1 contribution, free vacuum pumps
 

for the vacuum bag junkies on a tight budget, or you just like free stuff, i will give you this.

i personally use a commercial vacuum pump $$$, but any old 115 volt compressor from a discarded refrigerator or air-conditioner that still runs, will yield 20-30 inches of vacuum from the suction line side (depending on the condition of the valves). careful with the first run, cover the discharge port, or tube it into a can as any extra oil will blow off (at high pressure) until it reaches level inside case. save the oil, you'll need to pour it back in later. when the compressor craps out from moister in the valves, hit another trash pile.

be careful cutting loose the compressor from the unit as it most likely is under pressure, do it outside, and out of sight as it is unlawful to discharge refrigerant (R12) into the atmosphere (for service techs anyway, hint hint). keep the relay and capacitor if it has one.

DO NOT touch the terminals on a charged capacitor or you will be blown across the floor, in which case you will no longer need the compressor or anything else because you will probably be dead. to discharge a capacitor, simply touch the terminals together with the tip of a screwdriver. if you get a nice blue spark, do it again. then it's harmless.


how would i know this? i'm a refridgeration/hvac and ems tech, tah dahhhh!

RE: 1 contribution, free vacuum pumps
 

I already use a refrigerator compressor to degaze my silicone mold (remove bubble in the mixed silicone). Work well but it's a very old compressor and I don't know how much inches of vaccum he goes..

RE: 1 contribution, free vacuum pumps
 

I have found that thrift stores have a large stock of fridges for fairly cheap.When I was looking for mine the thrift store by my house had 2 one was 9.00 and the other was 16.00 the only problem is you have to buy the whole thing.

RE: 1 contribution, free vacuum pumps
 

OK, I'll bite.. I take it that the compressor on a refrigerator has it's own motor and/or vacuum tank? When you break the lines going to the evaporator doesn't it gas off freon/134??? It would be great if one of you AC/Refrigeration gurus could give a little tutorial on exactly what you need to do starting w/what I assume must be a WORKING refrigerator? How do you tell what is the high/low side?.. Safety precautions? I hope these are good questions cause I would really like to do this....perhaps a drawing/plans w/a vacuum controlled switch/vacuum tank so we uneducated types would know what goes where? I'm sure others besides me would appreciate the info.. or if there is some HOW TO guide on here.. it would be great to find...

thanks,

Deadstik...[8D]

RE: 1 contribution, free vacuum pumps
 

Hi did you ever get a reply, i have been asking the same questions.

RE: 1 contribution, free vacuum pumps
 

Edit... to note that I'm not advocating releasing any HFC's, to appease the enviro-folks :)
Also, refrigerant under pressure can be dangerous. Proceed at your own risk.
Obviously, disconnect the power first... and discharging any startup caps is definitely good advice.
Add other disclaimers as required, until you feel better about it ;)


It's not rocket science... you just pull the compressor out of the fridge, after
carefully cutting the tubing (leave yourself enough to work with. A few inches will do) and
removing the (usually) four bolts and electrical connections. (Cutting the tubing is the biggest
real "potential" hazard. You don't want to be sprayed in the eyes, or have the pressurized
refrigerant shoot oil under your skin or something. If you're going to do this, and are worried,
wear your eye protection and leather gloves... especially when making that first cut)

Wire it up, plug it in. One side sucks, one side blows. You want the suction side.
(Note earlier tidbit about that first run... it will possibly blow oil and make a mess. Be prepared)
Attach your hose to the suction side, and you're all set. They typically pull about 28" of vacuum

I've even used these for auto AC repair, at home, where I didn't see the need to spend an extra
several hundred dollars for a quality vacuum pump. I'd consider them expendable, but will note
that I used the same one several times a year for about 5 years, before it finally croaked.
Some models will require you to also snag the startup capacitor from the fridge. Some have it attached.
Window A/C units are another good source of pumps. (The fan or T'stat usually dies before the compressor,
and given the expense to repair versus buying new, a lot of these things end up on the junk heaps)

RE: 1 contribution, free vacuum pumps
 

Thanks very much for the update. I went down to Salvation Army and they have some Refrigerators for $10... so I guess my next project is set. BTW.... Where would I pick up a vacuum control switch to turn the compressor off and on? Also.. I noticed one design here used an airtank as a vacuum tank. Please forgive the dumb questions, but as you said, one side sucks, and I am assuming that goes to the tank where you make your connection to whatever you are bagging and the blow side just goes to the outside. I guess the problem is I need to see a block/connection diagram to "get this". I appreciate the help, I've always felt the only stupid question is one you didn't ask.

