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Old 07-17-2014, 09:52 PM   #1
SamHarper
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Default Plexiglass vacuum chamber

A friend of mine (Dave, pbuh) had a bunch of 1/2" plexiglass he said I could use, so I made a vacuum chamber. I just finished it. This is me holding it up by the lid so you can see that it's holding a vacuum.



I'm going to put some rests on the bottom to lift the wood up a little. I'll probably also add a gauge at some point.

I'm using Gold's Gym 6' stretch band (same stuff as Theraband) for a gasket. I originally got it to make slingshots, but it works great for a gasket because it's wide enough that I can just cut out the middle of it, and there's no seam around the edges.

Originally, I used some silicone glue to glue it to the lid, but it wouldn't hold a vacuum. So I pealed that off, cleaned it up, and put another one on there without gluing it. It's just sitting between the lid and the rim. It seems to work!

I bought one of those round vacuum chambers made out of a pyrex dish on ebay a while back, but I don't like it because with its shape, it's not as easy to put square pieces of wood in it. And it's not very tall, so you have to be really careful when you initially put on the vacuum and all those bubbles rise up. With this square plexiglass one, I can get more wood in it at a time, and it's taller, so I don't have to worry so much about the bubbles getting up in the valves and pump and stuff.

I found a guy on craigslist who makes grills, and he had some scrap pieces of expanded metal. I'm going to use that to make a weight like Curtis Seebeck uses to keep the wood submerged in the Cactus Juice.

<--happy me
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Old 07-17-2014, 11:42 PM   #2
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Well, the vacuum only held for a couple of hours. I guess I'll go ahead and get a gauge so I can see what kind of vacuum I'm getting.

Any idea how I can check to see where it's leaking?
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Old 07-18-2014, 12:43 AM   #3
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I decided to set the timer on my phone and see how long it would hold a vacuum and compare it to my old one, so I propped the lids up on props so when the vacuum broke, they'd drop a little, and I'd hear them so I didn't have to go check. My new one held a vacuum for 44 minutes before it dropped. The old one is still holding.
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Old 07-18-2014, 12:46 AM   #4
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ill be the dummy. what in the heck is this for?
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Old 07-18-2014, 12:52 AM   #5
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ill be the dummy. what in the heck is this for?
I'll ride that pony with ya....


I assume we are trying to treat some wood in some way?
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Old 07-18-2014, 12:56 AM   #6
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It's for stabilizing wood for knife handles.

https://www.youtube.com/watch?v=uvII1FTm3YM
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Old 07-18-2014, 05:39 AM   #7
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You might try submerging it in food colored water to locate the vacuum leak. That should give you a clue as to what area of the chamber the leak is in. Or you could use a spray bottle with colored soapy water and spray all the joints to see if it sucks color bubbles inside.

If you clamp the lid down and reverse the air flow, it should hold some light pressure as well. Then check with soapy water. "Light pressure" being the key

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Old 07-18-2014, 05:57 AM   #8
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Yea I think id spray the outside seems with colored water and see where it sucks in at. I've heard of people running a constant vacuum. I'm not sure how this is accomplished. Perhaps some kind pressure valve. That is assuming you can't just let it run at max without burning out the pump. I assume the pumps are not strong enough to create too much force.

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Old 07-18-2014, 06:30 AM   #9
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If you wanted to get all fancy, you could wire in a pressure indicating transmitter, and a control to cycle your vacuum pump on, when the pressure dropped.

But, by the time you did all that, you could just buy one of Curtis' chambers.

I wonder if a small clamp, on each corner, would fix the leak.
Heck, it might not even be the lid. It might be one of the valves.
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Old 07-18-2014, 06:45 AM   #10
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Awesome. What pump are you using?
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Old 07-18-2014, 07:44 AM   #11
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I'm using this pump. I got it at a pawn shop.

