Reeves drive sheave hub bore repair

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Russ Hanscom
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Re: Reeves drive sheave hub bore repair

Post by Russ Hanscom »

Have you discussed the problem with an electric motor shop? They might be able to give you the feasibility of putting a new, longer shaft in the motor.
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BadDog
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Re: Reeves drive sheave hub bore repair

Post by BadDog »

Sorry for the delay, got busy, and also trying to avoid the late night posts in favor of posting with a clear head.

spro: Thanks for the further information. I've been into lots of motors, but never changed a shaft, so the information is much appreciated. As for the welding, I've seen shafts welded in shops before, and John S was famous for all the welded and repaired shafts he used to post on the other forum. My understanding is that with reasonable care not to let the heat get out of hand in the windings, it's basically a straight up process that is done all the time. Am I wrong? Is there some trick I'm not aware of? I also would only be welding up the fillet of the joint, just a band really, not a whole shaft like JS frequently posted.

Russ: I have not discussed it with a shop. I tried to call one earlier, but found out they stop answering calls at 4 PM. Haven't had a chance to call back, but it's on the list of things to check into. If their skill and on hand setups make it cheap and fast for them to do, I'll be down there in a heart beat. Or at least get their thoughts on either welding or shaft replacement options.
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wlw-19958
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Re: Reeves drive sheave hub bore repair

Post by wlw-19958 »

Hi There,

I dug out the VS pulley. The bore is 7/8", Hub is 4" long and
the OD of the pulley is 7-9/16". It looks like this:

Image

Image


Does this look correct?

Good Luck!
-Blue Chips-
Webb
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BadDog
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Re: Reeves drive sheave hub bore repair

Post by BadDog »

That does appear exactly the same, right down to the color. I just checked the measurements and that also appears the same.
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Re: Reeves drive sheave hub bore repair

Post by BadDog »

Finally getting back on this. I knew it would be time suck due to my lack of experience in this area, so I did my other important tasks first.

So I got the motor off and disassembled. Getting the plastic fan (TEFC) on the back off without breaking it proved to be the most difficult problem so far. And I was surprised to see that there is still an inside fan, just to keep things circulating I suppose. Either I've never been inside a TEFC before (don't recall), or I just never mentally noted the inside fan. However, in this case it's somewhat important in that it obscures access to the bearing. Without a clam-shell puller or one of those nice OTC jobs, neither of which I have, getting that bearing off without damage looks iffy at best.

I also looked closer at the possibility of removing the shaft. Not to replace, but just to make extending it easier and safer without risking heat introduced to the rotor coils. I expect there is a step to locate on, though it's not entirely obvious. If not there would need to be some reference or fixture to locate the shaft in the rotor when installing. Combine all this with the lack of obvious safe support locations on the rotor coils, and the bearing risk, I've decided I prefer to leave them in place.

So, unless one of you more experienced (or not) gents shoots it down, my plan going forward is this.

1) Procrastinate a bit more (plenty to do anyway) while awaiting your review. :D

2) Mount the whole thing between centers, dial to confirm truth, and then turn a 1/2" x 1/2" locating stub on the end of the shaft. This is small enough to get well beneath the keyway and yet substantial enough to hold the stub while welding.

3) Turn an extension stub to match. I'm planning to use 4140 1" shaft as the base. Good material, machines well, and still within standard welding processes for the task. The critical surfaces (bore and od plus seat face) will be turned in a single chucking to maximize concentricity. The goal is a soft press fit. If I blow it slightly under, then the goal is a shrink fit. If over, I'll start over... ;) Part, flip, face, and add center. May do this with 4 jaw depending on TIR, but center isn't hugely critical on this piece (though someone in the future may curse me).

4) While turning both pieces, the mating faces will receive a heavy ~3/16 chamfer for welding. Ground will be set nearby on the stub shaft, insulate rotor coils, and with no conducting contact with outer bearing race, there should be zero tendency for current to go in undesirable paths. Welding will wrap the rotor coils in a wet towel, and be accomplished located with heavy tacks followed by 1/4 round stitch welds to help reduce warpage. Let cool slowly.

5) Remount in lathe using stub center only to turn weld below true mating surfaces for clearance. Just a clearance groove, so if it's out a thou, no matter (or so my thought goes).

