Vacuum pumps question revisited!
- Thread starter blufive
- Start date
I've seen people deair silicone with a 1 gallon empty paint can and one of those inexpensive pistol grip plastic vac pumps. Look for the one that has a built in gauge.
With RTV I don't think time is of the essence as much as ability to pull atmospheres.
If you are talking about the red pump from harborfreight that you hook up to a compressor I think it pulls between 28 and 29.
When you say "and to possibly use while casting" if you mean setting resin in a RTV mold then I would think you would want to use pressure not vaccum.
With RTV I don't think time is of the essence as much as ability to pull atmospheres.
If you are talking about the red pump from harborfreight that you hook up to a compressor I think it pulls between 28 and 29.
When you say "and to possibly use while casting" if you mean setting resin in a RTV mold then I would think you would want to use pressure not vaccum.
exoray
Master Member
With the HF venturi, I can get about 27/28 inches on my big compressor in the garage, with a smaller compressor that I have in the house I only get about 23/24 inches... So real world results will vary depending on your compressor and the volume of air it supplies...
Without spending a fortune you won't get much more speed on the pull then the HF one does, but you might get a little better vacuum... Try a Google search (or ebay) for Gast brand vacuum pumps... You can also go on the cheap and rip one out of an old fridge or freezer but results will vary and you will need to probably put an oil blocker inline...
TheSt.LouisKid
Sr Member
One shop I worked out of bought a vac pump from a auto parts supply store. Its used to vacuum out radiators or something. Its been awhile so I can't remember exactly what its used for. I imagine if you called and asked around you could get more info. Supposed to cost a few hundred less.
LeMarchand
Sr Member
I KNEW there was more going on in his workshop than vacforming when i was talking to Rylo on the Phone the other week.....Originally posted by blufive+Feb 14 2006, 02:48 PM--><div class='quotetop'>QUOTE(blufive @ Feb 14 2006, 02:48 PM)</div>No baby, that bulge in my pants when I left your house was all me.
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Marc
TheSt.LouisKid
Sr Member
Thats what I'm talkin' about. Damn, I'm gettin' old and memory is getting rusty.
blufive
Sr Member
Okay, I bought a 30 gallon compressor and attached my Harbor Freight vacuum pump to my new vacuum chamber.
The Harbor Freight pump requires a constant 90 PSI to maintain the 28-ish inches of mercury. The tank holds 155 PSI and is drained rather quickly. I'd say the air supply dips under 90 PSI in 1-2 minutes and then the vacuum isn't as effective.
Should I look at a different vacuum pump? I'm not opposed to the idea but I don't want to have to buy a larger compressor. I've only had this one for 2 weeks.
The Harbor Freight pump requires a constant 90 PSI to maintain the 28-ish inches of mercury. The tank holds 155 PSI and is drained rather quickly. I'd say the air supply dips under 90 PSI in 1-2 minutes and then the vacuum isn't as effective.
Should I look at a different vacuum pump? I'm not opposed to the idea but I don't want to have to buy a larger compressor. I've only had this one for 2 weeks.
exoray
Master Member
Put an on/off valve on each side of the HF pump, when the compressor tank drains, close the valve between the pump and tank, and then the valve between pump and air compressor... Let the compressor build back up then open the pump to compressor valve immediatly followed by the pump to tank valve and it should then continue to pull down... Once you get down, and assuming you don't have a leak, closing the valve should hold the vacuum just fine...
exoray
Master Member
Mine tank holds vacuum fine overnight, with a closed valve... Get the 1/4 turn ones, they make life a lot easier... And if you are around you can always fire up the compressor and bring it back down if it starts to rise after a few hours...
On the flipside it leaks a little while under pressure so I need to leave the compressor hooked up when pressure casting...
OhioAstromech
Well-Known Member
<div class='quotetop'>(terryr @ Feb 25 2006, 07:23 AM) [snapback]1193133[/snapback]</div>
From what I understand 28 inches of mercury is as deep as you can get on earth and it changes depending on altitude.
People in Denver will get a better vacuum then someone in Death Valley.
Scot
This is the same thing I use for my Vacuum Chamber and it pulls 26 to 27 inches of mercury.
From what I understand 28 inches of mercury is as deep as you can get on earth and it changes depending on altitude.
People in Denver will get a better vacuum then someone in Death Valley.
Scot
if the mold is small enough to fit in your pressure pot, there is no need to vac the rubber. Just cure the mold under pressure and it will have better results than vac.
GeneralMayhem
Sr Member
That's been my impression as well. If you have a good pressure pot, the vacuum chamber normally is not even neccesary.
blufive
Sr Member
My vacuum pump goes to 29-30 inches of mercury. The people at Silicones Inc. told me you had to have 29 inches to properly deair RTV.
<div class='quotetop'>(OhioAstromech @ Aug 7 2006, 01:06 PM) [snapback]1295587[/snapback]</div>
From what I understand 28 inches of mercury is as deep as you can get on earth and it changes depending on altitude.
People in Denver will get a better vacuum then someone in Death Valley.
Scot
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<div class='quotetop'>(OhioAstromech @ Aug 7 2006, 01:06 PM) [snapback]1295587[/snapback]</div>
This is the same thing I use for my Vacuum Chamber and it pulls 26 to 27 inches of mercury.
From what I understand 28 inches of mercury is as deep as you can get on earth and it changes depending on altitude.
People in Denver will get a better vacuum then someone in Death Valley.
Scot
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