Hub motor grinding sound

S

Skedgy Sky

100 W
Joined
Nov 17, 2012
Messages
240
Location
New Britain, CT, USA
I was riding back home on this rated "48v 800watt" hub motor and about 14 minutes into the ride (3.4ish miles), or about 2 minutes from home I took this video to ask you guys.

What's causing this grinding sound? It must be heat related but the motor is only a little warm to the touch (I'd say about 30 degrees Celsius). Running it on 18s LiPo with Lyen's 12FET controller.

http://www.youtube.com/watch?v=Txdb9I6_LYo


At this point pedaling was harder than when the grinding isn't there and the wheel won't spin freely (off the ground) much.

Right after I got off the bike, I took it to the basement (about 2 minutes after getting off) back to where I usually keep it. I spin the wheel with my hand again and the grinding is gone. I power the bike back up, throttle up.. and no grinding (as far as I could hear).

Also: can someone also confirm this is a Golden Motor hub motor? ;) (was bought as a non-branded/generic kit so I have no idea what brand it is... even after all these months of having it)
 
Sounds like metal on metal noise. Could be disk brake or maybe a bearing. I say eliminate the disk break as a potential for the grinding and if it is still there, investigate the bearings.

My 2¢'s
 
parajared said:
Oh yeah! I remember now.
When I took the side cover off a magic pie I just put it back on, but it turns out you have to get the bolt holes lined up the way it came off. I fixed it by unbolting the side cover again and twisting it so the stuff didn't grind.
Click to expand...


Are you saying you had this problem come up after you put the cover back on? ... I haven't changed anything with my hub.
What exactly was grinding in yours? I cannot tell from your post. ...was it also a problem that came up after some minutes of riding?
 
I had a similar noise on one of my bikes. It came every time after I'd used the back brake for a long time or when I used it hard. When the disk was cold it had enough clearance, but when warn, its diameter increased just enough to touch the top of the caliper. I solved it with two washers that lifted the caliper up another mm to give clearance. It's best to check these easy things first before dismantling your motor.
 
Sounds like a minor rub to me too, the disk maybe, or perhaps the freewheel rubbing the cover. Sometimes a freewheel is very close to the cover, and after pedaling some, it screws a hair tighter, and starts rubbing there.

I'd not suspect a bearing first, but it could be that. I'd say just look hard for what rubs on the outside of the motor.

My dirt bike takes a hell of a pounding, and always has something on it rubbing lightly like that. Sometimes it's the rear derailur, since I may be using the largest cog, but mostly it's just the cheapie disk I have is warped.

If the wheel is really really hard to turn, and more silent, then you have a shorted phase wire, sometimes from a fried fet in the controller, sometimes from cut insulation on motor wires, sometimes from a melted winding.
 
OK, to narrow it down more. Does it happen all the time or only when you are pedaling?
 
e-beach said:
OK, to narrow it down more. Does it happen all the time or only when you are pedaling?
Click to expand...


It's not the disc brake because I have those adjusted to not touch the brake rotor. I use regen. braking for 90% of my braking needs anyway (so disc brakes get little use.. therefore do not heat up. I have also felt them after rides... cool to the touch as if they weren't used)

When it started grinding, it put some slight drag on the motor which I also experienced when I tried pedaling.
It's not a blown phase wire or anything, I've been through that already on my past controller (oops :p) and this is different. Grinding went away 3 minutes after I put the bike inside (yesterday).. so could be related to motor heating up/cooling.

It DOESN'T happen immediately. I've only been on maybe 5 bike rides so far and this may be the FIRST time it grinded to the extent shown in the video (meaning, other times either it didn't happen or I didn't notice).

It happened after 12 minutes of a mostly uphill ride home... lot more load on the motor than on the first trip I made (downhill).

I was on a pretty aggressive ride 3 days ago in the snow and on the grass... but I also made frequent stops so the grinding must have not came up then (motor was cooler to the touch too than yesterday).
...it's when I didn't make frequent stops yesterday (the video) that I heard the grinding come up towards the end of my ride.

I saw a video from someone else somewhere with a rubbing sound from his front hub a few months ago.
Quick search for the video file I happened to download of this brings me to this post:
http://endless-sphere.com/forums/viewtopic.php?f=3&t=43521 His video is in 10th post.
It sounds familiar to my hub.

I will most likely be going on another ride today and will see if this comes up again.
 
If you have regen breaking take the rear caliper off the disk break to remove it from the list of suspects. It could be misadjusted or even stuck.

Have you taken your motor apart recently?

Beginning to wonder about metal contraction in cold weather.
 
I've had the kickstand rubbing against the tire before. It turns out I moved it in toward the tire when I rubbed against a curb.
 
I came back from my ride. Again, after some time of riding (towards the end of the ride home) the hub motor started making grinding noises. I let it rest for a few minutes and they slowly went away. ...another 5 minutes and I couldn't hear the grinding anymore.