Dan

RE: 1 contribution, free vacuum pumps
 

I feel this is an easier, safer solution if you have an air compressor.
[link]http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=3952[/link]
It's not free, but is is cheap and never wears out and there is no concern about oil or dumping refrigerant into the atmoshpere.[8D]

RE: 1 contribution, free vacuum pumps
 

Dan/Deadstick,

I use 2 vacuum switches. One I purchased from an Airtrol dealer which coincidentally is just a few miles from my house. Airtrol 4200-x10. The other I made from a vacuum advance and a microswitch.

The vacuum advance switch is good for the higher vacuums 10-20"+ Hg. I use the airtrol switch for bagging white foam which is in the 5-10" Hg range. Trouble with the airtrol is that its hysteresis (difference between on and off) is not adjustable. Often when it cycles, it will turn the vacuum on for about half a second then shut off. This would happen many times. The vacuum level is adjustable, maybe they have a model whose hysteresis you can adjust as well.

The vacuum advance switch took a little doing to get it to work right. I'm now happy with it, but keep in mind if your switch fails in the ON mode, your wings will get crushed. I sleep better using the Airtrol switch.

If you're interested, I'll post pix of the home made switch.

Nitro-woman:

If the harborfreight vacuum works well, I don't think anyone should try salvaging refrigerator pumps. It's only $15, and it's ready to go. I'm rusty on my chemistry, but if I recall correctly, refrigerant acts as a catalyst in converting O3 to O2. In other words, it doesn't get used up, so a little refrigerant goes a long way in depleting O3. I'm no enviro-freak, and I realize there's plenty of debate whether or not there's a hole in our atmosphere, etc, but for an extra $5, and no mucking around old refrigerators, I'd go with the harborfreight vacuum. I just wish I had seen it before I spent $40 for mine.

RE: 1 contribution, free vacuum pumps
 

Hi,

I'd like to see pics of your vacuum control switch system. I haven't done any checking as to who actually makes them, but I'm sure McMaster Carr will have something. I'll be doing white foam and hopefully fiberglass wings/fuselages.....so. thanks for the help. That clue about the Harbor Freight vacuum looks to be really trick. I would be concerned as to how to control the amount of vacuum. I've got a big compressor.. so air isn't the problem... but controlling the amount of vacuum would be. I can see pumping out an air reservoir tank ( like a wal mart air tank).. and I am assuming I would have to somehow control the air compressor tank.... looks like another question for you vacuum line folks.... sure is nice to have great people on this board to answer these questions.... thanks

Deadstik..

RE: 1 contribution, free vacuum pumps
 

The way I use the Harbor Freight vacum pump is as follows:
I have a cheap vacum gauge that I tee into the line to the bag.
I then just clamp off the line when it reaches the desired vacum with a large hemostat.
No muss, no fuss and it has been very sucessful for me. [8D]

RE: 1 contribution, free vacuum pumps
 

Usually, my bags have lots of leaks. Instead of hunting them down, I prefer to use a switch.

Here's a picture of my setup:

On the right is a reservoir made of 4" PVC pipe. The tube coming out of it is connected to the vacuum advance, the airtrol switch and a cheap vacuum gauge (out of the picture). The vacuum pump is connected to the reservoir elsewhere (also not pictured).

The dark red microswitch on the bottom left is normally on.

After a certain level of vacuum, the advance arm starts to pull. On top of the bellcrank-like thing is an ez connector connecting 2-56 pushrod wire with 2 wheel collars. The wheel collars give the pushrod some play (adjustable hysteresis). The Nyrod on the left end was crimped slightly to give some friction so that the microswitch lever can't turn itself off by pushing the pushrod back to the off position. It has to be pulled by the bellcrank in order to be turned off.

In its operation, you would adjust one wheel collar to shut off the vacuum when it reaches the desired maximum vacuum, and the other wheel collar to turn it back on when it reaches the minimum desired vacuum. That way you maintain a range of vacuum in the reservoir which presumably travels to your bag.

RE: 1 contribution, free vacuum pumps
 

Gday from down under, you can make an adjustable vacuum switch with a syringe , a spring , and a micro switch with a springy leaver on it , or 2 micro's wired one to turn on the other to turn off, when the syringe plunger gets to it. you can also adjust the spring tension/ length, to vary the on off period ( no big words here) sorry no camera, use you lump between your ears and you'll be able to figer it out. TTFN :D ;)

RE: 1 contribution, free vacuum pumps
 

"If you can read, Thank a teacher. If you can read English, Thank a veteran".

I have come back to modelling after some thirty years, retired at last! To try and catch up a little. I have been reading the various posts and enjoying them, especially helping someone who didn't seem to want to help himself. However, I started this post with a quotation I had never heard before but sums up our situation in England as well as yours in USA.
Thank you for being our ally, as they say "the price of freedom is eternal vigilance"

Carry on the good work.

RE: 1 contribution, free vacuum pumps
 

Old Git, You are the first to coment on that quote. It moved me enough to make it part of my signature. I thank the UK for being our ally. It seems that even though at one time we were at war with each other we are now able to count on each other when the chips are down. God bless us both.