Air compressor motors?

[Crank1]

So I'm interested in purchasing a very used 220 Speedair air compressor. The problem being that the compressor has a 3 phase motor on it, which I do not have 3 phase at my residence, and without wanting to put a phase converter on it, my father in law told me about the vacuum pump motor in the barn off of the old milk house. It is a Century 5 horse 220 motor, and looks like it'll replace the one that is currently on it, the only problem is that I seen the RPM on it, and it only spins at 1850 I think, while most other motors I've seen, spin at 3450. does that make this a no go on the motor in the barn? Or could I swap some pulleys(if I could ever come up with any) or have any other option? This would be the cheapest way to get a compressor lined up for my new garage.

http://cleveland.craigslist.org/tls/2751255287.html

Here's the compressor in question...
Thanks folks

 

[930dreamer]

I'd match the new motor rpm to the old one, most older compressors just chug along.

 

[socapots]

you could probably also change the size of the pully on the compressor and or new motor to add rpms... No idea how that would be calculated though.

 

[Stuart in MN]

Find out what the rpm is on the air compressor - you may luck out and it will be the same rpm as the milk house motor.

 

[Haystack]

You can certainly use it. You will need a different pulley for the motor to bring the pump back to the rpm it was at previously. There are many useful pulley calculators on the internet that will be handy for figuring this out.

 

[rlitman]

Don't put a smaller pulley on the motor. That'll wear out belts.
Just get a 1725RPM motor. They're a little more expensive than a 3450RPM, but the compressor will run quieter too.

You'll want to match the "frame" style between the old and new (is it a "184T" by chance?)

 

[sberry]

Why buy something already broke?

 

[larry_g]

Your dealing with a simple 2:1 ratio here. If your lucky your motor speeds will be the same. If not then you may have to get a motor pulley 2x the size of the one on the compressor if the current motor is 3450. There may be other issues with your free motor but I'd give it a go. Check the hp requirements of the pump to make sure that it is able to run with a 5hp motor. Grainger catalogue has the information.

lg
no neat sig line

 

[Mmfh]

Another option would be a VFD, they can be a bit spendy new but used could be a deal if you could find one.

(Variable Frequency Drive) like a Phase Converter will take single phase and give you 3 phase. A VFD is also cool if you want to have variable speed for the motor you are wanting to control.

This might not be the way to go but its always good to know all the options.

Mm

 

[socapots]

Don't put a smaller pulley on the motor. That'll wear out belts.

im not familiar with why this would happen.
any more explaination?

 

[olytdi]

smaller pulley means tighter arc and that will put more stress on the belt. Pully size is optimized for motor rpm in relationship to compressor rpm. The best route is to get the motor with the proper hp and rpm and keep the pulley ratios the same. Someone mentioned "chuggin" and that's exactly what these older compressors are designed to do -- pump slowly and quietly...

 

[Chris Adams]

In the real world, I've done three to one pulley swaps, much less two to one.

These are pretty 'soft start' so burning a belt only starts at about a 2 inch pulley.
Most compressors in the 3 3-5 hp range have 6 inch small pulleys.
You can also change the OTHER pulley. I've used smaller pump pulleys three times, letting a much slower motor do the work.

These are V-belt setups, much like on an older car.
These are NOT fractional horsepower belts, whole different kettle of fish.

On a fractional horsepower (like a swamp cooler) you have a very tiny pulley and a HUGE pulley.
The little motor starts with a jerk, no smooth start.
So you have a two inch pulley going super fast, with an 18 inch squirrel fan barely moving.
Thus you 'burn' the belt. Or why you shouldn't use car belts on many swamp coolers.
You are looking at a very small jump with your compressor.
Gets better.
You do NOT have to spin the compressor to 'full speed'.
Assume the same size pulleys, if you spin the compressor at 53% of the 'required' speed the system will still pump up, draw less power.
What you will lose is CFM.

You DON'T want to 'over speed' the compressor. Under speed just costs you CFM, over-speed shortens the life of the compressor, dramatically.
Doesn't stop the factory from over speeding systems to drive up the CFM.
I fought with a IR compressor that was shoved about 20% too fast from the factory so they could claim higher numbers.

Measure your pulleys carefully.
Be sure they are the same size drive. Example, half inch V-belt.
Be sure they are similar in horsepower.
A 3/4 horse motor is not going to drive a 5 hp compressor.
Measure your pulleys down the V, not at the bottom, not at the top, but where the belt will ride. Easy to check by putting a belt around the pulley and seeing where it rides.
Then do the calculations.
Start by measuring the original pulley and see what the actual RPM of your compressor might be.

