My DIY compressor

[ales]

Here's the one I built back in 2004 and been using without a single issue since. The only difference to what you see in the picture is that the pressure regulator there did not work and I replaced it with a smaller simpler one that has a water trap incorporated in it



What you see here is a compressor from an old fridge (free), a tank sourced through a friend (free), and automatic switch (ca $20), a couple of pressure gauges (one free, one about $5), some piping and other hardware including one outlet welded onto the tank (about $25 together with soldering), four angle brackets I made myself from an old piece of L-channel (free) welded onto the tank and the legs on the tank made from the same piece of metal (welding was free). The replacement pressure regulator was also about $15 from Ebay. There is also an $2 pressure relief valve under the pressure switch. At first I thought of painting it to make it look pretty but did not bother - it sits by my paint booth and no one sees it. It's fantastically quiet ad the tank is big enough for the compressor to be fast enough to keep the pressure up. By quite some margin, I might add. The only time you hear it, really, is when it switches on and off. Hope it's helpful in some way and as Khier said, the old fridge compressor option is perhaps a better one than the noisy tyre compressor.

[rsxse240]

To the original poster...Even though your setup was effective, I highly discourage using a "shop compressor" or some gas station air supply. Most of the time those compressors are oil lubed and the air coming from them is saturated with oil vapor which will destroy your paint job before it even hits the model. ask me how I know this. I did the exact thing you were talking about when I was about 14, it worked effectively, but riding my bike a mile to and from the local gas station carrying a "spare air" tank was getting really old really fast. I went to sears like THE DAY I got my driver's license and bought a 12 gallon Craftsman oil-less compressor for $160 and I've been using it for over 20 years now problem free...though the tank has gotten quite rusty inside and out over the years...but that's what moisture traps are for (I use 3 on my rig, one on tank, one on table and one on gun. the ones on the tank and table are dual moisture/debris filters and the one on the gun is a harbor freight pistol grip filter...LOVE IT!)

Wow, that fridge compressor is really cool! i've thought about doing that since I heard of it, but this is the first one I've actually seen!

I don't want to jack this thread, although the original question was answered by the same person asking the question...I was hoping a new thread on this and possibly a detailed how to may come of it. I would LOVE to ask some questions about it.

[ales]

Thanks for your interest.

Thought I'd make this a separate thread with some more pictures and text.

Here's the overall view of what the compressor looks like now.



The air intake is at the very top of the picture and the green hose is where the air goes to the airbrush. The other pipe you see on the right is blocked off - it was used for freon when the compressor was installed in the fridge. Also you can see I've added some rubber linings onto the legs to protect the floor.

View from the other side



The pipe in the foreground delivers the air to the tank. You can also see (moving from the right) the regulator/water trap with a manometer and a quick disconnect coupling for the hose, the automatic shut-off switch (it's adjustable for the pressures you need) with another manometer below it that shows the pressure inside the tank and a safety relief valve below that (the brass part with a ring).

Here's what that looks like from the other side.



You can see that the pressure switch is mounted on a coupling welded onto the tank and the air goes to the regulator already from the switch. You can also see the simple electrics - the power lead goes to the switch and then from the switch to the compressor.

Here's where the air goes into the tank (the location seems awkward but I wanted to reuse the existing hole)



In theory there should be a hose running from the brass coupling here to the switch but my system wouldn't work with it on and works perfectly with it off - so off it is.

Since the compressor is not oil-free I have to use a moisture filter. I was lucky to get it from a friend (borrowed ... quite a few years ago now ). It's something that is used in air lines at pharmaceutical plants here.



In addition I also have an Iwata pistol grip filter/water trap installed right before the airbrush so I've not had any issues with oil/moisture contaminating the air that goes out the airbrush. Overall, as I've said, I'm extremely happy with this setup - it's quiet and efficient. If you have any more questions - ask away!

Best,
Alex

[rsxse240]

Thanks for posting this, Alex! I have an old fridge that the freezer doesn't get cold and my wife wants a new one for the kitchen, so our current fridge will be relegated to the garage and the current spare fridge is going to become an air brush compressor that I can use while my wife is sleeping! haha

as for questions, I do have a few.

1: What kind of pressure will the compressor hold...say if there were no tank and you just ran straight from the compressor through your shut off switch/regulator/air brush?

2: I know those compressors get hot, but since you aren't compressing freon to a bajillion PSI, how hot does this set up get? Do you think a cooling system would be benificial or just over engineering?

3: How well do you think this would work if one were to build a similar setup on a 8 gallon spare air tank, like you'd get at walmart in the automotive section? Do you think the compressor could withstand the abuse of filling such a large tank? *thinking of power conservation and conversely if it would damage the compressor taking so long to fill a much larger tank.

and finally, how do you feel about the safety of the brazed copper lines holding up to the air pressure? If I recall, that's the way the original freon lines are connected anyway, right?

