hs-311 has 49 oz/in of torque . Thats 3.0625 pounds / in
so 49 > distance from motor shaft * weight of object at that distance away
NOTE: distance should be measured in inches and weight should be measured in ounces
Ex. at 6" long servo arm can only have an object weighing 8 ounces at the end.
More than that the servo won't turn and the gears will grind.