I finally finished the boom and got everything installed. The linkage for the Hydraulic cylinders on the outer two boom sections would need to be redesigned if it actually had to work but it gives the illusion it is working. That is what counts on a toy.
Outer 3 sections of the boom
Everything installed and working
Here everything extended
Hopefully my grandson can figure out how to fold and extend this boom. I didn’t run any piping on the boom figured for the target audience it would just add some complexity that he didn’t need.
-- Bruce, Boise, ID