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Torque constant and Motor velocity constant of DC Motor


I am using the 30:1 Metal Gearmotor 37Dx68L mm 12V with 64 CPR Encoder (Helical Pinion) and I was wondering how to obtain the values for the following:

  • Jm (Moment of Inertia of Motor)
  • kt (Torque Constant)
  • kv (Motor Velocity Constant)
  • b (Motor Viscous Friction Coefficient)

Any help is appreciated. This is my first post on this forum.
Thank you.


Many of the parameters you are interested in can be derived from the performance curves in our 37D gearmotor datasheet, which is available on the product page under the “Resources” tab.

Here is a link to a forum post I wrote which outlines how to can do that. Please note, unlike the motor discussed in that forum post, the inductance of our 12V 37D motors is about 2.3mH. Also, for moment of inertia calculations, the output shaft on our 37D gearmotors is stainless steel.

- Patrick