Lathe Motor Failure

[Hackman]

Just posting this because it might help someone else who encounters the same problem on their minilathe. I had grinding and gnashing noises coming from the drivetrain of my lathe lately and just assumed that the spindle gear had broken a tooth off. Went in today to replace the spindle gear but it turned out to be just fine. Finally tracked the grinding noise to the motor by running the motor without the drive belt attached. I figured the bearing must be shot in the motor so started disassembling the motor to replace the bearing.

Turns out the bearing was fine, but the plastic fan blade inside the motor under the motor front cover had cracked and was making the racket.

First picture shows the motor disassembled with the front cover on the left, the motor body on the right, and the cracked fan blade sitting on the lathe. The second picture is a close up of the cracked fan blades.

Not sure what to do yet, don't really want to buy another motor, but I think it's unlikely that I can buy just a replacement fan blade. Thinking about gluing the fan blade back together, but the idea of something spinning at high RPMs held together by crazy glue doesn't seem reliable to me. I think I'm going to try stealing the fan blade from a computer fan and modifying it to fit.

[in2steam]

Don't bother with the glue, if you broke it, the chances of any glue holding at the forces for which that motor spins is next to nil. Just replace the whole thing either with a better motor or new one from grizzly.

chris

[Bloy2004]

I'd agree... the fan looks damaged and expanded beyond reasonable repair. There are good epoxies that could mount that fan as is if for some need to slap it back together for immediate use.

Please keep us involved with your probable alternate fan modification. sometime in the near future i'll be required to add a fan to a motor and am curious seeing an option for mounting a third party part.

Thanks,
Bloy

[Hackman]

I found an old computer fan in the junk box and ripped the fan blades off. The fan blades were about half an inch too wide in diameter. No problem, thinking back to my car fixing days, fan blades look like a turbo compressor turbine, motor top cover looks like a turbo compressor housing, if they can clip oversize compressor turbines to fit small housings, I'm sure I can clip the plastic fan blades to fit the motor top housing. Took some trial and error to get the right diameter, but it finally fit without rubbing. It would have been a lot easier to clip the blades on a lathe to get a constant diameter, but the tool that's being fixed is always the tool that you need.

The picture shows the clipped fan blade mounted onto the motor. It's not great, but I figure this motor is toast anyways so if I can get some more life out of it great, if not, I would have had to get a new motor anyways. I had to file out the center of the fan blades by hand to fit the shaft. It's a really loose press fit but I think it will be ok for a while. If the motor seems to work ok for a few days, I'm probably going to redo the fan blade using the lathe so the clipping and center hole are more accurate.

Tested the motor with no load and it spins up to full speed with no noise so that is a good sign.

I think I read somewhere that the sieg factory winds their own motors. Does anyone know if these motors are a standard size and if bolt in replacements can be sourced other then sieg? I looked the price up for a replacement motor on little machine shop and it was $120. Is that the normal price for a motor or is the price at a premium because it comes from sieg?

Thanks!

[vtxstar]

It is probably not toast...yet. If you knew the current draw at a specific rpm (I know, I'm living in a dream land), you basically have the health of the motor. The brushes/commutator should be the high failure items. In your case, the fan gave up probably due to heat stress on the cast/formed plastic.

If you are able to move enough air through it, it should be fine. Some form of forced ducted air would have been the other option, though there is barely enough room for anything else under there.

"Standard" motor? The mounting certainly isn't standard. The armature needed that blue epoxy for balance so they certainly aren't milspec motors.

I wonder who has replaced the motor with another solution?

[Cam129]

$120.00 for the motor is a somewhat reasonable price, it just isn't cheap, sure it would be great to buy an OEM motor for $49.00. From what I know of motor shops, chances are they could find a near match, but it would most likely cost more. Grainger is a major source of motors [Dayton brand].

From pictures and information at LittleMachineShop.com the Seig factory does indeed make their own motors. Asian motors have a history of not having reliable information on the motor label. I understand this to be true of the mini lathes.

Other people had adapted various motors to operate the mini lathe. The pictures I've seen show these motors mounted external of the lathe and the change gear cover removed. The potential safety issues are obvious. I strongly recommend against using anything other than an OEM motor, made for your mini lathe.

Your plans to replace the fan, "run it till it stops" and then buy a new motor, sounds reasonable.