Shengmilo MX02S Hub motor gear damage

[smitel]

My Shengmilo MX02S is starting to become more noisy uphill or at speed (>20km/h). Like a rubbing sound.

I've disassembled the motor to investigate and found the following.
- A red (rust?) spot.
- Many gray (plastic?) bits floating around the house near the gears
- Gearteeth with missing parts
- A mostly missing tooth

I think the grey stuff looks like it's the same color as the gears from the side, or something is getting smeared there.

My plan is to get new gears (with bearings), clean out the gunk, replace the gears.
Does this make sense?
Anybody see anything I should worry more about?
Could the clutch maybe be failing or be out of alignment?

 

[fechter]

I can see some of the gear teeth are broken off. Little chunks of gear plastic will get jammed between the gears and may be the source of your noise. If you completely clean off all the gear teeth and put new grease, it may still work. It would be good to know why the teeth broke in the first place. Finding new gears might be challenging and in most cases you'd have to replace the entire motor.

 

[amberwolf]

In the few investigated cases, gear teeth broke off either because of shock loads on the wheel (curb jumping) especially if the wheel was spinning in the air and the motor was running during landing, or because of "instant start" controllers with enough phase current to overstress the root of the teeth.

The former may crack the entire gear in places, the latter almost always just breaks off teeth at the root.


A failing clutch fails in two ways:

--it may slip when engaged, at first only under the highest torque conditions (startup, hills, etc), later under lower and lower torque until it won't engage at all. This is usually wear of the clutch surfaces.

--it may fail to disengage, so the motor doesn't freewheel. This may be caused by debris in the rollers/ramps, or corrosion.

 

[Kdubbs914]

In the few investigated cases, gear teeth broke off either because of shock loads on the wheel (curb jumping) especially if the wheel was spinning in the air and the motor was running during landing, or because of "instant start" controllers with enough phase current to overstress the root of the teeth.

The former may crack the entire gear in places, the latter almost always just breaks off teeth at the root.


A failing clutch fails in two ways:

--it may slip when engaged, at first only under the highest torque conditions (startup, hills, etc), later under lower and lower torque until it won't engage at all. This is usually wear of the clutch surfaces.

--it may fail to disengage, so the motor doesn't freewheel. This may be caused by debris in the rollers/ramps, or corrosion.

I just ran into this same problem and I bought new clutch and gears thinking I would be able to get it back on the road but the motor is not disengaging. So if I can't get it going off into the junk pile

 

[amberwolf]

I just ran into this same problem and I bought new clutch and gears thinking I would be able to get it back on the road but the motor is not disengaging.

What specifically is happening, both with the motor under power, and with no power applied but manually turning the wheel forwards, and then backwards (off ground)?

Is it this same exact motor? Is the clutch and gear unit exactly the same as the original, in every way?

 

[Kdubbs914]

The hub has been making noise for sometime but still running well. Took it apart to lube it up cause I had 4,000 miles and it's never been serviced. I found some teeth missing off the gears and I figured I would order new set and get it back up again. Well I was still riding it and on the last ride it started grinding bad even though I did lube it I lost most gears. Opened it up again the 2 of the 3 gears was shaved off. The gear and clutch set was a just off amazon I was thinking most China sets would be using the same stuff 3 years ago since it was the start of the ebike Era then.

 

[Kdubbs914]

The hub has been making noise for sometime but still running well. Took it apart to lube it up cause I had 4,000 miles and it's never been serviced. I found some teeth missing off the gears and I figured I would order new set and get it back up again. Well I was still riding it and on the last ride it started grinding bad even though I did lube it I lost most gears. Opened it up again the 2 of the 3 gears was shaved off. The gear and clutch set was a just off amazon I was thinking most China sets would be using the same stuff 3 years ago since it was the start of the ebike Era then.

When I added the new clutch it was barely turning would move but would grab at a half turn so I knew then I was in trouble with this.

 

[amberwolf]

The hub has been making noise for sometime but still running well. Took it apart to lube it up cause I had 4,000 miles and it's never been serviced. I found some teeth missing off the gears and I figured I would order new set and get it back up again. Well I was still riding it and on the last ride it started grinding bad even though I did lube it I lost most gears. Opened it up again the 2 of the 3 gears was shaved off.

Sounds like it's being used much harder than it is designed for--either too high a power level causing overheating of the plastics, leaving them soft enough to come apart under load, or too high a torque for the gear design, or if it's being used on less than smooth roads or if you have potholes or have to go on/off curbs, etc., the shock loads on the gears may rip teeth out by the roots.

The gear and clutch set was a just off amazon I was thinking most China sets would be using the same stuff 3 years ago since it was the start of the ebike Era then.

Ebikes have been a think for a couple decdes, much longer than three years.

But aside from that, there are dozens, hundreds, maybe thousands of different designs of motors, clutches, gears, etc., and if you happen to find one that fits that wasn't designed for it it's good, but lucky. Many are probably very similar...but if not identical:

Some things to check:

If the teeth are not the right size or shape, even if there are the same number, it may not correctly turn even if the teeth mate partially with the sun and ring gears.

If the teeth are the wrong number of them, the system may not be able to turn when assembled as they wont' really line up with the sun and ring gears.

Clutches can also be designed to run either direction. So you can get a clutch that fits the motor but freewheels the wrong direction.



There's also always the chance that wiring or cabling has been damaged and either phases or halls signals aren't making it thru.

 

[Kdubbs914]

 

[amberwolf]

That looks like the "peanut butter gears" that happen from torque applied to overheated plastics.