Motor Questions

[John K Jordan]

Actually, it was when I opened the machine to tighten up the loose pulleys that the problem first presented itself.

Could you have tightened a belt or something too much? Just wondering.

BTW, the capacitor on one of my small lathes (Jet mini) went out. It was 25uF 250v. The symptoms were it would always start if I spun it by hand, and would sometimes start by itself. With the capacitor blown the lathe was just as likely to run backwards as forwards. If it didn't start, there was an audible hum from the motor.

When the capacitor went out it made a strong and unpleasant smell and it looked warped and overheated.

I assume you checked the wiring for a loose connection or broken wire. That would give the same symptoms of a fried capacitor.

If you order a capacitor make sure it will physically fit in the housing. The Jet capacitors are so ridiculously overpriced that some people bought a different capacitor that didn't physically fit and mounted it some other way.

JKJ

[Alan Lightstone]

Further info from the motor repairman. He said that the windings are definitely fried, and just replacing the capacitor won't work.

i had tightened the pulleys, but only to factory specs, so if that was the cause (it likely was, and certainly was temporally) that would rot.

He did not measure the shaft diameter, but he did say it wasn't metric, and the mounting bolt locations weren't standard either. He said it must be a custom made, no-name OEM unit made for Laguna. Oh joy!!!

He's looking into options for me, and will let me know in a few days.

[Jim Dwight]

This probably is not it but the 1 hp (true 1 hp, draws 15A) induction motor I had on my old home-made table saw was not sealed. The motor slots would fill with sawdust occasionally and I would have to tear it down and blow the dust out. When they were clogged, it did what you describe. It is a capactor start motor. If you have it at a repair shop, they should see this if it is a contributor or the problem. It should be a sealed motor so this should not be the issue.

[Alan Lightstone]

Should be a TEFC sealed motor.

BTW, since I have to replace the motor anyway, is there an advantage to putting in a 5HP motor instead of the 3HP motor that's in it?

There is room, and my AC circuit can handle the extra power.

[Dan Friedrichs]

I'm really surprised you "burnt" the windings. Are you sure you trust the motor guy? I'd get the motor back from him and see for yourself - burnt windings would be obvious (they'd look like the coils on the stator - the outer part - had been on fire). Posting a picture here would help. I'd also double-check his claim about the bearings. Grab the shaft and lift up/down - bad bearings would cause play in the shaft.

If you want to replace it, you can certainly go bigger (5HP), but the cost goes up quickly. 3HP should be plenty. Even a 3HP motor is pricey - $300-$500 for a Leeson or Baldor.

Obviously, go with a TEFC motor. Speed should be whatever speed gives you the correct speed on the cutterhead (so it will depend on the pulleys, etc).

There is no difference between motors with just a starting cap vs motors with start and run caps.

[Alan Lightstone]

I'm really surprised you "burnt" the windings. Are you sure you trust the motor guy? I'd get the motor back from him and see for yourself - burnt windings would be obvious (they'd look like the coils on the stator - the outer part - had been on fire). Posting a picture here would help. I'd also double-check his claim about the bearings. Grab the shaft and lift up/down - bad bearings would cause play in the shaft.

If you want to replace it, you can certainly go bigger (5HP), but the cost goes up quickly. 3HP should be plenty. Even a 3HP motor is pricey - $300-$500 for a Leeson or Baldor.

Obviously, go with a TEFC motor. Speed should be whatever speed gives you the correct speed on the cutterhead (so it will depend on the pulleys, etc).

There is no difference between motors with just a starting cap vs motors with start and run caps.

Lots of good info, Dan. Thanks.

I don't know if I trust the motor guy. But if he wanted to rip me off, he would have pushed repairing the motor, which he isn't.

Let's see what he comes back with for options for a new motor, etc...

[Mike Henderson]

Stick a starting cap in it and see what happens. You have nothing to lose but the cost of a capacitor - which is pretty low.

Mike

[Alan Lightstone]

OK. Time to re-evaluate my options.

The motor repair guy called back. He basically said that a big issue is that the pulley is not standard size ID (since the motor shaft is unusual size OD), so that with a new motor they will have to bore out the inside of the pulley also. Between that and replacing the motor (he was quoting only 2HP motors, as he said that the outside dimensions of 3HP motors are greater than the one I have) are now in the ballpark of just rewinding the motor, replacing the bearings and capacitor.

Time to reassess my options. I'm going to get back the motor, buy a capacitor from grainger or Amazon, and test it out. If that doesn't work, I can either buy an identical motor from Laguna (although if it has no motor plate, I'm going to be very skeptical that it is a 3HP motor), or buy a Baldor or Leeson motor and have some machine shop bore out the present pulley or find a new compatible dual pulley with the correct ID and OD to get the speed correct.

Also not terribly anxious to get inside this machine to drill new mounting holes for the new motor.

Anyone know a good source of pulleys, and I'm assuming that they are very specific regarding ID, OD, and width for different belt sizes? It's a dual belt pulley, FWIW.

[Malcolm McLeod]

The old motor, whether metric or NEMA, has a frame size - hopefully it IS a standard. The frame size dictates the shaft diameter, length, and any key-way, as well as the bolt size/spacing/pattern for mounting. If you can determine its frame size, it will make any replacement a little easier. Sounds like you have options and contingencies for the motor well planned, so will just offer some options for the drive.

