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LHC
06-09-2012, 04:23 PM
Folks –

Sorry in advance for what might be a bit of an epistle. I tend to get long winded at times….

I have taken the 3 phase electric motor apart on my Raglan 5” lathe restoration project. I had connected a vfd (inverter) to it and ran it up a little when I initially removed the motor from the machine some months back. It seemed to run but there was an annoying squeak that turned into a bit of a screech as the rpms increased. I shut it down and set it aside for later, resigning myself to the fact that I would at least have to open it up and inspect the “innerds”.

Later finally arrived, and I took it apart a few days back. It’s an open frame style motor and as a result, there’s 50 years of dust and a few chips that were found inside. I gave it a good vacuuming, then wiped down the inside of the end caps with some mineral spirits to clean it up. Here’s a picture of the bits and pieces –

http://i307.photobucket.com/albums/nn286/LHC_02/Raglan%20Lathe/Electric%20Motor/1.jpg

The squeeking and screech that I heard might be traced to the surface of the armature that looks a bit scuffed, but otherwise in reasonable shape. There’s a few dings here and there, maybe as a result of chips and/or handling during assembly. Here’s a picture of the armature and a closer shot of the surface

http://i307.photobucket.com/albums/nn286/LHC_02/Raglan%20Lathe/Electric%20Motor/2.jpg

http://i307.photobucket.com/albums/nn286/LHC_02/Raglan%20Lathe/Electric%20Motor/3.jpg

Here’s a picture of the inside of the stator. Fairly decent, with some of the varnish obviously scraped from the surface in spots. There’s a large area of black “grunge” on the left side of the windings that looks like the first point of contact of oil/swarf that made its way inside the motor.

http://i307.photobucket.com/albums/nn286/LHC_02/Raglan%20Lathe/Electric%20Motor/4.jpg

----continue to part 2 posting----

LHC
06-09-2012, 04:26 PM
And here’s the inside of an end cover after I wiped it down with mineral spirits.

http://i307.photobucket.com/albums/nn286/LHC_02/Raglan%20Lathe/Electric%20Motor/5.jpg

The bearings seem to be silky smooth rotating them by hand. The grease has not gone stiff and appears to be in good shape, but I am going to have to replace it as it’s a good many decades old – if it ever was replaced, and the lathe itself is about 50 years old. Like many things on this lathe, there’s a general sense of light use and decades of inactivity.

Looking at the rims on the bearings I am able to make out some specifications but not all the numbers / letters are visible. The rotor end bearing is larger than the rear end of the motor.

They both look to be single shielded or single sealed – I am not sure how to tell myself but someone may be able to advise me on this. I can take some more detailed pictures if needed.

Here’s an example of the bearing at the rotor end. The sealed/shielded ends are the ones towards the inside of the motor, with the open ends being protected by the counter-bored recess in the ends caps.

http://i307.photobucket.com/albums/nn286/LHC_02/Raglan%20Lathe/Electric%20Motor/6.jpg

-------------------------------------
Rotor End Bearing Markings
120P V3
ENGLAND
HOFFMANN
-------------------------------------
Rear End Bearing Markings
?2037
ENGLAND
6 PT
--------------------------------------

I do not want to pull the bearings off and replace them as they appear to be in great shape. I do however want to wash out the grease and re-grease them. This brings me to the list of questions that have come to mind.

1 - How to flush out the existing grease without removing the bearings ?
My thoughts here are to immerse the ends in a little jar of gas (petrol) or mineral spirits and let it sit and/or slosh it around with a small brush to assist. Any other tricks or tips people can provide here? I guess the trick is to make sure the assembly is completely dry afterwards to ensure no contamination with the new grease being placed in the bearings. (I have read about the problems with mixing different types of grease). I have no problem letting things sit for a period of time to dry if needed – I’m not on any clock here.

2 - How much to pack into the bearing by hand when re-greasing?
From my diggings it seems to be 30-50% but I was thinking of using a syringe and poke the grease in that way, around the cage and roller elements. I understand the main purpose of the grease is to contain the oil for the bearings and too much will end up overheating etc.

