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Reservoir tank for Vacuum Pump?

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Reservoir tank for Vacuum Pump?

Old 03-24-2007, 02:25 PM
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Default Reservoir tank for Vacuum Pump?

Hi Guys, I've built a vac pump from an old refrigerator compressor and made a regulator from an automotive vacuum actuator. I still need the associated tubing, fittings and a Vac gauge. I have read about having a reservoir tank also, and was wondering the necessity of it. What are the advantages of it? Thanks, Prop
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Old 03-24-2007, 03:52 PM
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Default RE: Reservoir tank for Vacuum Pump?

Most people use an empty freon canister but with the restrictions on freon you could probably use one of the walk around tire inflator tanks sold at auto part stores or wal-mart, easier to get hold of. Put a tee on the tank outlet and plumb it in to the vacuum line, it will hold a greater volume so it takes longer for the vacuum leaks to bring the pressure back up enough to switch on the pump.You hold a steadier vacuum on the part and the pump is not running steady to maintain suction. [sm=thumbs_up.gif]
Old 03-25-2007, 03:07 AM
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Default RE: Reservoir tank for Vacuum Pump?

Ditto what culver said.

I have one of those 5 gallon tire inflator tanks and it works very well. On a leaky bag, the vac used to cycle on every minute or so. With the reservoir, it would last 10 mins or more. Of course, if your bags don't ever leak, then you don't need a reservoir.

Alternately, for a reservoir, you can use PVC Pipe.
To make a 5 gallon reservoir, use 41" of 6" pipe. Or 92" of 4" pipe.
The pipe is cheap, but the endcaps are expensive.

If you want to go inexpensive, I've found 1/4" polyethelene tubing works well to connect your vacuum pump to the reservoir, regulator and gauge and from the reservoir to a 4-way valve. You can find this at the hardware store for about $2 for 10 feet. I use silicone fuel tubing to connect to the 4-way valve to the bag. The flexible connection is convenient for positioning your bag where you want it.

Plastic Tees, plugs, and connectors for drip irrigation work well too. You can get a package of assorted connectors for less than one brass T.
Now is about the time when WalMart stocks this stuff.

I've found a 4-way plastic valve (for aquariums) really handy. This would mount at the end of your table. Now you can bag 2 (or more) wing halves at once. Also in the aquarium section, look for air check valves.

Good luck with your bagging.
Old 04-07-2007, 12:37 PM
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Default RE: Reservoir tank for Vacuum Pump?

I use 40 stage PVC with end caps. I then use nipples from plumming suppy to go to the bag.

Works great

Jeff
Old 04-07-2007, 01:39 PM
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Default RE: Reservoir tank for Vacuum Pump?

Thanks for all the advice and tips guys! I think I'll look around for an old air inflator tank to use as a reservoir. My buddy said he saw one at a pawn shop the other day for $10. Prop
Old 04-09-2007, 02:31 PM
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Default RE: Reservoir tank for Vacuum Pump?

Great link / supply for vacuum reservoir plans and components:

http://www.joewoodworker.com/catalog/vacuum_press.php
Old 04-09-2007, 03:54 PM
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Default RE: Reservoir tank for Vacuum Pump?

Hi Jake,

milli thanks, just what I'm look for.

Regards.

Karl.
Old 05-08-2007, 01:53 PM
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Default RE: Reservoir tank for Vacuum Pump?

I use a $20 7-gallon compressed air "carry tank" from Wal-Mart. That's big enough that you can use it as a surge tank on a small to medium-sized vacuum former as well.
Old 05-08-2007, 03:34 PM
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Default RE: Reservoir tank for Vacuum Pump?

Found this old water pressure tank being thrown away, I sealed up the bottom with a threaded cap and it works great.
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Old 05-09-2007, 07:50 AM
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Default RE: Reservoir tank for Vacuum Pump?

Awesome find on the Tank!!

It looks like the Foam Ferry spent some time unloading at your place..he he

That's probably about the amount I need to order...I'm sure I'm gonna screw some of mine up since this will be my first attempts at cutting...he he

Have Fun!!

