Hi Joe - welcome to HomemadeTools.net
Interesting build! I'm going to move this discussion into our Tools in Progress subforum so that you can get some good ideas.
Hi. I'm Joe, a 55 years old geophysical engineer and I have a hobby for aircraft static modeling, so I'm looking for ideas to make a homemade tank compressor using a refrigerator type compressor for airbrushing purposes.
The piston and diaphragm types run hot very easily and are too noisy and I need a quiet environment to work.
In the recent past I build up one but I had trouble with an oil mist in the air flow no matter what type of oil filter I used.
I want to know what went wrong in the design and have the opportunity to correct it.
I would appreciate and welcome any ideas.
I to have been unsuccessful in eliminating oil contamination from one of these fridge compressors, they are just not suitable for spraying as they run in an oil bath (ok for workshop use).
Your best bet for a silent environment may be a slave tank filled where noise is not a problem, maybe from a car tire inflater this could be an old fire extinguisher or don’t laugh a car inner tube I remember my father spraying the wing of his car by this method using my Celspray gun with me on the foot pump, turned out pretty good too.
As I recall airbrushing only needs about 10 psi at very low volume so an air reservoir at about 40 psi should last a while.
I am sure you will get more suggestions.
Last edited by olderdan; 05-25-2017 at 05:43 AM. Reason: ommision
I saw a small air brush compressor made out of a foot operated tire pump being powered by a windshield wiper motor as I recall for a tank the guy was using a 2ltr drink bottle he had everything mounted in a large aluminum brief case Gel battery and all supper quiet and portable built in charger as well
Joe; Your idea of the refrigerator compressor won't work because of the oil problem you already noticed. It's the design of the compressor to pump a little oil as it operates, actually you would run it out of oil eventually. I don't know a lot about air brushing. But it sounds as if you could purchase an refillable air tank, (big box store). I've made them out of old "r" type refrigerant tanks, a 50 pounder is ideal, but I don't know if the make them that size anymore. And than you can fill them at a gas station, their compressors are usually big enough to give you all the air you'd need. Pedro Contrero
I'm a model builder (static and model trains) and what I found works best for me is a small CO2 tank. You can buy or lease one from a home brewing shop and they will supply dry air for quite a few models. I have my regulator set around 15 psi and it seems to work very well; a bonus is no noise from a compressor.
USE A DIAPHRAGM COMPRESSOR OR OILLESS COMPRESSOR. DIRECT DRIVE COMPRESSORS CAN BE NOISY, BELT DRIVEN COMPRESSORS RUN SLOWER AND QUIETER.
WHEN YOU COMPRESS A GAS ITS TEMPERATURE RAISES AS YOU ARE PUTTING THE HEAT OF THE GAS IN A SMALLER VOLUME SO YOU PUT THE HEAT CONTENT INA SMALLER VOLUME AND THE TEMPERATURE RISES. THEN YOU ADD THE TEMPERATURE OF THE COMPRESSOR SO YOU SEE A CONSIDERABLE TEMPERATURE RISE.
REFRIGERATION AIR COMPRESSORS ARE DESIGNED SO THAT THE COLD REFRIGERANT GAS ENTERS THE CRANKCASE FIRST, THEN IS ROUTED TO THE INTAKE VALVE, GOING INTO THE CYLINDER ON THE PISTON DOWN STROKE. IT IS COMPRESSED ON THE UPSTROKE AND IS ROUTED TO THE CONDENSER AS A HOT GAS. CRANKCASE OIL IS CARRIED ALONG WITH THE GAS AND TRAVELS THROUGH THE ENTIRE SYSTEM AND BACK TO THE COMPRESSOR.
IF YOU ARE USING AN OLD PISTON, NOT A HERMETIC COMPRESSOR, ONE WAY TO SEPARATE THE OIL FROM THE GAS WHEN USED AS AN AIR COMPRESSOR IS TO EITHER USE AN OIL/AIR SEPARATOR WITH A BLEED LINE FOR THE OIL TO RETURN TO THE INTAKE OR CRANKCASE.
THAT MIGHT NOT DO A GOOD ENOUGH JOB SO AN ALTERNATIVE WAY IS TO SEPARATE THE INLET AIR FROM THE CRANKCASE, BRING THE AIR IN THROUGH THE INLET SERVICE VALVE RIGHT TO THE CYLINDER HEAD. THE CRANKCASE MUST BE VENTED TO THE ATMOSPHERE OR PRESSURE BUILDUP WILL PUSH OIL PAST THE PISTON RINGS.
HERMETIC COMPRESSORS WILL PUMP OUT ALL THEIR OIL, SO YOU MUST SEPARATE IT FROM THE COMPRESSED AIR AND SEND IT BACK TO THE CRANK CASE.
A SINGLE STAGE COMPRESSOR MUST NOT TO MAKE MORE THAN 150 PSI, 90 PSI IS BETTER. IF YOU EXCEED 150 PSI THE OIL VAPOR IN THE COMPRESSED AIR MAY IGNITE DUE TO THE HEAT OF COMPRESSION, COMPRESSION IGNITION LIKE IN A DIESEL ENGINE. THE BLAST WILL RUIN YOUR DAY, MAYBE YOUR HOUSE.
Back in the early 70's I worked at a place that had a huge old air compressor used for impact guns and tire machines. As you might imagine the old compressor spewed lots of oil. We wanted to paint a car so we needed to good air supply. We found a filter that held a whole roll of toilet paper. (have not see one like it since) it worked really well, absorbed all of the oil and moisture, then a regular filter collected the little paper particles that came from the TP. Worked very well.
Once while working part time at a full service gas station an older gentleman drove up in his 48 or 49 chevy complaining that since he had changed his oil his oil pressure was continuously getting lower and lower. I had him park his car over the pit then I pulled the top off the filter only to find a roll of toilet paper. When I asked him about it he said that the old filter looked like that was what it was so he thought he would save the 2 dollars of the cost of the filter. It nearly cost him his engine. I drained his oil and pulled the pan the screen was nearly blocked. So I cleaned everything put the pan back on installed a proper filter filled the crankcase with ATF started the car let it run for a while drained it pulled the pan again cleaned the screen and the pan put everything back together changed the filter and re filled with his favorite brand of oil
For what it cost him he could have had his oil changed properly at the station every 3 months for 2 years, but he did become a regular customer
Toilet paper as an air filter restrictive but good just catch the chunks, toilet paper as an oil filter BAD.
there are several heavy equipment fuel filters that use a cartridge made out of wound string you can even get house hold water filters that use a string wound cartridge
I believe that Grayco still makes an oil separator air filter that uses a string wound cartridge
Last edited by Frank S; 05-25-2017 at 07:58 PM.
Lou N has the right idea. Skip the air compressor and use a CO2 tank. I have used one for 50 years and it works great!
It is quiet and the CO2 is clean and dry. You will need to get proper sized fittings to hook it up to your airbrush/spray gun. Most hardware stores will have the fittings you need. Just make sure you get a good regulator.
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