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Cheap Vacuum Pump - $10.00 - 7/24/2006 4:39:25 PM   
jetflyer



Posts: 1007
Joined: 12/26/2001
From: League City, TX, USA
Status: offline 		This is by far the cheapest way to get started vacuum bagging. What you see here is a venturi style vacuum pump normally used to draw a vacuum on automotive A/C systems. This unit works off compress air from your typical shop air compressor. It says it's capable of drawing 20 Hg of mercury which is plenty for wings and other items you might want to vacuum bag. It sells at Harbor Freight for around $12 to $15 but is usually put on sale several times a year for $10. I purchased a Festo fitting previously from McMaster Carr which worked perfectly to allow me to re-fit the connector on the vacuum side of the unit for connecting directly to 6mm tubing. Operating this unit is quite easy and requires about 90 to 100 psi to make it work. You basically use your air compressor valve to give you 90 to 100 psi and after it vacuums down the bag use the Festo ball valve to close off the vacuum and then turn off your air valve on your compressor.

You can see the process of vacuum bagging my wings for my Discovery jet.
http://www.houstonhobbies.com/jets/discovery/discovery-jet-session8.htm

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RE: Cheap Vacuum Pump - $10.00 - 7/25/2006 4:37:13 PM   
Troy-RCU



Posts: 511
Joined: 1/18/2002
From: Oceanside, CA, USA
Status: offline 		I've seen that too but you need to make sure your bag does not leak, which in my experience is not always as easy as it sounds.


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RE: Cheap Vacuum Pump - $10.00 - 7/25/2006 6:42:33 PM   
dolanosa



Posts: 227
Joined: 10/4/2005
From: Chicago, IL, USA
Status: offline 		Jetflyer,

You still have to use a compressor for this, right? I'm using a brake bleeder hand vac and truthfully, it works great but it get's old after a while. I'm looking at Ebay for some Gast vacuum pumps...any suggestions on this type?


Butch


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RE: Cheap Vacuum Pump - $10.00 - 7/26/2006 5:30:35 PM   
jetflyer



Posts: 1007
Joined: 12/26/2001
From: League City, TX, USA
Status: offline 		Butch,

If you have an air compressor I'd just order the air vacuum pump from Harbor Freight - see link below
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=3952
Stock# 3952-0VGA
And you will need a fitting from McMaster-Carr to allow you to hook up 6mm tubing to the front of the Air Vacuum Pump.
http://www.mcmaster.com
Part #51115K364

If you don't have an air compressor I'd consider buying a complete setup from Aero Space Composites because there pumps are designed to run continuously - see links below
Vacuum Pump link - http://www.acp-composites.com/acp-vbs.htm
Vacuum Accessories link - http://www.acp-composites.com/acp-vbes.htm

You will need to get the EZ-VAC bag connector that they sell. I had good luck placing the connector in the center of the vacuum bag. Unless you are doing huge pieces, buy the NYLON BAGGING TUBE in 36" wdths along with the QUICK LOCK SEALS. I did a double fold of the bag before I clipped the Quick Lock Seals on.


Troy-RCU,
Yes you are correct you need to make sure the bag does not leak. I use to think this was hard to accomplish but it really is not. I use a Nylon Bagging Tube this is only open on 2 ends along with Quick Lock Seals. You need to make sure you place the EZ-Vac bag connector a good ways in from one of the bag ends. Allow enough room to double fold the bag and Quick Lock Seal the ends. To avoid having to run my Air Vacuum Pump continuously I installed a Festo ball valve just after the EZ-VAC bag connector. This allowed me to keep the vacuum without running the pump. About every 30 minutes or so I would kick on my air compressor to get the air vacuum pump working and then open up the Festo valve. Yeah I got some leakage, but nothing that would ever cause any problems. I probably could have even re-vac every 1 hour instead of every 30 minutes.

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RE: Cheap Vacuum Pump - $10.00 - 7/26/2006 11:13:45 PM   
Troy-RCU



Posts: 511
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From: Oceanside, CA, USA
Status: offline
quote:

ORIGINAL: jetflyer
About every 30 minutes or so I would kick on my air compressor to get the air vacuum pump working and then open up the Festo valve. Yeah I got some leakage, but nothing that would ever cause any problems. I probably could have even re-vac every 1 hour instead of every 30 minutes.

You left that part out of your original post... It's kind of an important detail.
I've used the best aerospace bagging materials (at previous job) and my cheapo garage materials and with reservoir systems the pump still turns on at least every 20-30 minutes. It's good your having success with this system. Great for bagging wood skins.



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RE: Cheap Vacuum Pump - $10.00 - 7/27/2006 2:33:02 AM   
dolanosa



Posts: 227
Joined: 10/4/2005
From: Chicago, IL, USA
Status: offline 		Thank you for your input. I was really thinking of getting one of those Gast ones so if I want to do some "hard vacuum" bagging, it would do it. After a while, I figured I still needed the vac gauge, fittings, vacuum switch, external tank, etc and all the necessary bagging materials. That might cost more than the ACP Autovac bagging system.

One more thing. About more inexpensive items to use. Please tell me if these would work. Mylar film: I have yards and yards of mylar baloon material. Is that ok? I also have a few yards of flag material (polyester). Can that be used as well? Thanks in advance.

Butch


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RE: Cheap Vacuum Pump - $10.00 - 7/27/2006 5:20:43 PM   
Troy-RCU



Posts: 511
Joined: 1/18/2002
From: Oceanside, CA, USA
Status: offline 		If you buy all of the commercial vacuum bagging products you can spend a fortune. I have had a lot of success with very basic materials and they are found at two places: Home Depot and Pep Boys.

