TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Acceleration Whine Caused by gears, not motor

Discussion in 'Model S: Driving Dynamics' started by aaronw, Apr 7, 2013.

Tags:
  1. aaronw

    aaronw Member

    Joined:
    Dec 19, 2012
    Messages:
    281
    Location:
    United States
    #1 aaronw, Apr 7, 2013
    Last edited: Jun 24, 2013
    Hi all,

    I was commenting to a friend of mine who works at Tesla about the acceleration whine, which I must admit doesn't bother me at all. Anyway, my friend told me that the noise comes from the gears and went on to describe trade-offs with different types of gears between noise and efficiency. The model S uses helical gears which have multiple teeth engaged at any one time. The more teeth that engage at once the quieter the gears are but the greater the loss due to friction. Having fewer teeth engaged means greater strain on the teeth since there are fewer teeth to absorb all that force. My friend said that there are complaints that there isn't enough whine from some people.
     
  2. 100thMonkey

    100thMonkey Member

    Joined:
    Jul 1, 2012
    Messages:
    914
    Location:
    Seattle area
    that makes me wonder if he is talking about the same whine that bugs me. what I hear is a sound much like that of letting air out of a balloon, it's more like a squeak and it sounds like it comes from somewhere in the lower left console. sounds more like interference in a speaker or something, as if there is a separate nav speaker. it doesn't sound at all like it's coming from the back motor/gear box.
     
  3. DriverOne

    DriverOne Member

    Joined:
    Aug 20, 2012
    Messages:
    421
    Location:
    Austin, TX
    Mine's recently started letting out a plaintive whine (air out of a balloon, nice analogy!) at hard acceleration once you hit 40mph. I love the whine up until then, but now it sounds like the whine of a sad kitty. Sounds to me like it's coming from the rear, though, not a front speaker.
     
  4. AnOutsider

    AnOutsider S532 # XS27

    Joined:
    Apr 3, 2009
    Messages:
    11,923
    Hmm, weren't the original reports that it was something with the frequency of the lines or something like that?
     
  5. Doug_G

    Doug_G Lead Moderator

    Joined:
    Apr 2, 2010
    Messages:
    15,850
    Location:
    Ottawa, Canada
    That's completely wrong. The Roadster's whine clearly comes from the gears as it changes with RPM. The Model S whine is a function of pedal position, NOT the motor RPM.
     
  6. Zextraterrestrial

    Joined:
    Mar 11, 2010
    Messages:
    3,636
    Location:
    Humboldt/Los Altos
    I have an RC heli with a herringbone style gearing and it makes a bit of a whine unlike the other helis with straight teeth on the gears

    but if it was gear noise in the S it would be there when you were driving faster not accelerating harder like Doug said.
     
  7. qwk

    qwk Model S P2681

    Joined:
    Dec 19, 2008
    Messages:
    2,817
    Yep. Mine had no noise up until about 400 miles. Now it has a faint noise under about 20kw acceleration and regen. Not very bothersome to me, but definately not gear noise.
     
  8. aaronw

    aaronw Member

    Joined:
    Dec 19, 2012
    Messages:
    281
    Location:
    United States
    The noise I am talking about is under hard acceleration and is definitely gear noise. The other noise like "air coming out of a tire" sounds like hiss to me and sounds like it might be coming from a speaker under the dash or something.
     
  9. cinergi

    cinergi Active Member

    Joined:
    Sep 17, 2010
    Messages:
    2,169
    Location:
    MA
    I'm aware of 4 different noises in my car in this area ...

    1) The "balloon" whine that varies with power output at certain speeds
    2) Gear noise that varies only with speed; inaudible until about 50 MPH; a very low-pitch drone. I had this checked and cross-referenced with another Model S and it's normal. (I watched as they listened to it via a "stethoscope" while on a lift)
    3) Electrical noise via the speakers that's directly proportional to power output -- IOW I can hear the A/C frequency being fed to the motor. This is not the same as the buzzing from the lights.
    4) Increased tire noise under hard acceleration (of course)
     
  10. William13

    William13 Member

    Joined:
    Mar 19, 2011
    Messages:
    943
    Location:
    South Bend
    #10 William13, Apr 9, 2013
    Last edited: Apr 9, 2013
    +1 Cinergi, I note these four distinct noises.

