Recovering a damaged DC motor

[Analias]

I recently purchased a 3.8HP treadmill motor on ebay. Unfortunately, the packing could have been better and the motor appears to have been dropped on it's spindle and the back of the motor housing broken out. The seller was pretty cool and immediately gave me a full refund including shipping. He told me not to bother shipping back.

I don't think the shaft, stator, or bearings were damaged. I discovered the damaged housing when I applied 12V DC to the motor to test if it would spin, which it did. I have this crazy idea of trying to recover the motor. I'm looking for a sanity check on my approach or alternate ideas.

Looking at the pictures, it looks like I could machine out the rough area that was created when the housing broke and replace it with a piece of aluminum machined to host the top of the bearing and press it back into the housing. The two screws holding the housing on could be used to secure the new aluminum bearing cover. Since I want to convert this motor to a servo, I could also make provisions for mounting the encoder.

Any thoughts, ideas, or caveats?

Oh, yes - that's the destroyed fan you see in the first pic that use to be on the end of the motor. I was planning on removing it and mounting a separate fan for independent cooling anyway.

-Freeman

 

[KMoffett]

Will the broken piece fit back down tight against the end plate? Or, is the bearing push out so the flake can't sit back against the end plate. If the latter, can you use a buffer block and hammer to tap the bearing back in. Then I would just use JBWeld to reattach the flake.

Ken

 

[Analias]

I thought of that Ken. It does look like it will fit back in. The problem I foresaw was getting epoxy into the bearing. The bearing would have to be pressed hard enough down that I don't see how epoxy wouldn't get into it.

 

[xalky]

Well, perhaps you could take the motor apart, do the repairs, clean it up and put it back together. This way if the JB weld oozes out you can just file it, sand it, whatever it takes, after it sets, and then just put it back together. If it's a nice clean break you could use just a regular 2part epoxy if you dont need much gap filling.

 

[iron man]

I have a bunch of these tread mill motors what is the diameter of the metal housing it fits over? Ray

 

[Analias]

I have a bunch of these tread mill motors what is the diameter of the metal housing it fits over? Ray

Oh oh... I'll let you know once I get home. Replacing the housing would be the best solution.

I'll measure the housing and the diameter of the motor body. I'll also post a picture of the label, in case that helps.

Would anything else help?

Thanks for the offer, hopefully it will fix the problem.

 

[davidh]

like above, if it fits back together, just a little adhesive as mentioned and drill and tap a couple small kmachine screws to hold it. it does not look important except to keep the bearing and shaft from exiting (thrust) and you will not be using it where a thrust load would be applied. . . . . . just thin,ing outside the box. . .

 

[Chucketn]

I, too, have several treadmill motors sitting around. I have one that a buddy twisted the armature shaft off trying to remove the flywheel. As the armature was broke inside, it was unuseable. I saved the end caps. If Iron Man doesn't have one to fit, I might. It's not the brush end, right?

Chuck

 

[rangerman]

I agree with the suggested epoxy method of repair and it's the easiest approach.

You can also just make and install a large washer/spacer with an ID slightly larger that the shaft diameter and an OD larger than the OD of the bearing.
You could then drill and tap threaded holes to attach the washer/spacer to act as a bearing retainer flange/cap in order to prevent the bearing from sliding out during operation.
Just make sure you get rid of the irregular surfaces.

 

[Analias]

Ray, Chuck;

The diameter of the body of the motor is 116.0mm. I measured it several times and it came up +-.02mm each time.

It looks like the bottom edges of the brushes got munged pretty badly and will need to be replaced. It's not wear, they both look like a chalk that was freshly broken. Where would I go to get replacements?

I've included a shot of the motor label. If anyone is wondering how I was going to drive this beast, I have a KBIC-240DS in route.

Oh, anther thing. It looks like JB weld may not be such a bad option after all. The housing came off without any problem and the bearing stayed on the shaft. I should be able to "glue" it back together without worrying about getting JB weld on the bearings.

-Freeman