I tried coloured water, and it's definitely leaking at the lid. I've got my edges as smooth and flat as I can, so I guess I just need a better gasket. Maybe I could try using two gaskets, one on top of the other.
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Old 07-18-2014, 07:45 AM   #12
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Curtis Seabeck runs his pump continuously, but I'd still like to have a chamber that doesn't leak. My other chamber is still holding a vacuum this morning.
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Old 07-18-2014, 07:48 AM   #13
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Do you know anyone that has a machine shop, with a mill?
It'd take about 58 seconds to mill that top edge perfectly flat.
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Old 07-18-2014, 07:50 AM   #14
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It looks like it didn't leak between the chamber and the gasket. It only leaked between the lid and the gasket. Hmm. When I took the lid off, the top of the gasket was wet, but the bottom of the gasket was dry. I sprayed water on both sides of the seam.
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Old 07-18-2014, 07:52 AM   #15
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The way I got the top of the chamber flat was by using double sided tape to tape a sheet of sand paper to a flat slab of polished granite, then rubbing the chamber on the sand paper. I went down to 400 grit. But like I said, it's not leaking on that side. It's leaking on the lid side. That surprises me because the lid side is the smoothest part of the plexiglass. I don't see how it's possible to get it any smoother.
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Old 07-18-2014, 09:00 AM   #16
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Iíve tried a lot of different things and ways for a vacuum chamber, I broke down and bought a Pyrex chamber and itís the best Iíve found. Easy to clean up because itís round. You know how easy Cactus Juice it to clean up with soap and water. Iíll never use anything else.
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Old 07-18-2014, 09:04 AM   #17
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Yeah, I got one, too (in one of the picture above). It's definitely easy to clean. I just don't like the shape because the square pieces of wood don't fit neatly down in there, so I can only stabilize two pieces at a time. And I'd rather it be taller so when those bubbles rise really fast in the beginning, I don't have to worry so much about them going up in the valves and pump. But it does hold a vacuum well!
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Old 07-20-2014, 05:57 PM   #18
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I tried a different gasket material, and this time it held for somewhere between two and three hours. That's an improvement. I ordered a vacuum gauge. If it turns out I can get a good vacuum by leaving the pump on, that'll be good enough for me.
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Old 07-21-2014, 10:18 AM   #19
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I don't see how it could get any better than leaving the pump running. As any air enters, it will be pumped out.
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Old 07-21-2014, 12:15 PM   #20
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Yeah, it just may not get as good of a vacuum if it's leaking in while being pumped out. But I guess it depends on how fast it's leaking in. I'll find out when I get my gauge.
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Old 07-21-2014, 12:32 PM   #21
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The whole idea of a vacuum is to pump the air out of the wood so it can collapse the cell structure to a point of maximum absorption point. I say put a good gauge on it and run the pump constant. FWIW there are those that will tell you that you need a 5 cfm pump and that a 2 stage pump will pull a deeper vacuum. I say bull... 30 inches of vacuum is 30 inches of vacuum no matter what pump you use.
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Old 07-21-2014, 12:42 PM   #22
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Quote:
Originally Posted by rubydog View Post
I say bull... 30 inches of vacuum is 30 inches of vacuum no matter what pump you use.
I am with you.
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Old 07-21-2014, 01:00 PM   #23
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I've got access to pumps at work that will pull a vacuum down to about 5mTorr. I'd need at least 3/4" Lexan to make the box with, 208V ran to my garage............might have to look into this. lol
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Old 07-21-2014, 01:19 PM   #24
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I think you are looking at it from a different angle that may not be correct sam. A constant running pump would be exactly the same thing as a container with a perfect seal. I think you are seeing it as a running pump will be pulling in air from the outside of the container if there is a leak. While this could be possible, the pressure should not change.

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Old 07-21-2014, 04:24 PM   #25
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Quote:
Originally Posted by LeanMachine View Post
I think you are looking at it from a different angle that may not be correct sam. A constant running pump would be exactly the same thing as a container with a perfect seal. I think you are seeing it as a running pump will be pulling in air from the outside of the container if there is a leak. While this could be possible, the pressure should not change.
A static closed container is just that. Nothing is removed and nothing is added because it is sealed. A container that is constantly being pumped down removes any air from the material inside the chamber and displaces it through the pump and the oil in the pump hence the reason the pump oil gets contaminated
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Old 07-21-2014, 07:57 PM   #26
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Quote:
Originally Posted by rubydog View Post
A static closed container is just that. Nothing is removed and nothing is added because it is sealed. A container that is constantly being pumped down removes any air from the material inside the chamber and displaces it through the pump and the oil in the pump hence the reason the pump oil gets contaminated
As usual, Terry's pretty
Much always right with anything that involves wood! Run your pump the whole time. (Spellcheck tried to auto correct to say "run your pimp"). Haaaaa
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