    #4 present on delivery
    #1 began after 500 miles and mildly increased until 5000 miles
    #3 began/increased after the 4.3 firmware
    #2 only noticed since this thread
     
  11. PeterK

    PeterK Model S Owner

    Joined:
    Jan 17, 2013
    Messages:
    1,148
    Location:
    Cambridge, MA
    I don't think it's any of the four, when I really punch the accelerator hard I hear a tone from the rear that a Tesla motor engineer told me is harmonic vibration of a connector on the inverter. I kind of like it - enhances the extreme acceleration experience.
     
  12. tbleakne

    tbleakne Member

    Joined:
    Feb 14, 2013
    Messages:
    139
    Location:
    Claremont, CA
    With respect to 1) and 3), there is the frequency fm of the rotating magnet field in the motor. If it was a synchronous motor like the LEAF's, this frequency would be proportional to RPM, but since Tesla uses an induction motor, fm is higher than RPM. I believe the torque is proportional to (fm - RPM), so fm rises as you apply more acceleration at the same RPM.
     
  13. qwk

    qwk Model S P2681

    Joined:
    Dec 19, 2008
    Messages:
    2,817
    If that was the case, this sound would be there from mile 1. Mine didn't start until about 400-500 miles. Quiet as a cemetary before 400-500 miles.
     
  14. MikeK

    MikeK R#129, TSLA shareholder

    Joined:
    Jun 29, 2012
    Messages:
    1,133
    Location:
    San Francisco Bay Area
    There's definitely a "drone" that is audible in my car at highway speeds. It's most clear right around 70mph. It is related in some way to motor load, but whether it's gearing or electronic or both I'm not certain. What I can say is that if I put the car in neutral (so that it's not trying to apply regen), it rolls quietly at that speed.
     
  15. bellwilliam

    bellwilliam Member

    Joined:
    Jan 9, 2013
    Messages:
    111
    Location:
    LA
    +1
    this is what I hear also. pretty loud...
     
  16. mrbry

    mrbry Member

    Joined:
    Dec 13, 2012
    Messages:
    73
    Location:
    Los Angeles, CA
    Yep, my P85 wasn't initially like this, but after the first 1K miles (I'm now at 4K miles), it started happening. Service center couldn't diagnose it when I checked back in February.
     
  17. derekt75

    derekt75 Member

    Joined:
    Jul 16, 2012
    Messages:
    592
    Location:
    San Jose, CA
    My car is pretty quiet.

    Around corners I hear the tires, which is pretty cool. Sounds like the shush of an eraser on a chalkboard.
    When accelerating, I hear a faint medium frequency (500 Hz - 3 kHz?) sine wave sound (whoooop) that I associate with other linear motors (e.g., electrically launched roller coasters or even the magnetically braked "Drop Zone" ride). I'm guessing it's the electronics (inverter?), but maybe it's the gears (which is only the differential, right?).

    Other than that, it's just the standard wind and tire white noise.

    On test drives, there was a whiny sound just after accelerating that I was told had something to do with the battery, but I don't hear that on my car.

    - - - Updated - - -

    While torque increases with the slip rate, this only works up to a point, and that point is usually when the slip is a small fraction (10%-20% of the motor RPM). If the field rotates at 10X the rate that the shaft is turning, then you get about 0 acceleration since the field is spending almost half of its time braking the motor. Motors are rarely operated with a slip rate greater than the max-acceleration slip rate because motor speed is unstable there (lower rotor speed -> increased slip rate -> less torque -> lower rotor speed -> etc).
    If the motor is turning at 1000 RPM, field rotation of 1100 RPM might be strong acceleration while 1010 RPM might be weak acceleration. If the motor is turning at 9000 RPM, field rotation of 9500 RPM might be strong acceleration while field rotation of 9100 RPM might be weak acceleration.

    So to a reasonable approximation, I think the magnetic field rotation rate should be essentially the same as motor speed and therefore reasonably proportional to car speed.
     
  18. goyogi

    goyogi Member

    Joined:
    May 22, 2011
    Messages:
    415
    Location:
    ::Silicon Valley:: ::Home of Tesla::
    I, too, noticed it after about a month which would be about 1000 miles or so. Maybe the gears were breaking in and now the oil needs to be changed out? Total guess on my part.
     
  19. William3

    William3 Member

    Joined:
    Aug 7, 2008
    Messages:
    162
    I'm getting this too.
     
  20. brianman

    brianman Burrito Founder

    Joined:
    Nov 10, 2011
    Messages:
    15,487
    Gears?
     

Share This Page