Let's Make Robots!

needing help on a crane/boom to r/c

hello  everybody im new to this forum

 i build custom radio controll semis for a living .all one of a kind.73 build to date.

my new build is a crawler recovery truck .im at the point where i need to start thinking and building the boom,i want to make a working crane/cherry picker/boom/controll arm what ever you want to call it.

 the arm it self had to extend i say about 24 inch and has to pick up about 4 pounds

im running a 7.2v main battery and a 4.8v receiver battry.i would like to operate the boom from my radio.