Official Luthiers Forum!

This has been talked about before and I have posted my first version some time ago. But I am just putting together a couple of these for a friend/customer of mine and for myself as well so I thought I would show what they do and how well they do it. These are compressors from refrigeration units, these particular ones were used to cool fresh water aquariums in schools where they reared juvenile salmon for a class project. These compressors would be slightly larger than a typical house fridge compressor and more along the line of the ones used for pop coolers in your corner store. Anyway, when I got them they had a closed line that looped into the fish tank and a radiator and thermostat, I have removed all of that in this first picture:



This next picture shows the wiring that is required, very little!



This next one shows the compressor with the fittings on and actually running. There is a vacuum line with Pesco fittings, the same fittings as LMI uses, you can get them through industrial supply houses. Also I have included a small inline valve so that you can release the vacuum to remove the clamp without having to take the line out.



Here is a picture of the LMI bridge clamp (thanks Larry! ) in vacuum from this compressor. The draw down is right away, like a couple of seconds.



These compressors came with a couple of extra pieces that a house fridge would not have so I set up another of these units in a very simple fashion to show what you would do for a house fridge compressor (I have one of those as well and they are nearly as fast and will do all you want in guitar making and more!). These compressors will have three copper lines (sometimes painted black), one large one (as seen on the left) that has been crimped at the factory, I think that is used to initially fill the unit with oil. The second largest (1/4 inch pipe) will be your vacuum line, in the picture it is the one with the tee installed on it with the Pesco fitting on one end and the dump valve on the other. And last will be a smaller copper line that will now become your vacuum exhaust. It is on the right in the picture below.



I have a large reservoir that I made for another of these that I have installed at the work bench, but rarely use it. These things draw a quick vacuum, I can draw my brace clamp fixture over a radius dish in 5 or so seconds without the reservoir.

What is great about these, beside the price? They are WHISPER quiet! They make as much noise as your fridge and once they are under full vacuum they are actually under zero load so become even quieter. They will last for a very long time and are all but free from your friendly neighborhood land fill or appliance repair guy. It took me about an hour or so make up the first one once I got all the pieces together.

So, try this method and leave those noisy and expensive vacuum pumps for the science lab!

If anyone is interested I have one extra of these that I have assembled. Ready to go the price is $200 plus shipping. They weigh just under 30 pounds. It is complete with the Pesco fittings so all you need to do is plug it in, plug in your 1/4 plastic hose and you are ready for vacuum BABY! You can make them for a lot cheaper and you should be able to get most of the fittings in your home town (my town has a population of 15,000 and we are a LONG way away from anywhere! and I got all but the Pesco fittings locally).

Hope some find this useful and I will be pleased to add any detail that is missing.

Shane

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Canada

Thank you for posting this info Shane!
It's great when alternatives to high dollar solutions are shared.
And it's green also, recycling!

Can't beat that,
Thanks,
Joe

No problem Joe. The other plus to these is that, in my opinion, they are actually superior to the vacuum pumps that seem to be floating around. Hey, even Charles Fox is using these now, took him a while to catch up but at least he made it! !!!

Shane

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Canada

Neato! Do you have any idea what vaccuum they can pull? Can they reach 25" Hg?

Cheers,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

Hey Dave, they will pull a full 28". I didn't put gauges on these ones but I do have a gauge for the one I built into the shop and for another smaller one I built. And once the vacuum is pulled it holds pretty well as well, although leaving these pumps running is no big deal, the sound of my florescent ballasts is loader than the pump.

Shane

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Canada

Hi Shane,

That's great, thanks! It's official - those old fridge compressors suck, big time!!

I'm going to find one and make a set up. My current vaccuum pump doesn't suck enough....

Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

I'll take a shot of my built in unit tonight, under vacuum and show you the guage reading. The do SUCK!

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Canada

I'm getting one tomorrow for $25 at a repair shop near me. Thanks for the tutorial Shane it came at a good time for me.

