[Bryce Paputa]

Yeah, one of these servos is not going to cut it. Lets assume that the 4 bar linkage is 6 inches long, and that 2kg~5lb, that would require 30lb-in, or 480oz-in, of torque to hold, plus the weight of the mechanism, plus the torque to accelerate it, plus inefficiencies like friction. This is well above the stall torque, you'd need some where between 16:1 and 4:1 of reduction depending on the servo used, which would probably mean that you would need a continuous rotation servo which has even less torque (not to mention that it would be insanely slow). A NXT motor might be a tiny bit better, but not much. Why can't a DC motor be used?