Electric Knuckle Coupler for Garden Railway G scale

Edit Oct 2017: after a lot of revisions, I have a much better design with a Moving Knuckle now working:
https://www.thingiverse.com/thing:2553019

This has significant advantage that the servo is not actively holding the knuckle closed.
I have also updated the main knuckle coupling geometry so that the 'other' couplings are now all single piece. Unfortunately the revised geometry of the coupling means that it is not fully compatible with this original hook design.



Edit 30 May 20