No problem Chris, you won't be disappointed! Just make sure that you keep the exhaust end pointing away from your wood as it does emit a bit of oil vapour for a while. You can actually dump some out (hold the unit upside down) my Refridgeration buddy says in our application these things are running at no load so they need hardly any oil . He is the expert and my other system works just fine!

Shane

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Canada

Here is the picture of the one I have installed at my messy bench. In this series of pics is a close up of the guage showing that it is drawing 25 inches of mercury.









Hope these help. I still need to add a dump valve but for now I just pull the hose out of the fitting, which is quite simple to do, and the vacuum is gone! What is not in the picks is a large storage tank that I made from PVC that is mounted on the ceiling. I don't typically use it but if I wanted to laminate something very large I would just evacuate the tank first and then use the valve bank to pull into the storage tank to get things started. But for things as large as a radiused dish for clamping braces, the storage is not necessary for me.

Hope this helps those that want to set something like this up!

Shane

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Canada

I was just checking my local craigs list....There were 3 working refrigerators in the free section. There were also several adds of people looking to take your old appliances for scrap metal. I think I'll find a free fridge, take the compressor and then get someone to haul the rest away for scrap.

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Jeremy Vonk

Woah - thanks for posting that Shane. First I've heard of it!

"Hmmmm.....the wife has been praying for our fridge to croak for a year now - maybe I need to help push it into the grave - hey, now I know what to get her for Christmas!"

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The member formerly known as erikbojerik....

That's slick Shane. Thanks for showing us your setup.

Is there any reason a compressor from an old window air conditioner wouldn't work.

Kirt

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Horton, MI

Air Conditioner compressors will work as well. Since air conditioning is not an issue where I live I don't have a lot of experience with them so I don't know what capacity the compressor is but give it a try!

Shane

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Canada

So would a auto ac compresser but you would need a motor to turn it.

Rats - I yanked one off a fridge today at the local dump, but no worky.

Note to self: start with a working fridge.

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The member formerly known as erikbojerik....

Did you remember to get the capacitor and thermal overload? Could be one of those is also bad. Worth a check out.

Open circuit inside the compressor.

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The member formerly known as erikbojerik....

Well I guess the only concellation Erik is that there will likely be another fridge there today!

I asked my refrideration buddy about prices for these things new and in my part of the world a typical house fridge compressor is about $100 and the ones like I have posted in this thread are about $250. That should help you decide on a good deal for a used price.

Shane

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Canada

I take it that when you put your finger over the intake/ suck tube that it doesn't seem all the strong? Mine didn't seem powerfull at all but when I put an Auto vacuum gage to it the gage peged out at 29". Does that sound correct?

Yup, that's correct! You should good to go now.

Shane

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Canada

Oh, there are at least 10 there now standing upright, and another 20 or so crumpled up into a big pile along with trashed bikes, BBQ grills, etc. And yes, new compressors here in MD are $150-$250 - but strangely, none of my local repair guys seem to have used compressors. And I seem to be one step behind in the craigslist race to pick up free working refrigerators...

Incidentally, the one I got actually had 4 tubes (in addition to the crimped one) - do you reckon there were 2 pump circuits in that one?

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The member formerly known as erikbojerik....

I'm not sure Erik. If it were me I would take a couple more out the fridges at the dump, I am positive some of them are still working just fine. Once you have one up and running on your bench you can do what Chris did and just check the lines to see which are drawing and which are pushing.

Shane

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Canada

Do you have any links or know of any books that discuss the designing of the clamps and jigs ?

I've harvested compressors from a fridge, a freezer, a dehumidifier, and I think an air conditioner, just to experiment. They all do the same thing. Move air. It's my understanding they can run continuously without incident for many small shop purposes. (the occasional 1/2 hour increments)

So, check your trash day pickings, harvest away, put it on a gage, and expect 23 to 28"Hg vac.
BTW, DON"T dump all the oil out (nasty to clean off a blacktop drieway, DAMHIKT...) And keep it upraight, cuz the oil can run out of the copper lines, and cause premature burnout. I have no idea what that oil is, but it ISN'T automotive...

happy vaccum clamping!