Building an air compressor - what else do I need and how?

[gh0st]

When I bought my house the previous owners left behind an air compressor project. This thing is pretty huge and overkill for what I need, but I'd love to get it running. The compressor itself is a Quincy 230-32 sitting on a John Wood tank that's rated for 200 PSI. They also left a 3hp 3450 RPM electric motor, an electronic pressure switch and an economatic drain.

Does the compressor look ok? Seems like there is a fitting on the top that's missing something. The electric motor doesnt have a pulley, so I'll need to source one of those. Is there anything else I need? I have no idea how long this has been sitting. Would there be any reason to break it down and clean it up inside? Does anyone have a guide for putting something like this together?

 

[justanengineer]

Thats a really nice single stage compressor head, should be ~20 cfm at ~120 psi. To start off, you need a different motor. For that pump youll want a 5 hp 1725 RPM motor and a pulley sized appropriately to reduce the pump's speed down to ~7-900 RPM at the pump. Once you have that the rest is fairly easy plumbing. The fittings on the head get plumbed into the cutoff switch as does a line to the tank. Then you just need to connect pump to tank and add a filter to the pump.

As for the condition of the pump itself, I'd make sure it has oil then spin it over at the proper speed and listen to it. Old Quincys are tough as nails, mine's been in service since the early 50s and still going strong. If it sounds good it likely is. OTOH, if it was spun too fast too long via that 3450 motor any number of things could be worn.

 

[alwaysFlOoReD]

Sometimes it's easier to find a motor HP you need but it's 3450 rpm. Is there a reason that you couldn't reduce a 3450 rpm motor by 1/4? Edit; by using a pulley 1/4 the diameter of the pump pulley. That would get the pump spinning at ~860 rpm.

 

[gh0st]

To start off, you need a different motor. For that pump youll want a 5 hp 1725 RPM motor and a pulley sized appropriately to reduce the pump's speed down to ~7-900 RPM at the pump.

OTOH, if it was spun too fast too long via that 3450 motor any number of things could be worn.

I don't think it was ever run with this motor. I think this was a project they were planning on putting together but never got to it. Is there anyway I could use the motor I have? I would think that you could play with the pulley size to get the right RPM. Just took a look and a 5hp 1750 motor is ~$500, more than I would want to spend on this

 

[Trey T]

That motor is fine, just get a proper size pulley to keep the pump RPM below 900.

Youtube quincy 325 rebuild and watch the last several video of the series.

 

[CNGsaves]

Take off the side inspection plate to the Quincy compressor and see what the internals look like. Turn it over by hand and observe/listen for any problems. Is oil clear and not foamy/watery ??

My bet is you've got diamond in the rough.

+1 to take your time and do it right in setting up what will likely be last compressor you'll ever need.

Tell us again . . . HOW . . . you get these parts ?? Left behind by prior home owner??

This is sounding like a YOU **** score !!

 

[justanengineer]

Sometimes it's easier to find a motor HP you need but it's 3450 rpm. Is there a reason that you couldn't reduce a 3450 rpm motor by 1/4? Edit; by using a pulley 1/4 the diameter of the pump pulley. That would get the pump spinning at ~860 rpm.

Youre likely correct, he could probably find a pulley to get him down to the right ratio and it may work. The Quincy pump pulley is ~12" IIRC divided by 4 = 3" motor pulley on a 1"'ish shaft, quite possible but getting close to the bore:diameter limit assuming 1/2" v-belts. My main concern tho would be any power and torque differences between a 5 hp @ 1725 RPM motor and a 3 hp @ 3450 RPM motor. Granted, loadless starting and all so maybe it'd work, I dunno.

Ive got the lil brother to that pump with roughly half the displacement and Quincy recommended a 3 hp motor for it, so I'd put a WAG the OP's is a 5 hp pump, and Ive always seen Quincys (granted, oldies) with 1725 motors. $20 worth of pulley might be a cheap way of trying that motor, I just buy enough motors used via auctions/fleas/etc for cheap (<$50) that I look at them as basically disposable, even on craigs around here they go for only ~$100. The deciding factor for me when experimenting with motors and this pump would be how quickly the oil pressure came up. Even with the tank at 100+ psi, you should have near instantaneous 0-900 RPM on the pump and the associated pressure. If the oil pressure is slow to rise, get a motor with more guts.

edit: Also check to make sure near max pressure that the pump isnt slowing down and letting the oil pressure drop.