6) Mount in mill to extend keyway slot from existing shaft through new shaft to the end.

7) Clean up the bottom of the wallowed sheave bore, press in a bushing with undersize ID, turn bore for slip fit on shaft maintaining truth on the sheave. This is just to locate the bottom so that there is no tendency to wiggle. The top 2.5" will be the real locating surface, which is the supporting the sheave belt contact area, and drive key.

8) Reinstall with new longer shaft...

Anyone see where this should be changed or improved? If I haven't missed something, or induce unacceptable warpage, this should provide a sheave easily running true enough for this task. I think there is no way this will come out with zero warp, but hopefully it will be minimal. Otherwise, I would have to weld on an over size shaft and setup to turn to size after welding. I suppose that wouldn't be too hard to do using the nose bearing in the fixed center? Not grinding shop accurate, but good enough for this?
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Re: Reeves drive sheave hub bore repair

Post by BadDog »

I should add another point that encouraged me to stop where I am. I spoke with a local shop who said they might be able to replace the shaft for less than $100 (possibly as low as $50 with rotor in hand, depending on what it needed. Now that they can see it and I can provide relevant internal measurements, maybe Monday I can find out if they can in fact do that without gambling a drive down town 45 minutes each way.

Now, off to mark other things off my to-do list...

Oh, and now I realize I forgot the rotor pic.
Attachments
shaftsm.jpg
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Re: Reeves drive sheave hub bore repair

Post by spro »

You see the shaft is contained in the rotor by sleeves and stepped shaft by which the bearings' inner race contain the location. A hub for larger extension wont allow the outer bearing to be removed or front case etc. attached afterward. In the equivalent Baldor, there are those spring type shims ( 3 -4 fingers). It is constant relocation of the bearing race, if it would creep forward. There are no set screws for this and they don't wear unless a bearing has seized but they influence position. All this stuff has to go on the shaft before building the outside.
If a larger hub is a welded extension, you can't change the outer bearing without pulling the shaft again.
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BadDog
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Re: Reeves drive sheave hub bore repair

Post by BadDog »

Very good points. But I'm not planning on changing shaft diameter. I'm only adding ~3" at the same diameter, then turning down the weld to make a single constant diameter shaft. The motor also uses the wavy-washer spring to manage expansion and preload.

The hub will be bored over size where it is wallowed out. The short inserted bushing will then be bored on size for a slip fit for the shaft. So no dimensions are changing other than length of shaft.
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Harold_V
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Re: Reeves drive sheave hub bore repair

Post by Harold_V »

4140?
Without saying too much, I strongly advise you to reconsider that decision if welding is a part of your repair. If you must use chrome moly, make it 4130. It will keep you out of trouble.

Harold
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BadDog
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Re: Reeves drive sheave hub bore repair

Post by BadDog »

Please, say whatever you like. I assume you are talking about hardening with the welding, and not being able to hold the heat due to desire to protect the coils? I thought of that, but didn't think it would be an issue in this case. On hand, it's between 4140, and hot roll or cold roll. I have other bits of reclaimed shafting, but shied away from that because I know nothing about the weldability of whatever alloy they may be, I just know they turn nice. Perhaps this is a case of not making do with what's on hand.
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Russ Hanscom
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Re: Reeves drive sheave hub bore repair

Post by Russ Hanscom »

You are trying to keep the rest of the work from getting too hot - which results in rapid cooking in the weld area. Normally a bit of preheat and the 4140 would be fine with a machineable weld. With the .4% carbon and quick cooling, a hard weld may result. A lower carbon steel might be better. Also use a 7018 rod which usually produces a machineable weld.
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Re: Reeves drive sheave hub bore repair

Post by Harold_V »

What Russ (Hanscom) said.
And, the problem isn't just a resulting hard weld. That could be managed by grinding.

If 4140 isn't subjected to proper pre and post heat treatment, the risk of cracking is very real. An armature isn't going to tolerate that kind of heat treatment, so you are well served to change the nature of the material used, even if you must resort to mild steel, which is most likely what the original shaft is made of. I certainly endorse the use of 7018 for welding.

Harold
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