Marble ball release mechanism

Based on a beam engine design, will release 21mm balls one at a time from a 25mm electrical conduit.

Drill two holes through the conduit.
Use model aircraft push rods to connect the servo arm and the top of the "pistons"
Use 6mm wooden dowel, wood glued into the piston tops

Lightly sand the conduit to glue the device onto it and use cable tie through hole in back to secure.

It works when on a gentle angle. Too much tilt will force more than one ball through at a time. Play with the timings on the servo.