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Thread: Old Motor Help

  1. #1

    Old Motor Help

    I have a fairly old motor,and one that is quite big at 1 hp. It worked fine a few months ago, but now when I snap on my bandsaw, it just humms. I even tried jump starting it by turning the wheel by hand, but to no avail.

    Now the bandsaw is my back up saw so it sits idle for long periods of time. I doubt its suddenly gone bad, but rather just kind of stuck. Its in a hard to get at spot so I prefer a method that might get it running that is quite easy. My dad suggested spraying some WD-40 on it, waiting for it to dry up, then starting it, but my understanding is that WD-40 is a water dispersion product and really does not dry. If it would work I would try it.

    The only thing I can think of is to pull the motor out, get it apart and then stone the comm a bit. Maybe a little graphite lube and see if the cleaned up armature and brushes gets it going again.

    I have always been kind of "scared" of digging into these motors, but I would like to get into electrical motor rebuilds. I worked on 3 million dollar locomotives and 15 million dollar yachts so what can be so bad about a 200 dollar motor? Anyway I have about 5 electrical motors that need repair/ maintenance. Do you guys think you can educate me on some of the more simple rebuilds? I look forward to learning new things and don't mind a bit of wrenching.
    I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"

  2. #2
    Join Date
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    Floydada, Tx
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    The first thing is, Is it a sealed motor? If not then you can try to blow it out with a air hose. I have seen several motors that where so packed with sawdust that it had to be chiseled out. If it is sealed, look for lube ports on it. Place a few drops of oil in there and crank it over a few times to see if this helps. You might have to pull the end of it to clean it up, which should not be a big deal. I never use any kind of lube other then a little grease on the bearings, other wise it can get into the wrong area and course arching.

  3. #3
    Join Date
    Nov 2006
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    Mountain Home, Arkansas
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    Travis, wish I had the knowledge to help. If you don't mind a digression from your topic. We have a guy in town who is semi-retired. He has been operating an electric motor repair shop for quite a few years. He is a valuable local asset. I'm sure he has saved a lot of people a lot of time, money and headaches. He is nearing the end of his road and if no one replaces him, many of us will have problems like you are facing. Since most of the work is bench work, with little lifting, it seems someone wanting to get away from backbreaking stuff could do well with a small specialty shop like his. We need one per town in America.
    "Folks is funny critters."

    Think for yourselves and let others enjoy the privilege to do so, too. ~Voltaire

  4. #4
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    I'm afraid you're going to have to remove the motor to analyze it well.

    Set it on your bench and make sure it turns easily when it's not plugged in. Check especially to see if anything is rubbing. Push on the shaft and rotate it and pull on the shaft and rotate it. See if there's any hint of rubbing anywhere, or any significant difficulty in turning it. Pull in the direction that the belt was loading it and see if its rubbing. If so, your bearings are probably bad. As a machinst I'm sure you know better than I how to check bearings.

    Now, plug it in and see if it runs with no load. If it won't start, give the shaft a good spin. If it starts running, the starter capacitor is bad. Let it run for a while with no load and see how hot it gets. If it gets excessively hot, you probably have a couple of coils shorted (insulation breakdown) and you should trash it.

    If it won't start running with a really good spin, I'd give up on it. You're probably better off buying a new TEFC motor than spending money rebuilding old open frame motor for woodworking applications.

    Mike
    Ancora imparo
    Go into the world and do well. But more importantly, go into the world and do good.

  5. #5
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    Regarding rebuilding old electric motors, I don't think it's worth it for small motors (certainly under 5HP). By the time you really fix one up, which would include replacing the bearings, the starter capacitor and rewinding the coils, you'll have spent more than a new motor would cost. And you can usually find deals on motors on eBay and surplus houses. The only small motors that are worth rebuilding are ones with special frames that you can't find easily.

    At least that's my opinion.

    Mike
    Ancora imparo
    Go into the world and do well. But more importantly, go into the world and do good.

  6. #6
    Join Date
    Dec 2006
    Location
    Melbourne, FL
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    Free Motor

    Got a good price on a 1.5 hp motor if you want it.

    $0.00

    As far as I know it ran fine when last used.


    It is 220 V only

    You pay shipping.

    I can send pictures of motor and name plate if you are interested.

    Or any one else who might want it.

    Motor is in Florida.
    Last edited by Pete Simmons; 12-29-2007 at 08:54 PM.

  7. #7
    Join Date
    Dec 2006
    Location
    Melbourne, FL
    Posts
    472

    Here is some Pics

    1.5 hp motor
    Attached Thumbnails Attached Thumbnails motor1.jpg   motor2.jpg  

  8. #8
    Join Date
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    I will add one thing to Mikes advice. If it doesn't start by spinning it, it could be the start switch inside is stuck. That goes along with the sawdust packed in there.

    Depending on the motor, I might disagree with Mike on scrapping it. You said old. As in how old? Does it have a hump on the outside for a capacitor? If not it might be a RI motor, those are worth fixing. But they fell from favor in the late(?) 40's. And of course I have a weakness for old motors too. But the are often better built than new ones. But not maintenance free.
    God grant me the senility to forget the people I never liked anyway,
    the good fortune to run into the ones I do,
    and the eyesight to tell the difference.


    Kudzu Craft Lightweight Skin on frame Kayaks.
    Custom built boats and Kits

  9. #9
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    I went back and reread your original posting, Travis. You mention a commutator on the motor. The advice I gave you was for an induction motor. Commutators are usually found on DC motors. If you have a commutator on the motor, and it runs on regular AC, the motor is a universal motor. But this would be unusual in an older 1.5HP motor.

    If you have a commutator on the motor, clean the commutator with something like a pencil eraser and check the brushes to see if they are making good contact. They could have worn down.

    If there's no commutator on the armature you have an induction motor and my previous advice is appropriate.

    Jeff Horton suggested that if the motor won't start when you spin it, the problem could be the centrifugal switch on the shaft. In my experience, this is unlikely. The centrifugal switch closes (makes contact) when the motor stops turning (actually when it's turning slowly). When you get a lot of insulating swarf (like sawdust) in the motor it gets between the contacts and the switch won't make contact. Then, the next time you try to start it, the starter coil and capacitor are not energized, which causes the motor to just humm and not start rotating. If you give the shaft a spin (and the switch is the problem), the motor will begin running in whatever direction you spun it. If the centrifugal switch is the problem (blocked with swarf) you can often fix it by blowing high pressure air into the motor through the holes in the frame.

    Regarding old and modern motors, like most electrical things, we've learned to make motors better over time. You'll find that a modern motor has better efficiency, smaller size, will require less maintenance (sealed bearings), much better insulation on the coils, and offer some frame advantages (like TEFC) over old motors. There's a lot of personal satisfaction in getting an old motor to work but beyond that, a modern motor is a better choice for most woodworking applications.

    Mike
    Ancora imparo
    Go into the world and do well. But more importantly, go into the world and do good.

  10. #10
    Join Date
    Oct 2006
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    Quote Originally Posted by Mike Henderson View Post
    I went back and reread your original posting, Travis. You mention a commutator on the motor. The advice I gave you was for an induction motor.....

    Could be a R/I motor. And put out a lot more torque than a Cap. Start motors of the same size.
    God grant me the senility to forget the people I never liked anyway,
    the good fortune to run into the ones I do,
    and the eyesight to tell the difference.


    Kudzu Craft Lightweight Skin on frame Kayaks.
    Custom built boats and Kits

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