 

[burnedzr2]

You can find compressor duty 5 hp motors on ebay for $350. search 5 hp baldor motor.

I bought one for $325. last year but they have gone up to $350, now

 

[alwaysFlOoReD]

I bought a used 5 HP from kijiji for $80. I was keeping an eye on the classifieds and jumped when I saw it.
There's gas engines for cheap too.

sent while sitting on the throne

 

[theoldwizard1]

Is the unloader built into the pump ?

 

[Trey T]

Is the unloader built into the pump ?

From his photos, he has both unloader towers (low and high) and hydraulic unloader (right side) valve, just not plumbed yet.

 

[gh0st]

Take off the side inspection plate to the Quincy compressor and see what the internals look like. Turn it over by hand and observe/listen for any problems. Is oil clear and not foamy/watery ??

Tell us again . . . HOW . . . you get these parts ?? Left behind by prior home owner??

That's the plan for tonight. I called up Quincy and they mentioned that any QR-25 manual should do for mine. I'll flip through the manual and try to learn as much as I can. It turns over really easily and you can feel a little puff of air coming out.

Yeah, on the day of the walk-through the previous home owners mentioned that they would leave it behind if I wanted. I knew nothing of it at the time and it was in pieces, but figured it would at least make a good project.

 

[CNGsaves]

^ ^ That's a YOU **** for sure . . . . free Quincy compressor with house purchase !!

 

[gh0st]

I took off the inspection cover tonight and it looks clean inside. There was no oil and the bolts were just hand tight, but everything looks good on the bottom end. Cant tell which is which, but either the intake or output side looks pretty rusted up. I blew out both ends with air and some shredded paper came out, not sure if there were tenants living in here at some point. Would this warrant a further inspection and taking the head off or should I just try to run it and if it works it works?

 

[gh0st]

^ ^ That's a YOU **** for sure . . . . free Quincy compressor with house purchase !!

I certainly cant complain

 

[bsaint]

A 5hp 2 pole motor has nominally half as much torque but spins twice as fast as a 4 pole motor of the same hp. So you can always get a pulley half the size of the factory pulley.

What it comes down too is the 3 hp is not enough power to run that pump as it was intended.

 

[gh0st]

I was thinking of getting a 2" pulley to run the compressor at ~450 RPM. The compressor is spec'ed to run between 400 and 900 RPM. Would that still not be enough? Looks like you can find Baldor 5hp 230v single phase 1750 RPM compressor rated motors for around $360 online. I'll use this 3hp to make sure the compressor works and then maybe I'll buy the 5hp motor

 

[Grigg]

A pulley can be to small without enough contact with the belt to transmit the required load/HP. For that reason I think you'll be better off with a 1750 RPM motor and a more reasonable size pulley.

I'd suggest pulling the whole thing apart and checking it out. It'll cost some for gaskets and the small parts you'll likely need but then you know what you have and very likely won't have to go back into it for a number of decades.

I have a pair of quincy 240 compressors that ran fine when I got them (used mostly unknown condition) but now one has stuck/dirty intake valves, and the other a small knock... looking back I should have started by taking them apart and going over them one end to the other, now I have to find the time, would have been easier a few years ago.

 

[Milton Shaw]

Nobody else has mentioned this but you need to pressure test that old tank to be sure it is safe to operate at all. Hydro test that tank to at least 300 psi to have a safe working pressure of 175 psi. A hydro test could save your life if that tank was not drained often enough. Even draining one daily it will still have some rust in the bottom. Some welding supply places and fire extinguisher places will do hydro testing.

 

[G_P]

I took off the inspection cover tonight and it looks clean inside. There was no oil and the bolts were just hand tight, but everything looks good on the bottom end. Cant tell which is which, but either the intake or output side looks pretty rusted up. I blew out both ends with air and some shredded paper came out, not sure if there were tenants living in here at some point. Would this warrant a further inspection and taking the head off or should I just try to run it and if it works it works?

If you try to remove the head, be prepared for that badly rusted bolt to snap off.

 

[strutaeng]

A pulley can be to small without enough contact with the belt to transmit the required load/HP. For that reason I think you'll be better off with a 1750 RPM motor and a more reasonable size pulley.

I'd suggest pulling the whole thing apart and checking it out. It'll cost some for gaskets and the small parts you'll likely need but then you know what you have and very likely won't have to go back into it for a number of decades.

I have a pair of quincy 240 compressors that ran fine when I got them (used mostly unknown condition) but now one has stuck/dirty intake valves, and the other a small knock... looking back I should have started by taking them apart and going over them one end to the other, now I have to find the time, would have been easier a few years ago.

