# motor bearing problem



## major (Apr 4, 2008)

darvex said:


> I had the bearing replaced and it sounded much better, much quieter.
> 
> Now, about 3 months later, the motor is making the same loud bearing noise that it did before.


Not normal.....normally the motor bearing will outlive an EV and in most cases its owner. Something is wrong.



> My questions are:
> 
> Could I have received a bad bearing?


Yeah, I suppose, but unlikely. However it may have been damaged from improper assembly.



> Could the shaft be bent and put undue stress on the bearing causing it to be louder?


Ohhhhh! You got a bent shaft? I guess that is a question by you, not a statement. But get it checked.



> Could the bearing be improperly seated in the front motor mounting plate?


I suppose.



> Could the motor and trans be out of alignment to such an extent that the bearing is overstressed?


I suppose.



> Could there be some other reason or cause for this bad bearing noise?


I suppose.



> I am using a Lovejoy spider coupling with a plastic insert that should compensate for a small misalignment.


Cool. That can compensate for a few thou misalignment, but not a bent shaft.



> To fix the problem, I've got to take most of the system apart. I would like to replace the bearing but I'm afraid that the new bearing will also fail.


Get your bent shaft fixed. And the rest of the system inspected and/or assembled by a machinist or professional.

Also, post up some pics.

Regards,

major


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## etischer (Jun 16, 2008)

It should be easy to determine if you have a bent shaft, you can buy dial indicators from Sears. 

I vote for misalignment. Are the mounting bolt holes over sized for the bolt? Are there any dowel pins or centering rings to positively locate the shaft centerlines?


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## JRoque (Mar 9, 2010)

Hi. With a plastic insert in the lovejoy joint, misalignment should be less of a problem. I would expect that insert to disintegrate before the bearing goes out. Which of the two bearings is making the noise?

For what is worth, I bought a brand new motor off eBay that came factory boxed. Upon starting it, I noticed the bearings were busted. My guess - and by seeing one of the fan fins slightly bent - is that someone dropped it while being manufactured and damaged the bearings. I replaced the bearings myself with new, high quality ones. Are you sure they gave you a new set of bearings and not just repacked the old ones?


JR


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## darvex (Mar 29, 2009)

There are 2 locating pins in my adaptor plate so once I have the motor and trans bolted, they will always be in the same relationship to each other. 

The thought about a dial indicator is a good one. I'll have to try that when I take it apart. 

I have enclosed a picture with an arrow that shows the location of the lovejoy coupling. 

Thanks for the help.

If you have any more suggestions, please let me know.


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## major (Apr 4, 2008)

darvex said:


> There are 2 locating pins in my adaptor plate so once I have the motor and trans bolted, they will always be in the same relationship to each other.


Yeah, but in the right place?



> The thought about a dial indicator is a good one. I'll have to try that when I take it apart.


Yeah, the dial indicator is a good idea. I'd say a must. And I'd try to use it before you dismount anything. See if you can verify what is in place now.



> I have enclosed a picture with an arrow that shows the location of the lovejoy coupling.


I don't like the looks of that. I think it would be nearly impossible to keep concentricity and perpendicularity/parallelism to the necessary tolerance. And then the tailmount could be applying a bending moment which is stressing the bearing. Just speculation on my part. But I doubt if it was the fault of the bearing causing it to fail.

Another thing which is not visible on the pic is the DEH and bearing. Lubrication can be a factor with bearing failure. It is a sealed bearing? Is it open to the elements on the outboard side? Is it getting too hot? Things to consider. Normally motor bearings have 2 high temperature seals and are permanently lubricated with high temperature grease. This makes them cost more than the standard shielded std greased bearings. So, was the replacement bearing the correct one?

Regards,

major


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## madderscience (Jun 28, 2008)

If the motor shaft is bent, then it will probably be difficult or impossible to turn by hand, and/or it will probably vibrate badly when run up under no load. 

based on the photographs I am going to go with the inadequate adapter plate theory. With a large amount of standoff like that, held together by bolts it won't take a lot of force to push things out of alignment under load enough to damage stuff. 

Unless of course the 2nd bearing that failed was the /other/ bearing in the motor. Always replace in pairs 

Good luck, and stick with it. You'll get it.


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## darvex (Mar 29, 2009)

Thanks, guys, for the helpful thoughts. I'm working on it.


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## dragonsgate (May 19, 2012)

If the motor sounds good when you bench test it and the shaft is running true then the problem is in the way the motor is connected to the transmission. The adaptor plate looks questionable to me. It does not look strong enough and may be flexing. The love joy type coupler is not going to last no matter how well aligned the motor and trans are. The back and forth torque will tear the rubber spider out in no time.


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## electro wrks (Mar 5, 2012)

You need to determine if the trans. input shaft needs the support of a pilot bearing- normally mounted in the end of the ICE crankshaft. If so, it could be the input shaft bearing that's going out. Experience and some knowledge of the design of the trans. are the best way to determine this. Try moving the shaft (with the motor removed) side to side with finger pressure. If it moves at all (assuming no worn bearings), then a flexible coupling won't work- they need two rigidly mounted shafts to work properly. You'll have to figure out some way to support the input shaft or make a rigid coupling.

If the input shaft doesn't move side to side and is well supported, you'll still need reasonably good alignment for the flex coupling to work. One alignment trick I've used when I couldn't use a straight edge, laser, etc was to rotate the whole assembly by hand with no load and check for the spider binding in the jaws. If the shafts are reasonably in line, the parts are in good shape, and the spider is floating in the jaws, you're close to ideal alignment. You'll have to support the motor or, better yet, pull the trans. and have the shafts vertical to do this.

The plastic spider you using is probably a polyurethane one. The poly ones, as I recall, have several times the torque capacity of the rubber ones. Misaligned, they can put a heavy side load on shafts and bearings.

How and where is the one side of the coupling attached to the trans. input shaft? Pictures would help here.


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