Chuck
Old 05-09-2007, 01:14 PM
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Default RE: Reservoir tank for Vacuum Pump?

Chuck, I get all the foam I need for free from the local furniture store in town. Seems it's used in packing for a lot of the pieces they receive. I've gotten to know the guys in the warehouse, and they put aside the "good stuff" I can use. Some of it's pretty crappy but there's usually some good 1 lb closed cell material. Also, you can keep your eye out for new construction where they're doing a stucco facade. I've found up to 3" thick 1lb CC in the dumpsters after the job is done and once, had a job foreman just give me some after I explained what I was needing it for. Hey, I might be in GA near ATL the 2nd weekend June, where is Carterville in relation to there. I was planning on staying at an RV park just north of ATL. maybe we can get together while I'm down that way. Tim
Old 05-10-2007, 04:07 AM
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Default RE: Reservoir tank for Vacuum Pump?

Hey Tim..

Cartersville is probably about 60 miles north of Atlanta off I-75...

Yeah..That would be kewl...Shouldn't be too far if your staying on the north side of ATL...

Have Fun...

Chuck
Old 05-26-2007, 08:33 AM
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Default RE: Reservoir tank for Vacuum Pump?


ORIGINAL: culver

Most people use an empty freon canister but with the restrictions on freon you could probably use one of the walk around tire inflator tanks sold at auto part stores or wal-mart, easier to get hold of. Put a tee on the tank outlet and plumb it in to the vacuum line, it will hold a greater volume so it takes longer for the vacuum leaks to bring the pressure back up enough to switch on the pump.You hold a steadier vacuum on the part and the pump is not running steady to maintain suction. [sm=thumbs_up.gif]
Single-use freon tanks (or the similar disposable helium tanks they sell for inflating balloons) do not have an anticorrosion liner or coating on the inside. They will eventually rust out and may implode. Should work for a while though... and you can get them for free from a dumpster behind a heating and air conditioning place.

$20 for a 7-gallon Wal-Mart air carry tank seems like a better bet.

Another thing you could try would be to put a container INSIDE the vacuum bag with the wing, maybe a mason jar or heavy glass jug with a hole in the lid, and something porous over the hole so it can't get blocked. When you evacuate the bag, you'll evacuate the jar or jug as well. This will greatly increase the volume of vacuum in the bag, so that leaks and outgassing weaken the vacuum MUCH more slowly.

If your resin sets up in reasonable time and doesn't outgas a lot, that may be all the machinery you need to regulate and maintain the vacuum. (I've been meaning to try this with a FoodSaver setup, but haven't done any vacuum bagging lately.)
Old 05-29-2007, 08:41 PM
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Default RE: Reservoir tank for Vacuum Pump?


[quote]ORIGINAL: drcrash


ORIGINAL: culver


Another thing you could try would be to put a container INSIDE the vacuum bag with the wing, maybe a mason jar or heavy glass jug with a hole in the lid, and something porous over the hole so it can't get blocked. When you evacuate the bag, you'll evacuate the jar or jug as well. This will greatly increase the volume of vacuum in the bag, so that leaks and outgassing weaken the vacuum MUCH more slowly.


That's technically no different than plumbing in a vacuum reservoir (i.e. the same mason jar with some cheap fittings).
Old 05-29-2007, 09:49 PM
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Default RE: Reservoir tank for Vacuum Pump?

ORIGINAL: TeamSeacats


ORIGINAL: drcrash

Another thing you could try would be to put a container INSIDE the vacuum bag with the wing, maybe a mason jar or heavy glass jug with a hole in the lid, and something porous over the hole so it can't get blocked. When you evacuate the bag, you'll evacuate the jar or jug as well. This will greatly increase the volume of vacuum in the bag, so that leaks and outgassing weaken the vacuum MUCH more slowly.
That's technically no different than plumbing in a vacuum reservoir (i.e. the same mason jar with some cheap fittings).
I agree, the effect is substantially the same, with only a modest reduction in complexity.

