Build a Silent compressor from Junk. Tech Week Special

This explains how to make a small,silent,compressor suitable
for airbrushing and cleaning parts from a refrigerator.
Any type of refrigerator,dehumidifier,air conditioner,etc
could be used.
COMPRESSED AIR CAN BE DANGEROUS.MAY CAUSE INJURY OR DEATH!
Make sure you understand what you are doing,and why.This is only a
guide.Guaranteed 5 feet or 5 seconds,which ever comes first.
If you kill yourself,don't call me.
You will need a compressor switch,WITH an unloading valve.An
adjustable switch would be first choice.It will allow you to decide at what
pressure the pump turns on an off.If you don't use a compressor switch,the
pump won't shut off and something WILL BREAK.Also need a 1 way check
valve,VERY important.
Look inside the refrigerator,the big black lump is the
compressor.There are 3 Copper tubes coming out of the compressor.One is
plugged,forget that one.The larger of the other 2 is the intake,it can be
cut off where convient.The smaller of the tubes is the pressure side.It
probably steps up to approx. 1/4" diameter after about 6".You need to cut
the 1/4" diameter tube,leaving approx 3/4" ,and install a T compression
fitting.Compression fittings are available where ever they sell plumbing
stuff.One side of the T goes to unloaderswitch,the check valve goes on the
other side of the T.Install the check valve so that air can come out of the
pump,and through the check valve,but can't go back in.Once the system is
pressurized,the pressure switch turns the pump off,and the unloader valve
releases the pressure upstream of the check valve.If you don't do it this
way,the compressor won't restart unless it has less than 20 psi in the
system.From the check valve I run the air through the small radiator that
came with the water cooler.It also came with a thermostatic switch that
controls a fan,when the pump gets too warm the fan draws air across the
pump and blows through the radiator.Exiting the radiator the air goes
through a T on the back of the compressor switch,and into the moisture trap
and regulator.The regulator controls the output pressure.The compressor
switch turns the pump off at 120 psi and turns it on at 80 psi or lower.
110 volts from the wall goes to one side of the compressor switch,the
2 wires from the compressor go to the other side of the switch.
And that's it.A small tank would't be a bad idea,I recently added
a large moisture trap after the radiator to act as a small tank.
A 150 psi pop off valve would be a good safety feature,it would
need to be installed before the regulator.If the compressor switch
sticks on,it will prevent something breaking.I think all the
real compressors have them.
Make sure your compressor switch has an unloader valve,
it looks like an air fitting on the side of the small black
switch box.And don't forget the check valve.
Any industrial supplier that sells pneumatics should have check
valves.Mine was 1/4" NPT female.
I don't know how long this type of compressor will last without
lubrication.They use oil in the Freon to lube the pump,I don't know how
critical this is.It may or may not be a problem.When you drain the Freon
make sure you flush the oil out of the system,or it will get in your
paint.I used Brake Kleen.Green Peace hates me.It might not last 100,000
miles,but it is QUIET and will deliver more than enough pressure,and
volume,for airbrushing,cleaning parts and inflating soft tires.
And how hard is it to find an old refrigerator?

Copyright Unkl Ian 2003

 

Thanks Ian, I have always wondered how to do that.
You rock.

 

OR,you can spend up to $1000
to buy one similar from your local art supply place.

 

GREAT! I'm noticing a lot of the old-style propane tanks are showing up in the recycle dump... After PROPER VENTING AND CLEANING, and some new fittings, these would be bitchin tanks to use with such a compressor.

-J

 

Or a temporary flame thrower... HEHE!

Sounds like a cool setup ian.. thanks

 

Silly......you should have saved this for next week!!!.....

 

this IS next week!

 

Thanks Unk! How about a biggie (poor boy) compressor now. Maybe from a scrap Jap twin. (Or did I just think of that?) Why not? Too much compression (heat)? Not enough?

 

[ QUOTE ]
How about a biggie (poor boy) compressor now. Maybe from a scrap Jap twin.

[/ QUOTE ]
OK,gimme a couple minutes.I have to figure out how to change the valve timing.
It needs to work more like a 2 stroke.
Probably use a 4 cylinder,easier to find.

Actually,I've heard of people using 4 cylinders as self contained compressors.2 cylinders operate like a usual engine to power the other 2 which act as a compressor.
Where is Macgyver these days?

 

BTTT

 

Unk, found a guy thinking along your lines down Argentine way.....
Here's a link:

http://www.briansmodelcars.com/tutorials/tutorial.asp?TutorialID=28&CurPage=1

Gawd, I love "how to" from junk!

 

Same concept,but I hesitate to encourage people to weld fittings on pressure vessels.Before I figured out what I needed for valves and switches,I burst a brand new piece of hose.
This stuff is rated maximum operating pressure 250 psi.Sounded like a gun shot.
Just glad no body was hurt.

Occasionally you can find new portable compressor tanks at Harbor Freight,Princess Auto,etc.If a compressor is damaged in shipping,or incomplete,they will strip it for parts and sell the bare tank.

 

A usefull place to find a tank with some of the fittings allready attached is a truck breakers. Most of the biger trucks use air brakes,so they have tanks of various sizes bolted to them, they will have the blow off valve and inlet and outlet fittings on them,they can also be used if you want to put air bags on your ride.
john.

 

I have always looked at the truck tanks, lots of em are alloy and look kool too, my home made compressor runs a dive tank.... only problem is it doesn't run enought CFM for much painting.

 

MMMMMMMMMMmmmmmmmmmmmmmmm, interesting.

 

I actually think i saw a site that sold air compressor parts... had gear box's for lawn tractors an hydraulic pumps... i'll see if i can find it again.

 

One thing to watch out for using the fridge motor method is the gas, it's freeon and a greenhouse gas,just don't breath it in when you cut the pipe. I have used a pair of side cutters to snip it off on the long side, let all the gas escape and then trim the ends up once it is out of the fridge.
john.

 

So, the corrollary to all this is, if your old fridge compressor quits, its just beacuse the freon has gone below 20 psi, not necessarily that the comp is dead?

 

Unk- your comment about the 4 stroke to two stroke might not be necessary. Shram does or did build a six cyn. tractor that three cyls. was motor to move the tractor and three cyls. air compressor. Also truck parts store good sorce for cheap tanks. 36 inch long, 8inch dia. - $35.00 brand new with alot of pipe thread openings

 

[ QUOTE ]
your comment about the 4 stroke to two stroke might not be necessary.

[/ QUOTE ]
I was thinking if the intake valve opened when the piston was going down,and the exhaust opened when the piston was going up,it would be more efficient as a compressor and move twice as much air compared to leaving the 4 cycle cam timing in place.
It could be done with a special cam for a combination engine/compressor,with double lobes on the compressor cylinders.
Or the cam could be driven at crankshaft speed for a plain compressor.
Double Over Head Cams would make it easy to set the timing.
A DOHC 4 cylinder compressor? Tim Allen would be proud.

 

[ QUOTE ]
if your old fridge compressor quits, its just beacuse the freon has gone below 20 psi, not necessarily that the comp is dead?



[/ QUOTE ]
The Freon could have leaked out,or the thermostat broke,or?
As long as you can still hear the compressor run when it's supplied with 110 volts,it should work.
Anyone here work in the Refrigeration field?

 

Hmm, or what the EPA fine for venting freon would be...

Course, they gotta catch ya first!

 

Anyone real concerned about the environment,and/or the EPA,
could to it to any Air Conditioning repair place to be drained.
They would have all the correct equipment to capture and recycle Freon etc.

 

How about capturing the freeon an taking it up to the parts store... its worth its weight in gold.

 

I guess a lot of people are taking the old Ford and Volvo etc. A/C compressor and rigging it up in their jeeps and 4X4s for air pressure out in the boonies:Here's a pic of the unit:

and info on the installation

http://www.jedi.com/obiwan/jeep/yorkair.html

My question is, What kind of 120V electric motor could spin this fast enough to do the homebuilt (stationary) route. Anyone done it??
(Sorry Unk, didn't mean to hi-jack your tech post.)

 

Well... you could try using large and small pulleys to see if you can get the rpms correct.

From what i have read the york you want is from a volvo because it has the longer stroke.

I am looking to do the onboard air in my truck when i finally get around to getting back to work on it.

garth

 

... Speaking of Revs... how do those lil rev meter things work? Are they by Virbration? Or are they a touch it to the spinnin part an it tells ya how fast you nearly cut your finger off?

 

There was a thread a couple days ago,on the RRT,about using AC compressors as air compressors.
Like anything else,some types and makes are better than others.

[ QUOTE ]
(Sorry Unk, didn't mean to hi-jack your tech post.)

[/ QUOTE ]
The thread is called "Build a Silent compressor from Junk".
You just suggested a different junk source,which could make it mobile.
Has anyone built one of these?

 

This post got me going to build my own compressor. I have an old compressor that works but the tank has pin holes in it and won't hold more than 20psi. I'm no welder and wouldn't trust welding it up.

A buddy gave me an old oxygen tank thats been in his garage for about 8 years and never used. My plan is to mount the motor and pump to the wall up high and run line down to the tank.

My problems are:
1. How do I modify the tank for another outlet/inlet
2. Can I use regular airhose to connect the pump to the tank or should it be hardline?
3. Would I be better off mounting the tank upside down? That way any moisture could be drained off.
4. If I were going to use it for simple painting would I have to run a second, smaller tank to keep any surging down? Or would a pressure regulator help with that?
Both the air compressor and the oxygen tank were free so I have nothing to lose with this setup.

 

Those tanks are pretty thick,so in theory,you could drill and tap
the walls of an EMPTY tank to accept NPT fittings.
I don't know what kind of thread is on the end for the high pressure valve,
or if it would be possible to adapt something.
Any Oxygen tank should be large enough to eliminate any surging.