An idea how to make sure there is no ingested water inside a motor

Electric Motors and Controllers
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thunderstorm80   1 kW

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An idea how to make sure there is no ingested water inside a motor

Post by thunderstorm80 » Dec 19 2018 3:11am

No matter what tight sealing you have, water/humidity will always find it's way into a motor due to pressure breathing.
I've had two ideas how you can negate the water issue.

1. What if, after every rainy ride, you would induce the motor's windings to a series of heating&cooling phases by providing a DC current into them?
More specifically, selecting one winding, and driving a DC phase current which is more or less with the proper magnitude to the resistance. Such DC current will only try to move the motor briefly until it's locked into position, so there won't be any torque you would need to resist while doing it.
When you reach 110-120degrees according to the CA, you would stop and let the motor cool back to ambient. Afterward, you can apply the same DC current again.
Since water evaporates at 100 degrees at sea level pressure, and assuming the motor can't be 100% sealed, then the motor's cavity also have that pressure, perhaps just a bit more. Boiling water need a lot of volume to take over, and so it will find it's way out via pressure breathing. Once the motor cools back it will draw again ambient air, but that would have much less water vapor contact then what you were letting out by boiling. Since not all the water will get cleared by boiling in the first phase, doing it over for a second and perhaps a third time can help.
I tend to believe, that if there was actually a pool of water inside, then there would be visible traces of condensing water vapors on the first heating phase, as it exits the motor's cavity.

2. Drilling a small hole in the motor's cover, as close as you can to the air-gap between the stator and the rotor and plugging it back with a rubber plug. After being exposed to rain, once the conditions are dried outside, you take off the plug and do your ride without it. The heating/cooling oscillations will quickly help to get rid of any ingested water, but dust/airborne road debris will be eventually collected in over the time...

3. Combining the two: Unplugging the rubber plug from #2 only when doing #1, in the safety of your home/garage, therefor eliminating any danger from dust/debris going in.

What do you think?
I tend to believe #1 is enough, since drilling a hole poses other risks for motor.

minimum   100 W

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Re: An idea how to make sure there is no ingested water inside a motor

Post by minimum » Dec 19 2018 3:24am
The BLD6343 is a M16 thread Immersion-proof Breather made of PC (polycarbonate). It maintains pressure equalisation and prevents water ingress in equipment subject to use in harsh environments. It requires a 17mm diameter fixing hole and is supplied with a O-ring and back nut for fitting. Ideally suited to equipments or instruments subjected to temperature, altitude or barometric changes. The immersion proof breather protects against distortion or other damage that would normally occur due to such changes.
If you can fit it.

Punx0r   100 GW

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Re: An idea how to make sure there is no ingested water inside a motor

Post by Punx0r » Dec 19 2018 9:09am

Weep hole as you suggest in No.1 and if your motor is nice and warm when you park up the bike all the better to help drive out any moisture.

Oh, and apply varnish/lacquer etc to the insides of the motor to resist moisture/corrosion.

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motomech   1 GW

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Re: An idea how to make sure there is no ingested water inside a motor

Post by motomech » Dec 21 2018 7:43pm

Unless the motor is totally immersed, I think any water entering will be steamed out by the heat produced in normal use and is not particularly a problem.
More of a problem, IMO, is the grit, salt and other contaminates that will build up during prolonged wet riding. For this, the sensible thing would be to do a though cleaning at the end of the rainy season, which would include re-packing the main bearings w/ water-resistant grease.
Motomech '11 Motobecane Fathom team, Q100H 201 frt. mounted, 14S Multistar LiPoly, elifebike 9-FET 17A controller. Mean Well HLG-320H-54A, Crazy Bobs on Alex DM32's 21 to 22 MPH.

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