3 – A friend of mine has recommended the use of NLGI-2 grease for this application and sent me a great .pdf from Exxon Mobil explaining the ins and outs of greasing electric motor bearings. I’m going to search out this stuff later this week. However, looking though this document revealed that the greasing “ports” on my motor are not like the standard industry things on the larger HP motors. There’s a single port with a little screw in the end that you take out for adding grease, but there’s no “exit” port to allow for flushing the old grease etc. In fact, the design on the inside of the end cap shows a very small opening where the grease could get into the open side of the bearing. This has me to wondering if it’s even of any use. I mean you can only jam in so much grease with no exit being provided for ! Being ignorant on this subject, I must admit that I poked some oil in these before I ran the motor up for the first time. Anyway, if anyone has some comments on all this – fire away.

Here is a picture of single port on each end for grease. Note that the orientation on the machine is as shown here – the electrical fitting coming out the bottom and the grease port/tube running horizontal. Not exactly a gravity feed system !

http://i307.photobucket.com/albums/nn286/LHC_02/Raglan%20Lathe/Electric%20Motor/7.jpg

Here’s the inside of an end plate showing the grease entry point into the open side of the bearing – not that large really. And again – nowhere for the grease to exit.

http://i307.photobucket.com/albums/nn286/LHC_02/Raglan%20Lathe/Electric%20Motor/8.jpg

Sorry for the long posting – I tried to get all my thoughts questions and pictures together in one place ! Better than not enough info I guess...

Thanks very much for any help people can pass along.

Cheers,
Lewis

darryl
06-09-2012, 04:53 PM
Well I've never seen a ball bearing set up like that to be greased without removal. Where does the excess grease go? Nowhere except back into the housing in front of the bearing. The inward face of the bearing might well be sealed, which would be evident by seeing a rubber-faced disc pressed into the end of the bearing rather than a steel-faced disc. The steel-faced 'end cap' is a shield rather than a seal. I can't really tell from the pics, but if they are seals, then grease should not be able to get through. If they are shields, they can be washed through from the open side.

I would not use any solvent that has additives that could be left behind once dry. That eliminates gasoline, but white gas would be ok, or any of the other normal solvents could be used. My favorite of late is brake clean, since it's easy to blow into bearings to get the dissolving action spread into the bearing carriers. You definitely have to be careful of it splashing back into your face or on your cloths.

Also my favorite of late has been synthetic wheel bearing grease. I just work it in with my fingers from one side until it looks clean coming out the other side, then wipe out the excess from both sides and call it good. I've had pretty good luck at removing and re-installing the shields or seals without damage, but that's a learned skill as well. With one side open already, you might be able to poke a wire through to push the other seal out. In your case the seal would stay on the motor shaft, but at least you get to clean the residual gunk away. Snapping the seal or shield back in is easy, but make sure you get it fully re-seated.

John Stevenson
06-09-2012, 04:56 PM
Ain't got a clue mate, never seen inside an electric motor before ...........

MaxHeadRoom
06-09-2012, 04:57 PM
Personally I would remove the bearings and replace with modern sealed types, if the rotor rubbing was caused by bearing wear then then they need replacing anyway after 50yrs use.
Mic the OD ID and width and any local bearing co will come up with the equivalent.
Max.

LHC
06-09-2012, 05:11 PM
Darryl -
Thanks for the tips. I'll take a closer look at the inside face of each bearing and see if it looks like metal or rubber. It seems to me it's metal, which as you say would indicate it's a shield. I agree, the fact that there's no exit point for the grease is odd. Perhaps the end cover castings are some sort of universal thing and the ports are not even meant to be used. White gas = mineral spirits ?

Max-
My plan "B" (distant one at that at the moment) is to remove the bearings and replace with modern ones, but I don't really have the gear to do that, and from the always accurate and never wrong youtube site - I see these fancy things called induction bearing heaters just so that you can slip them over the shaft when installing them.

LHC
06-09-2012, 05:15 PM
Ain't got a clue mate, never seen inside an electric motor before ...........


Now you have ! :D

darryl
06-09-2012, 05:25 PM
From this far away, those bearings don't look bad. I am tending to think that the worn markings you're seeing on the armature and field is due to foreign material having gotten in there and rubbed around all these years. But it certainly is possible that the armature is not centered within the field- the endbells could be allowing for that if they don't center perfectly or without play when re-assembled. Of course, if the bearings aren't a snug fit in their bores, that would allow the armature to go off-center as well.

