26.5" hg does not suck enough

[clonesix]

A vacuum chamber has been on my wish list ever since I started to pour RTV. I finally put one togetther using an aluminum stock pot and 1" plexyglass for a lid. The problem is that my 1/4 hp Gast rotary vane vacuum pump only pulls 26.5" Hg, and that just isn't enough to get the air out of rubber.

I can get the bubbles to come to the surface, but they don't want to pop.

How much vacuum do I need before the RTV really boils?

 

[micdavis]

You really do need 28 or 29. Sorry.

Makes all the difference.

 

[Jedifyfe]

So, it does suck then....

 

[Got Maul]

LOL- I was just looking for one of these today ! Thanks for the info on the vacuum. If you find a good price, could you pm me a link ?

 

[blufive]

I believe 29 is the magic number.

I bought a commercial vacuum motor to make sure I didn't have to worry about how much vacuum was enough. I used to have one of the Harbor Freight thinggies and it just didn't do the trick for me.

 

[clonesix]

I need 29" minimum? Do I need a 2 stage pump for that? I think that will drive the price up a bit.

 

[asavage]

I need 29" minimum? Do I need a 2 stage pump for that? I think that will drive the price up a bit.

Look on craigslist for an old lab sargent welch. Those puppies are like 2k in grainger, but I see them occasionally for around a hundred bucks. A 2 stage rotary like that will run you 600 on ebay. I just bought one (an edwards 12 btw).

 

[clonesix]

In this case, ebay is my friend. I have this bad boy on the way http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=130223952755&ssPageName=STRK:MEWN:IT&ih=003

at $210 shipped, it wasn't cheap, but I wasn't going to go shopping around for a better deal. I guess this means that the 1/4 hp pump pictured above will be going to ebay if anyone needs an extra vac pump.

 

[blufive]

That's the model I have. It will definitely meet your needs.

 

[Java]

LOL- I was just looking for one of these today ! Thanks for the info on the vacuum. If you find a good price, could you pm me a link ?

Can't believe you took my pressure pot with you to Cali and you don't remember that it's mine. :wacko