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Author Topic: 2 vs 3 cylinder air compressor  (Read 4635 times)
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Slide
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« on: August 09, 2016, 04:29:44 PM »

I need a compressor... That's the short version. My neighbor told me he has a 3 cylinder compressor that is taking up space and he may sell. I peered across his garage and it looked like a squat 80 gal tank,but everything else is unknown.he thinks it may be a 5 hp motor.

I am going to check it out when he does have free time.

What is the advantage, or is there one, to a 3 cylinder compressor? I don't see it very often, however I only look in the 1300-1500 dollar range.

Once I get manufacturer or model info, I will post up.
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hotrod
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« Reply #1 on: August 09, 2016, 06:15:48 PM »

Multi-cylinder compressors generally are setup to spread the work of compression across multiple cylinders.
That makes them more efficient, so in a shop that uses a lot of air and needs high flow rates or high pressures, the multi-cylinder compressors will use less power to produce the same compressed air output.

If you do all the compression in one step (single cylinder) you use a lot of energy to fight the heating of the air as it is compressed.
By doing the compression in smaller steps, the output from cylinder 1 has a chance to cool a bit before it gets directed into the intake of cylinder 2 etc.

If you are just using it for occassional air usage, (filling tires, blowing off chips on a drill press etc.) the power savings are going to be basically non-existent.
If you have to run a high airflow demand tool like a sand blaster day to day it will make a difference.
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Captthundarr
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« Reply #2 on: August 09, 2016, 06:19:06 PM »

What Hot Rod said....
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« Reply #3 on: August 09, 2016, 06:27:13 PM »

Make sure it's 220 single phase so you can run it in ya shed.  undecided 3 cyl might be a two stage with 175 psi unlike a single stage with 125.
  Sid.
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Interested Observer
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« Reply #4 on: August 09, 2016, 06:58:05 PM »

It likely is one of two things--a three cylinder single stage compressor (most likely), or a three-stage compressor. 
In the single stage version the cylinders are generally the same size and operate in parallel, producing reasonably large flow and quicker pressure buildup.  For the equivalent CFM, the three cylinders, acting in sequence on the rotation allow a smoother and smaller torque requirement than would be the case with fewer cylinders.
In the three-stage version, the biggest cylinderís output goes to the input of the (generally smaller) second stage which in turn feeds the third cylinder.  This configuration is used for more efficient creation of high pressures, i.e. more than 125 psi, which you probably donít need.  Also would require higher rated storage vessels and connections.

Check that the tank has an ASME or equivalent pressure rating.
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« Reply #5 on: August 09, 2016, 07:26:03 PM »

It is a Speedaire model 3Z167b. There looks to be an etched "671" also on the name plate next to speed air.

He said its single phase and he has been running it off his dryer plug. I believe he said it has a 5hp electric motor on it.

I googled the model number and came up with nothing at all.

As for what I will use it for? I'm going to tear down an old pick up, and rebuilding it with a custom home built frame. So some paint, some plasma, some tig (those are next on the shopping list. I've been practicing at friends shop)... A few other things. Small blast cabinet that's been sitting there since my old air compressor was sold and never replaced...
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« Reply #6 on: August 10, 2016, 12:42:04 AM »

A big air compressor can be inconvenient.  Most tasks do not need much air and it is a hassle to wait for the tank to fill up on a big one.  A way around this is to have a medium-large compressor and a small one.  The little guy can be used for most things.  A hose can be used to connect the little and medium-large ones if a bigger job is being done.  Both compressors work together.

Just an idea.  I had a big one once and left in the garage when I moved.  It was more trouble than it was worth.
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« Reply #7 on: August 10, 2016, 08:43:38 AM »

I took a closer look at he compressor. Looks like a large matting of old oil leaks. Considering I can't find any info on this compressor, I'd rather not have a headache to find parts for a rebuild and maintenence.

Going back to my 60 gal 2 stage 5 horse by Quincy idea. New with warranty. No guess work. Free shipping.
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Ron Gibson
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« Reply #8 on: August 10, 2016, 09:27:01 AM »

  Leaks or seepage? Those old compressors seeped a little oil out the gaskets. A friend bought a new 5 hp IR compressor and it ran so fast it sounded like it was ready to fly apart.
  I've got an old cast iron 2 hp compressor that i bought used 49 years ago out of a service station (they still had them then) and it's still running. Not used every day but has pumped a lot of air.
  Just my opinion but I would rock the crank back and forth at several places to listen for looseness and turn it over by hand to hear it pump and the valves sealing. If seems OK it will probably out last the new one. 
 
IMHO and YMMV
Ron


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« Reply #9 on: August 10, 2016, 11:17:47 AM »

He had mentioned that he and a friend had just rebuilt it a few years ago,when he first brought up the info of the compressor. Really making it sound like it was a 2 year old rebuild with next to no hours on it. So to be definitly leaking, it doesn't seem like a good idea...

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