Portable shop compressor build

[alwaysFlOoReD]

I've been gathering pieces for a compressor build for years and I finally had all that I needed. The last was a portable tank that had a non-working motor. I paid $75.00 for a 25 gallon Craftsman tank with a triple compressor head and all fittings. I have on hand another 2-stage compressor head that I bought from Princess auto brand new from the surplus section for $75.00, and a 5hp 240V 22 Amp electric motor also bought for $75.00. Some more fittings ended up costing me about, you guessed it, $75.00.
I didn't get a pic of the old setup.
A proof of concept with the new motor and head on the old tank and old fittings;

It worked but the way the fittings were installed there was lots of adapters and bushings to get various types of fittings to work together. I didn't like how it looked and suspected airflow would be compromised if I didn't clean it up.
I tore it all down and cleaned and quickly sprayed the tank. I found an old spray bomb that was real close to the tank color so I saved a bit of work. this is going to be a working compressor so I'm not worried about bling paint jobs.

The bottom of the tank had a stainless extension with a valve on the end for a drain valve. I like the idea as it's easy to reach;

Here I'm trying to fit all the parts together;

There is a mistake in the previous picture. There is supposed to be a line from before the checkvalve in order to unload pressure for when the compressor starts up. It makes it a lot easier on the electric motor if it isn't trying to overcome 150 psi when it starts. I had it plumbed after the check valve.
I caught it before I got to far and made up the following;

Some pics of the wiring job;

Dip the ends of the wire in dielectric grease;

The ends of the wire stripped ~ 1/4". You don't need more;

Ratcheting crimps...no more bad connections;

I did get it all together and it filled the tank in 3 minutes and 18 seconds. The tank is 25 gallons. The motor rpm is 3450. The motor pulley diameter is 4.75". The head pulley dia. is 14.5". The pressure is 135 psi.
I'll figure out the cfm later and post more pics later,

Richard

 

[alwaysFlOoReD]

The tank held air overnight and didn't lose any pressure. Here's the latest pics;

The blue thing in the last pic is a water trap. I still have to fab up a belt guard and a metal plate for the electric motor wire access;

There is two air quick connects, one regular m style and another with a bigger orifice and shutoff valve. The bigger one is to help feed an 80 gallon tank that I plan on putting the triple head onto with another 5 hp motor that I have. That should get me close to 25 cfm combined, and with another two smaller compressors that I have may get me to 40-45 cfm. I'm wanting to do some sandblasting in the future.

Richard

 

[alwaysFlOoReD]

And I get 9.65 cfm.

25 gal / 7.48 gal per ft^3 = 3.34ft^3
135 psi/14.7 psi = 9.18
3.34 * 9.18 = 30.7 ft^3
30.7 ft^3/ 3.18 min. = 9.65 cfm

Instructions copied from E-How

1] Determine the volume of your air compressor tank in gallons. This should be clearly marked on the tank itself by the manufacturer.
2] Divide the tank volume by 7.48 (7.48 equals the number of gallons in one cubic foot.) The number that you get after the division is the tank volume expressed in cubic feet.
3] Release the air from your compressor.
4] Begin refilling the compressor with air. Record the amount of time that it takes to refill the tank while paying close attention to the compressor's tank gauge. You will need to record the psig (pounds per square inch) at two separate times in the refill process: once at the moment the compressor kicks in and once at the moment the compressor kicks out.
5]Take the psig indicated on the compressor's tank gauge when the compressor kicked in and subtract it from the psig indicated when the compressor kicked out. For example, if the compressor kicks in at 75 psig and kicks out at 100 psig then the difference would be 25 psig.
6] Divide the difference between the two recorded psigs by 14.7. The result will give you the amount of pressure added during the tank's filling cycle in terms of atm (atmospheric pressure).
7]Take the volume of the tank expressed in cubic feet (calculated in Step 2) and multiply it by the amount of pressure added during the tanks filling cycle in terms of atmospheric pressure (calculated in Step 6). This is the number of cubic feet that your compressor pumps in the time it took for your tank to fill (recorded in Step 4).
8]Convert this number to minutes. To do this, take the number of cubic feet found in Step 7 and divide it by the number of seconds it took to pump this amount. Multiply the result by 60 and you have the CFM of your air compressor.


Richard

 

[RangerSVT]

Nice project. I have a 20 gallon tank that I was planning a little project involving a 5 hp motor and supercharging it. Screw compressors are known for quiet operation with very high cfm output...

SVT