An aside- I just took apart a dust collector motor that had failed. The bearings were still fairly good, at least they weren't sloppy and gritty. This particular motor had some areas where the windings has shorted to the field laminations. A couple of the lamination tangs had been blown to bits and the copper windings blown to bits in spots. I wanted to save the field laminations for another project, so I had to remove the windings. With any well-made motor this would involve cutting into the wire bundles as there would normally be a varnish or whatnot impregnated into the windings. Not so here- this was a typical shi**y chinese motor with no varnish and only minimal 'string' holding the bundles together. The string had all gone rotten- it was all over the inside of the housing in small pieces, and what remained on the wiring was breaking off easily just by wiping with my fingers. Pair of side cutters and five minutes I had all the wire removed. It should not have been nearly that easy.

LHC
06-09-2012, 05:40 PM
Darryl -
No issues with lack of varnish on this motor - there's residue all over the place and the field windings look like they are really tight and glued together with it.

I just ran out to the workshop and checked - the closed end of each bearing is metal - not dark rubber. So it looks like I have single side shields on these bearings. There`s no hint of grinding or rough running when turning the bearings by hand - they are as smooth as silk.

And an unrelated question to the bearings - is there an easy way to wash off the black goo that has accumulated on the inside of the field windings in one spot over the years? I seem to recall that WD-40 would work but I don't want to use something that's going to strip off the varnish. I could just leave as is if there's any doubt as there is not that much of it.

Thanks,
Lewis

J Tiers
06-09-2012, 10:45 PM
There are various spray-on cleaners/washes, like "Electro-Wash" and the mass air flow sensor cleaning sprays. They are made of materials which don't damage most electrical stuff. Electro-Wash would be my first choice.

As for the greasing, there are supposed to be TWO ports..... you remove the covers/plugs, put a fitting on one, and pump in grease until it comes out the other one. Then remove fitting and replace plugs.

The two are normally located so that you won't fill the bearing, which would be bad.

You don't have two grease ports, so I reckon your plan of removal and manual re-greasing is best. The new grease should last a good long time.

The new Departure manual suggests a hot solution of "Oakite" cleaner, which sounds similar to purple cleaner, a strongish base. Possibly it is washing soda based. Another suggestion that I am told works quite well is pine-sol.

Yes, these are water based, but you can do a WD-40 dunk, or another light oil wash-thru, and/or use a hair dryer to dry them, while manually spinning them to assure the water is gone. Using hot solution helps also.

darryl
06-09-2012, 11:03 PM
-'while manually spinning them'- this avoids the temptation to see how fast they will spin up using compressed air. Something to be avoided unless you want to destroy the bearing.

LHC
06-10-2012, 08:03 AM
-'while manually spinning them'- this avoids the temptation to see how fast they will spin up using compressed air. Something to be avoided unless you want to destroy the bearing.

:D I can remember once a long time ago in a friend's place of work using the compressed air to spin up an old turbine and marveling at the gyro forces at play as we held it in our hands.....

Deja Vu
06-10-2012, 08:20 AM
Folks –

It seemed to run but there was an annoying squeak that turned into a bit of a screech as the rpms increased.

The squeeking and screech that I heard might be traced to the surface of the armature that looks a bit scuffed, but otherwise in reasonable shape.



I didn't see anyone addressing the squeak or screech.
I'm guessing that it was the bearing races spinning in the seats.

becksmachine
06-10-2012, 08:37 AM
I didn't see anyone addressing the squeak or screech.
I'm guessing that it was the bearing races spinning in the seats.

I was wondering if I was the only one concerned about that.

The bearings and grease look fine to me, I think the over riding problem is to figure out why the rotor looks like it has been rubbing on the stator.

Dave

Deja Vu
06-10-2012, 08:50 AM
I'm suspecting that the "rub" on the rotor was caused by an excessive radial load on the motor shaft at some time in the past.
Those aluminium end caps/housings (I think that's what they are) would have enough flex under heavy side loads to cause the rub.

I've seen motors that this "rub" appearance was actually a final tweaking of the rotor during assembly to achieve clearance.

