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Parallax Servos

BoeBotBoeBot Posts: 37
edited 2010-09-11 09:05 in Robotics
Just a question about the parallax servos. How much weight can they pull. I assume they must be powerful because they aren't very fast. They've gotta have some torque right? Could they pull ten pounds?

Comments

  • Martin_HMartin_H Posts: 4,051
    edited 2010-09-11 08:30
    When you say pull, do you mean be a motor for a robot that weighs ten pounds, or be the motor for a robot that is towing a ten pound load?

    The reason I ask is that a light weight robot towing ten pounds would likely lose traction, so the robot itself would need to have significant mass to tow ten pounds which would add to the load.

    In any event their torque is listed as 3.40 kg-cm or 47oz-in depending on you system of measures. Here are some of the formulas you would use to figure this out:

    Torque = Distance * Force
    Distance = Wheel Radius
    Force = Torque / Wheel Radius
    Force = Mass * Acceleration

    That last one is important when climbing hills. I couldn't find the formula for breaking static friction which would also be important to find.

    But at this point I don't think we need to do detailed calculations as ten pounds is 160 oz. Your wheels would need to have a radius smaller than an inch to have a chance of these equations balancing out which is impractical.
  • ercoerco Posts: 20,256
    edited 2010-09-11 09:05
    Servos come in many sizes; speed and torque vary based on their internal gearing. Heavy-duty servos have metal gears, ball bearings, or both.

    The Parallax servo is a mostly light-duty device. If you want something beefier, head to your hobby shop and have a look at http://www.hobbypartz.com/servos.html

    You didn't say continuous rotation (CR) or not. Using CR servos as robot drive motors is quick & easy to do, you just mount a wheel on them. But a robot much heavier than a BoeBot will overload a normal servo and strip the gears or break the output shaft.
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