Well done.. those bell cranks could also be made of wood/ply or even thick plastic card. When I was scratch building R/C model boats I used plastic tubing and wire which went through the plastic tubing or even plastic rod through the tubing, which was also used for model aeroplanes.... anything can be used if thought about (I have even seen dowel with cup hooks screwed into the ends). A well detailed and explained video.

my grandad used triang lever frames connected to fishing line,with a pen spring attached to the sleeper