INTRODUCTION
People often have water inside their hub motors for quite long periods of time without actually noticing it, for the most part it takes a long time for water inside the motor to actually cause damage that you as a rider can notice,
there's cases where water might be sitting in there for months and months before any kind of symptoms show up like the motor being stuck when it freezes, other cases that are signs that you could have water ingress, is erratic behavior with the HALL sensors because water can saturate the electrical connections between the HALL signals and cause those signals to lose integrity or get sort of pulled to ground so your motor controller can't respond appropriately.
This problem gets even worse on e-scooters because of the physical size of the wheels
the hubs are way more close to the ground than an e-bike wheels are, making water ingress on e-scooters much more likely to happen, just a simple puddle in the road can bring easly water inside the hub.
This problem gets even worse on e-scooters because of the physical size of the wheels
the hubs are way more close to the ground than an e-bike wheels are, making water ingress on e-scooters much more likely to happen, just a simple puddle in the road can bring easly water inside the hub.
HOW WATER CAN GET INSIDE THE HUB MOTOR?
So you might be wondering how did all this water got inside your hub motor in the first place
If you ride in the rain or if you go over big puddles, water will eventually find it's way inside the motor, even if the hub motor is protected and well sealed against water ingress.
There's basically three ways on the electric hub motors for water ingress:
1. The first and the most obvious is the motor side plate seals, when a hub motor is put together there's just a flat surface linking the rotor with the magnets to the side plate, there's usually some kind of a sealant or silicon material prior to close up the motor side plate, so you get a good full seal, but some times the sealant could be made of a bad quality or was just misapplied (There's been cases I've seen large gaps in the seal or sometimes it's just omitted completely), so that's one of the kind obvious vectors that can be solved.
2. The second source of water ingress would be through the axle and the ball bearings,
(this is the most dificuld challenge to solve)
Some hub motors have a rubber shaft seal that forms a pretty tight bond on a smooth portion of the motor axle so as the side plate spins it's generally got a double lip rubber seal against the shaft so you don't get too much water coming in but some hub motors lack any kind of seal on the shaft and in another cases that seal gets compromised due to poor quality or bad design,
you can't have a 100% waterproof sealed axle and ball bearings, that's impossible but a good design and some ingenious solutions can improve the prevention of water ingress by 98%
3. The third and kind the less obvious but possibly the most common source of water ingress is through the insides of the cable itself,
the cables themselves all go into a sheath and it's very common that that sheath could not be sealed properly around each of those individual wires, so if you get water pooled up from the connector area then that water can migrate its way inside the sheath through the inside of the axle completely bypassing the shaft seal and then emerge from inside the motor where the cable split out on the other side, some manufacturers know this issue and try to mitigate the problem by adding some bunch of silicone at the exit point of the cable to try to reduce the occurrence and likelihood of water ingress but the water can also travel from inside the strands of the copper wires and then emerge where the copper wire strands come out.
So when in use, the hub motors they get warm when you're riding a escooter and then when you stop running they cool down and those heating and cooling cycles cause a pressure differential to occur, it gets warm the pressure builds up and air escapes and then when it gets cool now you form a vacuum inside the motor and that vacuum is going to draw in any air to fill the voids and equalize the pressure but if there is water in that pathway the water gets sucked in so that can cause a pressure differential that sucks the water through the cable or that sucks it through the side cracks, so if the motor is cooling down out in the rain, all of the little gaps that might exist have water seam inside them so it actually draws the water in and each heating and cooling cycle can suck in more and more water.
the cables themselves all go into a sheath and it's very common that that sheath could not be sealed properly around each of those individual wires, so if you get water pooled up from the connector area then that water can migrate its way inside the sheath through the inside of the axle completely bypassing the shaft seal and then emerge from inside the motor where the cable split out on the other side, some manufacturers know this issue and try to mitigate the problem by adding some bunch of silicone at the exit point of the cable to try to reduce the occurrence and likelihood of water ingress but the water can also travel from inside the strands of the copper wires and then emerge where the copper wire strands come out.
So when in use, the hub motors they get warm when you're riding a escooter and then when you stop running they cool down and those heating and cooling cycles cause a pressure differential to occur, it gets warm the pressure builds up and air escapes and then when it gets cool now you form a vacuum inside the motor and that vacuum is going to draw in any air to fill the voids and equalize the pressure but if there is water in that pathway the water gets sucked in so that can cause a pressure differential that sucks the water through the cable or that sucks it through the side cracks, so if the motor is cooling down out in the rain, all of the little gaps that might exist have water seam inside them so it actually draws the water in and each heating and cooling cycle can suck in more and more water.
SOLUTIONS:
You've got 3 options:
1. If you can tolerate the occasional drip of oil, put some ATF in the motor and pick up the added benefit of better cooling.
