A vacuum chamber can be a useful thing to have around the shop. It can be used for all manner of purposes, from science experiments to degassing paints and epoxies. They’re not something you’d find in every workshop, but never fear – you can always build one from scrap you’ve got lying around! (YouTube video, embedded below.)
[VegOilGuy] begins the build with a simple plywood box, which gets screwed together and then tarted up with bodyfiller and paint. This helps to make the box airtight, as well as improving the aesthetics. A slot is then cut in the lid, and then filled with an excessive amount of silicone sealant. A flat plate covered in aluminium foil is placed on top, and the silicone is left to cure for several days.This is used to create a flat sealing surface for the lid to be placed on later.
Once the seal is complete, it’s a simple plumbing job to finish the chamber. [VegOilGuy] does a great job of demonstrating copper soldering and the proper way to install the necessary taps and check valves. Combined with an electric pump, the vacuum chamber passes its tests with flying colors, completely ruining some marshmallows in the process.
With a few dollars spent online for the special bits, it’s a build that any handy maker could throw together in a weekend. You can always go another route, though – like using an old fridge compressor to get the job done.
[Thanks to Keith O for the tip!]
Helpful hint – don’t forget when you build these things that there’s a *lot* of air pressure trying to make this into something that looks more like a pizza box.
For example, if you pull a modest 5psi vacuum inside a one-foot-cube chamber there’s more than 4000 lbs of “squish” from the outside trying to undo your work.
Pick your materials accordingly.
That is so true, but I never would believe it, Because you dont think the air pressures there because your perfectly safe in it. I saw that metal tanker on utube get crushed, couldnt believe it!
Soldering: clean and flux both the fitting and the pipe. Insert pipe into fitting and apply heat. Once up to temperature, lightly place your solder where the fitting meets the pipe. Because physics (specifically capillary action), the solder will be sucked into the joint in a uniform manner.
i think 5 psi x 144 sq in is more like 720 lbs, not 4000.
5 psi x 144 sq x 6 sides = 4,320 psi from all 6 sides.
how is 5psi a “modest vacuum”? that’s a third of an atmosphere
PSIA is 14.7 – 5 = 9.7. IIUC 5 psi vacuum would be 9.7 x 144 x 4 = 8,300+ pounds of pressure yes?
Plywood with bondo and paint? For a vacuum chamber? I guess it might be ok for degassing resin but that’s about it.
Pick up an old paint pot, autoclave,or pressure cooker and build off that. You’ll have a better chamber for about the same amount of work. I have picked up several paint pots from thrift store for almost nothing.
Wow, thanks for the idea.
I have an old paint pot that I have been keeping for this purpose, but I would have never thought to use that dusty old pressure cooker I have the attic.
The only problem with pressure cookers are the seals will not always handle a vacuum. They are often made so that the pressure helps seal them and they leak with reverse pressure.
So take a piece of 3/4 acrylic or polycarbonate and a some rubber and make a lid. You can also pop holes in the lid for a gauge and bulkhead fitting to connect to the pump.
Also a used 40quart (liter) stock pot from your local thrift shop will hold vacuum nicely.
” It can be used for all manner of purposes, from science experiments to degassing paints and epoxies.”
Clothes dryer?
Cat dryer?
No. Definitely NOT cat dryer. That’s what the microwave is for.
Vacuum distillation?
Been there, done that.
For the lid, note that acrylic will shatter in the manner of glass when it fails. Not dangerously, the shards aren’t glass-sharp, but something to consider.
Polycarbonate is more like aluminum, in that it’ll bend quite a bit before it breaks. It’s much better for cases where there might be a failure mode.
I’ve found that the glass plate from old microwave ovens will make a good vacuum plate – the top surface is flat, turn it upside down and use it as a lid. It *does* hold the vacuum, and it even holds after I’ve drilled a hole for a bulkhead union tube connector. Yes, I’ve sucked these down to the milli-torr range, they hold up quite well. The glass is rather thick and will hold a lot of stress.
After drilling, put it back to oven for 20min. Should help with stress buildup recovery.
Those cheap vacuum gauges can be tuned if you take them apart, down to the point of exposing the “clockwork” or the units, bend the needle up so it cannot hit the peg and then do some careful subtle bending to the main curved “tube” (usually copper) until the relaxed state of the needle is to rest at zero then straighten out the needle so it rests gently on the peg. Carefully put the unit back together and you’ve got a calibrated meter (or at least zero adjusted :-) )
If lest than half an atmosphere of vacuum is acceptable one can use these two devices and a few resistors to build a negative feedback loop when used to control the vacuum pump. A trick to put some desired hysteresis in the circuit is to allow a bit of current to bleed off the switched circuit and into the control input through a high resistance resistor.
DC12V Auto Circuit Modifications Voltage Comparator LM393N Remote Control ( ~$7 )
https://www.ebay.com/itm/DC12V-Auto-Circuit-Modifications-Voltage-Comparator-LM393N-Remote-Control/182094080043
Details about Pressure Transducer, Vacuum Pressure -14.5 to 30psi, Can Work for Boost Vaccume (~$15.50)
https://www.ebay.com/itm/Pressure-Transducer-Vacuum-Pressure-14-5-to-30psi-Can-Work-for-Boost-Vaccume/171159218794
As it is it’s just a presentation that it is possible to suck some air out of a wooden box.
No calculation whatsoever whether it would be safe to do so.
No precautions for anything that could go wrong.
Calculations are … a bit difficult because reliable numbers of the strength of plywood are hard to come by. Making a box a lot bigger as needed and then experimenting whether it’s up to the pressure would have been more usefull, and maybe even a bit spectacular.
Vaccuum usually (Usually !!!) is not very dangerous, but for experiments like this I would at least have liked to see some steel wire gauze / mesh wrapped around the box to prevent pieces from flyig very far.
Hello I am trying to achieve a near perfect vacuum in a small (12 x 10 x 6 in) aluminium box and was wondering if anyone had recommendations on what pump will achieve this. Or if the one in the video is enough then a link.
Most HVAC style pumps will get to 20-40 microns.
Fraser, how perfect do you need to be? High vacuum would mean polished stainless steel not aluminum, a good conventional vacuum pump for roughing and turbo molecular pump or vapor diffusion pump for high vacuum.