Vacuum chamber ideas

How about decapping an air tank or gas cylinder and welding flanges to rejoin the end?

Experiment with a paint pot first?

Couple paint pots mouth - to - mouth via a foot flange containing a central shelf?

--Winston

I have one of the regular ones, cost about $200 new, and it works like a charm. Are you talking about something a lot bigger?

Steve

Section of pipe. Or two stainless-steel salad or mixing bowls if you want to grab things form the kitchen. Rather than frig with a weak shape, start with a strong one.

I am going to need a chamber that is somewhere in the order of 14X14X6 inches. If I went with a chunk of pipe, that would have to be something like 16" diameter. The down side to this would be cost and bulk. The more empty space inside the chanber the longer evacuation time.

Also if I used a 16" inch pipe it would also be difficult to make a door. The door would have to be hinged and by the time I dod all of that work, it would get pretty pricy.

Look at a package of bacon you get from the market. No air bubbles, no leaks, no freezer burn.

I had one of the food savers and I did't like paying the price for the bags and I tossed a lot of meat that got freezer burned when the bags developed a slow leak.

Also if the stuff you are sealing is juicy it sucks the juice out of the bag and fouls the pump.

Sounds like a use for an oilless compressor tank after the pump fails. See curb. :)

--Winston

I presume you are aiming for rough vacuum (air pressure is about

30 inches-of-Hg, and you'd be satisfied with 0.5 inches-of-Hg). The force on the sidewalls, about 15 psi, means that flat-sided boxes aren't suitable. Usually, one sees a glass bell jar atop a castiron plate, gravity and a greased rubbery gasket hold the vacuum, or aluminum or SS pipe-spools with flanges on the ends for bolted-compression gasketing or O-rings.

Cylinders and hemispheres (like the bell jar dome) can be made of light construction, and still be safe. The lid, though, will require machined plate or flanges, so a machine shop is called for. One with welding equipment, preferably.

Trivial to make a door. No hinge required. Take a 6 inch length of 16 inch pipe, weld a plate on the bottom (years of vacuum experience says

1/4" steel plate would probably do nicely, thinner would work if you domed it a tad) and put a flange (better yet, get 6" with a flange cut off a pipe at the junkyard) with an o-ring groove (hey - metalworking!) on top. A crapped out 16" valve body and a blank flange for the bottom might doing it from stock parts with no cutting. For 16" a 1" Lexan top (if you want to see what happens) should work - we used 1-1/2 or 2" for a 24-30" dia unit much like this (a bit bigger) that was primarily used for vacuum-casting epoxy. The vacuum holds the lid on quite well indeed. Making it cheaply is a matter of picking the right junkyard (try one that gets stainless steel scrap from a university), and seeing the right things in the junk.

If you want the opposite of doing it right, try a 12" port and a sheet of window glass. Does a heck of a job on a tubomolecular pump running full speed (it didn't break right away, so the researcher/culprit actually got the high vac pump running before he filled it with glass shards.)

If evacuation time is an issue for you at food-sealing pressures, you need a better pump...

You probably have an external vacuum sealer. Seal a meal. The chambers are over a grand. I have thought of making one also. As too cheap to spring for a chamber one. Bags are a lot cheaper and you can package tuna in retort bags for a better product. I was thinking a small stainless sink, but I like the steam table pan idea better. I was going to weld some studs on the bottom to attached some stringers or weld some stringers to the bottom of the sink. Pan sounds better. Then maybe weld a stainless steel bar top grid for sealing. Have not figured out the lid yet, as I would like a transparent lid. I have read about someone using a refrigerator compressor as the vacuum pump. Pulls 28" of mercury, which is what the better chamber sealers claim.

What will you use for the self-powered remote control sealer?

jsw

Dumb question guys - why not place the bagged food inside a pressureised chamber with the mouth of the bag exiting from a gap/slit in the pressure chamber?

Applying air pressure inside the chamber would force excess air etc from the bag which could then be sealed.

/--------------------\ / \ ========##BAGofFOOD## ====< air press in. \ / \--------------------/

^ ^ ^ heat seal here

Think toothpaste. :)

Otherwise I like your idea.

--Winston

Im rather courious how they close the bag from outside the vacuum chamber once they pump out the air?

Gunner

I am the Sword of my Family and the Shield of my Nation. If sent, I will crush everything you have built, burn everything you love, and kill every one of you. (Hebrew quote)

What do you think is particularly difficult about that? An electically operated clamp and a resistance heater would do it. These things have no problem operating in a vacuum. The control and power wires pass through vacuum-tight connectors - for instance:

OK I can answe that. If you were to pressurise the outside of the bag everything inside the bag would try to escape, including the stuff you wanted to keep in the bag.

Think about a kid stepping on a packet of ketchup.

Roger Shoaf

I had several ideas here. My firat idea was to get a standard impulse bag sealer, put it inside the chamber and just run the power wires through glands in the sidewall. Once the desired level of vacuum was drawn the power could be applied to the sealer.

In researching plastic sealing however I found a place that sells parts and controlers. It seems that the state of the art is to measure the temp of nichrome sealing element by measuring the current that is being drawn so you do not over heat or underheat the bag you want to seal. (The resistance changes as the temp rises)

This seems to be the way to go. but that opinion may change when I price their controler. Optionally, one could mount the guts from the off the shelf bag sealer outside the chamber and run the lower voltage to the seal bar inside.

The bag is sealed between two pieces of silicone foam rubber and several insulating and teflon strips to hold the melted plastic while in resolidifies.

One thing for sure is that I am going to try an alternate cross sectional geometry on the heating element. They sell one that has a radius top edge to prevent the sealing bar from overheating the edge of the band like the flat bands are prone to do.

Roger Shoaf

Glands? Use feedthrough capacitors to prevent all air leaks.

As my thoughts have evovled over the past week or so, I am thinking about using tempered glass for the top and bottom of the chamber and to use Lexan for the side walls. While lexan is very flexable, my idea now is to glue on ribs to the sides so as the vacuum wanted to suck the sidewalls in, the top and bottom of the ribs would be supported by the edge of the glass top and bottom. Tempered glass is really tough stuff. As an example think about a pinball machine. I have seen this 1/4" glass survive people standing on the glass and slamming down beer bottles etc. In 3/8 or 1/2 you could probably park a semi on top. Shopping around I found a place that would sell me 14 X 16 X 1/2 tempered glass for about $25

If a full vacuum was pulled on a 14" X 16" panel each square inch would have about 15 lbs of pressure pushing on it so the total force against the top would be about 3,360 lbs. and the same for the bottom for a total of 6,720 on the sidewall, If the sidewall was made of 1/4 inch lexan that would be something like 15 square inchis of lexan supporting the 6,720 lbs. so that would be a load of 450 lbs. per square inch so that would definatly support the weight.

For the long side of the side wall, assuming I make this 6 inches high each long side would have to hold back a force of 1440 lbs. While that much force would usually cause the side to cave in, by bonding the ribs to the side If I divided the side wall into 5 segments, that would give each segment only 288 lbs to support. Piece of cake.

Roger Shoaf

Im not sure it will be of any use..but Ive a number of Honeywell UDC2000 and UDC 2500 controllers that may be of assitance.

They are temperature/IO controllers for ovens and other heating applications. Uses a remote termocouple and have a number of outputs programmable

I am the Sword of my Family and the Shield of my Nation. If sent, I will crush everything you have built, burn everything you love, and kill every one of you. (Hebrew quote)