Nasty motor whine with tensioned belt

I finally put my first rig together over the weekend and I discovered that when I tensioned the belt even slightly, the motor would start emitting a high pitched metallic whining noise at high RPM.

Here are some things I have done to diagnose the problem:

  • Changed from a 260 kV motor to a 190 kV motor. Both produce the whining noise.
  • Tried my motor on a friend’s board, no whining noise.
  • Changed the wheel and wheel pulley with a buddy’s, and the motor still produced the whine.
  • Changed the length at which the motor pulley sat on the motor shaft. No noticeable reduction in noise.
  • Unscrewed the motor mount screws slightly (Effectively removing all tension on the belt), and the noise immediately stopped. Bingo!

When there is no tension on the belt at all, the motor purrs nicely, even at high RPMs. The second I add any tension and screw in the motor mount screws tight, the motor start whining terribly.

It’s also worth noting that the motor pulley and the wheel pulley are very nicely aligned. I initially thought this might be the problem, but changing the alignment didn’t have any noticeable reduction in noise.

Anyone have any ideas what this might be?


Sounds like too much tension…but could be some belt whine or bearings …

Video please

Install and idler pulley and loosen your belt

we’ve had this conversation in another thread…I’ve re read ur post…looks like ur belt is too tight…if that’s the case that whine you hear is the bearing in the motor…a tight belt puts pressure on one side of the rotating bearing, heating it up, making the bearing lube burn up…and that’s no good… I leave mine loose…looks taught enough when you look at it, but when you push against it, it feels bouncy but not loose…also, if you hold the motor and try to spin the wheel, you should see the belt pull tight on one side, and become slightly slack on the other side…all teeth engaging,and no large bowing of the belt on the slack side of the belt…for me that is perfect…

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