 

[sberry]

I can see going down this road if this comp was free, maybe some gave it to you or the price was 50$ but to start out at 400 for something that already doesn't work is a hard way to go.

 

[Chris Adams]

I can see going down this road if this comp was free, maybe some gave it to you or the price was 50$ but to start out at 400 for something that already doesn't work is a hard way to go.

Yeah, 400 is probably way too much, but I will say that the pictured is a Manchester 200 PSI tank.

I have one just like it, and I paid, gasp 200 bucks for the tank itself, no compressor, no motor.
It is a very good tank.

I have sold a number of 60-80 gallon compressors this year.

I have kept one.

 

[brownbagg]

no way that compressor pushing 3000 rpm it sling itself off the tank. most motor I see run at 1700 rpm

 

[Torque1st]

Crank, find out what the exact specs are on the compressor motor and the milkhouse motor. Without that info your question is useless and any replies are just hot air.

 

[larry_g]

I'm amazed at all the answers here. To the OP, Call the seller and get the numbers off the compressor. Get the model number of the compressor, the pump model number, and the motor specs. Once there you may be able to come back here and get some decent advise. FYI once you get the model number of the compressor and the pump head look it up in the grainger catalog. It is all there. It even specs the motor pulley in some cases.

lg
no neat sig line

 

[larry_g]

Crank, find out what the exact specs are on the compressor motor and the milkhouse motor. Without that info your question is useless and any replies are just hot air.

And knowing the motor specs of the current motor on the compressor is only good if you are certain that it is the original motor to the compressor. Good start but working back from the pump head requirements is also necessary.

lg
no neat sig line

 

[Torque1st]

And knowing the motor specs of the current motor on the compressor is only good if you are certain that it is the original motor to the compressor. Good start but working back from the pump head requirements is also necessary.

lg
no neat sig line

The unit looked fairly OEM from the pictures. I know that is an assumption but in this case it looked fairly safe.

 

[Norcal]

Another option would be a VFD, they can be a bit spendy new but used could be a deal if you could find one.

(Variable Frequency Drive) like a Phase Converter will take single phase and give you 3 phase. A VFD is also cool if you want to have variable speed for the motor you are wanting to control.

This might not be the way to go but its always good to know all the options.

Mm

A VFD w/ single phase input over 3 HP gets real expensive, in most cases a drive rated for double the HP of the motor has to be used as they will be derated 50%, (5 HP motor,10 HP drive), they will usually be a 3 phase input model & will also need to have the option of disabling phase loss protection.

 

[Crank1]

Well the guy gave me a price of $250 if I come pick it up, and with looking on craigslist in the surrounding 5-6 different areas they have there, there is nothing below 500 bones that looks anything worth my money. This one seems to be decent, but single stage and 3 phase, the pump motor in the milk house is 5 horse and at 1850 rpm I believe. I'm assuming the motor on there is ea 5-7 horse. I am trying to get a decent shop compressor without spending a cool grand at a box store. I do not know the specs of the motor on the pump, nor do I have this guys number, but I need to find out, I guess.

The motor on the vacuum pump we currently have looks like this. http://www.google.com/products/catalog?q=century+5+hp+farm+duty&hl=en&prmd=imvns&bav=on.2,or.r_gc.r_pw.,cf.osb&biw=1280&bih=707&um=1&ie=UTF-8&tbm=shop&cid=5818957670249367250&sa=X&ei=NGj1ToWCNIXb0QGdyL2VDA&ved=0CFcQ8wIwAQ

There are a few variables and I realize I should have the answers before asking for help, but the current 3 phase motor may spin the same rpm, so I could swap pulleys to the motor I have, if the shaft is the same size.

 

[Crank1]

Also, the pics the guy sent me of it, says the tank is dated 1958, and made by Beaird in Shreveport, LA. Does this mean its not the 200 psi manchester tank?

 

[Chris Adams]

Also, the pics the guy sent me of it, says the tank is dated 1958, and made by Beaird in Shreveport, LA. Does this mean its not the 200 psi manchester tank?

Possibly not. The tank in the picture looks exactly like a mid 80's to 2000's Manchester. I find it hard to believe that setup is from 1958. Are we sure he isn't reading patent numbers?
It looks more like the setups made in the late 80's to early 90's, at least from the rather poor pictures.
CL at its finest. Uncertain pictures, backed up by interpretations of other peoples stories.

If it is truly from the 50's it won't be rated that high, won't say ASME etc.
I would pass on it, unless you have some way of inspecting the inside of the tank.

Taping on it to hear corrosion is only about 70% accurate.
To do the 'tap test' you hit it with something like a small brass hammer. A rusted tank will usually sound dead, or very dull, as you move from the side to the center, on the bottom.
Ding, clear like a bell, Ding, muddy ding, thud, as you move over the rusty patch.

