Repairing rough running 5 HP single phase motor

For $12.00, I bought a 5 HP, SINGLE PHASE Baldor compressor motor that has a problem. When I spin it up by hand, it turns, but a little
roughly and then spins by itself, but not for very long. It stops too soon. It is not, by any means, seized, but there is too much friction compared to what it should be. I did not run it under power yet
It is ball bearing based, which I concluded after seeing grease fittings on it.
My hope is that it should be an easy fix. Either the grease caked, or perhaps the bearings need replacement. Any thoughts on how to proceed?
thanks
i
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I did the same just a few months ago. I was bequeathed two complete(ly broken) and water-damaged 5HP compressors. Both had Baldor motors. One motor was well and thoroughly burnt out. The other was "grumbling" like yours.
It's a little of a trick to get the motor apart and get the bearings out, but no big deal. The hardest part will be to get the shaft end bearing off the shaft, since it usually corrodes in place. Lots of oil and fine grit paper are the trick to getting the shaft back to its original o.d. without damage. You'll need a small gear puller to start the bearing moving on the shaft. Then it should slide off easily.
The bearings are stock NGK items in my local bearing shop -- about $14.00 each.
Take care pressing them back into their seats -- they aren't tight fits, but you should avoid any pressure on the inner race. Make a tool, if you aren't lucky enough to have a bearing pressing mandrel that fits. A large wrench socket that is no more than, say, 0.050" smaller than the o.d. of the outer race will work well as a tool.
LLoyd

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On Tue, 09 Aug 2005 13:51:13 GMT, Lloyd E. Sponenburgh

Thanks.
My 5 HP motor is not corroded, as such, and not oily. It looks awfully like the 3 HP Baldor motor on my home Curtis compressor:
http://igor.chudov.com/projects/CurtisCompressor/
or here
http://igor.chudov.com/projects/CurtisCompressor/02_Installed/dscf0004.jpg
only the 5 HP one is bigger. I will try to check it out tonight.
I have a gear puller of some sort, not sure if mine is big enough.

Thank you. What is NGK?

Thank you. So, your vote is to just replace the bearings, not to try to just re-grease them?
i
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You could hit it with a grease gun, run it for 15 minutes or so with no load, see what happens. Problem is that you need to flush the old crud grease out. Only way to do that is to run the old grease by the seals, not a good thing. $28 for two new bearings plus $12 purchase price is still a very good deal.
The headstock bearing on my 10" Logan lathe was similar. Crudded up bearings, really sounded rough. Soaked it for a couple of days in laquer thinner, spun nice and free. As soon as it dried out, back to crud stage. Someday I'll clean it with MEK or something with real punch, in the meantime, the new bearing is working fine.
Ignoramus6689 wrote:

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That makes sense to me. I will try to just pump a bit of new grease into the motor to see if it solves the problem. If it does not (most likely), I will take it apart and take the bearing out.
How would I find the spec for the bearing, should I just call Baldor or their dealers?

Thanks. So, all in all, it is not an incredibly difficult project. Pull old bearings out with a bearing puller, buy new bearings, and install.
Er, how does one install bearings properly? Should I just use a piece of water pipe and a piece of wood to bang on the pipe to push the bearing on the shaft?
That sounds like a fun evening project.
i

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Bearings are usually stamped with their designations. If not, measure them. But if you have them in hand, just take them to the bearing shop -- they'll duplicate.

You're mixing metaphors. Don't EVER BANG on a bearing. Push it in, nice and square, and as gently as the fit will allow. The "piece of pipe" was what I was refering to when I mentioned a wrench socket. Sockets usually have the advantage of being round, square on top and bottom, and stout enough to take substantial pressing force.
If your Baldor motor is like mine, the bearings lightly press into the end bells, then the bell-with-bearing slides easily onto the motor shaft with a pretty loose fit.
My biggest problem was keeping that 90lb beasty still on the bench while I worked on it... hadta build some cleats to still it.
LLoyd
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On Tue, 09 Aug 2005 15:30:48 GMT, Lloyd E. Sponenburgh

That's great to know.

I got it. I will clean up my workbench, put the motor on it and will see how hard it is to get bearings out.

That's wonderful.

Yes... I'll see how it goes. Thanks for the encouragement.
i
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A brand of bearing. Japanese origin; good quality.

If they grumble, they're shot. Replace them.
LLoyd
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On Tue, 09 Aug 2005 14:41:20 GMT, Lloyd E. Sponenburgh

Got it. Thank you Lloyd. Yes, they do grumble, like they have sand in them.
i
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If you have an open bearing that rumbles there is a decent chance you can clean and repack. Sealed bearings are usually not responsive, you cna't get enough old crud out to cure the problem. A gritty noise is usually brinneled, rusted, or other damage to bearing surfaces, bearing is toast.
Ignoramus6689 wrote:

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Would it be correct to assume, though, that with new bearings, the motor will be effectively "like new" (sans capacitor life expectancy)?
i

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I
Be careful to not damage the switch inside the single phase motor when you disasemble it.
If this was my motor, I'd power it up before proceding with any repair.
Jerry

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thanks... will try not to damage anything...

That sounds like a good idea...
i

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Jerry sez:
"If this was my motor, I'd power it up before proceding with any repair."
Great advice! Determine if there is also an electrical problem before investing a lot of time/money/aggravation in bearings.
Bob Swinney
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I agree 100%.
If anyone finds this little project interesting, I can make pictures along the way. If not, I will just do it without taking pictures.
i

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I wish I had photos of the centrifugal switches I've damaged while disassembling single phase motors.
Jerry


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Jerry, what should I be watching out for when disassembling? Are they in the back of the motors?
For disassembly, should I mount the motor with the shaft vertical?
i

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Yet another of the benefits of having 3 phase power. The starting switch is often the source of much trouble in single phase motors. I recall all too well a flooded room, thanks to a starting switch failure in a sump pump.
Harold
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On Tue, 09 Aug 2005 14:48:10 GMT, Ignoramus6689

a heads up..DONT buy India made bearings. Only US, Japanese, European, and marginally..Chinese bearings.
Gunner
If you are going to use that phrase then you should use the full phrase of "Fuck Off and Die and Rot In A Ditch and Get Eaten By Maggots and Pissed On and Shit On By a Dysenteric Elephant (but not necessarily in that order)."
Crash Street Kidd
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wrote:

Forget the Chinese bearings.
A good while back we rebuilt the spare spindle for a IR T-25 air compressor (being used as a natural gas compressor by the local gas company). He keeps a spare because of all the problems that compressor gives him. Anyway it was put in service about 2 years ago with the bearings that he had gotten from the local NAPA. Well less than a year later we had to take the compressor back apart because it was making noise. Inspection found the balls in the bearings looking kind of like a baseball with half of them being shiny and the other half being pitted. Lousy steel in those balls. They where replaced with some good USA bearings which will hopefully hold up much longer.
Wayne Cook Shamrock, TX http://members.dslextreme.com/users/waynecook/index.htm
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