*video* New GM mini rear hub is wobbling! Is this normal?

Kevinator

100 W
Joined
Feb 2, 2010
Messages
145
Location
SoCal
Just got this Golden Motor mini rear hub this week. It seems to wobble like its got a bent axle or crooked bearrings. It doesn't sound like its running smoothly either...it lopes. Here's a video with the GM mini using an ecrazyman 24V/18A controller. It wobbles and sounds the same with or without the disc rotor (tried a couple), and with this controller, and another controller I tried.

[youtube]6BTMAFoT0Vw[/youtube]
 
A gear motor I had did have a similar sound, caused by an imperfect fit of the gears inside. But it was not that distinct, and did get quieter after the initial break in. Made in china. What can ya do about it, spend a fortune sending it back?
 
Yeah this sucks. My new hub motor sounds like its got rod knock.

I have no idea where the bearings are placed inside the motor, but if they're on towards the outside of the casing, I'd say the one on the drive side might be crooked. The drive side cover for the motor also doesn't appear to sit flush. If its holding onto the bearing inside, that could explain my wobbling motor
 
Kevin,

Couple of things...

1.) The drive side cover is surely not flushed down... check the threads on those high areas (where it is noticable not sealed to the hub face) to be sure they haven't stripped (many times there are 1-2 which have stripped... I just force an SAE metal thread of slightly larger diameter into the holes).

2.) Once you have the cover tightened down, remove that chineese thread on disc brake and double check the disc side cover bolts are tight and that the cover is flush with the hub all around.

3.) Put it back in your dropouts and run it again, I can't tell for sure with that disc on the mount but it looks like the actual hub flange on the disc side has a bit of a bend in it (it appears that way in the beginning of the video)... Tightening the covers will take care of the outter wobble but if there is still runout, I would pull both covers again and check the mating surfaces of the gears are aligned properly (inspect for debris also).

4.) Almost 50% of the motors (geared) I receive from China are cover out of true condition... This is normally because they strip a few threads on one or two of the mount holes (not sure if this is automated or manual mistake)... 98% of the time I can correct the errors with larger diameter metal screws and proper cover torque... a few times the issue has been internal seating but that was usually fixed by proper tensioning of the cover faces (it forced the gearing back into proper position)... a few times the actual hub flanges have been out of true and the runout was too large to correct, I've lost 3 geared hubs that way (out of more than 70 so far).

Hope that helps...

-Mike
 
Kevin, I bought a V1 that did the same thing a couple months ago. I wasn't too happy about it. With the freewheel on, it showed up even more. It became a non issue for me after I installed it on the bike and found out the clutch was bad. It was a new motor ----- not a used one. I returned it to the vendor, who replaced it under warranty.
 
Kevin,

I just broke my hub down (people have been giving me crap for not posting pics of the internals) its a bit different than yours but I left some of my cover screws a tad loose to acheive that seperation you saw and yep... I had the wobbles... Torqued them all down finger tight then 1/8th turn further and wobble be gone!

A quick fix for those with freewheel wobble issues:

This is normally caused by 1 of 2 issues:
1.) The hub cover surface (where the freewheel contacts the hub) is not 100% flat and thus the freewheel doesn't seat correctly
2.) The hub cover itself is not true and flush.

The fix is nearly the same for both issues:
Fix 1.) Simply obtain a neoprene washer - very thin but diameter to fit between the freewheel and the hub face, this will compress when mounting and basically level out the mounting surface
Fix 2.) Somtimes, no matter if you do torque the cover bolts into place properly - there will still be a bit of "runout"... this can also be corrected with a gasket, you can order plain engine gasket DIY sheets and cut your own gaskets for this purpose... when torqued into place the gaskets should handle the uneven nature (within reason) and if you wanted to say coat the wiring with a conformal coating and fill with Oil... well it's not a bad start.

Hope this helps!

-Mike
 
mwkeefer said:
Kevin,

Couple of things...

1.) The drive side cover is surely not flushed down... check the threads on those high areas (where it is noticable not sealed to the hub face) to be sure they haven't stripped (many times there are 1-2 which have stripped... I just force an SAE metal thread of slightly larger diameter into the holes).

2.) Once you have the cover tightened down, remove that chineese thread on disc brake and double check the disc side cover bolts are tight and that the cover is flush with the hub all around.

3.) Put it back in your dropouts and run it again, I can't tell for sure with that disc on the mount but it looks like the actual hub flange on the disc side has a bit of a bend in it (it appears that way in the beginning of the video)... Tightening the covers will take care of the outter wobble but if there is still runout, I would pull both covers again and check the mating surfaces of the gears are aligned properly (inspect for debris also).

4.) Almost 50% of the motors (geared) I receive from China are cover out of true condition... This is normally because they strip a few threads on one or two of the mount holes (not sure if this is automated or manual mistake)... 98% of the time I can correct the errors with larger diameter metal screws and proper cover torque... a few times the issue has been internal seating but that was usually fixed by proper tensioning of the cover faces (it forced the gearing back into proper position)... a few times the actual hub flanges have been out of true and the runout was too large to correct, I've lost 3 geared hubs that way (out of more than 70 so far).

Hope that helps...

-Mike

Hey Mike, thanks for all the detailed information and great suggestions! I finally got some time to play with this new hub again, so I decided to give them a try.

I removed the screws to the side cover and separated it from the motor. All the screws appeared to be ok, and came out pretty easy. The side cover slid out about 5mm and I could tell it wasnt straight, but still can't figure out whats bent. It fits snuggly enough on the axle that I cannot make the cover wiggle side-to-side very much at all, so I know its not wobbling because of any play in the bearing. When I spin the cover, its easy to see it doesn't spin true. Either the cover is poorly machined with a bearing that was pressed in straight, or the cover is straight and the bearing was pressed in crooked.

Lightly spinning the rest of the hub showed that it still has some wobble even without the crooked side cover attached, but not as much.
 
DervAtl said:
Kevin, I bought a V1 that did the same thing a couple months ago. I wasn't too happy about it. With the freewheel on, it showed up even more. It became a non issue for me after I installed it on the bike and found out the clutch was bad. It was a new motor ----- not a used one. I returned it to the vendor, who replaced it under warranty.

Derv, are you referring to a GM v1 or a BMC v1?
 
mwkeefer said:
3.) Put it back in your dropouts and run it again, I can't tell for sure with that disc on the mount but it looks like the actual hub flange on the disc side has a bit of a bend in it (it appears that way in the beginning of the video)... Tightening the covers will take care of the outter wobble but if there is still runout, I would pull both covers again and check the mating surfaces of the gears are aligned properly (inspect for debris also).

You've got a good eye Mike. I didn't even notice that bend in the flange until you mentioned it. Sure enough, looks like the motor took a drop on that spot. After running my finger long that spot, the"bend" is actually a flatspot that is at an angle to the flange edge. Fortunately the spoke holes aren't bent, but I sure hope I don't develop any cracks in that area when i go to lace this hub.
 
I wanted to mention that it appears that a 9 speed freewheel would be a viable option for people who don't have a requirement to run a disc brake on the rear, and plan to lace their own wheels. On the disc side of the motor, there's a 9mm-wide nut that goes snugs up against the inside of your dropouts.

It would easy enough (easier said than done right?) to:
1) find a 3mm-wide nut to replace the 9mm-wide nut on the disc side
2) find a few washers to make up the extra spacing on the drive/gear side for the 9 speed freewheel
3) dish the wheel enough to account for the above changes...the rim needs to move ~3mm to towards the drive side. Spoke angles will suck unless you help it with offset rims.
 
Be careful if you decide it is good enough to ride.

I had my Crystalyte 408 side cover fail, likely due to
- a similar issue with poor bearing mount creating a cyclic load.
- crapping casting quliaty, combined with
- pedal force

Eventually I had the bearing suddenly deattach from the side cover, with the end result of me laying in the middle of the road bleeding, hopeing that a car won't run over me.

I would show the videos to your supplier, and ask for a replacement.

Good luck,
Adrian
 
Kev,

If those GM hubs are the same dimension as mine, you can squeeze a DNP 9spd freewheel on but it requires some spacers as you said and some dishing to recenter the tire/wheel.

-Mike
 
Kevinator said:
DervAtl said:
Kevin, I bought a V1 that did the same thing a couple months ago. I wasn't too happy about it. With the freewheel on, it showed up even more. It became a non issue for me after I installed it on the bike and found out the clutch was bad. It was a new motor ----- not a used one. I returned it to the vendor, who replaced it under warranty.

Derv, are you referring to a GM v1 or a BMC v1?


BMC V1
 
adrian_sm said:
Be careful if you decide it is good enough to ride.

I had my Crystalyte 408 side cover fail, likely due to
- a similar issue with poor bearing mount creating a cyclic load.
- crapping casting quliaty, combined with
- pedal force

Eventually I had the bearing suddenly deattach from the side cover, with the end result of me laying in the middle of the road bleeding, hopeing that a car won't run over me.

I would show the videos to your supplier, and ask for a replacement..

Good luck,
Adrian

Ouch Adrian, your description paints a very vivid picture, and those snapshots of the broken hubs in your link sure does back it up. Thanks for the info, glad to know you didn't get run over by a car!

I had concerns about something catastrophic like that happening. I have experience with wobbling automobiles, aka "death wobble", and know that things that can set off a harmonic disturbance can shake things right off your car, or make it bounce off the ground. A bicycle may experience it less, but it'll still constantly be loading/unloading the frame and everything else unnecessarily as it fights against the gyro action that it wasn't intended for. I was going to use this on an aluminum frame, and I don't think this bike, or its folding hinge will be happy with the extra flexing.
 
I sent Golden Motor an email about my wobbling new hub motor a week ago and haven't heard back yet. I think the bearings were pressed in crooked on both sides. In the 2nd video I demonstrated how the side cover spun crooked when turned by hand. With that side cover pulled out like it was previously shown, I decided to also spin the other half of the motor, and it also wobbles! Its like bearings on BOTH sides were pressed in crooked! :shock: :roll:

The disc side of the hub doesn't appear to have a cover. Even if it did, I dont think there's any way to adjust for the wobble with shimming :( I'm guessing the weird loping sound from the gears is due to them trying to spin true around the axle while the ends have crooked bearings.

I had also posted over in the GM forums under the staff section, but no respone from GM on there either.
 
UPDATE:

So here I am 8 years later getting ready to run this Golden Motor mini 24v rear hub (#MBG24R) soon lol :lol:

I never did get any real help from Goldenmotor regarding my concerns back in 2010 and shelved the hub in favor of a cyclone mid drive.

Eventually I decided to lace up the GM mini for another project bike, but still to this day have not actually ran the motor on a bike yet. I've moved that wheelset to my current project bike now, a Tidal Force S-750 frame.
20180807_112329.jpg

I've done a lot of reading lately, trying to catch up on the ebike world. Looks like others reported issues with too much current and side covers shearing off. I'm currently working on rebuilding my battery packs. I won't be able to get this motor on the road for a couple of weeks, but it will be interesting to see how it does.
 
I had some time to tinker today so I hooked up the ecrazyman 24v controller and powered up the wheel on the bike upside down. it's been a few or many years so I forgot I had to change the phase and hall wiring order. It growled as it slowly spun a few times and stopped. Once I fixed the wiring, the motor spun up to full speed.

The wobbling isn't as noticeable at slow speed, but as the rpm ramps up, you can tell it's not balanced and the loping sound gets louder as the bike starts to rattle due to the wobbling gyrations. And as Adrian mentioned previously regarding his crystalyte 408 side cover failure, the cyclic load is obvious with the freewheel on.

I guess I'll have to shelve this goldenmotor POS again and find a replacement hub motor that has the same dimensions so the Sapim spokes don't go to waste. I'm tempted to run this motor just to see how.long it takes for the gears to break and the side cover sheer off.
 
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