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Asok
Newbie
Joined: 09 Nov 2006
Posts: 17
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 Posted: Tue Sep 09, 2008 8:01 am Post subject: Looking for suggestions for a 17 to 21 CFM pump |
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| In the next week, my CAD guy, is going to draw up a 2 x 4 table and then a metal fab shop is going to build it. So, I need a pump. I would like a 17 to 21 CFM pump. Any suggestions? |
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cod
Master
Joined: 05 Nov 2006
Posts: 322
Location: San Francisco
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| Posted: Tue Sep 09, 2008 5:29 pm Post subject: Re: Looking for suggestions for a 17 to 21 CFM pump |
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| Asok wrote: | | In the next week, my CAD guy, is going to draw up a 2 x 4 table and then a metal fab shop is going to build it. So, I need a pump. I would like a 17 to 21 CFM pump. Any suggestions? |
I would think that if you find one of that rating that isn't several thousand dollars you should buy it regardless of brand- assuming it works. That level of pump is usually quite pricey.
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Asok
Newbie
Joined: 09 Nov 2006
Posts: 17
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| Posted: Tue Sep 09, 2008 8:09 pm Post subject: |
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| I know I am going to spend about $800 to $1000 on the pump. |
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clonesix
Novice
Joined: 19 Jan 2007
Posts: 63
Location: california
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| Posted: Wed Sep 10, 2008 12:01 am Post subject: |
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That is a pretty big size of pump. What size reseve tank were you thinking of using? A 30 gallon tank can be evacuated by a 7 cfm pump in less than a minute.
be sure to post pics when you get going on your machine. |
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Asok
Newbie
Joined: 09 Nov 2006
Posts: 17
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| Posted: Wed Sep 10, 2008 5:33 am Post subject: |
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| I was thinking 2 30 gallon tanks. |
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stagepin
Newbie
Joined: 01 Aug 2008
Posts: 13
Location: Fairfax, Va
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| Posted: Wed Sep 10, 2008 6:30 am Post subject: |
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| Asok wrote: | | I was thinking 2 30 gallon tanks. |
If your water heater tank is 20 inches in diameter and 3.5 feet tall, each one has 7.5 cubic feet of air. That's 15 cubic feet that you're evacuating. 2 minutes with a standard vacuum pump will do it.
edit: In thinking about it, if you plumb it right, you can evacuate in series if you're really concerned with time. If you're connecting the tanks in series, make two vacuum ports and separate the tanks with valves. That way you can buy two cheaper vacuum pumps, evac in about 1-2 minutes, open the valve separating the tanks, then you're good to go.
tank A -> vac port/pump -> valve -> tank B -> vac port/pump -> valve |
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ANH trooper
Master
Joined: 20 Oct 2005
Posts: 305
Location: UK
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| Posted: Wed Sep 10, 2008 3:32 pm Post subject: |
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You might be able to get away with using a pump with a smaller CFM rating. I have a 2'x 2' platen and a 10CFM pump with about 55 gallons of air tank capacity. I actually have three tanks plumbed in series, and the pump takes about 90 seconds to get to -28 in/hg. Once the vacuum is applied to the hot plastic with the pump running, I only lose 1 maybe 2 in/hg from the tanks and it takes no time to get back down to -28 on the tanks. The pump shows -30 at the platen with the pump running.
Just something to consider and could save you a fortune  |
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kayaker43
Expert
Joined: 13 Jun 2007
Posts: 175
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| Posted: Fri Sep 12, 2008 7:01 pm Post subject: |
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I have a super clean Gast 21 CFM pump for sale. Its an oil lubricated rotory vane type so it gets an inch or so more vacuum than a dry vane unit. It is missing the oil reservior but you can get those from gast.
This pump uses a separate 1 1/2 HP 1725 rpm motor, I have the pump and coupler, and may be able to dig up a motor too?
If interested, PM me and I'll pull it out and get pictures. I'm thinking $400 no motor or $500 with motor. I also have a 30 CFM pump if anyone is building a big machine?
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Doug Walsh
www.build-stuff.com
Hobby-Vac and Proto-Form machine plans
Also other plans books and videos for people who like to build things |
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