2. Put a drain valve and a vacuum valve pump at the perimeter of one of the side covers to easily drain any water as well as allow water vapor to escape.
3. There's another completely opposite approach to dealing with this problem, so if you're unable to sealed water ingress from through the cables, your side plates or if you have a motor without shaft seals, you can just put large vents holes on the side of the motor itself, water will freely get in but it also gets driven out as soon as it's warm, and that surprisingly works almost as well as properly sealing a motor to prevent water damage because the water that gets in doesn't stay pooled and trapped inside the hub for long periods of time, it gets driven out every time you go on a long e-scooter / ebike ride.
How about coating the whole motor with electric sealant paint?
In my opinion I disagree with completely coating the stator or the magnets with electric sealants.
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The most I coat is the end lams (the part facing the magnets) and the circuit board for the HALLs,
I use a very specific set of coating materials, mostly I use blue wax insulator coating for the electronics (HALL board sensors) and for the rest (stator and magnets) I use a highly stretchable and conductive superhydrophobic materials for anti corrosion purposes,
I also use epoxy on the ends of the wires
sheath and on to the HALL sensors metal wire connections just for extra percaution.
these materials are excellent at thermal dissipation / distribution and will definitely prevent corrosion inside the hub motor for a long time.
I definitely would avoid coating the stator copper wiring, because it already has a high temp coating, and any more will reduce the rate at which a hub motor sheds heat.
If you coat the entire motor and magnets with regular selant paint it will most likely result having bad thermodynamics = overheating the motor, which will affect the overall performance of the motor which subsequently reducing its lifespan or in a worse case scenario having irreversible damage to the stator wiring and magnets.
I use a very specific set of coating materials, mostly I use blue wax insulator coating for the electronics (HALL board sensors) and for the rest (stator and magnets) I use a highly stretchable and conductive superhydrophobic materials for anti corrosion purposes,
I also use epoxy on the ends of the wires
these materials are excellent at thermal dissipation / distribution and will definitely prevent corrosion inside the hub motor for a long time.
I definitely would avoid coating the stator copper wiring, because it already has a high temp coating, and any more will reduce the rate at which a hub motor sheds heat.
If you coat the entire motor and magnets with regular selant paint it will most likely result having bad thermodynamics = overheating the motor, which will affect the overall performance of the motor which subsequently reducing its lifespan or in a worse case scenario having irreversible damage to the stator wiring and magnets.
Remember, the problem is not the water getting in but not letting the water out.
I've had ventilated motors since 2006 and have never had any water related issues with any of them because having a ventilated hub motor the water can escape through natural evaporation process or just by centrifugal forces caused by the rotational motion of the hub
The only problem with this option is the debris (small rocks and mud) that can get inside the hub and damage the stator and the magnets.
What solution do I use?
I use a combination of drain valve and a vacuum valve pump at the perimeter of one of the side covers and the insolation of the motor with wax insulator coating and superhydrophobic materials, I also made an diagonal triple rubber lip for the inside the axle and a inverted rubber screw for the outside axle, this inginious design (still in testing) when in rotational motion, makes a centrifugal force to expel any water that's in the entrance of the axle.
Note: the diagonal triple rubber lip and the inverted rubber screw does not exist for sale yet,
I just custom made them for experimental reasons so it's still in testing phase and it will be available soon.
FIXING AN ALREADY WATER DAMAGED MOTOR:
One of the most common unnecessary jobs people do is replacing the HALL sensors on a motor that's been water damage because the HALLs weren't working when it was wet,
I first give it a chance, thoroughly dry it and if the HALL then toggles there's no need to replace, What we need to do to prevent them from being vulnerable to water again is really seal up all around the exposed wires of the HALL board so if there's water coming in in the future it's not at risk of actually causing an electrical bridge between the ground and 5v to the signal lines.
I first give it a chance, thoroughly dry it and if the HALL then toggles there's no need to replace, What we need to do to prevent them from being vulnerable to water again is really seal up all around the exposed wires of the HALL board so if there's water coming in in the future it's not at risk of actually causing an electrical bridge between the ground and 5v to the signal lines.
Definitely we want to make sure that stator is totally dry before reassembling the motor
We also need to brush clean the side plates of the hub and the magnets if there's signs of corrosion, sometimes the water damage if it's in there long enough, will really cut into the nickel plating that's coating the magnets and protecting them, and you can get some really swollen rare earth and in that case it may be beyond the point of repair and salvage, so if you see really swelled humps of rust on the magnets that when you clean causes the magnets to disintegrate and that could be kind of a game over point for the magnets and in that case you would need to replace the magnets for a new ones (same exactly size and count)
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