How does the rpm of a dc motor vary with the load weight?

Question

I realize there's no specific formula for this, but any rough idea how the rpm would vary if say I had a 12V dc motor currently at 1,000 RPM unloaded. If I was to then add 200g on an 8cm long rod centred perpendicular to the motor, what effect would this have on the RPM?

Oh, and are the torque-rpm gradient values for the motor irrelevant in this case because the load is vertical (i.e. parallel to the axis of rotation and not perpendicular to the 'radius')?

Any advice much appreciated!

Answer 1

Most motor manufacturers can supply you with a torque curve (torque @ RPM) for a given motor.

You are going to find that adding your 200g on the end of the arm is going to unbalance the motor, and a fair amount of the torque is going to go into lateral movement of them motor. You can estimate how much by using the centroid of the motor weight and the center of the 200g weight at your 8 cm. The system is going to generate force to attempt to spin about the centroid of this mass and arm system.

Answer 2

A "brushless DC motor" is unquestionably an AC motor with a circuit, noted as an inverter or controller, to transform the DC into AC for the motor. The converter and style of poles on the motor make certain the shaft velocity(converter-output-frequency/style-... the quantity of torque the motor can preserve would be desperate by employing the vehicles length and construcion. extra beneficial motor, extra torque. Neodymium extra torque. Smaller motor, steel extremely of neodymium, much less torque. attempting to squeeze lots of torque from a small motor many times potential lots of warmth generated and absence of performance. i'm unsure what 70 kilograms potential. Any motor could be made to advance 70 killograms with gearing. you're able to desire to make certain the mandatory torque of the motor to make certain if a motor of the size you're speaking approximately can do the interest. Torque is measured in newton-meters or foot pounds. in case you're searching for the motor to advance 70 pounds from a small lever with out any gearing, forget it. A motor of that length won't come close. yet once you're merely speaking approximately lifting, it somewhat is extra available with gearing.