Vent Hole to let Moisture escape

hias9

1 kW
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Jul 11, 2018
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422
Are there any long term experiences on DD hubs with a vent hole in one sidecover which is sealed while riding, but open when not using the bike?
If the bike is stored inside, could this be an alternative to painting the stator with varnish?
 
Good idea. Do you have experience with these?
I think I am going to try the standard size (M12) instead of the XS size (M6) because they are IP69k rated.
 
larsb said:
Not exactly what you ask but i’d consider adding one of those gore-tex vents if you want air in/out but not water

I can see that working as a pressure equalizer, but absolutely not working for getting moisture out.
 
On my motors which use Statorade, I have the sidecovers and the wire channel through the axle sealed.
I think moisture (as a vapor) can however still get sucked into the motor when pressure inside the motor is lower than outside.
These vents let air through, so the pressure can equalize.
Not sure however if this really helps.
 
When I think again about it, I am not sure if it really makes sense.
Wouldn't a (sealed) hub motor only suck air+moisture inside when the inside temperature is lower than the outside temperature?
Normally the inside temperature would almost always be higher than the ambient temperature.
 
Any reasonably sealed hub will not need water outlet due to splashes entering the hub. What the vent does is that it stops the suction of water into the hub when temperature and pressure goes down after driving. I think it solves the majority of the issues (i cannot prove it though)

As a comparison: I’ve had sealed controllers where water was sucked all the way through the phase wires into the controller due to the heating/cooling effect and i think hubs are subject to the same.
 
hias9 said:
Wouldn't a (sealed) hub motor only suck air+moisture inside when the inside temperature is lower than the outside temperature?
Normally the inside temperature would almost always be higher than the ambient temperature.

Hot air is less dense than cold air. When the motor cools, the air inside needs to get more dense. And since it's not completely air tight, outside air will get pulled in.
 
hias9 said:
When I think again about it, I am not sure if it really makes sense.
Wouldn't a (sealed) hub motor only suck air+moisture inside when the inside temperature is lower than the outside temperature?
Normally the inside temperature would almost always be higher than the ambient temperature.

Everything that gets hot, also can cool off. When it does cool, this is the ingress mechanic.
 
It sounds crazy, but it was proven that a hot motor cooling down can draw-in moist air through the strands of the phase wires. Of course this was in a hubmotor that was comprehensively sealed up against outside water/rain...

The trick is not to also seal the cable-ends, but to eliminate the pressure difference. This is why the goretex vent has been recommended in the past. When the motor gets hot, any moisture vapor can escape, but liquid water cannot get in.

I would still pull the motor apart and seal it with the recommended high-temp motor sealer (*red?), unless you live in a super dry desert...
 
One more aspect. Gore vents do stop condensed liquid and liquid droplets, but they pass (in or out) humidity preferentially to air (N2 O2), because H2O is a smaller lighter, faster moving and polar vapor molecule. I don't see any risk of the humotor not having plenty of gas exchange no matter the effort made to seal it up, so I wouldn't bother with the gore vent.
 
I have also sealed the phase cable ends with silicone to avoid that moisture comes inside that way.
The sidecovers are sealed with high temp silicone and also the wire channel through the axle is sealed with silicone from both sides.
I run the motor quite hot. Thermal foldback is not applied before 140 degrees celsius at the windings.
Highest I had so far was 160 degrees at the temperature sensor on the windings.
Stator has been rewinded with 200 degrees rated wire and all other components like hall sensors and insulations replaced with ones that are rated for the higher temperatures. Statorade + Cooling fins bring the temperature down quickly.

@Luke: Would you recommend adding a gore vent in this case?
 
hias9 said:
I have also sealed the phase cable ends with silicone to avoid that moisture comes inside that way.
The sidecovers are sealed with high temp silicone and also the wire channel through the axle is sealed with silicone from both sides.
I run the motor quite hot. Thermal foldback is not applied before 140 degrees celsius at the windings.
Highest I had so far was 160 degrees at the temperature sensor on the windings.
Stator has been rewinded with 200 degrees rated wire and all other components like hall sensors and insulations replaced with ones that are rated for the higher temperatures. Statorade + Cooling fins bring the temperature down quickly.

@Luke: Would you recommend adding a gore vent in this case?

You can rest easy knowing if it was able to get hot without without issues, its going to get the atmosphere back inside itself just fine when it cools off if you add a vent or not, even with anti-capillary anti-wicking wire (typically silicone or urathane goop impregnated between the strands all the way down the jacket from the wire mfg), its going to exchange gas and vapor like it was un-impeded through shaft seals and interfaces (though they may be excellent at keeping out liquids).

A good amount of the RnD testing I do is performed under hard vacuum conditions. Its kinda silly the amount of effort it takes to seal reliably over chamber thermal cycles and the effort to seal pass-throughs to be gas tight, I wouldn't feel any risk hazard of it happening by accident with hubmotor parts and seals.
 
Sooo...the recommendation concerning moisture and corrosion inside the motor is...conventional vent (not the more expensive goretex), and red motor sealant on the stator?

(It's my understanding that over 100F, any moisture evaporates easily...)

https://endless-sphere.com/forums/viewtopic.php?t=34135#p500686
file.php
 
I read the thread, didn’t really see any hard facts though, just one guy renovating a hub..why did you link it?

there was a link to a Justin video (that i didn’t have time to watch yet): http://www.youtube.com/watch?v=gwlbAJLzI_w
 
spinningmagnets said:
(It's my understanding that over 100F, any moisture evaporates easily...)

Over 100C maybe, which should evaporate all water. :lol:

If someone has moisture problems then a hole, not a vent, would be needed. Like a 1" hole with a plastic plug. Take out plug from time to time to dry it out. Otherwise keep closed.
 
Comrade said:
spinningmagnets said:
(It's my understanding that over 100F, any moisture evaporates easily...)

Over 100C maybe, which should evaporate all water. :lol:

About 80F (not C) water begins rapidly evaporating as it is a "chainlink" molecule. So at 100F it will rapidly evaporate, given a less-than-100% humidity level in the air within a given space.

100C *boils* the water, which fairly ensures vaporization, but it will evaporate rapidly well below that. ;)
 
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