I agree about the small pulley not making enough contact and slipping. Did the original pulley have two belts? Download the manual at the Quincy website. I bought a 7.5-10 HP Curtis pump and tried to run it with a small pulley slowed down with a 5HP, but was too much for the 5HP. I then got a 7.5 HP, but had a slipping problem. The 12" pump flywheel has three grooves and I was using a 3" motor pulley with two belts. I had to use three cogged belts to make it work. And those were 1725 RPM motors. I think I'm running the pump around 500 RPM.

You might also like to consider a magnetic contactor. I couldn't see the pictures you posted, but real 5HP and above motors don't have built-in thermal overloads and rely on the overloads on the magnetic starter.

Good luck!

 

[Trey T]

a quincy 230 is spec'ed at 2-5hp, not the same as the 240 model. Just do a google search on its pump curve and it will tell you a more detail specs.

These single stage compressors are meant for continuous duty and a 5hp motor will be best but 3hp will work as it is intended.

To ensure that this 3600rpm can work properly, what's the diameter of the pump pulley?

 

[bsaint]

A pulley can be to small without enough contact with the belt to transmit the required load/HP. For that reason I think you'll be better off with a 1750 RPM motor and a more reasonable size pulley.

I dont think it will matter on a pump this small. He's prob going from 6.5" to 3.25". Id be worried if he was going down to 1".

I've built quite a few Frankenstein systems over the years and sold them without complaints.

 

[gh0st]

To ensure that this 3600rpm can work properly, what's the diameter of the pump pulley?

measured with a tape measure it's 16 inches

 

[87jeepwrangler]

measured with a tape measure it's 16 inches

if your large pulley is 16 inches, you will need a 4" pulley on the motor to spin the pump at 900 rpm. that's assuming a 3600 rpm motor speed.

 

[larry_g]

if your large pulley is 16 inches, you will need a 4" pulley on the motor to spin the pump at 900 rpm. that's assuming a 3600 rpm motor speed.

If that pump is spec'ed at a 2-5 hp motor then it's going to take 5 hp to spin it at 900rpm. The 240 pump is spec'ed at 400 to 900rpm so assuming the 230 is the same speed range then the 3 hp is going to spin it in the 500 rpm range. Your going to have to run it and check the current draw of the motor to fine tune the pump speed.

Trey said;
a quincy 230 is spec'ed at 2-5hp, not the same as the 240 model. Just do a google search on its pump curve and it will tell you a more detail specs.

Trey, can you provide a link to the 230 specs, all I could find was the 240 model. Thanks

lg
no neat sig line

 

[gh0st]

if your large pulley is 16 inches, you will need a 4" pulley on the motor to spin the pump at 900 rpm. that's assuming a 3600 rpm motor speed.

I was going to go with a smaller pulley. I dont need the thing to run fast, it's going to provide more air than I need as is. I'd rather try and get some more torque out of the motor

 

[87jeepwrangler]

I was going to go with a smaller pulley. I dont need the thing to run fast, it's going to provide more air than I need as is. I'd rather try and get some more torque out of the motor

slower should equate to quieter and more longevity. sounds good.

 

[redmondjp]

I was going to go with a smaller pulley. I dont need the thing to run fast, it's going to provide more air than I need as is. I'd rather try and get some more torque out of the motor

The main thing is to make sure that your motor is not overloaded. Test the motor current with an AC clamp-on ammeter once you get everything up and running.

My brother swapped a 5HP electric motor onto a formerly-gas-powered 2-stage compressor and it actually draws about 10% above its rated full-load current (he wasn't even aware of this until we checked it while I was visiting him). So far, it hasn't been an issue as he seldom runs the unit so the motor has a chance to cool down after it runs. But if he starts using it continuously, it could damage the motor.

 

[gh0st]

Is there anyway to tell what a motor is rated for? It doesnt seem to list it on the motor...or maybe I havent looked hard enough?

 

[Grigg]

Without knowing the full load amps no, no way to tell from that picture.
They claim 3HP but I suspect if they did list the full load amps they'd be lower than what a real 3HP motor draws.

 

[Trey T]

^looks like a "true" 1.5HP motor bc it's has the "SPL" nex to the HP rating, probably pull 10-15A @ 110V

 

[Heavymetalmechanic]

That SPL rating always makes me burn a little inside, ****** lawyer double-speak... advertising regulations piss me off.