I thought of it when I was looking at Jim Young's simple setup for using a Food Saver. It also has no facility for resuming pumping once outgassing has diminished the vacuum, and I was wondering just how long it takes for the vacuum to weaken. (I suspect it's not long, given the near-zero air space inside the bag.)

http://www.rcgroups.com/forums/showthread.php?t=411348

Just putting a jar in the bag means that you don't have to worry about plumbing the connection to the reservoir, making sure it doesn't leak, or (more importantly) figuring out when and how to restart the pump when the vacuum weakens---just put "enough" vacuum inside the bag, and let it sit. The vacuum will still weaken over time, but only very slowly.

If you have a "real" vacuum pump and a vacuum switch, or if your pump is rated for continuous duty and you can just leave it on indefinitely, there isn't as much of an advantage, just a little simplicity. But if you're making do with something like a Food Saver, a hand pump, or a converted tire inflator (like this one: http://www.tk560.com/phpBB2/viewtopic.php?t=636 ), it could be a handy trick.

Old 06-03-2007, 09:57 AM
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Default RE: Reservoir tank for Vacuum Pump?

hi guys
i read the thread but didn t understand where you will use this kind of compressor item.
can anyone explain?
thanks
achilles
Old 06-03-2007, 12:39 PM
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Default RE: Reservoir tank for Vacuum Pump?

ORIGINAL: rxAxilleas
i read the thread but didn t understand where you will use this kind of compressor item.
can anyone explain?
For the two-stage vacuum setup for vacuum forming, I can plug it in as the "high vacuum pump" instead of the FoodSaver. (My wife decided she wanted one for, of all things, vacuum-sealing food. Go figure.)

Here's the basic, simplified plumbing for a one-stage vacuum system. This would work fine with a small vacuum pump, small tank, and small vacuum former:
Code:
 + - - - - - - - - - - +       
 |        platen       |        
 +--------+  +---------+       
          |  |                
          |  |                                       +-------------+
          |  |        +-------+                      |             |
          |  +--------+  ball +----------------------+   vacuum    |
          +-----------+ valve +---+ +----------------+    tank     |
                      +-------+   | |                |             |
                                  | |                |             |
                                  | |                |             |
                                  | |                |             |
                                  | |                |             |
                                  | |                |             |
                               +--+ +--+             |             |
                               |  high |             |             | 
                               |  vac  |             |             |
                               | pump  |             |             |
                               +--+ +--+             +-------------+
                                  | |
                                exhaust
You close the ball valve and turn the pump on to evacuate the tank. Then when you're ready to form, you pull the plastic down over a mold on the platen and open the ball valve. Air rushes from around the mold, through the platen hole(s), and through the pipe into the tank.

The reason for the tank is that a little cheap low-volume (but high-vacuum) pump can't pull the air out fast enough by itself. You want to pull the air out from under the plastic within about a second, before it cools much.

Using a tank lets you store up a bunch of vacuum and use it all in a hurry, just by opening a pipe into the tank. The tank can pull air about 100 times faster than the pump alone, but only until the tank fills up.

This works well for vacuum forming, because it generally takes you a few minutes between pulls anyway. (Clamping & heating the plastic, removing it afterwards, etc.) The pump can be pulling air out of the tank while you're doing that stuff, and then you can use the vacuum it's built up in a few seconds during forming.

The same basic scheme works for vacuum bagging, with a vacuum bag instead of a platen. (And usually with an even smaller tank, usually called a "reservoir," with a capacity of roughly a gallon.) The function of the tank there is also to store up vacuum---not because you'll be using a whole lot of it in a big hurry, but so that you don't have to run the pump continuously to keep up with small leakage and outgassing from your resin. The tank acts like a flywheel for vacuum, by making the space that the pump is pulling from much larger. A little leakage or outgassing into that much larger space will only slowly degrade the vacuum. If the vacuum drops too low, you can turn the pump back on again to pull most of the leaked air & fumes out of the tank, then shut the pump off again. In between, the reservoir sucks up most of the gases.

(You can do that automatically with a vacuum switch, or by hand.)

You need that intermittent pump operation if you use a tire inflator as a vacuum pump, because they're not meant to run continuously for long periods of time. They may overheat and seize up, or strip their heat-softened nylon gears, if you run them for more than 10-30 minutes. (Depending on the pump. Some of the incredibly cheap tiny ones can only run for a few minutes at a time, but bigger and better ones can run for up to an hour or more.)