Otherwise, as previously stated, debris got in the motor and spun around in there causing it.

LHC
06-10-2012, 08:51 AM
I didn't see anyone addressing the squeak or screech.
I'm guessing that it was the bearing races spinning in the seats.

They were pretty snug when I took the ends off the motor. I didn't mic the bearing OD and the seat yet to see if there's a lot of clearance though. I don't have an easy way of measuring the seats until tomorrow when I can get into my buddy's shop and borrow a bore gage anyway. Will check for any obvious scoring etc. in the meantime though. Thanks for the tip.

J Tiers
06-10-2012, 08:54 AM
If, as the OP says. there was crud in there, that would explain both the noise and the markings.

The bearings do not look as if they are scuffed, and if they were as free and full of grease as in the pics, there is almost no way they locked up and spun.

Normally, the forces on the bearing races are low, since that is pretty much the POINT of the rolling element bearing. only if something jams the balls will there be any such force. It IS possible to have a piece of crud get in and lock a bearing, but with the shields, and the apparent fact that they are free now, that is unlikely. The normal slow rotating "creep" due to the minute stretching of the race under load is not such as to create any squeal.

wierdscience
06-10-2012, 09:25 AM
You can simply use mineral spirits to wash out the bearings and the windings,it will not hurt the varnish.I would definitely avoid anything water based,you don't want to introduce moisture in the lamination stack.

As for the grease,it has a place to go.One side of the bearing is open correct?That side is open to the shaft bores in the end bells one of which is unsealed and open to air,and the other has a tin shield over an empty cavity.When greasing a motor or even a pillow block bearing they only take one pump of grease every year or so.The old hillbilly method of "pump it till you see grease come out" is totally wrong.

The bearings I would replace,it's what $40ish?You need a good three jaw puller anyway and an electric hot plate is a better bearing warmer than the induction heaters are in my experience.You only need 250f on a bearing to make it a drop on in most cases.

If you don't want to heat the bearing,I have installed plenty of small ones with a section of Aluminum pipe and a hammer.Just make sure the pipe contacts the inner race only and is a large enough ID to slip over the shaft.

If you want to try and regrease the bearings and reuse them,go ahead,but don't rule out the possibility of having to go back into it later and change them anyway.I am a firm believer in the concept of bearings being seen and not heard:)

lakeside53
06-10-2012, 10:22 AM
I agree -just replace them with sheilded and forget the greasing.

If you know a little about bearing numbers and quality, dig around on ebay for REAL name brand bearings of "electric motor quality". Stay away from the no-name Chinese bearings - they are rarely EM. $5-10 shipped is typical, often a lot cheaper if the smaller types.

"Electric motor quality bearings" are usually selected for running noise. If you don't care, most will work.


You don't need an induction heater. Lots of way to heat a bearing if you are careful. I use a convection oven (not a radiant oven) at 250F (165F or so so for "sealed"); heat bearing for 20-30 minutes. Cold insertion works, but heat makes it easier. A simple 2-3 jaw puller can work; a bearing spitter is better. Sounds like good excuse to buy a couple of cheap tools.

lakeside53
06-10-2012, 10:34 AM
They were pretty snug when I took the ends off the motor. I didn't mic the bearing OD and the seat yet to see if there's a lot of clearance though. I don't have an easy way of measuring the seats until tomorrow when I can get into my buddy's shop and borrow a bore gage anyway. Will check for any obvious scoring etc. in the meantime though. Thanks for the tip.

The end bells have a fairly loose fit on the bearing - they are designed to allow the bearing to "move". IMO... "feel" is the best measure. Unless they are obviously loose, they'll be fine.

Arcane
06-10-2012, 02:14 PM
It looks like that motor might have originally had bushings and at some point had the endbells bored out to take bearing.

Chuck K
06-10-2012, 09:27 PM
Is it possible that the squealing you heard was the normal sound made by a motor powered by a vfd? I've used them on a few machines and each time the motors that ran quiet when powered by a rpc made an annoying squealing noise when powered by the vfd. Just a thought.
Chuck

Abaker
06-11-2012, 07:03 AM
Is it possible that the squealing you heard was the normal sound made by a motor powered by a vfd? I've used them on a few machines and each time the motors that ran quiet when powered by a rpc made an annoying squealing noise when powered by the vfd. Just a thought.
Chuck

I never would have thought of that. I'm so used to the VFD whine I don't even think about it any more.

