Hello.
Just to confirm, it sounds like you are talking about our 4.4:1 Metal Gearmotor 25Dx63L mm MP 12V, either product #4861 (the version with an encoder), or product #3225 (the version without the encoder). Is that correct?
If that is correct, then most of your calculations so far seem okay. You could get a better value for motor torque constant (Kt) by factoring in the no-load current draw into your calculation, like so:
Kt = stall torque / (stall current - free run current)
However, depending on what you are aiming to do with these values, you might consider doing these calculations using the performance specs for the motor with the gearbox instead of the motor without the gearbox. That way your values will have the effects of the gearbox factored in.
We have not characterized the moment of inertia for our motors yet, but you could approximate that using the dimensions of the output shaft. The output shaft is made of stainless steel, and its dimensions can be found in the motor’s dimension diagram, which is available on the product page under the resources tab. Alternatively, you might be able to come up with a better estimate using the experimental procedure described here. Ultimately though, I would expect the rotor inertia to essentially be negligible once anything of substantial inertia is attached to your motor or once your motor is loaded in a real application, so it might be better to focus on characterizing that inertia first.
The viscous friction coefficient (B) can be determined by dividing the no-load current by the no-load speed and multiplying by the motor torque constant.
- Patrick