Homemade, inexpensive vacuum chamber for degassing

Ytierian · Post by **Ytierian** » Fri Aug 31, 2007 2:37 pm

I went and built a Vacuum Chamber for degassing small amounts of either RTV or Resin

I've also taken pictures and posted on my site a quickie instruction set for building your own

http://www.citlink.net/~ytier/Vacuum%20Chamber.htm

Have fun

Ytierian

Darkov · Post by **Darkov** » Sat Sep 01, 2007 5:15 pm

Nice concept.....just a couple of words of advice and warning.

You do need at least 25" of Hg to degasse rubber properly.

That hand vac pump would be to difficult to use to degasse resin before it started to cure.

Also that GLASS fish bowl

.....man you are asking for trouble there. If you were to bump that thing when it was under vaccum. You would have yourself one heck of an implosion.

Just my 2cents

DX-SFX · Post by **DX-SFX** » Sat Sep 01, 2007 5:39 pm

Also that GLASS fish bowl .....man you are asking for trouble there. If you were to bump that thing when it was under vaccum. You would have yourself one heck of an implosion.

Yep! I've had an acrylic sheet shatter once and that was f**king dangerous. A non spherical glass bowl imploding like that should have you pooping your pants immediately after the loud bang followed by a rapid liberation of blood. Seriously, you're mad to recommend this. Don't risk it.

Sparky · Post by **Sparky** » Mon Sep 03, 2007 11:50 pm

You can use the harbor freight paint pot as a vaccum chamber.

http://www.kc6sye.com/techmages_10_10_05_b.html

If you subscribe to the idea that the pot is to dangerous to cast in just use it for degassing.

You could reduce the amount of volume in it (of air that you have to pump out). By filling it with some solid material. Someone here has used pink foam to create shelves in the pot and to give the floor of it a flat plat form.

Umi_Ryuzuki · Post by **Umi_Ryuzuki** » Tue Sep 04, 2007 1:23 am

Yes, the hand pump would take too long to get enough vacuum to degass most materials before they cure...

_______

If the fish bowl has a flat base, or top that is six inches in diameter,...
Then that six inch diameter circle has an area of about 28.27 square inches. If you were to pull a full vacuum, that would be aproximately 15 lbs per square inch of atmosphere on the circle... Per Square Inch...

28.27 x 15 = 424.05 lbs of atmosphere on the fishbowl at full vacuum...

does that add up right?

And that is just on the flat circular area....

Zen-Builder · Post by **Zen-Builder** » Tue Sep 04, 2007 2:42 am

I go with the stuff that my LHS sells.
They are resin kit producers and also supply many other makers with stuff.

Arsenic Hipster · Post by **Arsenic Hipster** » Tue Sep 04, 2007 6:52 am

Umi_Ryuzuki wrote:
If the fish bowl has a flat base, or top that is six inches in diameter,...
Then that six inch diameter circle has an area of about 28.27 square inches. If you were to pull a full vacuum, that would be aproximately 15 lbs per square inch of atmosphere on the circle... Per Square Inch...

28.27 x 15 = 424.05 lbs of atmosphere on the fishbowl at full vacuum...

does that add up right?

And that is just on the flat circular area....

And if the surface is flat the glass will be loaded in bending... Glass doesn't bend very well.

DX-SFX · Post by **DX-SFX** » Tue Sep 04, 2007 3:57 pm

"If" the glass was a perfect sphere, the pressure would be exerted evenly over the entire surface. The whole thing would be in compression which glass does very well, however, it's not a perfect sphere in this case and the forces are uneven. Also, it is almost certainly a very cheap low grade of glass which is not toughened and liable to splinter. When it goes, it will go like a nail bomb.

Umi_Ryuzuki · Post by **Umi_Ryuzuki** » Sun Sep 16, 2007 3:49 pm

Follow up on the pressures exerted by the Vacuum process.

Sort of a counter point to Cobywan's pressure pot incident...
I think we all learned something from that right?
Don't use pressure cookers, the twist on latches shear away.

I have always made it a point to stand to one side of my pots when applying pressure or vacuum. Today I had two thoughts.
1. I need to move that small pressure pot...

2. The vacuum lid as a small crack, I need to make a new one before it
gets worse...

BOOM!!!

As for Vacuum Chambers,...

Why you probably don't want to use a large glass fish bowl...

1/2" (127mm) thick Plexiglass(perspex) shattered by vacuum.

Those are all separate pieces with "sharp pointy teeth..."

Second shot of the Shrapnel.....

Pieces were tossed about 4-5 feet out from the chamber.

Scared my roomies more than it scared me..
All I wanted was some boat rail stanchions...

Engineering analysis then kicked in... Lets put the pieces back together.

DX-SFX · Post by **DX-SFX** » Tue Sep 18, 2007 3:02 pm

I rest my case.