacuum, even the vacuum canning applications. Hm... might be a fun video; take a small 8 oz mason jar suck it down to 29.9 in/Hg set it in a nice safe spot with a slow motion capable camera on it, back of oh... 100 feet or so and take a shot at it, with heavy clothing and a face shield of course you know just in case a flying shard of glass...


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## WILD BILL (Jan 26, 2012)

I will not cheat on strength on my next one. I have fellow that is going to fab one for me. I am looking for a discarded beer Pony Keg, Either that or a propane tank..Cut one end off and my viewing window( the top) a 1"- 1 1/2' Acrylic. All the fittings will be in the tank..

Does anyone know what vacuum a refrig/freezer compressor is capable of pulling?

Bill


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## Hrawk (Oct 25, 2010)

Ever considered chopping the bottom off an air cylander or a scuba tank to use as your main chamber ?


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## LittleBear (Mar 24, 2012)

WILD BILL said:


> Does anyone know what vacuum a refrig/freezer compressor is capable of pulling?
> 
> Bill


I was pulling -28.5 inches of mercury with one at <100 feet above sea level.


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## WILD BILL (Jan 26, 2012)

Hrawk said:


> Ever considered chopping the bottom off an air cylander or a scuba tank to use as your main chamber ?


I wouldn't do that to my Scuba tank but I would do that my old propane tank. I would rather find an old beer keg (pony)

I was pulling -28.5 inches of mercury with one at <100 feet above sea level. 

Was this with an old refrig compressor.I have heard of folks using them  

Thanks

Bill


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## LittleBear (Mar 24, 2012)

Yep just chopped the compressor out of an old abandoned frig rewired it, added oil, and plugged it in.


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## jskeen (Feb 7, 2011)

I've done that with the fridge compressor too. Worked great until the poly vapors finally gummed it up and it died. I would suggest putting a burp jar between it and the chamber if there is any possible way you might suck some liquid into the tubing thought. Might save you having to go scrounge another compressor.


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## WILD BILL (Jan 26, 2012)

lbspd said:


> I've done that with the fridge compressor too. Worked great until the poly vapors finally gummed it up and it died. I would suggest putting a burp jar between it and the chamber if there is any possible way you might suck some liquid into the tubing thought. Might save you having to go scrounge another compressor.


Thanks for the tips

Bill


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## trobbie66 (May 13, 2012)

WILD BILL said:


> I will not cheat on strength on my next one. I have fellow that is going to fab one for me. I am looking for a discarded beer Pony Keg, Either that or a propane tank..Cut one end off and my viewing window( the top) a 1"- 1 1/2' Acrylic. All the fittings will be in the tank..
> 
> Does anyone know what vacuum a refrig/freezer compressor is capable of pulling?
> 
> Bill


Remember those tanks are designed for internal pressure! External pressure is a very different animal!!


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## WILD BILL (Jan 26, 2012)

trobbie66 said:


> I will not cheat on strength on my next one. I have fellow that is going to fab one for me. I am looking for a discarded beer Pony Keg, Either that or a propane tank..Cut one end off and my viewing window( the top) a 1"- 1 1/2' Acrylic. All the fittings will be in the tank..
> 
> Does anyone know what vacuum a refrig/freezer compressor is capable of pulling?
> 
> Bill


Remember those tanks are designed for internal pressure! External pressure is a very different animal!!
[/quote]

Sure enough, but I am swaying towards the shape and contours of the keg to well, handle 30 inch bar. Since an implosion would result from the atmospheric pressure, I would think that a round, stainless steel,rimmed, keg would fair, far better than repeated use, with say ,1/2" acrylic in a rectangular design. Just as a round propane tank would work as well.


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## LittleBear (Mar 24, 2012)

IMO a chopped pony keg or propane tank should be more than strong enough as long as the lip is flat and smooth enough, and the lid thick enough for the diameter of the opening. 1/2" Lexan is ok for 10" to 11" wide with a wide flat lip but in my opinion anything wider or with a thin lip would definitely need a thicker top sheet.



WILD BILL said:


> btw. Got a chance to hold some of your pieces, beautiful work!


Thank you for the complement it means a lot but, ouch embarrassing, that "s" on pieces implies that you saw not only the LD3 but also the somewhat less than astatically pleasing mini- slingshot-magnet two part stand a fun idea but...


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