It has been one hell of a long time since I last posted and sadly this will just be a short one, I hope to get some posts up soon!

I have a ton of MY6812 motors that were originally intended for a hexapod design of mine (and still intended to) of which I want to operate the motors in their stall torque region for a short period of time so save me designing(spending) for a massive rated torque. Bare in mind, running a motor in the stall torque region for long periods of time can cause major damage!

Information on DC motor constants and operation can be found here.

In this test, I used pretty basic setup of a MY6812 motor screwed into a plan of wood with a spanner acting as a torque arm, providing a force on a scale mounted next to the motor. The scale has a full scale measurement of 5kg and the spanner used has an arm length of 150mm meaning a maximum torque measurement of 7.4Nm of torque.

The scale itself has four load cells on the base meaning the entire scale needs to be on a rigid surface for an accurate measurement. I also used a piece of wood to spread the load of the spanner across the surface of the scale.

The scale was zeroed with the load spreading block and spanner in place

Using my power supply in a constant current, I varied the current through the motor and noted the force provided by the motor. Plotting this in google sheets with a trendline and viewing the resultant equation gives the torque constant for this motor.

Operating the motor at 10A stalled

Stall torque vs current curve

A DC motor should under non saturated operation have a linear relationship between torque and current, along with voltage and RPM. Through some theory, it turns out that the two constants, named Kt (torque constant) and Ke (voltage constant) are actually equal.

From this knowledge, a theoretical Ke can be calculated. There are many sources for information on the MY1016 motor, one of which is here. Given an open load velocity of 3000rpm at 24V, this translates to a Ke of 0.07639437268rad/s/v (note the different units). From the above graph, my measured Kt (from the slope of the curve) was placed at 0.0711Nm/A which is an error of -6.93%! Not bad for a cheap setup.

The full results and calculations can be found in this google sheet.

A few more specifications for this motor
Phase resistance: 0.4ohm (Calculated from voltage drop at 10A)
Phase inductance: 400uH (Measured with BM4070 LCR meter)