I have found that if you run the motor at the max Hz setting of the VFD you get the least whine. If you still have the noise after all this then try that and see if the noise drops off.

LHC
06-11-2012, 09:04 AM
Well I did a little test with a bit of the grease on the end of a toothpick and some gasoline in a little dish. The stuff did not "melt" as I was hoping, and after some time I swished it around but it still didn't have any effect. Tried mineral spirits next - same result. Based on this, a simple dunking and shaking around is not going to remove this grease easily, and will only end up leaving a bunch of solvents in the bearing. If I can't clean them out, I guess I am pretty much resigned to replacing them, or picking out most of the original grease where I can, adding more, then hope for the best.

Taking this motor apart is somewhat mindless now that I have done it and see how it's constructed. These 3 phase motors are rather simple actually. I do have a question on putting it back together though - are there any precautions as to proper alignment or do the endbells sliding onto the bearings pretty much line everything up?

I'm pretty sure the screeching and squeeking was not the vfd whine. It was too erratic at one point and certainly not the constant whine of a frequency drive.

On the boring out of the endbells - I suspect that if this is in fact what has happened, it was something undertaken by the manufacturer, as the bearings are original England sourced bearings and the electric motor and lathe are all "made in England". The place I got it from bought it new back in the 60s and I'm pretty sure they never opened up the motor - or many other parts of the machine as I am learning as I take it apart.

Also, picking up the stator assembly after I thought I had it vacuumed out, I could hear all sorts of little bits falling to the cardboard underneath I had on the bench. Here's a picture of rudest looking one.

http://i307.photobucket.com/albums/nn286/LHC_02/Raglan%20Lathe/Electric%20Motor/9.jpg

Will report back when I get a bit further along .... thanks for all the tips and advice.

lakeside53
06-11-2012, 11:34 AM
If you use spray can BRAKLEEN brake cleaner in the red can (Tertachlorethylene - the non-California stuff) it will flush that old soapy grease out. I'd just replace the bearing and be done with it. As Jerry poined you early in these posts, heat (like from a hairdryer) can help.

The end bells will line everything up. Put a dab of gas on the inside of the bearing housings.

When you assemble, run it and tap the end of the shafts with a rubber hammer to get it running with minimum noise - this is just removing any assembly stresses by freeing things up so the wave washer (assumed you have one, and if not, you should) can preload the bearings slightly.

lakeside53
06-11-2012, 11:41 AM
I never would have thought of that. I'm so used to the VFD whine I don't even think about it any more.

I have found that if you run the motor at the max Hz setting of the VFD you get the least whine. If you still have the noise after all this then try that and see if the noise drops off.


You can't just set it to max carrier unless you are operating within certain restricted parameters. Take care on old motors also.

The new Hitachi WJ200 series has a nice feature. The carrier frequency can be set such that it is at max (set) until it needs to drop based on motor power and rpm. At lower power/speed it will be as high as 12kz; at high power/speed it will be at 2khz, but you will never hear it because of the machine noise.

LHC
06-11-2012, 12:30 PM
If you use spray can BRAKLEEN brake cleaner in the red can (Tertachlorethylene - the non-California stuff) it will flush that old soapy grease out. I'd just replace the bearing and be done with it. As Jerry poined you early in these posts, heat (like from a hairdryer) can help.

The end bells will line everything up. Put a dab of gas on the inside of the bearing housings.

When you assemble, run it and tap the end of the shafts with a rubber hammer to get it running with minimum noise - this is just removing any assembly stresses by freeing things up so the wave washer (assumed you have one, and if not, you should) can preload the bearings slightly.

Thanks. Yes, I do have a wave washer. Should I just snug up the 4 long assembly bolts that are holding the two end caps and the center portion all together, before I do the run up and tapping on the ends or tighten them down well? Might not matter much I guess seeing as the wave washer is providing the correct loading anyway.

What's this "dab of gas" on the inside of the bearing housing business? (Sorry for the dumb question if I am missing something obvious here).

lakeside53
06-11-2012, 08:04 PM
Tighen the bolts on assembly.

