Torque is a measure of turning force given by multiplying force by perpendicular distance hence a longer lifting arm means more torque is required.

A featherweight weighs 13.6kg so on a 15cm arm needs approximately 2kgm of torque to hold all of the mass of the other robot in the air, you don't necessarily need that much torque as you are unlikely to be carrying all of the weight of the other robot.