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Setting up a worn-out motor armature in a steady rest.

52 Ford

Stainless
Joined
May 20, 2021
Air gap isn't a concern for this question.

It's a very old repulsion motor with hand-stacked laminations and a very generous air gap which predates the practice of rotor balancing. Can't replace the shaft because the lamination stack isn't welded or poured. All of the laminations are held in place by a key on the rotor shaft and compressed by a big nut. Once removed, I'd never get a new shaft back in and the whole thing would be junk.

The motor is fitted with extra-large, 3" long bronze bearings which are held in place by lots of iron and are more than adequate to handle the vibration caused by the bow in the shaft. These motors are known for having bad vibrations anyways because they were never balanced. That technology didn't exist when they were produced. Even with the bow in the shaft, the motor runs just fine. As they say, "If it ain't broke..."

The only part of this rotor I would be machining for the purpose of this question is the power output shaft since the undersized bearings have taken up the journal wear just fine. This output shaft needs to be concentric to the axis of rotation when installed in the motor, therefore the shaft journals are the correct surfaces to reference when setting up, not the lamination stack.


On another note, is there any reason a guy couldn't stick weld the power output shaft to build it up before re-machining? Or are submerged arc/spray welding processes necessary for this? I know those are frequently used on bearing journals to minimize distortion, but for an overhung shaft that's already shit-shot to begin with...
I guess my only concern would be hardening/embrittling it accidentally.
If I were to stick weld it, I'd fill the keyway with 6011 and then do the majority of the build up with 6013 or 7018 (whatever you have on hand). I wouldn't bother with fancy preheat or post heat. On a 1" shaft, I'd stick to 1/8" or 5/32" electrodes. 3/32" 6011 (or 6010) to fill the keyway and the old centers on the ends of the shaft.

Ideally, you'd use a rotary weld fixture, but you can get by just fine welding stringers along the length of the shaft.

Opportunity for a lot of good welding practice. :)

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52 Ford

Stainless
Joined
May 20, 2021
So how does one achieve a good welding ground on a shaft which is to be spiral-welded? Would be a real shame to blast pits into the journals...

One really easy way is to tack weld a bolt to the end of the shaft, ground to that, then remove the bolt and grind the tack welds off.

That is what I'd do. Another option, if you have the enough shaft length would be to clamp to the worn area of the shaft, weld up to the clamp, then move the clamp onto the part that's already welded.

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Big B

Diamond
Joined
Jun 26, 2009
Location
Michigan, USA
You can't weld it up and bring it back to specs until you have found center.
If the journals are bad you can't use them for your steady.
We would have two choices, on a heavy motor ( >100 lbs ) which is 95% of our rotor rebuilds.

The easiest is press out the old shaft and press in a new shaft.

The other option is to use two four jaw chucks, one on each end so it can be adjusted to perfect using a dial indicator, ( finding a good surface for your dial indicator on a rotor or armature that has been damaged may be a challenge ) then turn a journal for your steady to ride on. Set up your steady, remove your tailstock chuck, drill the end of your shaft, you may have to use a cutting tool to cut the hole true if a existing center hole won't allow you to drill a perfect hole, switch to your center, and remove your steady.
Now you can turn your shaft and journal down until it is true, weld it up, and turn it back down to specs.

A rotor that is swinging off center, or out of balance will cause vibration and destroy components.

I made my tailstock chuck adapter for a South Bend Chuck. I can just screw it off my small South Bend lathe and screw it onto my tailstock adapter when needed.

PS having a live tailstock makes it easier to attach a chuck but it can be done on a conventional also. It just takes a little more work to make the chuck live.

I'll have to post my adapter online when I get a chance, so you can see how simple they can be.

Our electricians used to send us armatures that had damaged shafts and although I didn't do the work beyond cutting a new keyway in the shaft after it was repaired, I paid attention to what they were doing throughout the process. And they did it pretty much like you describe but it seems like they did the welding first and then did the center and turning so that warpage from welding wouldn't be an issue. Most of the motors were from about 10 to 50 HP. Anything smaller and they scrapped it and bought new unless it was something special. From time to time they also put new shafts in them but those jobs never made it into my area as the machining was done before the press work.
 

Big B

Diamond
Joined
Jun 26, 2009
Location
Michigan, USA
Air gap isn't a concern for this question.

