Kite Aerial Photography (KAP)

Step 5 Trigger assembly - internal

For the 'guts' of the trigger I created a cam to rotate around the spindle and trigger the clicky pen. For this I busted open an old vhs cassette and used one of the tape spools. The inside diameter of the spool was a snug fit on the spindle, the vhs spool opening was widened a little to allow it to spin freely on the spindle.
Then I hot glued the modified push pins to the outside rim of the spool, these formed the 'teeth' that would step the spool forward eventually engaging the cam with the pen.
The cam was made from a small metal tongue found inside the vhs cassette. The tongue is bend to fit around the cassette spool with the tapered end sticking out. The cam was glued to the inner wheel on the spool and bent into position.
A small piece of tubing was used between the spool and the spindle to achieve the proper height needed to allow engagement between the motor and the teeth.

This was by far the most difficult step, take your time and make sure you've got the teeth spacing and cams set properly, there is not much you can do to modify this once you have it assembled. Your only option may be to dismantle and start the inner workings again, so be patient.