Motor Sounds - breaking in, not breaking down

[Bruce Arnold]

We've had a couple of posts lately from guys wondering if there was something going on with their motor because of the sounds it makes. @Reid gave a good description in one of the threads of how they work and why they might make a different noise at times. When my motor sounds louder than normal, I coast until the motor cuts off and then start pedaling again. It might take 1 or 2 tries -- occasionally more -- but the gears will find the sweet spot again and it gets much quieter.

With just under 1,300 miles on my CCS, this seems to happen more now than at first.

A pessimist or a worrier might think that spelled impending doom. Given what we know about hub motors, I've concluded that it is just a question of the motor getting worn-in.

Here's an example from another hobby of mine. When you first buy a mechanical watch, you will get a lot of variance in whether it gains or loses time. Sometimes it will swing pretty far in one direction or another. It might be gaining 4 seconds a day, and suddenly start to lose 20 seconds a day. After 1-3 months, when the mechanism has worn in, it will settle into a fairly predictable pattern. There are still some variations based on temperature, what position you leave it in at night, even the amount or kind of activity you have during the day. But those variations will be within a predictable range, not swinging from here to there as before.

Gears is gears, whether tiny watch gears or larger hub motor gears. In the case of our hub motors, because of the kind of work they do, we are able to hear differences in the sound the motor makes. It changes some over time. This is neither a feature nor a bug. It just is.

Kinda thinking out loud here. I could be way wrong.

 

[Reid]

Gears is gears, as Bruce notes.

In my one-bike experience, engagement of the geared hub motor seems to vary depending on the relative internal positions of the not-always-perfectly-concentric internal parts. Is the carrier of the planet gears out of perfect concentricity by a thousandth of an inch? (?) Harmless noise may result.

Yet, now with probably over two thousand miles on my own CCS, the motor engagements are mostly, nearly silent these days.

It used to be the bike would positively whine on one out of three or four power applications. I would have to let off power and try again, to find the sweet, silent spot.

Today I hardly ever bother to try to find a silent engagement because for reasons unknown the motor is almost always silent running. That is: no pedestrian can possibly hear the motor operating sound. All these motors are liable to have their own inherent noise characteristic.

 

[Chris Hammond]

So, based on the prior posts about this, I began to pay more attention to this. I have noticed that there seems to be consistently a more "harsh" for lack of a better word, sound when accelerating at lower speeds in higher levels of assistance. I attribute this to the heavy load on the motor in such condition.
The other thing I have noticed is that there seems to be a resonant frequency that affects the motor sound at ~17 mph. There is an amplification of the motor sound that can be heard on my bike at any level of assist, but it becomes louder with each incremental level of assist. The sound is noticeable only briefly on each side of 17 mph and disappears otherwise.
Overall, the motor sounds to me are not surprising, not loud by any means, and not anything I am remotely concerned about.
I probably wouldn't have really given it much thought at all if it hadn't been for this forum. Not all knowledge is useful.

 

[Bruce Arnold]

So, based on the prior posts about this, I began to pay more attention to this. I have noticed that there seems to be consistently a more "harsh" for lack of a better word, sound when accelerating at lower speeds in higher levels of assistance. I attribute this to the heavy load on the motor in such condition.
The other thing I have noticed is that there seems to be a resonant frequency that affects the motor sound at ~17 mph. There is an amplification of the motor sound that can be heard on my bike at any level of assist, but it becomes louder with each incremental level of assist. The sound is noticeable only briefly on each side of 17 mph and disappears otherwise.

Those are interesting observations, Chris.

 

[Fran Fabrizio]

The other thing I have noticed is that there seems to be a resonant frequency that affects the motor sound at ~17 mph. There is an amplification of the motor sound that can be heard on my bike at any level of assist, but it becomes louder with each incremental level of assist. The sound is noticeable only briefly on each side of 17 mph and disappears otherwise.

For me, this is at 16mph, but same thing. That particular noise seems harmless, even a little pleasant/rhythmic.

