What's the name of the part that's placed on axis of a motor that has weight off-center, to create vibrations? Say, phone vibration motors have that.

  • 2
    Do you mean the weight itself, the eccentric rotating mass (ERM)?
    – user230
    Nov 21, 2014 at 19:51
  • 1
    @snailboat is correct - the part is the eccentric rotating mass or ERM, although sometimes it is referred to as just the "eccentric mass" when the context makes it clear that it's part of a vibration motor.
    – ColleenV
    Nov 21, 2014 at 21:31
  • @snailboat: Just the technical element with the mass. (without the motor).
    – SF.
    Nov 21, 2014 at 22:20
  • I believe ERM is the answer. Anyone up to posting it for easy +15 points?
    – SF.
    Nov 23, 2014 at 15:28

1 Answer 1


I believe you mean the eccentric rotating mass (ERM), sometimes called simply the "eccentric mass", as ColleenV notes in her comment.

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