Some vacuum pumps can run continuously, so you can simplify the setup, but they won't last as long as if you run them intermittently.




Old 06-03-2007, 01:02 PM
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Default RE: Reservoir tank for Vacuum Pump?

hi again,
thanks for the info!!!
i admit that it is an excellent and usefull device and i never thought how they do the forming.
althought it is simple proceedure it is very important to have the right tools.
thanks very much
achilles
Old 06-10-2007, 01:53 AM
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Default RE: Reservoir tank for Vacuum Pump?

5 GALLON PORTABLE AIR STORAGE TANK Take compressed air with you wherever it's needed. Fill the tank from any compressed air source. Includes all brass shut-off valve, 32'' air hose, and tire chuck.

* Maximum pressure: 125 PSI

ITEM 30476

[link=http://www.harborfreightusa.com/usa/itemdisplay/displayItem.do?itemid=30476&CategoryName=AIR%20COM PRESSORS&SubCategoryName=AIR%20COMPRESSOR%20ACCESS ORIES]5 gallon portable tank[/link]

Got it the store for $20.00
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Old 06-13-2007, 11:54 AM
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Default RE: Reservoir tank for Vacuum Pump?

I use a reservior system for all my bagging and I think its really the way to go if you can make one. I found a TORR portable vacuum pump at a local pawn shop here and snapped it up for $250. This pump new costs about $3000 from Torr. I found out when I got it home the pump had 2 bad bearings and seized after about 5 minutes so I pulled it off and disassembled the pump and removed both bearings. Replaced them for about $20 and viola! runs like a top. I even added a SECOND reservior (the portable air tank type) for about 30 gallons of volume. When I bag, the pump maybe runs once or twice in three hours for about 30 seconds. The only way to go.

BTW, I got tired of using the polyethelene sleeves for bagging as I was getting numerous holes after a couple of uses and found a supply of .020" Polyurethane sheet at the local Boeing surplus store and made custom bags sealing the edges with Windshield caulking. No more holes and epoxy will not stick to this leathery tough material. Wrinkles that can provide capillary channels for excess resin are also eliminated.

A low res pix of the pump is shown below:
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Old 06-13-2007, 10:07 PM
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Default RE: Reservoir tank for Vacuum Pump?

Excellent find at the pawn shop! Nice looking unit and sounds like it works well too.
Old 06-15-2007, 05:11 AM
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Default RE: Reservoir tank for Vacuum Pump?

ORIGINAL: Toomanyplanes

I use a reservior system for all my bagging and I think its really the way to go if you can make one. I found a TORR portable vacuum pump at a local pawn shop here and snapped it up for $250. This pump new costs about $3000 from Torr. I found out when I got it home the pump had 2 bad bearings and seized after about 5 minutes so I pulled it off and disassembled the pump and removed both bearings. Replaced them for about $20 and viola! runs like a top. I even added a SECOND reservior (the portable air tank type) for about 30 gallons of volume. When I bag, the pump maybe runs once or twice in three hours for about 30 seconds. The only way to go.
If that's the only way to go, I suspect most of us will never get there. [X(] If your pump is only running for 30 seconds every hour or two, you've got an order of magnitude or two more suckage than you really need. (On the other hand, when you start bagging 1:1 scale planes, you'll be all set, and it sounds like you got a real deal.)

For most modeling purposes, a very small pump and a small reservoir made from PVC pipe are fine. (The $20 7-gallon air carry tank from Wal-Mart is overkill, but hey, it's premade and cheap.) For a small intermittent-duty pump (like a converted tire inflator) you don't want a big tank, because a little one does the job nicely and you may overheat your pump just drawing the big one down. (The reservoir is supposed to let the pump run intermittently.)

BTW, Doug Walsh has some surplus 4.5 CFM Thomas oilless piston pumps for sale over at www.build-stuff.com for under $100, shipped. Overkill for most model bagging, but at that price, worth considering. (And great for vacuum forming.)

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