Can a Pothole damage a hubmotor internally?

Scottydog

100 W
Joined
Oct 26, 2013
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188
I have a 8000W QS 273 13" hub motor.

A few weeks ago I rolled unknowingly a fair deep pothole at maybe 3 mph, the impact was spine breaking! I had more than ideal tyre pressure which certainly would not have helped. I couldn't help but think that could damage have occurred to the motor, maybe the stator briefly hitting the windings etc?

I don't know if it is in my head, but at times I feel like the bike has lost some immediate acceleration or response. Sometimes I feel like that motor hum you get at 2 - 3mph is occurring at higher speeds where it didn't before like at 20mph then 30mph?

Has anyone heard of an impact causing internal damage, or am I just being a bit paranoid? :shock: :D
 
Just to add to this, I tried googling this question and found lots of topics regarding potholes and damage to wheel bearings. I feel like maybe some of the hum/vibration could be shock damage to the bearings and might be worth ordering some and swap out current ones and inspect the motor when it's time to change the rear tyre?
 
With full suspension you would think the shock of impact would be spread out a bit and it wouldn’t be that likely- what’s the weight of bike and rider?
 
electric_nz said:
With full suspension you would think the shock of impact would be spread out a bit and it wouldn’t be that likely- what’s the weight of bike and rider?
With full suspension it will be worse. YOU will feel less acceleration from the pothole - but your hubmotor will feel more.
 
Scottydog said:
Has anyone heard of an impact causing internal damage, or am I just being a bit paranoid? :shock: :D
I had an impact break a magnet off on a cheap no-name hub about 15 years ago. Yes, they can definitely see damage with enough of an impact, although broken spokes are a lot more likely than damaged internals.
 
JackFlorey said:
electric_nz said:
With full suspension you would think the shock of impact would be spread out a bit and it wouldn’t be that likely- what’s the weight of bike and rider?
With full suspension it will be worse. YOU will feel less acceleration from the pothole - but your hubmotor will feel more.
I don’t understand this. Assuming a steady speed and rear suspension half way between either extension, as you hit the pot hole the rear swing arm will expand downwards into the hole, then the weight of the rider will gradually compress the spring coming to the new lower equilibrium instead of the full weight of the rider crashing down . As you climb out of the pothole, the shock will compress instead of the entire weight of the rider hitting the edge of the pothole.
 
Scottydog said:
I couldn't help but think that could damage have occurred to the motor, maybe the stator briefly hitting the windings etc?
The windings are on the stator, so that's fairly unlikely. ;)

If the rotor housing deformed enough for the magnets on it to hit the stator, it'd very likely be a permanent and visible deformation, and it might also continue scraping them after that. It would certainly have deformed your rim (probably permanently and visibly) and likely damaged or even broken some spokes. (speculation; I've never seen a motor damaged this way, but plenty of wheels that were).

If the motor windings are not glued to the stator (few are), it is possible for a sufficient impact to shift them on the stator teeth a tiny bit (by however much there is space for this on the teeth, if any; depends on how tightly they are wound and how closely to the ends of the teeth). This might change the way the fields from them interact with the rest of the motor enough to notice by sound, but I'm not sure how much it would affect actual operation. That would have to be quantified under controlled conditions in a before-after test setup.

A change in spoke tension (possible from such an impact due to rim deformation) could change the sound of the wheel by changing the resonance of the wheel to the vibrations in the motor.

A magnet could break off if it was very poorly glued, but you'd likely feel and hear this constantly during operation; the higher the current thru the motor the harder the magnet would be pulled against the stator and drag as it tries to spin.

I don't know if it is in my head, but at times I feel like the bike has lost some immediate acceleration or response. Sometimes I feel like that motor hum you get at 2 - 3mph is occurring at higher speeds where it didn't before like at 20mph then 30mph?
Do you see the same measurements of current / watts at the same battery charge level under the same conditions as before?


Has anyone heard of an impact causing internal damage, or am I just being a bit paranoid? :shock: :D
In a geared hubmotor (which yours is not) the gears can break (they're usually plastic) but it isn't necessarily the impact itself that does it, it's possibly the sudden torque increase against the teeth from them being able to spin freely in the air momentarily and then suddenly nearly stopping upon the impact. (since sudden torque application is what often breaks gearing in other applications, worse the more "lash" there is in the system).
 
Seen many a flange broken. Probably Miro selling his on the local classifieds.
Internal damage could be perhaps a broken magnet breaks loose could cause damage, a loose hall sensor would be desintegrated with a blink causing zilch. Spun axles are common, rewiring aint fun but it aint hard either.
 
electric_nz said:
. Assuming a steady speed and rear suspension half way between either extension, as you hit the pot hole the rear swing arm will expand downwards into the hole
And thus exceed the acceleration possible due to gravity alone.
As you climb out of the pothole, the shock will compress instead of the entire weight of the rider hitting the edge of the pothole.
Also correct. And rather than the whole system seeing the same acceleration, the hub (and wheel, and swing arm) will see a higher acceleration, and the rest of the bike will see a lower acceleration. That's how a suspension works.
 