It's a very old repulsion motor with hand-stacked laminations and a very generous air gap which predates the practice of rotor balancing. Can't replace the shaft because the lamination stack isn't welded or poured. All of the laminations are held in place by a key on the rotor shaft and compressed by a big nut. Once removed, I'd never get a new shaft back in and the whole thing would be junk.

The motor is fitted with extra-large, 3" long bronze bearings which are held in place by lots of iron and are more than adequate to handle the vibration caused by the bow in the shaft. These motors are known for having bad vibrations anyways because they were never balanced. That technology didn't exist when they were produced. Even with the bow in the shaft, the motor runs just fine. As they say, "If it ain't broke..."

The only part of this rotor I would be machining for the purpose of this question is the power output shaft since the undersized bearings have taken up the journal wear just fine. This output shaft needs to be concentric to the axis of rotation when installed in the motor, therefore the shaft journals are the correct surfaces to reference when setting up, not the lamination stack.


On another note, is there any reason a guy couldn't stick weld the power output shaft to build it up before re-machining? Or are submerged arc/spray welding processes necessary for this? I know those are frequently used on bearing journals to minimize distortion, but for an overhung shaft that's already shit-shot to begin with...
I guess my only concern would be hardening/embrittling it accidentally.

Our plant used to weld a lot of motor shafts and then machine them back like new. Sometimes it wasn't a matter of cost to replace the motor. It was the cost of shutting down an assembly plant while you wait for a new motor.
 

Big B

Diamond
Joined
Jun 26, 2009
Location
Michigan, USA
So how does one achieve a good welding ground on a shaft which is to be spiral-welded? Would be a real shame to blast pits into the journals...

I don't recall ever seeing a shaft spiral welded in my time working. We didn't have a fancy welding positioner and the welders just started the weld closest to the armature and welded towards the end of the shaft, alternating welding one side then the opposite side. It was going to need a new center, turn the diameter and cut a new keyway anyway so it didn't really matter if it warped as long as there was something to indicate off of.
 

HappyWyo

Aluminum
Joined
Nov 30, 2019
Air gap isn't a concern for this question.

It's a very old repulsion motor with hand-stacked laminations and a very generous air gap which predates the practice of rotor balancing. Can't replace the shaft because the lamination stack isn't welded or poured. All of the laminations are held in place by a key on the rotor shaft and compressed by a big nut. Once removed, I'd never get a new shaft back in and the whole thing would be junk.

The motor is fitted with extra-large, 3" long bronze bearings which are held in place by lots of iron and are more than adequate to handle the vibration caused by the bow in the shaft. These motors are known for having bad vibrations anyways because they were never balanced. That technology didn't exist when they were produced. Even with the bow in the shaft, the motor runs just fine. As they say, "If it ain't broke..."

The only part of this rotor I would be machining for the purpose of this question is the power output shaft since the undersized bearings have taken up the journal wear just fine. This output shaft needs to be concentric to the axis of rotation when installed in the motor, therefore the shaft journals are the correct surfaces to reference when setting up, not the lamination stack.


On another note, is there any reason a guy couldn't stick weld the power output shaft to build it up before re-machining? Or are submerged arc/spray welding processes necessary for this? I know those are frequently used on bearing journals to minimize distortion, but for an overhung shaft that's already shit-shot to begin with...
I guess my only concern would be hardening/embrittling it accidentally.

I don't believe I have ever worked on a motor that old.
We do several a week, but they are new.
Preheat the shaft if you are worried about warping. I like to start welding on the end and work toward the center. If you start on the inside by the time you get to the end it will be so hot you will have trouble keeping the sharp edge of the shaft.
Use a piece of copper wire and wrap it around the shaft for a ground.
We use wire feed and weld (around) the shaft, but stick welding works too.
We can make a short video if you are interested.
 

Just a Sparky

Hot Rolled
Joined
May 2, 2020
Location
Minnesota

Hmmm...

That's funny. When I originally BROUGHT UP THE IDEA of replacing the shaft in this motor way back when, half the replies to my OP consisted of people telling me it was a stupid idea and would likely end in failure - and that repairing it in place was the way to go.

Now here you are trying to beat me up and sell me on the exact opposite: That my idea of repairing it in place is stupid and I should be trying to replace it instead!

Some days a guy just can't fucking win.

Go eat a Snickers bar Thermite and calm the FUCK down.
 

