10EE smoking and arcing

Hi,

I have a 10EE Monarch with the square dial, MG version. My lathe is smoking after it runs for about 10 min. It smells something like burning rubber. I opened all the panels and inspected all the bearings and motor housings. Everything is cool to the touch except for the commutator on the main drive motor which is rather hot. When it is running all three brushes spark. I don't know if this is normal.

I'm powering it with a 3 phase rotary converter. I originally had the converter on two 20A fuses which was ok for a couple of years. I know this machine can use a lot more than that, but I thought this was ok since I use it for small projects and don't load it with heavy cuts nor do I usually go above 1000 rpm. Recently it's been tripping the breaker. When it is hot, it would trip the breaker as soon as I reset them and engage the drive. If I let it cool down for 15 min I could run it for another 10 min until it starts tripping the breaker again. So, I upgraded my wiring and my breakers to two 30A breakers. Still less than it needs for full capacity but I think it's ok for me. Since then the breakers don't trip, but I get the smoke now.

I hope I'm not repeating issues that have been thoroughly discussed already. I've searched for this issue, and found a couple of threads, but they don't seem to match exactly my issue.

Any insight would be greatly appreciated. Thank you in advance.

First, don't keep running it like that. Smoking means deteriorating insulation, inevitably causing more trouble.

Does the speed control act the same as in the past?

Does the motor turn freely?

Try running it with the drive belt off. If it still sparks, you have a problem with the motor.

There are four brushes on the motor. Is the fourth making contact?

Is the sparking even on all brushes and constant on all around the commutator?

The brush holders are rotatable. Check to see if the brush assembly is loose. There are a number of threads dealing with adjusting it.

That would be a start. If the problem persists, I could be available around December to make a service call just for expenses, airline, Royal Hawaiian Hotel, etc.

Bill

In addition to the above I'd suggest measuring the resistance on the field and armature windings. A short in those would lead to what you're describing. From memory you should see around 3 ohms on the armature and 100 on the field. You might have to rotate the motor a little to get those but be careful as you can get the armature to act as a generator and most ohm meters don't like that, just disconnect the meter, rotate the motor a little and reapply the meter.

I wouldn't run the lathe until you've figured this out. Going from 20A to 30A breakers was the equivalent of stuffing pennies into the fuse box.

If you're seeing much sparking on the commutator, that's a big problem. If everything is running correctly, you will see a tiny, pinpoint spark at each brush. The commutator should be the color of a well aged penny, with no dark bands and no black commutator bars. What do you have?

It's also odd that a 30 A circuit breaker would be tripping without the overload assembly on the main contactor tripping first. That should NOT be happening! Do you have a clamp-on ammeter that you can use to check the current draw on each phase? Except at startup, it should never exceed the nameplate current, which should be 14 A per phase for a square-dial MG wired for 220 VAC.

Can you post a photo of the AC contactor, located under the cast-iron cover on the back of the quick-change gearbox?

Cal

I did my best to follow up on all the pointers posted so far. Here's what I found:

1. The speed control acts the same as it has in the past

2. I did not take off the belt, but I ran it in neutral and sparks are still present

3. All brushes are making contact

4. Brushes are sparking unevenly. Two brushes have pinpoint sparks across the brush, One has significantly brighter sparks about 1/8" in size, and one is throwing occasional 1" sparks.

5. The brush assembly is loose! This came as a big surprise. It looks like there is a bolt on one side that should tighten the assembly, but it has no effect when I turn the nut. Unfortunately I didn't mark the original location as I wasn't expecting it to move so easily. I'm not sure the rotational position of the assembly had any affect on the size of the sparks or the function of the motor. I will go and read up on the other threads on this issue.

6. I need some guidance on measuring the armature and field resistance. For the armature, do I probe across bars next to each other or 180 degrees apart or other? I couldn't find 3 Ohms anywhere, but I was struggling to get a stable reading on my multimeter. For the field coils, I couldn't see a spot to probe those. Let me know where to probe and I'll take a careful measurement.

7. The commutator color is like a penny but severely striped with black lines. The surface doesn't look smooth and the edges of the bars look really tattered. This doesn't look good. Picture attached.

8. I also took some pictures of what I thought was the AC contactors, but I'm not sure I got what you were asking for. Let me know if you wanted something else.

9. Also I don't have a clamp on ammeter to measure the draw on each phase. Replying to Cal's note, my 30A breakers are not tripping. They were tripping when they were 20A...or was it 15A. I don't remember now. If this is critical for the diagnosis, I can try to get one.

Thanks for the great responses.

The contactors you see are the DC forward and reverse ones. The contacts look all right from what I can see.

