OT? Smokin motor, need advice

[Gary DeWitt]

Slightly off-topic, but I need a hand. (Alright, you all can stop clapping now...sheesh) The 1hp motor on my delta band saw started smoking right after startup one day. Only thing I changed right before that was adding a shop vac to the same circuit for dust collection on the saw. Did this "starve" the saw motor or somehow damage it? Next thing I tried was removing the belt and plugging the saw directly into it's own circuit with nothing else running, same result. Motor still runs, without any excess noise (like bearings), but it starts smoking almost immediatly. Is this motor likely on it's way out? Will it need extensive rebuild, and is that worth it? What happens if I scrap this motor and install a 1.5 hp instead, will it overpower the saw? I'd like a little more power, especially for splitting 12" wet logs.
Any help on this much apreciated!

[Brian Weick]

She is on her way out- you probably strained the motor by adding the shop vac to it ,question- does it have a capacitor starter inside of the casing ?- If so that may have been the smoke you saw and that can be easily replaced if that is the case- check that first, then the windings .You have to pay attention to the amperage draw on each circuit. The other scenario is that the windings were overheated and shorting out - it will eventually , and probably in a very short time span, burn up. I am just telling you this based on what you wrote. It would be more economical to just get a new or used motor somewhere rather than having it rewound which will cost you some$$$ . I hope you are able to resolve your problem Gary, but I would check the amperage next time before you run the machinery . I would mark each outlet with the maximum amount of draw so you know. Just because it didn't trip the breaker doesn't mean your safe running several machines on one circuit. You still can starve the machine to some degree. It may have been on it's way out and this just started the whole process sooner than later.

[David Epperson]

Slightly off-topic, but I need a hand. (Alright, you all can stop clapping now...sheesh) The 1hp motor on my delta band saw started smoking right after startup one day. Only thing I changed right before that was adding a shop vac to the same circuit for dust collection on the saw. Did this "starve" the saw motor or somehow damage it? Next thing I tried was removing the belt and plugging the saw directly into it's own circuit with nothing else running, same result. Motor still runs, without any excess noise (like bearings), but it starts smoking almost immediatly. Is this motor likely on it's way out? Will it need extensive rebuild, and is that worth it? What happens if I scrap this motor and install a 1.5 hp instead, will it overpower the saw? I'd like a little more power, especially for splitting 12" wet logs.
Any help on this much apreciated!

Rule of thumb is that motors do not really run on electricity, they run on magic smoke, and when all the smoke gets out they quit running. But it really depends on what is causing the smoke. If it is the windings breaking down the varnish insulation, then yeah it's approaching toast status. If on the other hand it is some dust or oil contamination inside the motor frame, then it just may survive. You would probably need to pull the motor apart to tell the difference. Im not sure that replacing the 1hp with a 1.5 would be the way to go unless you look closely at the circuit.
after all if you DC "starved" a 1hp enough to damage it, wouldn't it do the same to a 1.5 that required even more current, even quicker?

[David Epperson]

It would be more economical to just get a new or used motor somewhere rather than having it rewound which will cost you some$$$ .

I worked at a motor rewind shop for a while and it usually turned out to be cheaper to replace a standard motor of less than 5 or 10hp than it was to get it rewound. Now if it was a a specialty motor or a frame size no longer made, then that changed things a bit. But that does not sound like the case here.

[Brian Weick]

Dave,
If he has the capacitor starter on the motor, he could have strained the starter enough that it fried the insides of the cap- that is a possibility- is it not?
Brian

[David Epperson]

Dave,
If he has the capacitor starter on the motor, he could have strained the starter enough that it fried the insides of the cap- that is a possibility- is it not?
Brian

Doubt it. But you bring up a good point. It could just be the starting windings that are strained, or the cut out switch not letting go. If it's the switch contacts fused together they could be polished out or replaced. If the cap was gone the motor would just sit and hum, untill it was spun manually in one direction or another.

[Gary DeWitt]

Thanks for the info, it's definitely something electrical burning by the smell. Starter cut out or capacitor seems possible since the motor does still run, and I suspected something like this, like it is stuck in start mode. I already have it out of the saw and will be taking it in to a motor shop later this week, will post results here.

[Paul Downes]

Just a couple of questions. Would blowing the motor out with compressed air help-as in the case of sawdust coating the motor inards and causeing heat build-up? Also, if you took the motor in and had it dunked,(recoated with resin) would that extend the life of a motor? An inquiring mind wants to know.

[Bill Boehme]

Doubt it. But you bring up a good point. It could just be the starting windings that are strained, or the cut out switch not letting go. If it's the switch contacts fused together they could be polished out or replaced. If the cap was gone the motor would just sit and hum, untill it was spun manually in one direction or another.

This is very true and perhaps the most common cause of the start winding burning out. The start winding is meant to be engaged for only a fraction of a second until the centrifugal switch cuts it out. David mentions the most likely possibility for the problem -- a bad switch. It could have fused contacts, but I don't think that is too likely on a small motor. More likely is that something on the centrifugal mechanism has broken -- it consists of a couple weights and springs.

You may be able to salvage the motor if you don't do any more smoke tests until after you open it up and find out where the problem is.

Bill

[David Epperson]

Just a couple of questions. Would blowing the motor out with compressed air help-as in the case of sawdust coating the motor inards and causeing heat build-up?.

Probably wouldn't hurt, but smoke from heat build up due to dust in the housing would probably not be immediate like was described.

Also, if you took the motor in and had it dunked,(recoated with resin) would that extend the life of a motor? An inquiring mind wants to know.

Usually in a rewind the whole motor is not dipped in varnish/resin, just the coils and stator. So there would be the issue of complete disassembly of the stator from the housing. On a 1 hp motor I'm really not sure what the gains would be, if any. A resin dip is not going to coat EVERY coil, it only reinforces the varnish coating that was originally on the wire before winding.

[Bill Boehme]

Also, recoating the windings is not desirable except when trying to salvage the insulation as a last ditch effort. Even though the glyptal varnish has good thermal transfer properties, it still inhibits heat transfer to some extent so that point needs to be considered along with the type of service that the motor is used in.

Bill