In my experience the rim is more likely to get damaged than the motor:

N4qib0J.jpg


FdMdOs4.jpg


This is for trying to drive offroad with a hubmotor :wink:
 
Hi everyone,

thanks for your thoughts! So I'm a bit of a hypochondriac at times so part of me wonders if feelings like something is different is just in my head! :lol:

That said the wallop the rear end took was insane so feel like would be normal to have concern. Think ordering a set of Euro/Japanese bearings to keep on hand would be worth doing so I can at least do an inspection when the opportunity arises.

The motor is not the spoked kind so there would be no give.

%E7%85%A7%E7%89%87-005.jpg


I don't now what the clearance is between motor and stator, but on an old 5000W motor I had I remember it looked like a sheet of paper was about the most you would get.

Amberwolf, so from what I can tell current levels are the same and also peak currents on the 2 power settings I use on the switch. However there is one think that I have noticed and I am pretty sure it is since this impact. On the cycleanalyst the min voltage reading sometimes shows a random low reading like say 23V or 18V which is way less that the 62V or similar you would see normally. The cycleanalyst is connected via the thin power cable via the key switch. I was starting to think if the Fardriver was getting random voltage levels to this supply could it affect it's operation. The other thing I believe I have been noticing is a very slight change in steadiness in the throttle which hasn't become annoying yet.

So there maybe something that occured, but not motor related. The bike is running 72V worth of Chevy volt modules with no BMS for reference for about 6 years now.
 
This was the build, planning to build a second more improved one.

https://www.youtube.com/watch?v=Eqgc7Va4yyQ
 
Scottydog said:
However there is one think that I have noticed and I am pretty sure it is since this impact. On the cycleanalyst the min voltage reading sometimes shows a random low reading like say 23V or 18V which is way less that the 62V or similar you would see normally. The cycleanalyst is connected via the thin power cable via the key switch. I was starting to think if the Fardriver was getting random voltage levels to this supply could it affect it's operation. The other thing I believe I have been noticing is a very slight change in steadiness in the throttle which hasn't become annoying yet.

That would be something within the battery or between it and the controller/etc. Connectors are typically the problem, but coudl be wires or cell interconnects.
 
Not a single 10 gauge spoke broken, wow :shock: shows you the strength of motorcycle and moped rims, tires and tubes.

j bjork said:
In my experience the rim is more likely to get damaged than the motor:

N4qib0J.jpg


FdMdOs4.jpg


This is for trying to drive offroad with a hubmotor :wink:
 
amberwolf said:
That would be something within the battery or between it and the controller/etc. Connectors are typically the problem, but coudl be wires or cell interconnects.

Yeah at times the power just feels softer, bit like if the throttle sensitivity settings were set to low sensitivity. Typically when I would open the throttle the bike would just leap forward with the tyre squealing over slight rises. It just doesn't quite feel that way despite the showing that the battery is putting out the same max power.

I'll just have to keep riding it and see if anything becomes evident!
 
How new is the motor, how many miles you got on it best guess, or how long?

I notice changes all the time in my Leaf 1500w dd, but shes an old beast that takes a licking and keeps on ticking.
Strange noises come at various load levels and slopes over time. Its just everything interacting with everything else, then you got the heat cycles of the controller, motor and battery including all the wiring, things expand and things contract but nothing too out of whack should come of anything. Just be more aware of things when your riding around, put yourself in the situation where things start to change and replicate that same situation to the best of your ability until you can figure out what it is, or just put up with it. Magnets inside can deglue or even move or even get a cracked magnet, the laminations could get damaged in some way over time like shoving a flat head screw driver between the motor and cover plate and shoving it in too far damaging the laminations, trying to separate the cover plate from the motor. Perhaps hall sensors can fall out of specifications, could be the case with cheaper hall sensors installed, hall sensors can be physically damaged. Could be the controller is switching between sensored an sensorless, could be anything.
 
I don't think you've broken anything. Almost all of the time it's the rim who gets broken, or the bearings.
The fact that your tires were inflated a bit too much probably saved the motor.
 
Hi guys,

So motor is brand new (but 3 years old) with maybe 800kms on it now.


I had a friend whose 5000W hub motor failed from rusty bearings (it appeared to be) and think it reduced the air gap in the motor. though maybe it was just excessive rust internally that seized up the motor?

In any case it's hard to say if the slight groaning sound it makes on acceleration, at certain speeds or when cornering has been there all this time. I'll just keep an ear out in case things change.

I have the tool to pull the rotor apart from the stator so will order bearings and have them on hand. Likely will do this when the tyre needs changing, which could be a year from now. I don't know how tough the bearings would be but the shock was pretty severe!
 
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