Again, not perfectly accurate.
Problem with old tanks and new cheap tanks is that people neglect to drain them of condensate water. Then they rust. When they rust far enough, they leak. It's virtually impossible to save a leaking tank. Not worth the time, risk factor (which is smaller than the exited people will tell you, but still a real concern).

You can't really trust that all the hardware, pressure switch, safety valve, check valve, drain, are still good since its been sitting. Each of these is cheap enough, by themselves, but add all of these to perhaps a pulley, a belt, an new air filter, and some mounting hardware as you switch from one motor mount to another and now you are spending too much. Then you find the compressors blowing oil...
Since you can't do a test run, you have to assume the compressor has seen better days.

I live in a better place to buy this stuff, and I see running mediocre brands of compressor going for 400 bucks all day long. Heck, I've sold a bunch for less than that and they worked great.
This one, if it really is that old, would be a pass.

Age is more a factor than motor or pulleys in that suggestion.

 

[Crank1]

These are the pictures he sent me. I'm thinking I might just pass on this compressor. Its a single stage compressor. 3 phase and possibly a compromised tank on the inside??? May as well pass, what do you all think?

 

[sberry]

A grand at the box store would be cheap, done deal, one shot, could wire it in and use it today.

You can't really trust that all the hardware, pressure switch, safety valve, check valve, drain, are still good since its been sitting. Each of these is cheap enough, by themselves, but add all of these to perhaps a pulley, a belt, an new air filter, and some mounting hardware as you switch from one motor mount to another and now you are spending too much. Then you find the compressors blowing oil...
Since you can't do a test run, you have to assume the compressor has seen better days.

Got to agree with that, have even learned this the hard way on occasion.

 

[Chris Adams]

If I lived near it, and was building a compressor right now, I would go look at it, run my bore camera around inside it, then, if it was nice inside, I would offer him 100 bucks max. I would then scrap the compressor, which has been run HOT.
See the shroud over the compressor fan? All the cooling air comes from the front of the pulley.
The pulley spokes are actually fan blades.

Think of that big piece of sheet metal (?) over the compressor the same as putting a piece of cardboard in front of your radiator.

Some idiot, lost the grille that protects other idiots from putting their fingers in the blades or wheel, has fabricated a protective cover. Total stupidity. Stand behind any running compressor and the cooling air flow is strong. On this thing, no air flow, thus no cooling.
The 3 phase motor is scrap metal anyway. You can buy them nice, working, for roughly what the recycler pays for them.

What this man has is about 280 lbs of scrap plus about 250 lbs of possibly rusted out tank.
Or a bunch of parts that may or may not be useful when you build a compressor.

Thank him nicely for his time, wish him happy holidays and keep looking.


P.S.
Building a Frankenpressor is actually fun, educational, and can be profitable.
It also can be a little bit of work, but you may learn new skills, which is always good.
First one I built, I started with nothing but a good tank. Bought a motor, new compressor and every part.
A great learning experience. I had used compressors for 35 years without knowing exactly how all that junk did what it did.
Since then I have built a number of them, as favors for friends, and for fun and profit.
Downsides to doing this;
They are HEAVY. You can hurt yourself, badly.
You can drop one on it's side, converting it to spare parts.
The tall ones, the 80 sold as a Husky or CH, is over 560 lbs, top heavy as can be.
Two men can seriously hurt themselves loading one.
I built a hoist system for them, it's still dangerous.
We used three men to load one in a pickup, with the Compressor removed and when it kicked back, one of the big strong men was lifted in the air. Could have been injured, just got lucky.

P.P.S.
If you want a big compressor, get a two stage, you will like it a lot better.
Be sure you need an 80 gallon before you bother with one. 80 gallon is about twice as hard to move around the shop as a 60.
Low 80 gallons, like the one in your picture are easier to handle than the tall 80 gallon. A lot easier.

 

[sberry]

Yes, there is a place for fixing a used one, my spare/backup/second/extra demand unit in my shop was used, given to me, I replace a head gasket, clean it up a bit and put a starter I already had on it, took about half a day and no out of pocket, even used the original belts as I recall. This was a different picture.
But it kind of boils down to,,, you want to use it or fix it? About the same for a guys first wire welder. Battery drills the same way.

 

[bad_idea]

i am in process of building a frankenpressor. I'm hoping to have $400-500 max into it for a good running quincy 325. I have learned quite a bit, but it has been a long project I tinker with as I come across bits and pieces for it.

That being said, I wouldn't touch that thing unless you want a project.

 

[kams1973]

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