• stratom commented on bfoz's instructable Pressure Cooker Vacuum Chamber6 months ago
    Pressure Cooker Vacuum Chamber

    Acrylic may crack but polycarbonate will not. Polycarbonate is essentially unbreakable/uncrackable, that is what it was designed for, so you do not need to worry about scratches or drilling holes in it causing stress cracking.One day when I was working with some Science Olympiad kids we decided to test just how crack resistant polycarbonate is. First test was to bent some polycarbonate until it broke. We were literally able to bend a 1/8th inch thick piece until it was folded over on itself 180degree bend and it never cracked. Not satisfied, we took a 1/4" piece of polycarbonate and a 22 rifle with a long rifle cartridge and shot the plastic. The bullet passed right though and made a neat hole but no cracking. Interestingly, the hole was significantly smaller than the bullet, like the hole closed up some.I have built vacuum chambers using 2.5 gallon stock lot and a 1/2" polycarbonate top with two 1/4" pipe thread fittings drilled and tapped into the center (about 2 inches apart from each other) and have used it for years. I pull down to less than 10 microns (essentially 29.92" complete vacuum).

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