If you have to change motor frame, but want to keep the driven sheave and belt as-is, there are two pieces of data you need for driver: 1) pitch diameter (PD) of the drive sheave (not the same as its OD); and 2) the belt (cross section) profile. Most sheaves and belts have this stamped on them, but either Laguna or a Grainger-like shop should be able to ID for you.

You can spec a new sheave for a replacement motor using the PD, v-belt profile/count, and bore (match to shaft). Or, if you're worried about future motor 'transitions' (i.e. a screamin' deal on a used motor that might last 2 weeks...), for slightly more $$ you can get a sheave with correct PD and v-belt specs, but get it with a QD bore. A QD bushing then adapts the sheave to the motor shaft. If the motor shaft has to change for whatever reason, you just spec a new bushing - - not the entire sheave. QD is very common in large sizes for sheaves, but if your's is too small, the QD option may be impossible. ...hope it helps.

(I like QD, but there are other options - split taper, taper lock etc.)

[David Kumm]

This thread teaches a lesson when buying machinery. Motors are an area where there is a lot of cost cutting. Smaller frame with lots of wire ( good insulation allows this ) allows for lighter weight, less strength to base and guts of machine. Smaller shaft and bearings, etc. The problem is that these motors run hotter, as do the bearings so it is important to look at the motor as more of a temporary part than a forever one. Means you must check that it can be either readily replaced, has a standard frame, has HP (kw ) appropriate for a standard replacement. There are 90 frame metric motors in machines that provide 10 hp but try to find a replacement over 5.5. If the motor isn't standard or high hp for the frame size, can it be rewound reasonably? Motor guys hate packing lots of wires into a small frame or rewinding a small diameter long body motor and the cost go up exponentially. If you are forced to buy a replacement from the machine company, you are doomed. If sales people can't give you the origin, frame size, bearing size, and efficiency, find a sales guy who can. If we don't ask and expect answers for slightly more technical questions, we will be responsible for the reduced quality. Dave

[Alan Lightstone]

This thread teaches a lesson when buying machinery. Motors are an area where there is a lot of cost cutting. Smaller frame with lots of wire ( good insulation allows this ) allows for lighter weight, less strength to base and guts of machine. Smaller shaft and bearings, etc. The problem is that these motors run hotter, as do the bearings so it is important to look at the motor as more of a temporary part than a forever one. Means you must check that it can be either readily replaced, has a standard frame, has HP (kw ) appropriate for a standard replacement. There are 90 frame metric motors in machines that provide 10 hp but try to find a replacement over 5.5. If the motor isn't standard or high hp for the frame size, can it be rewound reasonably? Motor guys hate packing lots of wires into a small frame or rewinding a small diameter long body motor and the cost go up exponentially. If you are forced to buy a replacement from the machine company, you are doomed. If sales people can't give you the origin, frame size, bearing size, and efficiency, find a sales guy who can. If we don't ask and expect answers for slightly more technical questions, we will be responsible for the reduced quality. Dave

Live and learn....sigh.....

[Alan Lightstone]

OK. Back in town, and I got the motor back. The motor repair guy left the housing open, so I can see the windings, which do indeed look burnt. Here's a photo of them:

IMG_3664 - 1.jpgIMG_3663 - 2.jpgIMG_3662 - 3.jpg

So, I'm no expert, but they look burnt to me, though I don't know what they're supposed to look like.

He was not impressed by the quality of the windings or the quantity. He is very doubtful that the motor is indeed 3HP as billed.

Again, he is saying a total rebuild, and replacement of the capacitor and bearings will run about $650.

Laguna said they have a replacement motor for me for $311 with shipping. I will try to pin them down and insist that the motor have an appropriate motor plate on it that says 3HP, but I am skeptical. Also skeptical about the quality of the motor from them. The first one is impressing no one.

I'll work on measuring the dimensions later, both of the mounting holes and the motor, shaft, and exterior dimensions, to see if people think just buying a quality 3HP motor and having a metal shop bore out the pulley to the correct diameter would be a better idea.

I'm wondering what everyone's collective thoughts on my best approach going forward.

[Malcolm McLeod]

I'm wondering what everyone's collective thoughts on my best approach going forward.

Get a windmill powered machine..??? Looks like FLA won't have electricity for a while.

I know you're on the opposite coast, but keep you head down. A fleet of utility trucks, linemen, and power poles left here at 6AM, headed in your general direction. I hope you don't need them! Take care.

On hopefully more useful note, I'd just buy a new sheave to fit motor if req'd. Machining a new bore is probably about break-even with buying new, and 'new' has no concerns about balance, concentricity, keyway, etc.

[Jerry Bruette]

Alan

Do you have room to put in a adapter plate, metal plate that would have holes drilled like your present motor and another set of holes drilled for a standard NEMA frame motor? The holes for your present motor would be through holes and the NEMA ones could be tapped.

Then you could purchase the appropriate sheaves and probably never have to mess with it again.

I would check with the surplus center for a motor. They may even have the sheaves you need.

[Alan Lightstone]

Jerry:

Interesting thought. I'm a little confused on nomenclature. Is a sheave what I am think of as a pulley?

The motor guy today said that the pulley on my motor was very custom with the two belts very close to one another. I'm thinking that I'll have to have the present pulley reamed out to the proper NEMA dimensions, instead of being able to find a compatible pulley.