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52 Ford

Stainless
Joined
May 20, 2021
I like welding. :) if you don't do much of it, this would be a good opportunity for practice, since it's going to be turned down anyway and it's not structural. As long as you're not trying to do something dumb like using harface rods or aluminum filler, I can't see how you could go wrong.

An easy impromptu rotary weld fixture would be two pairs of rollers (like the kind you use to balance surface grinding wheels on their hubs). Weld a small bolt to one end of the shaft and chuck it in a cordless drill. Use a zip tie or some velcro on the trigger to set the speed. Weld a bigger bolt to the other end of the shaft for the ground clamp to run on.

Break the bolts off when you're done and face the shaft off when yer done.

:)

Sent using Morse code on - .- .--. .- - .- .-.. -.-
 

52 Ford

Stainless
Joined
May 20, 2021
Too old and too lazy to "beat up" anybody. Jest tellin' yah what works and what is too much of a time-waster.

Haven't got enough TEETH left to chaw no dam' stickey Snicker's bar.

:)

But I've made a lot of 100 HP DC motor armature shafts from scratch. For Union scale wage.
Turned corn-cob stick-weld on a lot more of 'em. USUALLY damaged in just two places, all else OK.

FACTORY shaft was cheaper as a repair part.

But when a continuous mining-machine or loader was hard DOWN, and the shaft was back-ordered, it was worth it.

It ain't ALWAYS the case, but THIS one is too far gone in too MANY of its fits .. and too dam' small to BOTHER f**king with weldup and cutback.

You want to "win"?

Take that advice on-board.

Yer welcome...
Maybe a Snickers ice cream bar? Microwave it and drink it. Maybe mix some liquor in there. :D

Sent using Morse code on - .- .--. .- - .- .-.. -.-
 

52 Ford

Stainless
Joined
May 20, 2021
*sigh*

Foodreakin' Barbarians... Junk food produces junk health...

Best Palatschinken Recipe - How to Make Austrian Crepes

Double up on the eggs and cut-in a bit of Tapioca flour to improve flex and texture

Finish in copper-bottom stainless skillet, walnut oil coated, use a see-through cover to gage progress

Serve fresh out of the skillet onto a HEATED plate...

Sub Mandarin orange segments or Bulgarian whole-fruit tart cherry preserves for the Apricot and roll it up.

Spritz with lemon juice instead of sugar.

78th year, still beating the "adult onset Diabetes" family curse.
I get two full years out of one 2-pound box of Demerara "Sugar in the Raw".

:D

Diabetes is NO FUN and NO JOKE. Knock on wood, I don't have it, but I know plenty of people who do. As far as I'm concerned Dexcom is one of the greatest things to ever happen for people with diabetes. Having the ability for someone else to monitor your blood sugar remotely is awesome.
 

52 Ford

Stainless
Joined
May 20, 2021
*sigh*

Foodreakin' Barbarians... Junk food produces junk health...

Best Palatschinken Recipe - How to Make Austrian Crepes

Double up on the eggs and cut-in a bit of Tapioca flour to improve flex and texture

Finish in copper-bottom stainless skillet, walnut oil coated, use a see-through cover to gage progress

Serve fresh out of the skillet onto a HEATED plate...

Sub Mandarin orange segments or Bulgarian whole-fruit tart cherry preserves for the Apricot and roll it up.

Spritz with lemon juice instead of sugar.

78th year, still beating the "adult onset Diabetes" family curse.
I get two full years out of one 2-pound box of Demerara "Sugar in the Raw".

:D

I'll have to try that. I haven't had a crepe in years. :)

Heck - I haven't seen "Sugar in the Raw" in years. Good stuff, though!

Come to think of it - I haven't seen/done a lot of stuff in years! CoVid and all the other shit going on in my life. Been holding off on the shop expansion since the start of CoVid... I started on the shop right before CoVid. Literally working on a dirt floor in part of the shop right now.
 

52 Ford

Stainless
Joined
May 20, 2021
Dasn't take long to make 'em. Same again any sort of fruit desert from tinned, fresh, dried, or a mixture.

Keeps me away from buying trash foods. Saves a short ton of CASH, too!



You can still see enough of the floor to tell what material it is?

Sounds like a bad case of Old Iron deficiency anemia to me.

An "old iron enema" sounds awfully painful. I think I'd prefer to stay deficient. :D

Seriously, though, so much of my floor is covered in random shit I can't tell WHAT I'm walking on. I do a lot of blacksmithing, so it's about 25% mill scale, 25% grinding dust, then the rest is just a mix of little bits of metal and random crap. NOT FUN if you drop a small part over in that part of the shop.

