When the robot finds the "thing," it has to grab it and lift it off the ground to carry back to the catapult. Here's how this is built.
Cut off the ends of a servo horn and attach the horn to a continuous rotation servo motor. This is a normal servo motor with the electronics and end stop removed--just a dc gear motor.
Attach the 3d printed servo horn.
Push this into the leadscrew and secure with a 2-56 screw and nut.
Place the servo bracket against this assembly, making sure that the motor shaft can turn freely. Melt the servo bracket to the assembly using a soldering iron (or glue).
Attach the pincer to the extend plate.
Attach a servo motor to the pincer.
Attach the pincer assembly to the actuator assembly.
Glue the servo lid to the servo motor bracket.
Melt (or glue) the ping holder to the bottom of the servo bracket--adjacent to the servo motor.
Add the ping ultrasonic detector to the bracket.
The lifter assembly is now ready for attachment to the body.