Quote:
Originally Posted by wiiking123
Now that my team's season is over, we were thinking of doing some sort of T-shirt cannon attachment to our robot. Our plan is to make an assembly very similar to the camera assembly in the rookie kit using 2 hobby-like servos. Each servo has a torque of 125oz/in, and I am wondering about how much weight could each of these servos support, or how i would figure this out mathematically. Our turret my guess will weigh about 2-3 pounds. Also, is it safe to power these 2 servos off of the Digital Sidecar?
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There are 16 ounces to the pound, and 12 inches to the foot, so 125 oz/in torque is equivalent to about 0.65 ft/lbs. You can use a free body diagram to help you figure out if a given arm (with given mass and center of gravity) can be moved, however this means (at stall torque) the servo could maintain the position of an arm that weights 1 pound if the center of gravity of said arm is .65 feet from center of rotation.
However, it's unlikely these servos will work unless you plan on making a twelve inch long air cannon that only shoots confetti. And even if much larger servos that could handle the torque necessary to support a full-size air cannon were available, they would still constantly need power to maintain their position, otherwise they would just back drive.
A much simpler solution for a FRC team would be to utilize the KoP window motors to achieve the pan/tilt drive for an air cannon. These motors have internal worm gear drives to prevent back-driving, and thus can keep their position without having to constantly power them. You can then use a potentiometer to measure the angle the arm is at.