I am trying to exert a desired load of 0.07 N.m on a BLDC motor shaft whose length is 0.750in and diameter is 0.3125in (0.008m). I can go to a machine shop and get a small adjustable cylindrical coupling made for my shaft. But I need it to exert close to desired torque at a speed of 2100 rpm (220 rad/s). I tried doing some calculations, according to the formula
Torque = speed * mass * (radius)^2
If I solve this equation with T = 0.07 N.m, speed = 220 rad/sec, radius = 0.004 m, I get around 20 kg for mass, which is huge!!!. It is more than the mass of the motor. Can you please suggest a convenient way to load the motor. Thank you.