How can I obtain the torque in an operating Dynamixel?

[roboteer]

You can also try to fit a linear function to your particular actuator using the graphs that ROBOTIS provides for each particular actuator from the e-manual. See this link

Calculation of torque value of 'XM430-W350-T'

At that time if you look at the RPM graph its value is around 5 rpm so the motor is about to stall.