No joke, if I drop a small part at the anvil and can't find it in 30 seconds, unless it's something really special, I just remake it.

Edit: The original plan was to do the entire shop in 1-1/2" granite countertop scraps, but the county made the guy tear down the building I was getting them from before I had enough. Called the place an "eye sore" (you couldn't see it from the road) and them tried to charge him $12,000 to dispose of the scrap lumber after he paid thousands (tens of thousands?) to have the place torn down. I'll stop before I get mad, though.

Edit-Edit: I actually found some real wrought iron in my driveway a year or two ago. I have no clue what used to be in my front yard, but I've found all kinds of random shit. I found a wagon wheel hub from the early 1800's or late 1700's in a creek behind my house. Maybe 100 yards off my back door.
 

Scottl

Diamond
Joined
Nov 3, 2013
Location
Eastern Massachusetts, USA
This might seem a little unconventional but I thought I'd toss it out there.

Since the shaft is bowed first try to get it bent back closer to original. Then make an oversize bushing that is a very loose fit on the worn shaft. Using whatever works for you to get the bushing in concentric alignment with the armature use thick super glue, fixturing shellac, or even bondo to secure the bushing to the shaft so your steady has a good surface to run on. Then turn the shaft as needed.

Just remember that whatever you use to secure the bushing must be reversible without harming the armature.

To get the parts in alignment perhaps 2 V blocks with packing under the bushing one to adjust the height?
 

52 Ford

Stainless
Joined
May 20, 2021
Seems Vlad Putin thought he had the second-most-powerful army in the world.

But as turns out, it is only the second-most-powerful army in Ukraine.

LOL! I'm gonna have to use that one :D

Sent using Morse code on - .- .--. .- - .- .-.. -.-
 

Tom-AMS

Plastic
Joined
Aug 27, 2020
Location
TEXAS, USA
Got a semi-hypothetical learning question here.

Suppose you've got an old motor armature with a damaged output shaft. Chewed up so bad the key seat...
How would you handle a job like this? :reading:

My first thought would be to make a new shaft and use it to press the old shaft out while pressing this new one in...

Redneck Alternative:
Re-assemble, mount motor on lathe bed, in-place of tailstock; tram parallel with lathe's ways using the mount base, or housing OD or housing end, or wherever is best. Attach wires. Run motor while using a tool post grinder to grind worn output shaft enough yo round up an area suitable for steady - or more. Once round, disassemble, hold with 4-Jaw & indicate in steady rest, drill center, or re-weld or make a press on sleeve sitting tight against shoulder; with cross holes thru which you can "plug weld" to original shaft shaft, etc.
 

jackal

Titanium
Joined
May 4, 2006
Location
northwest ARK
Haven't read all the posts in this thread, but...

If it's not too heavy, chuck up the opposite end.
Get steady rest in area to catch part.
Put a nut 1/2" or I always have these small center drilled plugs ready.
Put indicator on top of bearing area and 'lightly' tap with tailstock pressure holding the nut/ center plug against the shaft.
When it is close enough, tig weld the piece ' tack' in a few places.
Then, adjust steady to the bearings, and rip away.
If part Is heavy, get it close.
Then mount your dial indicator on the shaft and spin it around indicating off of the tailstock quill, or live center ' body'
I used to do those Macsteel heat treat oven hinge pins that way.
Those pins were 18" diameter and 14 feet long.
No friction centering them.
 

madhog

Plastic
Joined
Apr 25, 2022
A very handy addition to lathes is a rotating 4 jaw chuck to use in the tail stock.
Mount the armature in a 4 jaw on each end. One can always find some undamaged round part.
clean up an area long enough to run in a steady clean up the center
Remove, weld the shaft return to lathe , machine to size cut new keyway
If the other end is damaged repeat
 

52 Ford

Stainless
Joined
May 20, 2021
A very handy addition to lathes is a rotating 4 jaw chuck to use in the tail stock.
Mount the armature in a 4 jaw on each end. One can always find some undamaged round part.
clean up an area long enough to run in a steady clean up the center
Remove, weld the shaft return to lathe , machine to size cut new keyway
If the other end is damaged repeat
Yep. A 4 jaw in the tailstock is super convenient. Especially if you plan on running a steady rest.

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