motor shaft repair 2

[humbleuser]

Hello everyone:

I have a 60HP Delco-Remy AC motor that is about 30 years old. The shaft broke on one end due to the hydraulic pump seizing (which needs to be rebuilt). I have yet to take the motor end caps off, but I was wondering if the shaft slides inside an "armature sleeve" or does the whole armature need to be taken out? Also, can the shaft be repaired or does it need to be replaced? Thanks.

 

[itsmoked]

stardelta put a lot of light on the subject.... Thanks!

Replace the motor!

 

[humbleuser]

OK. I pulled the rotor out a couple of hours ago; pretty straight forward job, actually. Looking at the broken end, it looks like it had been repaired before. The piece that actually holds the coupling hub is pressed (?) fit into a larger diameter section of the rotor. However, that part is not what broke, it's still pressed in there nice and tight. It looks to me like it needs to be drilled out on a lathe and a new section pressed in again. The other end is all one piece. Is this the proper way to fix the rotor shaft? Thanks everyone.

P.S.: Can jpg's be posted in the forums? I can take a pic of the broken shaft.

 

[electricpete]

This site doesn't have any capability for uploading files.

If you have the ability to place the file on the internet somewhere then you can link to it or include it in your post using the ubb tags.

=====================================
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[stardelta]

In my last posting I mentioned boring out the broken shaft from the rotor and replacing it. This is the ONLY way to guarantee that the strength of the shaft is not compromised, in fact a replacement shaft made from a modern steel such as EN24T may even be stronger than the original given the age of the motor. Any attempt to repair by sleeving stubbing etc will dramaticaly reduce the load carrying capacity of the shaft as the amount of metal will have been reduced and joints introduced, this will result in a unreliable repair. Shaft replacement is indeed straightforward and routine for competent firms but despite looking relativly easy is in fact a complicated procedure involving lathework, keyway cutting, pressing, heating balancing and testing and its best left to the experts.
The way I see it is that you have two problems here, the snapped shaft is one of them but this is a secondary issue and relatively easy to overcome by replacement. The second and more serious problem is WHY it snapped in the first place. My thoughts would be to find out how it happened as shafts do not snap without good reason. Then base your next move on the findings. You might pay a large amount of money for a repair and then a week later the same thing happens and it snaps again as a result of an underlying and overlooked fault. If as you say it has been repaired before that suggests to me a sub-standard repair method was employed that if repeated will be unreliable. Alternatively a ongoing problem may exist with the driven pump that is causing the shaft to fail, this may be imposible or not cost effective to repair given the age of it. If you were in the UK I could offer more advice but unfortunately thats not the case so I suggest you contact a local company thats both reputable and a member of EASA and speak to them about it. A final piece of advice is to get a guarantee, if they wont agree to it walk away and find someone who will. This is going to cost you money to put right but make sure its the right, amount spent on the right repair, and for the right reasons.

P.S.
If you do invite comments from a repair company I would be interested to hear what they have to say.
Thanks

 

[humbleuser]

I believe the shaft broke because the bearing on the pump that it was driving was bad. The pump shaft had been cracked for a while judging by the rust across a good portion of the shaft cross section. The pump shaft, bearing and seals are being replaced. The vanes on the pump are fine. I'm calling a few places tomorrow.

 

[MikeHalloran]

So, really, two shafts have failed, the pump shaft and the motor shaft.

That sounds like a misalignment problem.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[humbleuser]

I agree that it's a misalignment problem. I think the misalignment was caused by the bad bearing on the pump. The pump has a locating ring that fits on to a frame that is mounted to the end bell. I don't believe that this frame is off center. I blame the whole thing on the pump shaft bearing.