The grease is so the outside of the bearing can slide in the bell housing; they needs to move as the rotor expands with heat and allow the wave washer to do its job.

LHC
06-13-2012, 01:20 PM
I'm back with a bit of success - or at least the hint of success. It's been a bit busy the last couple of days but I did manage to find a local source for the CRC Brakleen - original formulation (chlorinated). Did a quick test this morning before leaving the house and put some of the grease on a nail again, and gave it a squirt. Started to liquify it within a short time so that looks like it will work. Another test that I had tried was kerosene - and while it was a bit slower, it was definitely working to solubize the grease as well. After about an hour it was breaking it down and there were little bits left floating around.

So, when I can get back to the workshop I think I'll try an overnight soak in kerosene and then a few sessions of blasting the brakleen and soaking with that.

Will update when I get further along, but wanted to say thanks very much again for all the tips and suggestions. The more you learn the more you realize how little you know......

Cheers,
Lewis

Mcgyver
06-13-2012, 04:14 PM
bearings are fairly cheap. And there is the issue that unless you match the greases one can be completely incompatible with another basically making it useless. Then there's the fact that slightly pooched bearings will still seem really smooth at hand turning speeds.

imo its not worth not replacing them since you have it apart.

as for noise and the marks on the stator, a contamination of some sort now cleaned out? Set the lathe up between lathe centres. In theory there should be negligible runout at the bearings (rotate rotor not the bearing race) but if there is a bit note it and compare it to runout in the middle, that'll give a hint if its bent/warped enough to rub.

LHC
06-13-2012, 04:25 PM
bearings are fairly cheap. And there is the issue that unless you match the greases one can be completely incompatible with another basically making it useless. Then there's the fact that slightly pooched bearings will still seem really smooth at hand turning speeds.

imo its not worth not replacing them since you have it apart.

as for noise and the marks on the stator, a contamination of some sort now cleaned out? Set the lathe up between lathe centres. In theory there should be negligible runout at the bearings (rotate rotor not the bearing race) but if there is a bit note it and compare it to runout in the middle, that'll give a hint if its bent/warped enough to rub.

That's a great idea - thanks ! My lathe is too far apart to set up the rotor between centers - but - I can take it into my friend's place of work and do it there.

Mcgyver
06-13-2012, 04:48 PM
looking at the pics again it seems the rotor was marked all the way around suggesting it is not bent or badly unbalanced...else the marks would be on one side. Are they similarly all the way around the stator? if so that would support the idea that something got in there

Michael C
06-13-2012, 06:32 PM
A few years back my 10ee took to making a screeching noise everytime I went above 1500 rpm. Couldn't for the life of me figure it out. Then the motor had a wire break inside. Took the motor to shop and they fixed wire and replaced the *looks good* bearings. Noise gone even at 3000 rpms. I guess every 50,000 hours the bearings need replacing even if they look good. Funny part was guys at motor shop insisted that my DC motor wasn't original to lathe that it must have come from an elevator. I quit arguing with them and let them be right.

cheers
michael

LHC
06-13-2012, 07:59 PM
looking at the pics again it seems the rotor was marked all the way around suggesting it is not bent or badly unbalanced...else the marks would be on one side. Are they similarly all the way around the stator? if so that would support the idea that something got in there

Yes, the stator is scuffed all the way around as well, so that would support the theory of debris. Still easy enough to check the rotor for warp though and will do that in a day or so for "completeness".

LHC
07-06-2012, 02:05 PM
Well I have been jumping around on the lathe tear down and only today got back to checking the bearings on the armature. I put it between centers on a lathe at a friend's place of business, and used a mag base with a dial indicator. There's absolutely no movement on the needle as we rotated and pushed and prodded each bearing. These things are staying put on the shaft and I'm just going to wash them out and re-pack them when the motor goes back together.

Thanks once again for all the feedback and tips. The brake cleaner seems to be the only thing that will truely solubize this old grease, and using it on the end housings worked like a charm.

Cheers,
Lewis

ogre
07-06-2012, 06:08 PM
This thread has been a huge educational trip to read from beginning to end. Thanks to all who said theyre piece!