Mold in the 9C hub motor

[medusa569]

It's been some years since I got into this motor. I was going to upgrade the phase wires ( running hot and melting) wire and so disassembled it. WhenI I saw the inside of the magetics all covered in black mold and 1/2 of the stator covered in the same mold. It was not on the side where the wires are fed. Odd as I have siliconized the seam outside when they were put together. I finally got it cleaned with gel bleach and then LA'sTotally Awesomecleaner and the scotch green scrubby pad. That stuff broke down like a thin film of mud. For the future is it advisable to drill a couple of weep holes on one side of the motor of what??

 

[99t4]

Odd as I have siliconized the seam outside when they were put together.

Really impossible for us to totally waterPROOF our hubmotors. Your sealing the side plates may have helped some, but the motor's heating/cooling cycles will draw in outside humid air which can condense on interior surfaces as they cool. Very difficult to prevent this, as the air enters thru the bearings, wires, even between the wire strands.

Are you experiencing that the mold is causing performance issues?

 

[Chalo]

It's been some years since I got into this motor. I was going to upgrade the phase wires ( running hot and melting) wire and so disassembled it. WhenI I saw the inside of the magetics all covered in black mold and 1/2 of the stator covered in the same mold.

Careful that you don't expose your hub to bacterial infection by removing its protective fungus layer!

Like 99t4 says, giving moisture an effective escape is more useful than trying (in vain) to keep all of it out.

 

[calab]

The wires bring fluids into the motor through heating, the cover plates expand and contract. You take the cover plate off, and put it back on and the cover plates are a bit off or you did not mark the cover plate taking it off so its put on in the same orientation as you took it off. I've placed the cover plate on and started tightening the bolts and the lip on the cover plate did not seal, bent the cover a little. No problems, no silicone just dry bro.

 

[medusa569]

Careful that you don't expose your hub to bacterial infection by removing its protective fungus layer!

Like 99t4 says, giving moisture an effective escape is more useful than trying (in vain) to keep all of it out.

So would weep holes be better than the larger bored holes. I don't think I have a hole drill jig that deals with metal.

 

[medusa569]

The wires bring fluids into the motor through heating, the cover plates expand and contract. You take the cover plate off, and put it back on and the cover plates are a bit off or you did not mark the cover plate taking it off so its put on in the same orientation as you took it off. I've placed the cover plate on and started tightening the bolts and the lip on the cover plate did not seal, bent the cover a little. No problems, no silicone just dry bro.

I noticed I don't have the seal ( something i need to repalce but don't have parts info) Comparatively the amount of water was small but still looking to ward of rust issues. I don't think plate infiltration was it but rather water seeping along the axle and the wire inputs areas. will silicone it up better this time.

 

[medusa569]

Really impossible for us to totally waterPROOF our hubmotors. Your sealing the side plates may have helped some, but the motor's heating/cooling cycles will draw in outside humid air which can condense on interior surfaces as they cool. Very difficult to prevent this, as the air enters thru the bearings, wires, even between the wire strands.

Are you experiencing that the mold is causing performance issues?

No issues that I can discern...just a slightly different sound when running. Off pitch as it were. The first time i cracked open this motor there was no rust at all.

 

[Chalo]

So would weep holes be better than the larger bored holes. I don't think I have a hole drill jig that deals with metal.

Even small holes would allow thermal cycling from regular use to breathe out accumulated moisture. If they're small, they won't take on much water from splashes.

 

[medusa569]

Even small holes would allow thermal cycling from regular use to breathe out accumulated moisture. If they're small, they won't take on much water from splashes.

That was my line of logic as well.

 

[Chalo]

That was my line of logic as well.

It's worth mentioning that the perimeter of the side cover is a great place to put weep holes, but it's best to remove the side cover for that, because the stator coils are right there behind it.

 

[amberwolf]

And to ensure it can drain correctly, it may work best if the holes go thru the outer circumference of the cover lips, to allow the most possible water to drain from it even down to the rotor surface the magnets are glued to (so it can't pool behind them in any gaps glue doesn't fill, and potentially degrade the glue or the magnet coatings).

Note that if the holes are too small, surface tension of the water will probably prevent it from passing thru the hole. You can experiment with this with something else to find the best hole size (or a web search may find documentation of such testing somewhere--I'm sure it's been done before many times, not just for hubmotors).

 

[E-HP]

And to ensure it can drain correctly, it may work best if the holes go thru the outer circumference of the cover lips, to allow the most possible water to drain from it even down to the rotor surface the magnets are glued to (so it can't pool behind them in any gaps glue doesn't fill, and potentially degrade the glue or the magnet coatings).

Note that if the holes are too small, surface tension of the water will probably prevent it from passing thru the hole. You can experiment with this with something else to find the best hole size (or a web search may find documentation of such testing somewhere--I'm sure it's been done before many times, not just for hubmotors).

What is the mold feeding on? I see pics of motors with little pieces of paper in between the stator teeth and windings and also string/twine used to secure the windings, but not much else. Would either of those rotting out cause any issues in the long run, or are they mostly used during assembly?

 

[amberwolf]

The winding binding is there to help prevent any movement in the wires, either from vibration or from current flow changes in the wires causing movement from magnetic forces. (assuming it's bound tightly)

The paper or other lamination/winding separator is there to prevent the winding insulation from being damaged by the sharp edges of the laminations, primarily during the process of winding, but also in the event of any vibration or other movement of the windings.

If the binding fails and allows vibration, and the separator is not present, then over time the winding insulation can wear against any of the lam edges it is pulled up against, and if it cuts thru that on one, it just shorts that winding to the stator (and thus the frame in most motors/bikes). But if multiple lam/winding shorts occur, you end up with phase-to-phase shorts.

It's likely that none of these shorts will be direct low-resistance shorts, but rather tiny gaps that can be crossed by high voltage (like the pulses of battery voltage applied by the controller), which may not actually blow anything up, but could cause incorrect operation or controller shutdown for well-protected designs (but could jsut plain destroy common ones). This is what I experienced some years back testing the SFOC5 with an MXUS 450x that turned out to have a single-phase lam/winding short, which was only verifiable using this:

https://www.amazon.com/UNI-T-Insulation-Resistance-Megohmmeter-Voltmeter/dp/B0989PL99Y

Regarding the mold/mildew itself...I can't actually imagine how it would grow in there on the metal surfaces without some kind of organics to feed on. (maybe oil?)

I would expect some corrosion from enough humidity to allow mold/mildew, though, given the other circumstances I have typically seen that--except for one: "tree rust". There's a black mildew I've seen on tree branches that kills the bark layer and causes it to shed (killing the branch), which grows here in Phoenix AZ even in very dry weather. Everywhere else I see that kind of thing, it's wet or at least damp...but in this case it must be feeding on the moisture of the branch itself, though this is much lower than that of the other places I see it (it's probably a different "species").

 

[E-HP]

The paper or other lamination/winding separator is there to prevent the winding insulation from being damaged by the sharp edges of the laminations, primarily during the process of winding, but also in the event of any vibration or other movement of the windings.

Thanks for the clarification. So the paper may perform some function after assembly, but if an issue does arise, it's not necessarily catastrophic for the controller (but may be hard to diagnose). Seems like if they upgraded to some other synthetic material, then mold would be an issue. How necessary are the bindings? I only see them on some motors.