1/50th logging cable grapple

This is a logging grapple, cable controlled, that can be dropped and used from either a Log yarder or crane. For reference of size, please take a look at the diagram picture I've included. The tongs can stretch to 8 feet wide.  The idea is simple: Two lines come down into the upper hoist, with another on the other side. The two lower ones, which are gray, are fixed to the upper carriage. The top one, in the left of the photo, goes into the upper carriage, and feeds over a pulley into the bottom, and down to the lower carriage/arms. The 'operational' cables are red, except for the upper cable to the left. (my mistake).  The red line goes down, feeds to the left over the pulley of the left grapple, over and then feeds to the right grapple and ties off to the pin on the right grapple. Pulling the upper line closes the jaws.  There are two other lines, yellow. THese can be either chain or cable to connect to the upper carriage. I've included the pin for the lower carriage/grapple arms, but feel free to replace with stronger material.  Note the upper pin is for tying off to a pulley on a highline type logging system.  Questions? modelmechanic@gmail.com