Sounds hub motors make

auraslip

auraslip

10 MW
Joined
Mar 5, 2010
Messages
3,535
Full throttle off the line is a grumbly rumble that shakes the bike in a nauseous nefarious way.

That perfect speed that matches the resonant frequency of the covers of the motors and makes them sing like the top of an acoustic guitar.

The soft mousey whine the motor makes as it's wheeled back in my house after a hard and hot ride.

That ever present electric hum that "sounds like the future" according to my friend.


Well, I understand ONE of these, but what causes the others?
 
Mini-motor emits a whiny growl.......
Not unlike my sister's miniature poodle.
 
auraslip said:
Well, I understand ONE of these, but what causes the others?
Click to expand...

IMHO, the root cause of most of the sounds a hub motor makes all come from Newton's Third Law of Motion. When the coils act on the magnets attached to the hub the coils will try to move too, in the opposite direction according to Newton's law. The magnets are rigidly attached to the hub but the coils are just tightly wound onto the flux ring bobbins. The coils can not move much, but they can move enough to make some low amplitude vibration. That is my guess anyway. I have heard similar sounds from switch mode power supplies back in the old days when the switching frequency was in the audio range.
 
Which one do you already understand?

Also remember that that grumbly sound happens primarily with DD hubs like the 9C, using trapezoidal controllers. I expect with a sine controller and/or a differently-built DD, it would be silent (like TidalForce is, according to what I have read--never heard one in person).

In contrast to my 9C (which on CrazyBike2 between the metal cargo pods could be mistaken for an ICE revving up!), my geared hubs by Fusin are much much quieter. The older ones have a notable gearing sound, but the newer one from this thread:
http://endless-sphere.com/forums/viewtopic.php?f=4&t=39877
is very quiet, both at startup from a stop under load and while riding. I tried to get a recording of the various noises each motor makes, but the camera's autolevel control either silences the audio or hears only the wind or road noise, or makes the motor noise sound incredibly loud when it is not. I'll have to wait until I can get my studio-recording-equipment back (someday) and record them all then.
 
I think all the noise in a direct drive hub comes from the controllers odd noises it gets are from feeding a trap wave to a motor that makes a kinda sinus-ish BEMF.


I remember Farfle's magic pie on the infinion controller made lots of noises, all the ones you described well. We put a Sevcon on the bike (a HUGE amount of work...), and poof! The motor was just dead silent all all speeds after that. No more growl, no more ringing, no more humming, just silent virtually torque-ripple-free torque.
 
I like the sound Luke's hub motors make...

You know snap crackle pop :lol:
 
Too bad they don't start squealing like a pig when they reach 200F. That would be handy. I just love the zzzzt noise my race bike makes, 9c on 100v. No grumble anymore, just a nice zinging turbo kind of sound. I think of motor grumble as the sound of a motor getting stalled. The dirt bike makes that sound all day.
 
The hub on the wife bike goes gerrrrrr, mine goes buzzzzz, obviously hers is a 4 stroke, mine is a 2 stroke!
 
I'll have to read through that paper miles. Sounds fun.

I'm mostly concerned with the grumble & rumble my new h series motor makes at WOT from a start. It doesn't sound good at all. Almost like the torque of it is causing something to deform and rub!

The other odd one is the high pitch whine the motor makes when I wheel it inside after a ride. It must be the bearings, but this doesn't always happen. I'd be surprised if this was a common one.
 
The intermittent whine can be brake rub, too, if the pads just lightly touch the rim or disc. It wouldn't always happen because it depends on flex of the wheel from sideloads. Happens on CrazyBike2's front disc wheel (whcih also has rim brakes). Sometimes if I have it leaning more to the side when pushing it around, it rubs the disc against the caliper just enough to make noise but not enough to feel any friction. Leaning a little harder cuases a squeal, and it does have some friction then (not much, but enough to notice).
 
The magic pie sounded a lot like a theremin from an old 1950's sci-fi movie when it spun down... and really sounds more like the hi-rpm MAC motor, high pitched. I remember the MXUS/9C style motors being really grunty, and had that one range of RPM where it had a really loud and annoying resonance..

Your HS/HT motor is pretty similar to the 9C/MXUS design, actually. Probably grunty in the low end.. has the weird resonances.. etc..

Come to think of it auraslip, have you only had 2 different kinds of motors in your eBike career?
 
You must log in or register to reply here.

Similar threads

Reid Welch
"Extreme MY1018" archival, closed out
Replies
11
Views
17,773
GIGATT
G
Back
Top