The louder whine I have, I'm less sure is harmless. As @Bruce Arnold mentioned, I'm also observing this happening more and more frequently now (~1,000 miles). On the ride in this morning, I'd say I had to pause and re-engage the motor every 3-4 engagements to smooth it out. It's definitely more common under higher load conditions (particularly hills, or what passes for hills in mostly-glacially-flat Minneapolis). When mine does it, the whole bike vibrates. I can feel it through my butt, feet and hands pretty significantly. If it were just a louder sound I'd be mildly annoyed but not worried. However, with the added vibration, I'm worried something is working more and more out of tolerance in that motor. I'm slowly going back and forth with tech support on it (slowness mostly on my end on getting answers back to them for things they ask me to check/try).

I hope I'm just going through a "growing pains" phase and it's eventually going to settle in as @Reid observed for his bike.

 

[MisterBritcom]

My bike makes the same vibration and noise as described by the other forum members in this thread. It has become slightly louder over time. At about 1k miles my back tire is holding up well, when it's time to replace it I intend to disassemble the hub for inspection, cleaning and lubrication.
It's understandable to be uncomfortable about noisy operation, but I don't let it keep me up at night. I figured when I bought the thing that it might not last more than a year or two, given that comparable bikes cost twice as much.
I have saved gas, tolls, wear and tear on my car and had a bunch of fun and exercise.

 

[philerooski]

For me the sound occurs between 16-19mph. It's very annoying because within that range is a common cruising speed for me. I hate to be that ebiker that sounds like a weed wacker riding down an otherwise pleasant multi-use path.

 

[Reid]

Am so sorry that some are experiencing more noise annoyance than myself. My CCS actually has gotten quieter recently.

Whether our motor is noisy or not, or whether it has this-or-that noise characteristic, don't worry.

Noise is the expected result of straight spur cut planetary gears, as opposed to helical gears such as are found in modern automotobile transmissions. Some Bafang motors will be this way, and others, another. The tiniest abberations in clearanaces will make, or not make, noise.

It is going to be just like the famed, planetary geared Model T Ford. 19 million were made. Most sounded like coffee grinders when they idled or were in low gear. Mine sure did, and it was PERFECTLY clearanced. Yet, my buddy Garland Poblett's 1915 Ford was the quietest I ever heard, and it was worn and well used and never given any particular attention. He drove it on national tours from the 1950s through the 1990s.

IT IS THE LUCK OF THE DRAW. A NOISEY MOTOR DOES NOT BODE EARLY FAILURE. MODEL T FORDS RUN FOREVER WITH NOISEY PLANETARY GEARING. SO WILL YOUR BAFANG, most likely.

Noise is just gear noise in these cases. You'll know if a truly destructive sequence ever begins....

 

[Pete N]

Sounds like I am experiencing the same noise/vibration (~300 miles on odometer) - whining, gears not meshing properly under load - I don't get the noise when I don't pedal hard, or set cruise and don't pedal at all, but then no exercise - stop peddling for brief moment and noise goes away until under load again. I was not sure if it was a motor or derailleur issue but from these posts it sounds like it is a somewhat common issue. Figure I will live with it - not sure where I could take the bike (CSC) for anything other than standard derailleur adjustment. Thought I had also read a post from Juiced support saying that it is a frequency vibration issue that can occur with the hub motor - but I am not seeing that post anywhere.

 

[Fran Fabrizio]

"stop peddling for brief moment and noise goes away until under load again." That's what I was doing too, until I realized that a momentary tap of the brake lever (enough to trip the motor cutoff but not enough to actually brake) is all that is necessary to get the motor to stop and then re-engage, usually much more quietly. I find that less disruptive than actually stopping pedaling, especially uphill.

This is the article you are referring to from Juiced support: https://juicedbikes.happyfox.com/kb/article/3-motor-rhythmic-sound/

 

[Fran Fabrizio]

Noise is just gear noise in these cases. You'll know if a truly destructive sequence ever begins....

@Reid Is more vibration also normal? That's the part that concerns me - at times, the vibration through the seat and feet can actually be somewhat uncomfortable when the gears have engaged in this more loud manner. It's the vibration that has me worried about there being impending failure moreso than the noise.