The brushes obviously are not making contact across their full width. The loose holder may be cocking them or they may be stuck. Check that they all slide easily in their holders. Get the holder locked down solidly in the middle of its range and try running. If they do not spark evenly across the width of the brushes and evenly between them, you need to reseat them. First be sure they have enough length left. If not, Monarch has them. Cut a strip of 400 grit wet or dry sandpaper about the width of the commutator. Lift a brush and slide the strip under it, abrasive up. Rock the armature back and forth with the paper wrapped around the commutator to sand the brush to the commutator's radius. Repeat on all four brushes. That should get them running properly and ready to adjust. There are adjustment instructions in old threads.

The armature doesn't look good. There are commutator dressing sticks available that you hold against a running commutator. If they don't clean up and run right, the commutator needs turning. That requires disassembly. Again, there are instructions in old threads. While it is out, have a motor shop do a "growler" test, which tests for shorts in the windings. If it fails, look for an armature from someone who has replaced the drive with a VFD or whatever. Even if you can find a motor shop that will rewind it, you don't want to pay the price.

One of my customers had an MG 10EE running erratically. One brush had a single bright spark, so I shut it off and wiggled the brush until it was free. That cured it. I tried a Steinmetz bill, "wiggle brush- $5, know which brush to wiggle- $495" but they didn't buy it.

Bill

Looks like Bill was posting at the same time as me. . .

You didn't say if the brush tension springs are applying good pressure to the brushes. The lever that holds the brush against the contactor looks like the hammer on a revolver. If it's all the way down and no longer pressing on the brush, then it's time for new brushes. Check all four brushes. You should probably go ahead and order a full set of brushes anyway, since you will need them sooner or later. Monarch has them and at last report they were reasonably priced.

I wouldn't hurt to pull all four brushes and look at them. See if one of them is short and/or broken. You commutator doesn't look too bad but could stand to be dressed when you change the brushes. Search for commutator dress stone/stick.

Having the brush timing wrong can result in sparking and other problems. You need to figure out why the bolt that tightens the brush ring isn't able to clamp the ring into position.

Once you've verified that the brushes are making good contact, etc., try adjusting the brush ring, see if you can get just a tiny pin-point spark at each brush. Don't do it with the motor running, just mark the location of the brush ring, rotate it 1/8" on the circumference and try again. If things got worse, go the other way. Keep going until it's running with minimal sparking and good speed forward, then see how it runs in reverse. Continue adjusting the brushes until you're getting about the same speed forward and reverse, then leave it alone.

As Bill said, you posted photos of the forward and reverse DC contactors. The AC contactor is behind a cover on the back of the lathe, under the headstock and behind the quick-change (feed/thread) gearbox. There's a round hole in the contactor cover for the reset button. That's the contactor that I'm interested in seeing.

My 10EE won't run on a 20A circuit either, too much current inrush at startup, so as long as it's not blowing fuses or tripping a 30A breaker, your overloads may be fine. Harbor Freight has an inexpensive clamp on Ammeter, currently on sale for about $14. You might want to invest in one.

Cal

Cal Haines said:

Looks like Bill was posting at the same time as me. . .

Click to expand...

Good stuff, the both of you!

I'll add:

- everything should be CLEAN. 10EE tend to get altogether too much old oil, coolant, and fine metal chips into their underpants for best electrical longevity. Get those OUT, and keep them out!

Clamp Ammeters:

"Time was" the more common ones only worked well on AC currents. They had to go over to Hall-Effect sensors to make ones that also read DC properly. Not ALL have done that. Don't waste yer money. Check the specs. Ones that do BOTH, plus the "usual suspects" of general-purpose voltages readings & c. are only about $45 - maybe cheaper-yet nowadays.

CAVEAT: This is NOT a 12 VDC automotive environment, nor a 120/240 VAC residential one. A "contactor switched" 10EE at full-gallop can generate shut-down or reversing spikes of over 1200 V.

Most General-purpose meters are rated for only 300 Volts (the cheap and common ones). Better ones are rated to but 600 Volts, but till.... So...I use 10K volt test leads or better on a Rigol or Fluke 'scope.

Commutator dressing:

A useful stone is only about ten bucks. Do NOT use emery/carborundum (Silicon Carbide) cloth or paper on a stick. It is notorious for embedding its sharp little crystals into the Copper. I don't even like Aluminium Oxide (Sapphire).

If no purpose-made stone, (I ordered mine off the 'net..) then "flint", or "garnet" paper, as sawdust-makers still use is softer Silicon Dioxide, (Quartz). Much less likely to embed, and its crystals are weak enough to not survive long if they do.

A hand power-tool, such as a drill motor, or a salvaged warshing machine 1/3 HP motor can spin the 10EE motor via the Vee belts. Don't get greedy on RPM - it is now a generator, and can BITE you!

OR - as a 230 VDC "at full gallop" 10EE motor CAN "make turns enough" to stone the commutator at LOW voltage, pull the power, jumper it off a 12V car battery, see if there is enough remanence you don't even need power to the field, ELSE feed it 12 VDC to the field also. 24 VDC is better if you have it handy.

