Old Motor Help

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I have a fairly old motor,and one that is quite big at 1½ 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.:dunno:

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.:dunno:

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.
 
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.:eek: 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.
 
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. :)
 
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
 
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
 
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.
 
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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.
 
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
 
Travis,
I'm with Jeff on this one. Before getting into the "old vs. new" debate, i'd add that since it suddenly went dead just sitting there for some time, i'd suspect dirt or insects have invaded. I had that same problem (more than one time actually). It's best addressed by pulling the rear bell housing off for a good cleaning. Even totally enclosed motors have access points for 6 or 8 legged critters - usually the holes for the wires are not sealed. Before removing the bell, stamp a pair of alignment marks on the bell and main housing so that you get it put back together the correct way.
I wouldn't spray WD40 into an old motor. the solvents can play havoc with your insulation and it does attract dust - making your problem worse over time.
Open frame motors do need a good cleaning from time to time.
Regarding the cost of fixing up the old rather than replacing it with a new motor - it's been my experience that bearings are not expensive to replace. Neither are capacitors. And, when i've got an old motor apart, i sleeve the leeds with shrink tubing (Radio Shack or any decent hardware store will have this) to maintain the integrity of the insulation. If it's a universal motor or a repulsion start / induction run (R.I.) motor, there will be brushes involved as well. They may need replacing - again, not expensive, though you may need access to a motor repair shop to get proper replacements. Occassionally, I've had to purchase over-sized brushes and sand or file them down to size. The ones in the motor may have numbers marked on them - this may help. If you know the hardness of your brushes, McMaster Carr (www.mcmaster.com) should have them (and any bearings you may need).
All of the above maintenance items are relatively cheap - much less expensive than a replacement motor. The rest is just elbow grease - cleaning things up. I did need to replace part of the centrifugal switch on one of my motors once, but that involved nothing more than some epoxy, thin wire, and a 3 sided scraper.
I like my old motors. If you've got a short in the windings, that may be a death sentence. There are shops that will rewind small motors (under 5 HP) but they're few and far between, at least in my part of the country. I had a small shaper motor armature rewound a couple of years ago. The motor was integral to the machine, so i needed to do it in order to make the shaper usable. The cost was somewhere between $100 and $150, including shipping to Minnessota. I got the shaper for free, so i figure the project was still close to reasonable. I'm admitedly a bottom feeder, and i hated to spend the money, but i do use the machine.
In my shop, i'd take an RI motor over a capacitor start motor. They draw much less amperage while delivering greater torque upon start up. The drawbacks are weight and maintenance. RI motor armatures are essentially set up with two sets of windings - the repulsion set and the induction set. The repulsion set delivers the start up torque very efficiently. Then, once up to speed, the centrifugal switch either breaks or grounds the circuit, depending on the motor design. The extra windings translate into greater size and weight. The brushes translate into more maintenance. The 1/4 hp RI motor on my scroll saw is about the same size and weight as most 1 hp cap start motors i've seen. I've got a 2 hp RI motor that's the biggest single phase motor i've come across.
Hopefully, you've just got some dirt in your motor.
Paul Hubbman
 
Give it a shot and tear it apart Travis. Once you get past the mystique factor, there's really not a whole lot inside a motor to go wrong. The worst case scenario is you mess it up and have to buy a new one... it's dead now so what will you be out other than some time? Best case scenario, a good cleaning, maybe new brushes or a capacitor, depending on the type motor, and a few bucks in bearings any your back in business. Even if it is dead for good you'll learn something.

I'd have to disagree on the quality, in this day and age of "build it to the bare minimum specs to get it though the warranty period". I really wonder how many of todays motors are going to be around and still running in 60 years? Over engineering was a wonderful thing.:)

Mike
 
Treadmill motors (New versus old motors)

I'll be the first to admit I'm not an expert on the subject of electrical motors. Aside from a few 60's and 70's era power tools in my Dad's shop I haven't had the opportunities to experience their care and feeding. I'm especially embarrassed to admit this since I have a MSEE courtesy of the US Air Force.

However, lately I've been researching treadmills to replace an older inferior treadmill I bought second-hand to start running indoors when the weather is bad. Also, my wife refuses to use the old one anymore because it has proved itself to be extremely unreliable. I have nutured it and bought several replacement parts for it, but in the end it simply was not designed for the use we give it.

Getting a good review for treadmills is difficult. Consumer Reports only tests a limited amount of treadmills and for some reason they are generally older models each year that are being phased out. Runners World uses more updated models, but base their reviews largely on a number of runners opinions, not necessarily the quality or the longevity of the machines. Consumer Search seems to buy hook line and sinker into the obviously single brand-named friendly web site reviews out there, and there are a growing number of companies and brand names (i.e. Sole treadmills) that build their own review sites partial to their product as well as employ fake "reviewers" to write favorable reviews of their product on other websites.

I did find a great web site specifically for treadmills, though. A treadmill repair store, www.treadmilldoctor.com, does not sell a single home treadmill. However, they are a clearing house of parts, supplies, and most importantly knowledge of treadmills and the treadmill industry. They visit the fitness machine factories (mostly in Asia) and talk to the company design and manufacturing personnel as well as do research into the fiscal health of the company.

One of the most important components of a treadmill is the motor. And the motors in treadmills come in all different sizes, shapes, and powers. They also come in different qualities. Basically, you can get a quality new motor, or you can get a crappy new motor depending on the quality of parts and the manufacturing involved. Treadmilldoctor bases a lot of the treadmill review score based on the type and quality of the motor involved.

I assume shop tools go the same route. A good overengineered old motor is quality, but a cheap used old motor is still cheap. My 2 cents anyway.
 
Shucks ... I thought you were going to talk about how you outfitted your old treadmill motor to your lathe to add variable speed capability. :wave:
 
Hang in there, Kerry,

I am in the middle of just a conversion. Still awaiting a few parts to arrive. I am documenting everything, including costs and sources. Thanks to the help of a new friend in Texas who is a retired electronic wizard, the wiring diagram is complete. It not only includes the variable speed feature but also a reversing feature, on-off switch for the entire system, run/stop switch for just the motor to isolate the control board from the frequent starts and stops of the lathe motor, and an emergency kill switch for when you've dodge a launched bowl and need to reach up from the floor to kill the entire system! A few other features I'll keep until I am ready to show off my tricked out lathe.

Well, they trick trucks on TV. I ought to be able to trick my lathe on my kitchen counter. Garage/shop waaaay too cold right now.
 
Hang in there, Kerry,

I am in the middle of just a conversion. Still awaiting a few parts to arrive. I am documenting everything, including costs and sources. Thanks to the help of a new friend in Texas who is a retired electronic wizard, the wiring diagram is complete. It not only includes the variable speed feature but also a reversing feature, on-off switch for the entire system, run/stop switch for just the motor to isolate the control board from the frequent starts and stops of the lathe motor, and an emergency kill switch for when you've dodge a launched bowl and need to reach up from the floor to kill the entire system! A few other features I'll keep until I am ready to show off my tricked out lathe.

Well, they trick trucks on TV. I ought to be able to trick my lathe on my kitchen counter. Garage/shop waaaay too cold right now.
If you don't at least put flame decals on your tricked-out lathe, I'll be highly disappointed. :p

Sounds like a cool project, and the outcome sounds very promising.
 
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