 

[TForan]

Normal or not, I sure wouldn't like noise and vibration.

 

[Reid]

@Reid Is more vibration also normal? That's the part that concerns me - at times, the vibration through the seat and feet can actually be somewhat uncomfortable when the gears have engaged in this more loud manner. It's the vibration that has me worried about there being impending failure moreso than the noise.

His coffee mill was made of tin. But tin was made to pack things in:

No Model T ever died of being noiser than hell: a reminder in reverse extrapolation of our Bafang motors' unaccountably variable cacophonies and bids to be worrisome crotch vibrators.

I am not making any fun of you, Fran. The motors are really alarming in their noise and vibration potential. I am a lucky guy for having a relatively silent Bafang. Yours may be a not-fun vibrator. Bafang probably tries to make a good product in order to survive. However, the very tiniest of defect in spur gear meshing makes a mortal hell of noise and vibration. The Model T really is and always was, usually a coffee mill. Steel gears against a steel gear. Look up epicycloidal gear teeth?

 

[Bruce Arnold]

@Fran Fabrizio Give it a few thousand miles and you won't be worried about it any more.

 

[MisterBritcom]

I tried Fran's method of blipping the brake to make the motor re-engage and I like it better than the stop pedaling method.

 

[philerooski]

I wanted to give an update since I recently passed 1000 miles. One thousand must be the magic number, because I hear the gears much less now than I used to. It seems to only happen between 18-18.5 MPH now, and I suspect with a few hundred more miles even that will improve.

 

[Bruce Arnold]

I wanted to give an update since I recently passed 1000 miles. One thousand must be the magic number, because I hear the gears much less now than I used to. It seems to only happen between 18-18.5 MPH now, and I suspect with a few hundred more miles even that will improve.

I do have the resonant vibration between 16-18 mph that @Chris Hammond talked about. It doesn't change the function of the motor at all. It hasn't gotten better or worse as the miles go by. I don't sweat it.

 

[Fran Fabrizio]

I think maybe this thread has gotten a little muddled. My motor makes three distinct sounds.

1. the baseline motor sound.
2. the resonant sound at 16-18 mph, which I've also concluded is normal.
3. An extremely loud grinding/rattling sound, accompanied by significant vibration transmitted through the entire bike frame. It is not something I'd describe as resonant or harmonic at all. This vibration is strong enough to be uncomfortable on my butt and feet. The sound of it is definitely "that motor is not happy at all" to me. It can happen at any speed or assist level, but happens more frequently when under more load or at higher assist levels. It's also getting progressively worse and more frequent overall. I would say it's 3-4x times louder than when the motor is operating well.

It's so hard to capture clearly on a phone's microphone at speed because the wind noise is terrible, but this video demonstrates it at 0:09 and a little better from 0:27 - 0:32 or so: https://photos.app.goo.gl/SZxYG4qU31xDdEUYA

My current plan is to get the bike a mechanical tune up at my LBS just to rule out any mechanical factors (loose spokes, etc...) and then send the wheel in for inspection (as suggested by Juiced support, which has been fairly responsive to my questions on this issue, for the record).

 

[Bruce Arnold]

Sounds like you have a good plan, Fran. I know you'll tell us the outcome.

 

[Randy Reck]

It's so hard to capture clearly on a phone's microphone at speed because the wind noise is terrible, but this video demonstrates it at 0:09 and a little better from 0:27 - 0:32 or so: https://photos.app.goo.gl/SZxYG4qU31xDdEUYA

Mine makes this exact same noise and has since day one. Two factors seem to determine the extent and severity of the sound--temperature and load, with temperature being the most important. I commute 5 days a week morning and afternoon. The noise is almost never present in the cool mornings, but also always there in the warm afternoons (when present, it also gets louder with increased load). I'm almost certain it is a mesh issue with the gears, likely caused by poor tolerances/QC. I have ~2,500 miles on this bike so far, and this noise doesn't appear to represent any imminent failure, so I plan to run it until it stops working and then buy a replacement motor/wheel.