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How do I know what the torque of a motor and what is a powerful torque?

blueokiris

I have many motors and have tried to build stuff like your quad copter or a little robot, but none of my motors seem strong enough. Do I need a motor with more torque or is it a power thing? How do you know what the torque is?

  • 0

    Hi Dylan,

     

    I don't think you need to measure the torque for a small robot project, but most typical small motors in home products like toys run at a very high speed. You'll need to gear down the speed, which has the effect of increasing the torque. In this manner, even a tiny (<10mm diameter) motor can be sufficient. You can get an idea of what gearing you need by figuring out how far you wish the device to move per (say) second, and if you know the diameter of the wheels, then you can make an approximate calculation. You'll need to make an assumption of the speed (e.g. in RPM) of the motor - you could assume 6000RPM for a small motor as found in a toy, which will be the right ballpark to make your calculations 'good enough'.

    Example:

    You want a speed of 100mm per sec, and your wheel diameter is 50mm.

    circum=pi x dia = approx 150mm

    So, this means that the wheel needs to rotate at 100/150 revolutions per sec, which is 2/3 rev/sec (i.e. 0.666 rev per sec)

    In RPM, that is 60*2/3 = 40 RPM

     

    Since your motor is assumed to be 6000RPM, your gear ratio needs to be 6000/40 = 150:1

    By coincidence, doing a google search for this reveals this gearbox which happens to have exactly that ratio.

     

    I don't know much about quadcopters, they may need special motors and control hardware (not usually found in home products).

  • 0

    Most motors suitable for driving something like a robot will have some sort of gearing or gearbox.

     

    A small, fast, wimpy motor uses a small gear to connect to a larger gear. This converts the speed into torque.

     

    You also see this in electric drills, they use a beefy DC motor, then a planetary gear drive to greatly increase the torque/driving ability.

     

    Some DC motors come with gearboxes already bolted on. They usually run around $15 and can be found in surplus houses.