I've been chatting with my dad, showed him your setup and he likes it. He's the electrical engineer by trade, so figuring out the shut off switches and what not will be cake. I've got the plumbing somewhat figured out already. I just need to start sourcing parts.

Thanks again, Alex. My wife will greatly appreciate a quiet compressor, as will I when I have those all night building sessions!

[ales]

Originally Posted by rsxse240

Thanks for posting this, Alex! I have an old fridge that the freezer doesn't get cold and my wife wants a new one for the kitchen, so our current fridge will be relegated to the garage and the current spare fridge is going to become an air brush compressor that I can use while my wife is sleeping! haha

That was the whole point - not so much the wife but the neighbours (I live in an apartment).

Now to answer the questions

Originally Posted by rsxse240

1: What kind of pressure will the compressor hold...say if there were no tank and you just ran straight from the compressor through your shut off switch/regulator/air brush?

To be honest I have no idea but it is not a fast compressor so I don't think it will be powerful (in the volume per minute sense of the word) enough to be used without a tank. On the other hand, the compressor is pretty powerful when it comes to steadily increasing the pressure in the tank. My system is set up for it to shut off at 8 bar and to turn back on at about 3.5 bar which means I never ever run out of air when using the airbrush normally. I did test the emergency valve once (it opens at 10 bar) and the compressor had absolutely no problem delivering enough pressure for the valve to open.

Originally Posted by rsxse240

2: I know those compressors get hot, but since you aren't compressing freon to a bajillion PSI, how hot does this set up get? Do you think a cooling system would be benificial or just over engineering?

I have had no issues with the temperature at all. The compressor does get warm but only warm so I would say there's absolutely no need for any cooling. Could be that the compressor I'm using is like that but since these things are designed to work in fridges for years without any cooling I think they're all like that.

Originally Posted by rsxse240

3: How well do you think this would work if one were to build a similar setup on a 8 gallon spare air tank, like you'd get at walmart in the automotive section? Do you think the compressor could withstand the abuse of filling such a large tank? *thinking of power conservation and conversely if it would damage the compressor taking so long to fill a much larger tank.

I'm not sure, if I'm honest. Personally I wouldn't use an 8-gallon tank - not only is it physically large but also unnecessary.

Originally Posted by rsxse240

and finally, how do you feel about the safety of the brazed copper lines holding up to the air pressure? If I recall, that's the way the original freon lines are connected anyway, right?

I've been using it like this for seven years now and there's not been an issue to make me worry about the copper lines so unless there's physical damage to them I'd use them.

Originally Posted by rsxse240

I've been chatting with my dad, showed him your setup and he likes it. He's the electrical engineer by trade, so figuring out the shut off switches and what not will be cake. I've got the plumbing somewhat figured out already. I just need to start sourcing parts.

Adjusting my switch was as straightforward as can be - there's an adjuster screw that basically adjusts how tight the springs in the switch are and hence which pressure triggers it. I'm sure there are more advanced models available but I went for the cheapest one available - it suited my purpose perfectly. As for the plumbing, my pictures should give you a pretty good idea of where things should go and if you need some things clarified then just ask.

Originally Posted by rsxse240

Thanks again, Alex. My wife will greatly appreciate a quiet compressor, as will I when I have those all night building sessions!

No problem!

Good luck,
Alex

[MidMazar]

That is a great creation and concept. Looks sweet actually. Only thing i can add like stated before this is a oil cooled comp, so there really is a lot of oil in the comp. Adding the moisture/oil traps is a good idea, but eventually the oil will be gone due to you using it. So that will stress the comp and eventually cause it to fail. Although on the other hand it might last long because the pressures are much less than in refrigeration.

Brilliant idea though, and thanks for sharing.


BTW How is it when you airbrush with it? Any problems?

[ales]

Originally Posted by MidMazar

That is a great creation and concept. Looks sweet actually. Only thing i can add like stated before this is a oil cooled comp, so there really is a lot of oil in the comp. Adding the moisture/oil traps is a good idea, but eventually the oil will be gone due to you using it. So that will stress the comp and eventually cause it to fail. Although on the other hand it might last long because the pressures are much less than in refrigeration.

Brilliant idea though, and thanks for sharing.


BTW How is it when you airbrush with it? Any problems?

Thanks! No, I've quite literally had absolutely zero problems with it - reliability or useability-wise. With the tank and the regulator the air delivery is smooth and consistent and all the filters I have mean that it's clean and dry too. Your other point is valid - it has probably been losing a little oil over time but a) it's possible to source a new one for free or almost free and b) it's probably possible to add oil to it through one of the pipes (I remember seeing schematics once and that's what I thought at the time).