I buy cheap tubes of acrylic caulking for sealing edges and a roll(s) of plastic painter's drop cloth for bagging material. One caution though, I have found some of the plastic sheeting to be porous and it'll never pull a good vacuum. I like to use Ace Hardware brand as I know it works every time. I have also found that Hefty bags work pretty good if you have something small/medium size to bag. You only need to seal one end and the plastic stretches into corners well...just don't over stretch it.

The tube and fittings can be found at most auto parts stores. I use regular vacuum hose and buy their plastic (or metal) "T" splitters or manifolds to run more than one line.

The Festo fittings are great and work well. In a pinch I'll simply put the tube in the bag (with a paper towel wrapped around the tip for air bleeder) and just caulk around the tube at the seal.

Bleeder cloth, paper towels. Usually two or three layers.

I'll even make my own perforated plastic barrier from the Ace plastic sheet and a woodpecker device to make pin holes.

The caulking can be messy if you aren't careful but generally I'll just make the envelope bag a little over sized so the caulking never gets close to the mold or part.

When you're bagging job cures over night, just cut inside of the caulking seal with scissors or exacto and pull out the part.

BTW, I use a twin diaphragm pump like this one and just run it constant over night. You can set up a reservoir system with a tank and an on/off switch system but it starts getting complicated and adds sources of leakage. They are expensive at retail places but they can be found for about $70-$80 bucks at surplus outlets or Ebay.



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RE: Cheap Vacuum Pump - $10.00 - 7/27/2006 5:48:16 PM   
skypupmut



Posts: 421
Joined: 1/9/2002
From: Sherbrooke, QC, CANADA
Status: offline 		I use refrigirator compressor for last 10 years
works like a charm and very cheap ( nada )
also use it fro A/C work

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RE: Cheap Vacuum Pump - $10.00 - 7/29/2006 3:44:30 PM   
CoosBayLumber


 

Posts: 3048
Joined: 1/20/2002
From: San Bernardino Calif
Status: offline 		I use same as the SkyPup does. Seems to be a place here in town on a dark street where old refrigerators get dumped. Found one, cut it out which hack saw, and left the shell there. It did not work, so went back three days later and yet another regrigerator unit was dumped durig the night.

Simple matter to leave old non-working pump inside unit that hacksaw will be used on. Nope, the second one was bad too. Came back whole week later and got a third one, to which I still use. Cost two drives, and another electrical cord, plus to solder on some fittings to the pipes had to be less than $10

Problem in many pumps is the displacement factor. The pump may suck down to 18-22 inches, but does it take 1/2 hour to do so? A refrig pump will usually suck down a vacuum bag in less than one minute. Can't do that with a hand pump.


Wm.


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RE: Cheap Vacuum Pump - $10.00 - 7/29/2006 8:20:35 PM   
dolanosa



Posts: 227
Joined: 10/4/2005
From: Chicago, IL, USA
Status: offline 		I had to "presuck" the air down with a vacuum cleaner first. Once I had most of the air out, I would switch to the hand vac. That still took a long time but I was using loooong cure epoxy. I guess that helped. I'll look in crsigslist to see who's giving away fridges and ACs. Hope they have something.

B


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RE: Cheap Vacuum Pump - $10.00 - 7/29/2006 9:28:44 PM   
XJet


 

Posts: 3590
Joined: 3/31/2003
From: Tokoroa, NEW ZEALAND
Status: offline 		I'm still using one of those cheap 2HP direct-drive compressors that I modified to act as a vacuum pump. It has the added bonus that it comes with a built-in vacuum reservoir in the form of the pressure tank.

It cost US$49 and took about 2 hours to modifiy from compressor to vacuum pump.

So far it's done over 100 layups and still works great. I did make my own vacuum switch though (solid state) which allows me to set and automatically maintain the required vacuum level. This is invaluable as (on at least two occasions) the bag had a leak and it meant the pump was cycling every 30 seconds or so -- but there was plenty of reserve capacity there -- it only ran for about 2 seconds each time.

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RE: Cheap Vacuum Pump - $10.00 - 7/31/2006 7:51:10 PM   
sticks-RCU


 

Posts: 132
Joined: 4/18/2002
From: ogden, UT, USA
Status: offline 		XJet,

How did you do the conversion for your vacuum pump?

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RE: Cheap Vacuum Pump - $10.00 - 7/31/2006 8:05:23 PM   
le fou


 

Posts: 247
Joined: 5/3/2002
From: Omaha, NE, USA
Status: offline 		XJet,

Can you also give us some details about your vaccum switch? I have a fridge compressor and I would like to make a vacuum switch for it.

Thanks,

Le fou

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RE: Cheap Vacuum Pump - $10.00 - 7/31/2006 11:03:18 PM   
Newc


 

Posts: 1047
Joined: 10/23/2002
From: Leesburg, IN, USA
Status: offline 		For what it's worth, each time I see one of these 'cheap' ways to build a vacuum bagging system which involves remanufacturing an existing pump so that it's appropriate to the application, spending the time and effort to get the entire system (valves, gauges, etc.)plumbed and the bags so that they actually hold a vacuum and don't leak too much, I am glad that I spent $100 for the complete ACP Composites system. That's cheap! And Easy! And works flawlessly! And comes with a great video to show some great ways to use the system and to increase your abilities.

< Message edited by Newc -- 7/31/2006 11:04:53 PM >

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RE: Cheap Vacuum Pump - $10.00 - 8/1/2006 2:48:11 PM   
jetflyer



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