BE AWARE.. that there is enough inductance there that breaking the circuit on that motor once powered, even if not rotating much atall, WILL generate a spike at 4 or 5 times whatever DC voltage it was eating off of. There IS no Sine-wave "zero cross" as AC owns claim to. It is always the max.

When on 12 or 24 VDC? A short zap of 30 to 90 Volts is not supposed to be "lethal", but more than one neg-48-world Telco munchkin has come to serious harm or cost when it knocked him off a ladder or simply caused him to drop an expensive bit of kit, so "beware".

Normal operating Dee Cee, "stick and fry" 230 to 300 Volts?

THAT very much CAN be lethal, so "best safety habits" are required, Day Zero on a 10EE onward.

Treat it as if it was conspiring to kill you, 'coz it doesn't actually give a damn about human life, one way or the other, nor ever learnt how to take prisoners.

2CW

9100 said:

Silicon carbide in particular is a semiconductor and may be a problem (or not). Since stones are readily available, why not get the approved tool?

Bill

Click to expand...

For most of us, the answer is "impatience" rather than cost!



Now.. "world class" procrastinator that I am I DID order the stone I knew I would need.

"World Class" packrat as well.. all I have to do now is FIND the silly thing next time I need it!

MSC has the proper stones.

For resurfacing the commutator: 3/8 X 3/4" $18.56 ea.
Medium: 32334799
Fine: 32334724

Brush seater: 5/8 X 1 1/8" $15.01 ea.

Med hard: 68854470
Med soft: 32360653

The resurfacing stones tend to be very brittle and snap off, if not supported with a finger pushing it up against a brush holder within a half inch or so from the commutator. They should take moderate pressure pushing them into the commutator to get them to cut making copper dust. I usually put on one or two layors of Nitrile gloves for electrical insulation and leather glove over top. If powered from the power line, I always have someone near by, and place cardboard around the area to cover all grounded metal surfaces I could come in contact with. Your fingers are very close to electrically charged rotating surfaces, proper caution and proceeding with care this really is easily done. Always pay attention to where your other hand is at all times! The armature needs to be turning toward that brush holder, not away from the brush holder. I frequently let the spring pressure off just that brush to keep from eating it up with the swarf from stone and commutator. I have had problems with resurfacing stones that are too hard and just pickup copper plugging the grit at any speed. A trip to a grinder or belt sander is needed to scrub off the plugged grit.
I have quoted Med, and fine stones, start with Medium and switch to fine if needed.


The seater stones are very soft, and break easily so I use the largest size. They create a nice stream of grit to contour the brush. Insure spring pressure has been reset if changed for the resurfacing.
I quoted Med hard and Med soft. Start with the hard first, if it just plugs with copper, try the soft. Fairly light pressure is needed to work properly.

I have been on a job sites and ordered just one of each stone, only to have trouble with one or both of them. The 4 stone mix seems to provide something that will do the job, even if you break the resurfacing stone on your first try.

Motor speed for these operations is only 200 to 500 RPM. Too slow the stones chatter, and too fast they plug up.

Bill

I'll be sure to order the stone set. I'll also try to get the brush set from Monarch. I'm going on travel for three weeks, so I'll not be able to post any results, but that gives me plenty of time to order the right tools.

Talk to you guys then. Thanks for all the tips.

...and I'll look for the clamp ammeter. I'm guessing you wouldn't recommend getting one from Harbor Freight.

For just checking the phase currents and other hobbyist level stuff, the HF meter will do just fine. If you were using it to earn your living, that would be another thing.

I have an Elenco ST-3030, which has a Hall-effect sensor and can read DC amps as well. I'm very pleased with it. (Elenco is a US company.) If you're looking for a little better meter, consider that one.

Cal

Back from my travel and while I was on the mainland (no Harbor Freight in Hawaii) I picked up a very inexpensive clamp ammeter ($15). Also I ordered two different kinds of dressing sticks from McMaster-Carr.

My first job was to figure out why my brush ring could not be tightened. I discovered that the previous owner had installed a spacer in the gap of the clamp. I was a little hesitant to remove it, but did anyway and the clamp now works as it should.

Next I decided to do a little cleaning as it is a recommendation in this thread (thanks Monarchist). As I wiped away the grime on the brush ring, I noticed the words "Neutral" with an arrow. A little more wiping and a small tick mark emerged showing the neutral position of the brush ring. To my horror, the brush ring was about 35 degrees away from neutral!! After positioning the brush ring at neutral and tightening the clamp (which works now), everything is A-OK! No sparks are visible! No overheating and no burnt rubber smell. I proceeded to clean the bars with the dressing sticks I got and it's a nice bright copper color now. I never measured the current but I'm happy to have a new clamp ammeter anyway.

Thanks to everyone who helped me troubleshoot. It was pretty depressing to have a giant paperweight in my garage. Now my Monarch is purring and back in action.

I'm glad that you got it figured out. And thanks for getting back to us with the results. You wouldn't believe the number of people that drop in with a problem, get some suggestions and never bother to even say thanks.

Cal