No, I haven't taken the hub motor apart and disc rotor does not obstruct anything. It freely moves through the caliper, even when the grinding happened..
 
Skedgy Sky said:
I came back from my ride. Again, after some time of riding (towards the end of the ride home) the hub motor started making grinding noises. I let it rest for a few minutes and they slowly went away. ...another 5 minutes and I couldn't hear the grinding anymore.

No, I haven't taken the hub motor apart and disc rotor does not obstruct anything. It freely moves through the caliper, even when the grinding happened..
Click to expand...

What was the air temperature during your ride and what was the air temperature when it was resting?

Also how many minutes were you riding before the sound started?
 
What was the air temperature during your ride and what was the air temperature when it was resting?

Also how many minutes were you riding before the sound started?
Click to expand...

Air temperature? .. outside? *checks weather* About 0C.

I let it rest outside... so temperature didn't change.

The whole story: I was riding.. noticed grining... stopped riding... waited for 2 minutes on side of road... then pedaled the rest of the 4 minutes home slowly (batteries were dying at this point... parallel set wasn't connected and I ended up with half the capacity that I thought I had but that's a different story...). Outside of the house I spun the motor again and the rubbing/grinding wasn't there anymore. (That's 5 minutes without power to the motor = 5 minutes of cooling that went on).
 
Skedgy Sky said:
Air temperature? .. outside? *checks weather* About 0C.
Click to expand...

0°C :shock:
I don't know how you guys do it.

OK, if you are sure you knocked the easy to check stuff off your list, nothing rubbing on the outside, then I must be inside the hub. It has to either be a bearing or part of the hub is rubbing the stator.

Perhaps the outside of your hub has contracted from the cold and the inside expands as the coils heat up the stator as you ride.

Sounds like a bit of a mystery really......

When it is starts happening have you stopped the bike, propped it up on the kick stand and manually rotated the tire to see if it is grinding on the inside of the hub motor?
 
When it is starts happening have you stopped the bike, propped it up on the kick stand and manually rotated the tire to see if it is grinding on the inside of the hub motor?
Click to expand...

Yes, I did exactly this. It was more difficult to turn than normal.
 
Skedgy Sky said:
Yes, I did exactly this. It was more difficult to turn than normal.
Click to expand...

OK, my guess is that you have a bearing going bad. Only a guess though. Maybe the grease froze...? You probably won't know for sure until the weather gets warmer. You may have to open the hub motor to know for sure..... :(
 
Certian sure it's not the freewheel rubbing on the cover? That's sooooo common.

Another possibility is a slight egg shape to the rotor or stator may be just allowing contact once the stator heats up and expands, or a bad bearing allows the stator to tilt into contact.

Might be time to remove the motor, pop off the covers, and see if there are any obvious rub marks on the stator or magnets. In the process, you can see if either bearing is obviously bad, adn while it's off the bike, see how close that freewheel is to rubbing on the cover.
 
parajared's posts sounded like they might lead me to solve this problem but he didn't post back as to whether his problem occurred after the hub warmed up.

The problem still persists, I'm about to take the hub apart. What should I look for?

It ruins the fun of riding when I have to stop for 3 or 4 minutes to let the motor cool down every now and then of riding (and when the motor's already warm, it means I have to stop every 5 minutes or less of riding).
 
Skedgy Sky said:
parajared's posts sounded like they might lead me to solve this problem but he didn't post back as to whether his problem occurred after the hub warmed up. The problem still persists, I'm about to take the hub apart. What should I look for?
It ruins the fun of riding when I have to stop for 3 or 4 minutes to let the motor cool down every now and then of riding (and when the motor's already warm, it means I have to stop every 5 minutes or less of riding).
Click to expand...

Play with bearings and see if they are grinding.
Look for warn or shinny metal where two parts have rubbed together. ie: stator against inside of covers or stater against magnets.

Good luck with it. :D
 
http://endless-sphere.com/forums/viewtopic.php?f=2&t=47474
 
I opened up the hub motor. Just as I thought, after seeing a couple of other people with this problem, there are visible marks of the stator rubbing against the rotor magnets. Since this only happens after the motor is warmed up, I don't understand... why/how it happens?

The included thread link up above just mentioned bearings, but I don't see how they can be the problem.

xuC0efp.jpg

1m9TnSw.jpg
 
Look at the cover in your pic. What I see is a completely fractured side. Have you been jumping the bike, or hitting many potholes? If those really are fractures, I'd say the thing is toast. Try pressing the bearing out. My guess is that it will crumble then.

How can a bad bearing cause rubbing?....The bearing supports the rotor and keeps it perfectly centered, so when the bearing goes, the centering becomes loose allowing the rotor to be off center and rub.
 
Maybe the covers were not put on correctly at the factory. Those cracks John talks about are they in the casting when cast or cracks ?
 
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