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Idiots guide to making a vacuum pump?

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Old 07-19-2004, 03:31 AM
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ColinM
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Default Idiots guide to making a vacuum pump?

I've seen various posts mentioning that folk built a cheap vac set up from an old refrigerator pump, but despite searching through the forums, I can't seem to find a good description of how to do this and what connects where and how etc.

So is anyone able to point me somewhere that shows all the bits and stuff needed and what to watch out for? If I strip down an old refirgerator, what do I do about the freon gas that's in it, just vent it to atmosphere and not breathe in the gas or what?

Thanks
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Old 07-19-2004, 09:52 AM
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Default RE: Idiots guide to making a vacuum pump?

Freon is a liquid so you don't have to worry about inhaling it. I know a lot of people have made their own pumps and that's great. For me I'm better off buying a cheap pump for under $100. The time I spend worrying about it and trying to make it work is not worth it.
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Old 07-19-2004, 10:31 AM
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Default RE: Idiots guide to making a vacuum pump?

Depending on the UK's environmental laws I'd play it safe and go to a used appliance dealer and ask if they had any old frige pumps and motors. Expect a low volume high vacuum capacity. Standard gas line fittings should work well to hook it up to your project.

HTH
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Old 07-19-2004, 11:13 AM
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Default RE: Idiots guide to making a vacuum pump?

If you go to a refrigerator repair shop/used appliance dealer, not only could you pick up a used compressor cheap (with the refrigerant already reclaimed), I bet the technician would get a kick out of your project and would be happy to help you with fittings and gauges.

-David
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Old 07-20-2004, 09:29 AM
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Ed Smith
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Default RE: Idiots guide to making a vacuum pump?

Once you have the old fridge pump you will need the following.

Some type of reservior. I use one of those portable air tanks sold in automotive stores, I think it is about two gallons. A properly sealed 1 gallon can or large juice can will also suffice, or a piece of large diameter PVC pipe with the ends capped.

A vacuum gauge to go on the tank.

A vacuum switch to allow you to set a variety of different amounts of vacuum. The switch is connected to the power supply and maintains the preset vacuum by cycling the pump on and off. My system will stay off for hours then come on for a few minutes to make up for any vacuum leak.

Some 1/4" copper tube and some rubber tube plus fittings to connect the whole thing up.

Once I had all the pieces it took me about an hour to hook it all up and amazingly enough it works flawlessly.

Ed S
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Old 07-20-2004, 10:24 AM
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Default RE: Idiots guide to making a vacuum pump?

Something like this I hope.

I'm in the process of collecting all the parts for one but didn't go real cheap on some stuff. I got all the parts I needed from this place, [link=http://www.joewoodworker.com/veneering/welcome.htm]Joe woodworker.[/link]

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Old 07-20-2004, 11:53 AM
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Ed Smith
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Default RE: Idiots guide to making a vacuum pump?

My system is a bit simpler.

I have only one reservoir. no check valve and no mac valve, (what is the mac valve?)

Ed S
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Old 07-20-2004, 04:55 PM
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Default RE: Idiots guide to making a vacuum pump?

From the web site :

Mac valve
This is the mechanical piece of the press that unloads the back pressure between the pump and the check valve.

I didn't know of everything to get and was lost also, then I found Joe's web site and ordered the kit from them. I thought it was easier than trying to locate everything seperatly.
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Old 07-21-2004, 07:37 AM
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Default RE: Idiots guide to making a vacuum pump?

(what is the mac valve?)
Some pumps won't start pumping again if there is a vacuum when they get powered up. The mac valve relieves the vacuum and allows the pump to begin building suction again.

To see if your pump needs a mac valve, simply close off the suction side, turn it on and build a vacuum. Turn it off and then try to restart it. If it won't start, then you need a mac valve.

I personally haven't run across this issue.

Just my opinion & everybody's got one. - Bob
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Old 07-21-2004, 10:09 AM
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Default RE: Idiots guide to making a vacuum pump?

You're right about some pumps not starting if they have vacuum already on their suction side. Sometimes it's just because the motor is too wimpy. Sounds like this MAC valve would resolve the issue.

-David
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Old 07-21-2004, 11:20 AM
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Default RE: Idiots guide to making a vacuum pump?

Im sorry for being obscure but what would you make with the vacuum pump?

chris
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Old 07-21-2004, 11:54 AM
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Ed Smith
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Default RE: Idiots guide to making a vacuum pump?

Before we all launch into long explanations, your question would indicate that you have no knowledge of the vacuum bag process. Is this correct?

Ed S.
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Old 07-21-2004, 03:36 PM
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Default RE: Idiots guide to making a vacuum pump?

that is correct sir.
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Old 07-21-2004, 05:32 PM
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Default RE: Idiots guide to making a vacuum pump?

In general:
We place an item inside a sealed plastic bag. We then use a pump to remove the air from the bag. The atmospheric pressure (outside) is then greater than the pressure inside the bag, so the net result is that atmospheric pressure applies a uniform clamping force to every point on the object inside the bag. The force is applied normal (perpendicular) to the surface at every point.

This pressure can be as much as 14PSI, which equates to a 7,000 pound weight applied evenly over a 500 square inch surface. Obviously, this may be too much pressure... so we use regulators to adjust the clamping force.

We usually measure the degree of vacuum using the units of inches of mercury (in Hg) or millimeters Hg (mm Hg). We use a vacuum gauge to make these measurements.

Items which normally get "vacuum bagged" are wood or composite-skinned foam core wings, flat or contoured sandwich panels, hollow-molded wing panels, etc.

-David
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Old 07-22-2004, 08:54 AM
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Default RE: Idiots guide to making a vacuum pump?

Thanks for the explanation

chris
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Old 07-22-2004, 11:46 AM
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Default RE: Idiots guide to making a vacuum pump?

You bet.

-David
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Old 07-22-2004, 09:29 PM
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Default RE: Idiots guide to making a vacuum pump?

I am glad im not the only one who didnt know what it was for
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Old 07-26-2004, 08:00 PM
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Default RE: Idiots guide to making a vacuum pump?

I built the vacume pump from parts from Joe woodworker.com that runs off of the pressure side of a typical shop compressor. It works just fine.
Sparky
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Old 07-28-2004, 04:23 AM
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ColinM
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Default RE: Idiots guide to making a vacuum pump?

Thanks for all the advice guys, as always, you are a mine of information.

I'll be giving it a go over the next week or so and will let you know how it all turns out, so thanks again. If you don't hear from me within a couple of weeks, please send out a search party.
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Old 07-28-2004, 06:20 AM
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Default RE: Idiots guide to making a vacuum pump?

Colin theres a place in Christchurch, near March, Cambs that has a pile of refrigerators about a mile high, I think he has a contract with the council to remove the Freon under license. Might be worth a drive, its not far from you.

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Old 07-28-2004, 08:30 AM
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ColinM
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Default RE: Idiots guide to making a vacuum pump?

Thanks for that Graham, but I've got a relative moving into a care home in the next week or so and he's donating his fridge to my vac bagging experiment, so I reckon I've got it covered. Fridge is only a year old and though it seems a shame to wreck it, no-one seems to want it so I might as well have the pump out of it before it goes down the tip.

But thanks anyway.

Wonder what they're going to do with a mile high pile of fridges?
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Old 07-28-2004, 11:25 AM
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Default RE: Idiots guide to making a vacuum pump?

Perhaps its modern ART [:@]
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