Different approachs to Air compressor needs

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Recently I have found myself loitering in front of air compressor displays, namely the 60-80 gallon units found in local stores. All the regular brands displayed (IR, Quincy, Bridgeport-Schrader, etc).  My oiless 33gallon craftsman has had a good life but can't really keep up with the new demands I seem to put on it everyday. Looking over various models and specifications has really got me thinking, and since I really hate wasting good material, here is what I'm wondering. Currently on craigslist there are atleast five 30 to 35 gallon compressors comparable to mine ranging from 20 to 50 dollars.  I can get my hands on a large 2-stage pump like those on a dedicated 80 gallon tank, I can also get my hands on a larger 220 electric motor. If I were to make a frame that could hold say, three of the 30-35 gallon tanks, link them together somehow, and fill them from the larger 2-stage pump and motor, wouldn't that be close to equaling an 80 behemoth?Anybody got thoughts on how you would link them? Pump specs? Motor specs? all comments appreciated.looking at new trucks while carrying two car seats around the parking lot to "test fit".......humiliating.
Reply:Linking the tanks is easy, use pipe. The one thing is that the pipe inlets forthe tanks may be too small to be efficient. I've seen several people just add more storage to an existing compressor. I'd done it several times.The motor/ flywheel/ rpm will be tougher. you need to match the pulley's size on the compressor with that on the motor and at the correct RPM's to get it to work right.Now here's another bit of info. Do you want a 2 stage like you said, OR do you want a 2 cylinder single stage unit? There's a big difference even though at first glance they look similar. A 2 stage compresses gas in cyl #1 then recompresses it in cyl#2. You get a higher output, usually 175 psi, but lower CFM's at say 90psi. IF you go this route, all the parts need to be rated at 175 psi, and many small tanks are not. That means new blowoff valves, and the fact you are probably 25% over what the design is made for. Not the best idea. On a 2 cyl single stage, both cyl compress air, than send it to the tank independantly. These top out at 125psi usually, but produce more volume, since basically you have 2 compressors running at the same time.You will also have to set up the switch to turn on and off the motor. The small 110v unit won't work on a 220v motor, so add that to you list to solve as well. You also probably will need an unloader with this setup. Most small units it's built it to the sensor, but larger units use a seperate one often.This all can be done, but you are going to probably need to find some place that sells specialty compressor parts and it may be a PITA to get this working right, since you will have to do a lot of the "design" on your own..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:I like big compressors.  That said....have you tried rebuilding your craftsman yet?  Mine was taking forever to refill (maybe 5-10 minutes).  Then I ordered a kit that included the cylinder and piston ring for like $35 and it was like new again  (maybe 1-2 minutes to refill).  I gave it a nice wax job and then parked it cuz I got a deal on a bigger one.   It's there if I need it and the cost of rebuilding it was cheap compared to a new one.My name's not Jim....
Reply:In fact with a 2 stage pump you will probably have to get a 200PSI rated tank. I have only ever found 150 or 200PSI and the 200 pound ones are pricey.Also keep in mind that old tanks do rust out. Buying a few older tanks may mean you wind up with some duds. You should plan to test your tanks, especially when putting a proper pump on a POS Campbell Hausfeld or Husky tank.
Reply:I wouldn't use pipe - use something flexible (like hydraulic line you can get at surpluscenter.com) Stick with something large, 3/4 - 1". That way you won't have to worry about rigidly mounting the tanks together and using pipe.If you want to DIY it - if you don't already have the tanks, wouldn't it just be easier to source an 80 gallon tank to mount your compressor/motor on instead of going through the effort to mount/link them all? Wait for the right deal if you want to be frugal. Remember, multiple tanks means multiple drains you have to work as well. Sometimes you can find deals on craigslist for big name compressors at a fraction of the price if you can haul it yourself. For cheap single large tanks, try looking for blown compressors people have replaced.Last edited by pierre71; 03-05-2010 at 04:12 PM.
Reply:Hi Swampy79,I had one small 5 gallon air compressor that delivered about 4 cfm at 125 psi.I really wanted bigger air delivery - something like a minimum of 16 cfm at 25 PSI.  That's about $1200 for a commercial unit.  I figured I could build it with a 5 hp electric motor and wait for a 1/2 price sale ($200 istead of $400) on the 3-cylinder single stage compressor and then get a tank... bla, bla, bla.Then there was a big clearnance sale of small air compressors - $120 per unit with 5 gallon tank that delivered about 4 cfm at 125 psi.  Hmmm... FOUR of those and some electrical wiring in the walls and whala!  Here's the crazy route that I took! I made a manifold to link their outputs together.Yes - it works.  For how long???Rick V
Reply:Rick, in many ways thats exactly whats done in commercial compressor applications in factories many times. They just use bigger machines to do it.I used to work at a place who's sister company repaired industrial compressors for industry. BIG honking screw machines to run air tools and presses. In critical use situations they often had 2 big screw machines and 1 or 2 backups. #1 would run nonstop (usually the one with the most CFM's) and under full load #2 would run in tandem to supply the air volume needed, often durring specific run cycles on certain heavy use machines. As soon as line pressure fell below a given pressure, the #2 unit would come on line. Should something fail, the backups would kick in automatically to keep up volume lost if #1 or #2 went down for some reason, usually when pressures dropped to absolute minimum. We'd basically do the same thing if we had an emeragency repair or had to take one down for maintenance and they were too cheap to have a backup. I'd usually get drafted to drag one of the big tow behind diesel units over to the job with my truck and have to do fuel runs with my transfer tank. Often it would take 2, maybe 3 trailer units, to make up for the  big downed unit..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan