BBS02 motor whine

mickyd

10 W
Joined
Sep 12, 2022
Messages
73
Location
Sunny San Diego
Greetings. Newbie to the forum today.

Wondering if any of you have experience diagnosing and repairing a VERY whiny BBS02 motor. Here's a video that compares the sound of my motor vs. my buddy's. NOTE: To rule out the main drive gear or nylon gear, they were removed in the video. That left just the motor spinning in its bearings.

https://youtube.com/shorts/XY7hkXcgps4

My motor still runs very strong and has been for a month or so, and ~200 hard MTB miles since the noise got louder. At higher RPM's, full throttle, its embarrassingly LOUD. The whine is not real obvious when in the higher gears with less motor RPM's.

Luna Cycle suggested buying a new motor core. I was tending to agree until I saw the following FAQ on the Bafang website https://bafang-e.com/oem-area/service/faqs/ under the section "Reason for motor noise and vibration?". Now I wonder if it could be an electrical noise caused by the controller, or possibly noise from the rotor bearings????

The Bafang FAQ states.....
"There may be two kinds of motor noise: mechanical noise and electromagnetic noise.

Mechanical noise:
Bearing failure
Excessive gear friction or gear failure
Rotor imbalance or poor gear positioning due to construction inaccuracies
Water or other ingress into motor housing
Resonance of motor and frame

Electromagnetic noise:
The main reason is bad matching of motor and controller. A sine-wave current from the controller is better than a square wave, and induces less noise. "

Any help / comments / thoughts appreciated.
 
E-HP said:
Was your motor as quiet as your buddy's when new?
Great question and YES it was as quiet...maybe even a tad quieter. Wish I would have done a video new. Now, its got 1250 miles on it.
 
mickyd said:
Great question and YES it was as quiet...maybe even a tad quieter. Wish I would have done a video new. Now, its got 1250 miles on it.

Then it is unlikely to be a matching problem between components, unless one or more of the components has been changed to different ones, and the noise started immediately after this.


The noise, if it has been gradually getting worse over time, is likely to be wear and tear, most likely in bearings.

As a temporary test measure you could try lubricating the internals of each bearing, one at a time, with a tiny bit of lightweight machine oil (such as 3-in-1, etc). When the noise stops or reduces, you've probably found the problem part and can replace it.

The most likely bearings to wear are the ones with the greatest load against them during rotation. So whichever ones those are are the ones I'd try first.
 
Putting oil in the sealed bearings ABSOLUETLY sounds like the path of least resistance for sure. Since they're sealed bearing, I'll get some practice pulling the seal, which I've never done. It looked pretty easy in a YouTube video I watched. I'll give it a try tomorrow.

The photo shows the 2 motor rotor bearings. The rotor blind bearing in the cover scares me the most if I have to change it since I don't have the proper puller. Its an 8mm ID, too small for an inexpensive Harbor Freight blind bearing puller that only goes down to 10mm. I might either try making a puller by heating / bending the tips of a flat blade screw driver OR.....I'll try the 'fill it up with wet bread and smash it in' method. :D https://youtu.be/y2ggE0rC3g0 I haven't been looking forward to trying that bread method but I hear it effective.

EDIT 9-19-22:
Bearing descriptions on Luna Cycle website:
Left - Rotor Bearing, 8mm I.D. - 24mm O.D. (blind bearing)
Right - Pinion Bearing,10mm I.D. - 26mm O.D.
 

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mickyd said:
Putting oil in the sealed bearings ABSOLUETLY sounds like the path of least resistance for sure. Since they're sealed bearing, I'll get some practice pulling the seal, which I've never done. It looked pretty easy in a YouTube video I watched. I'll give it a try tomorrow.

The seals are very likely not so sealed that the oil can't wick around them, so before you try removing them, try just adding a drop of the oil to the line between the seals and the races, with the bearings sitting face-up. At worst, it will just get oil on the outside. Best case it will get enough in there to change the behavior of the problematic bearing (if it is a bearing issue).


FWIW, whenever I'm troubleshooting a system especially one I'm not intimately familiar with, I tend to do the easiest methods of isolating a problem that are likely to really work. Sometimes I'll go down a dead-end path in testing that wastes time; the less time I spend on a path the less waste it is (and the less changes I do the less damage I might do to the system in the process :lol: :oops: ).


Applicable to many cases (but not all, and I don't know if it applies to this situation): If you have to remove a bearing seated where it can't be accessed, you can try freezing the assembly it's part of, and tapping on the other side of the housing / etc (facing up) with the bearing facing down. This changes the size of different metals at different rates, and may allow it to be removed more easily. If it doesn't help, you can try a little heating instead, with the same actions. Sometimes freezing the part that's inside the other, and heating the outside part will work, but isnt' always possible (should be in this case by freezing teh whole assembly and then heating the casing (like with a hair dryer), (since it's aluminum the heat should spread thru it faster than it heats the steel bearing race) while tapping to knock the bearing out. Worth a try at least.
 
Good info in seeing if the oil will wick past the seal first. It's such a quick task to oil, put the rotor and cover back on to test, and if it doesn't change the whine, take the cover off, remove the seal and oil. Thanks.

I'll also try the hot / cold removal method you describe. I could get real lucky if the bearing / bore interference fit is minimal. I'll try ice cubes on the bearing first and heat gun on the aluminum. That just might work. If not, I'll freeze the assembly. Again, another path of least resistance. Now I can't wait for tomorrow to try!!
 
Update on the rotor bearing evaluation as a possible cause of the motor whine. As a reminder, the whine occurs with the motor assembled with ONLY the rotor spinning in the stator, nylon gear removed, in turn, no other part rotating.

Removed a dust cover on both rotor bearings and they were very well greased, VERY smooth, with no obvious play. I can see no reason to suspect the bearings.
file.php


I bought a new bearing that press fits on the end of the rotor that I'll install tomorrow. No reason to think my original was bad but...... Removed mine with a flat punch alternating though the 4 rotor holes. Was unable to use a bearing puller behind it since it was flush up again the rotor.
file.php


The other bearing is the blind bearing press fit into the motor housing that could be be a chore to remove so.....one step at a time. Again with that one, no reason to think its bad.

Deeper dive tomorrow.

Found another YouTube post showing the same whine. Unfortunately, no comments on the fix. https://youtu.be/E60rjBIycO0
 

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“When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.” ~ Arthur Conan Doyle, The Case-Book of Sherlock Holmes.

I think that I woud replace those bearings anyway.
 
LewTwo said:
“When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.” ~ Arthur Conan Doyle, The Case-Book of Sherlock Holmes.

I think that I would replace those bearings anyway.
Yeah, I here ya. Come on over for a coffee and I'll watch you take that blind bearing out for me. :lol: All kidding aside, if the whining sound is found to be coming from that main rotor bearing that I've removed, I will leave the blind bearing as is. The old "If it ain't broke....don't fix it." philosophy. I'd really KICK myself if I somehow damaged my housing trying to remove it. But, we'll see. I may just get tempted to try that 'bread packing' method to get the blind bearing out, or just breakdown and spend the ~$50.00 to buy the 8mm blind bearing puller. So many decisions, so little time. I gotta get this mountain bike trail ready soon. My trail buds are bugging me to ride.
 
mickyd said:
Yeah, I here ya. Come on over for a coffee and I'll watch you take that blind bearing out for me. :lol: All kidding aside, if the whining sound is found to be coming from that main rotor bearing that I've removed, I will leave the blind bearing as is. The old "If it ain't broke....don't fix it." philosophy. I'd really KICK myself if I somehow damaged my housing trying to remove it. But, we'll see.
Sorry, I think my passport has expired.

If it does turn out be that wee little thing: could one locate two spots on the outside of the case and drill 4.2 mm (or 4.5 m) holes to line up with the bearing race. Then tap the bearing out with a 4 mm punch. The holes could be threaded for short 5 mm button-head screws to seal them up after the fact ... or perhaps put a grease zerk in one.

OK ... no room for the zerk ....
example..jpg
 
LewTwo said:
Sorry, I think my passport has expired.

If it does turn out be that wee little thing: could one locate two spots on the outside of the case and drill 4.2 mm (or 4.5 m) holes to line up with the bearing race. Then tap the bearing out with a 4 mm punch. The holes could be threaded for short 5 mm button-head screws to seal them up after the fact ... or perhaps put a grease zerk in one.
Passport?? I'm in San Diego. Everyone is welcome. :thumb:

Great suggestion on the hole drilling and tapping. I had thought about that as an alternative to the 'right' tool. My dad used to always say "Use the right tool for the job." My grandfather (his dad) used to say "Micky mouse the thing. Driving by 60 mph, you'll never know the difference." This is my struggle!! :lol:
 
Well, due to a time crunch to get a ride in, I threw the dice and decided to only replace the larger exposed pinion bearing and NOT replace the blind bearing. RESULTS.....no improvement. She's still just as whiny when at the higher RPM's. For my MTB ride, I just kept the RPM's down to minimize the sound, and also ride in the back of the pack!! :lol: It's such a quick teardown that I don't mind taking it apart again to replace the blind bearing. I'll keep you posted.
 
ebuilder said:
Mick, sorry to hear.
When you were in there and if you popped the seal of countersunk cartridge bearing...and didn't notice excessive radial play in the bearing, wasn't crunchy aka contaminated/degraded etc....I am afraid your whine many electromagnetic as mentioned by another poster and not mechanical. If so, quite rare.
Glad you aren't daunted going back in and best of luck.
Do you recall how many miles you have on the motor, has it had a hard life?...and run very hot?

PS. my curiosity was peeked a bit and decided to dig a little on your motor whine which is quite unusual for Bafang mid drive motors. What I came up with on other similar motors but unspecific to Bafang is...this can occur if fixed magnets within the rotor because dislocated or loose whereby a magnetic resonance is created. My guess and only a hunch is, this maybe a rotor issue and a problem with your fixed magnets becoming fractionally displaced or loose. That rotor spins almost 4000 RPM. I believe this was a real issue with CYC motors.
If the stator aka windings are intact and motor generates pretty typical power, then maybe due to fractional magnet dislocation or movement at high RPM when the magnets are being acted upon by centrifugal and magnetic force.
Only a consideration. I just don't believe its your bearings at this point because you didn't see any red flags while in there.
I believe CYC made an engineering change relative to the adhesion of their magnets to their rotor. With a CYC in particular, excessive high RPM approaching 13K RPM...BBSHD with field weakening hits about 12K RPM...and higher electromagnetic force likely puts higher shear force on the magnets and need for high adhesion. Of course adhesion is also compromised by high heat...inversely proportional...heat loosens adhesive bond and higher angular momentum of magnet mass isn't a good combination.
This touches upon it but isn't completely clear:
Go to minute 7:40 or so of the following video which talks about heat loosening rotor magnets...presenter experienced this:
https://www.youtube.com/watch?v=8rEtoc9uib4&t=154s

Great insight and detail in your post ebuilder. Much appreciated.

I am the one who mentioned the potential of an electromagnetic issue causing the whine. The Bafang webpage indicated that possibility. https://bafang-e.com/oem-area/service/faqs/

I really did a good job inspecting the bearings. I'm not a bearing expert but I took the time to feel, wiggle, listen for anything out of the ordinary. I even did high speed rotation of both bearings with my Dermal tool fitted with a felt conical tip.
Blind 8mm ID rotor bearing spin test - https://youtube.com/shorts/-PiPX_41A_s?feature=share
Pinion 10mm ID rotor bearing spin test - https://youtube.com/shorts/q9sZ96yEBVc?feature=share

Here was a test I did for radial play on my ORIGINAL pinion bearing. I had a 10mm pin slip fitted into the ID as I wiggled the outer race. Although the bearing felt smooth, I thought this amount of play might have been the reason for the whine but the new replacement bearing had identical play. $10 down the tube I think.
Pinion rotor bearing radial play test - https://youtu.be/2H_JsDz68sE

As I mentioned previously, I have 1,250 HARD mountain bike miles on my motor. Lots of steep rugged terrain but always conscience of motor speed / strain. Not afraid to walk the bike when I felt it was too much. My buddy rides with me most every time and it was his motor I compared the sound to (https://www.youtube.com/shorts/XY7hkXcgps4). His bike is geared similar to mine so assumed equal strain. Both motors have run very warm to the touch but I can quantify. NOTE......I am going to add a temperature sensor to the motor on this teardown. https://electricbike-blog.com/2015/06/07/installing-a-temperature-sensor-in-the-bbs02-unit/.

I am going to also teardown my buddies BBS02 at the same time as mine which will let me switch out rotors / controllers. After all, this is what buddies are for right? :roll: If my motor still whines with his rotor, I'll switch controllers. If it STILL whines, I only variables would be the remaining original blind rotor bearing that I didn't yet replace, or the motor core itself. I sure wish Bafang was responsive to user issues for help. MAYBE I'll try contacting them OR, really ANY electric motor guru. If any of you know one, I'd appreciate if you could refer me to them. My email is michael.john.daigle. It's a gmail account so you know the @xxxxxx

Enjoyed that video link you shared.

Out to the garage for some teardown.
 
LewTwo said:
If it does turn out be that wee little thing: could one locate two spots on the outside of the case and drill 4.2 mm (or 4.5 m) holes to line up with the bearing race. Then tap the bearing out with a 4 mm punch. The holes could be threaded for short 5 mm button-head screws to seal them up after the fact ... or perhaps put a grease zerk in one.

OK ... no room for the zerk ....
example..jpg
Hey LewTwo, for the record, if you were to drill the 2 holes where shown in your photo, you'd drill into the shaft that turns the main motor hear. :D No bueno. The blind bearing lives under the cover area I circled. That would be a 'mo betta' place to drill if one did drill. After thinking about it, I'd be afraid to drill unless that was my last resort and the bearing was shot. My methods in order would be:

  • Freeze the casing, heat around the bearing, and try tapping the back side of the casing with a plastic mallet and pray it comes out as suggested by amberwolf.
  • Find a shop that has a blind bearing puller to remove 8mm ID bearing.
  • Brake down and buy a blind bearing puller.
  • Weld a pull rod to the inner race.
  • Drill the holes thru the casing.
  • Buy the whole stinking $150 motor core complete.
 

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mickyd said:
Hey LewTwo, for the record, if you were to drill the 2 holes where shown in your photo, you'd drill into the shaft that turns the main motor hear. :D No bueno. The blind bearing lives under the cover area I circled.
OK ... but the point is the same: "there is more than one way to skin a rabid cat".
 
ebuilder said:
Great opportunity to try your friend's rotor. One thing to consider if you order another rotor based upon your friend's rotor quieting your motor...be sure you do your homework when ordering a new rotor. Contact the supplier with the serial number on your housing and approximately when it was produced. Reason this matters is Bafang was getting some failures early on with the BBS02 motor and they changed the internals. Possible the later rotor won't fit in your motor, so you need to need to make sure you look into this before you spend your hard earned money.

You will fix it, I am confident because of your attitude and due diligence.

Keep us posted because we learn from each other.
The rotor swap result will be VERY interesting. If that's the cause, new rotors run $70 - 90 while a new motor core with rotor $130 - $150. I usually use the one-third $$ rule when deciding fix vs. new. If I can fix it for less than 1/3 the price of new, I'll go with a fix.

I decided to wait a week to do the motor teardown and rotor swap. I needed a new rubber controller gasket which I ordered from Luna yesterday. Will take a few days to get it. I also purchased the temperature sensor that I am going to install as I FREQUENTLY push this motor climbing very steep terrain and it will be a good to monitor heat as an insurance policy. The author of the temperature sensor article I referred to above states the following temperature guidelines as measured INSIDE THE CONTROLLER housing as:

140F + Stop riding and let it cool
130F + Don’t use full throttle, only half throttle
120F + Take it easy
110F or less go whole hog

Seems a tad conservative to me but well see.
 
ebuilder said:
Sounds like a great plan.
Could you do a favor to the community when you install your temp sensor and do a little of review of it and how it works?
Would be something I would be interested in to learning about.
Speaking of temperature monitoring, a brilliant member of ES wrote new firmware for the BBSHD and I believe now available for the BBS02 whereby he has in his flash temperature monitoring whereby this temperature is listed under the 'range' of the display...where range used to go.
Not sure how his firmware ties into temperature monitoring....like a thermocouple or thermister located on the controller??...not sure. Perhaps you can explain a bit how your temp monitoring works, I would be interested as I live in a warm climate and sometimes push my BBSHD hard.

No question you will fix your motor Mick because you have what it takes.
I will absolutely share my temperature sensor install and evaluation. I'll probably start a new specific thread if there's none here already. Remember, I'm a newbie.

You asked if I can explain how my temperature monitoring works. You mean sharing my actual results, or how specifically the aquarium thermometer probe functions?
 
mickyd said:
The rotor swap result will be VERY interesting. If that's the cause, new rotors run $70 - 90 while a new motor core with rotor $130 - $150. I usually use the one-third $$ rule when deciding fix vs. new. If I can fix it for less than 1/3 the price of new, I'll go with a fix.

I decided to wait a week to do the motor teardown and rotor swap. I needed a new rubber controller gasket which I ordered from Luna yesterday. Will take a few days to get it. I also purchased the temperature sensor that I am going to install as I FREQUENTLY push this motor climbing very steep terrain and it will be a good to monitor heat as an insurance policy. The author of the temperature sensor article I referred to above states the following temperature guidelines as measured INSIDE THE CONTROLLER housing as:

140F + Stop riding and let it cool
130F + Don’t use full throttle, only half throttle
120F + Take it easy
110F or less go whole hog

Seems a tad conservative to me but well see.


Got the motor temperature sensor in today. +/-1°C accuracy, 158°max temp. Three pack for $11 on Amazon. 1 for my motor, 1 for my buddies, and 1 for the Mrs. saltwater fish tank.
 

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ebuilder said:
Awesome. When are you going to swap rotors with your buddy?

Shooting for a Tuesday tear down. I'll video and post the comparison. I have a ride planned for tomorrow so I didn't want to risk running into an issue. Plus, my new controller gasket is due to arrive Monday.
 
Well, switching out my buddies rotor with mine had no effect on the motor whine. The only variable is blind bearing which I have no reason to suspect. :( Doing it tomorrow.
 
mickyd said:
Well, switching out my buddies rotor with mine had no effect on the motor whine. The only variable is blind bearing which I have no reason to suspect. :( Doing it tomorrow.
Removed the blind bearing using the BREAD method. The method worked nicely. See the video.

https://youtu.be/4rxEvWwSMt4

I don't think the whine is caused by the blind bearing but I'll install a new one. This is my last resort trying to identify the cause of the whine. If its not the bearing, it must be an electromagnetic noise coming from motor core, which I have NO IDEA how to further troubleshoot.

While the motor was apart, I also tried switching the controller and that also had no effect on reducing the whine.
 
ebuilder said:
Brilliant Mick. Old hotrodder trick to remove the pilot bearing:

https://www.youtube.com/watch?v=65UG866ZTeQ

I look forward to your findings with new motor core. Good move to change the bearing while in there. :thumb:

Thanks builder. It was a fun adventure being the first time trying the bread method. Amazing how you can use bread as a hydraulic fluid!! Another friend of mine asked if you could use play-doh or silly putty vs. bread :idea: ? Great question. I'll bet that's even better. Less compressibility. I'm going to try it.

Enjoyed your video. Reminded me of my old motorhead days. Had several fixer uppers as a teen so I had my hands into every possible repair. Glad my bearing came out easier than the pilot bushing in the video.

I'll pray for a miracle that changing that blind bearing will cure the whine. If not, I think I'm going to dig into my motor core to see if I can find the source. Sure wish a DC motor guru could give some pointers. But, I'll cross that bridge when I get to it.
 
mickyd said:
I'll pray for a miracle that changing that blind bearing will cure the whine. If not, I think I'm going to dig into my motor core to see if I can find the source. Sure wish a DC motor guru could give some pointers. But, I'll cross that bridge when I get to it.

Well, I wish I had better news to report but changing my blind bearing didn't change the whine sound. Am I giving up troubleshooting yet?? Heck NO. Don't know my next step yet but going to let it percolate. Going to put in back together as I have a ride coming up Saturday.

Oh, and I also switched the entire motor core / rotor with my buddies and that made MY motor the quite one, and HIS became the whiner. So this issue HAS to be something about the motor core assembly.

Lastly, I also found out the play-doh DOES NOT work to remove this blind bearing. The play-doh simply deformed the rear bearing seal which caused it to bleed through into the bearings area then pop off the top seal, oozing out though the spaces between the bearing. It just isn't viscous enough. Sooooo, I went back to the bread technique I used earlier and again that was successful.
 
If running the motor without the gearing, or a load, and the whine changes intensity but not frequency when varying throttle input, then it's possible you're hearing the PWM of the throttle varying the average motor voltage.

If that's the case...there is a small chance that during manufacturing, a winding was done too tightly on the stator laminations, and nicked it's insulation just enough that at first it didn't make any connection to the stator metal. But over time vibration, moisture, etc. has made enough of a connection that it's interfering with current flow, especially if there is more than one winding damaged this way. It may even not be low enough resistance to measure at multimeter voltages, and only breakdown at higher voltages--I have a hubmotor that had this problem, and it took a special meter to test for this and find it. (it's in the SB Cruiser thread a few years back, when I was testing the SFOC5 with an MXUS).

The solution that worked for me was to drizzle Coronadope (a high-voltage insulating compound) into the windings, to fill the whole winding up and prevent any connection between them. It also glued the windings together...which if there was any noise caused by the rapidly changing motor currents physically moving the windings, would probably stop those, too.

So...there is a tiny chance that doing this for your windings would fix the noise. It shouldn't hurt anything even if it doesn't fix it, but there's no way to know for certain without testing it.

If you want to try it, this is what I used:
https://www.amazon.com/gp/product/B008OA7CAE


I also used this
https://www.amazon.com/MG-Chemicals-4228-55ML-Insulating-Varnish/dp/B008OA7DDK
to insulate the new phase wires I installed thru the modified axle slots. It may also work in place of the CoronaDope, but CD is intended for this purpose (fixing high-voltage transformer/etc winding shorts from defective insulation).

This is another version of CD:
https://www.amazon.com/AmplifiedParts-Corona-Dope-2-oz/dp/B00E1QZ2SY


Even if it is not an electrical short issue, it could be that the windings are loose on the stator teeth, just enough to vibrate and cause an actual sound. This stuff would also fix that kind of problem by gluing it all together.


As long as it is thin enough to run down into the windings and fill up all the spaces between them and the laminations, and doesn't conduct electricity, and can handle the temperatures expected inside the motor, any similar product should work.

Might not do anything at all to help, of course.
 
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