Help with 2 section tele boom

[Muddydisco]

Hi Guy's total noob here with things like screw motors and lifts etc. I want to make a 2 section telescopic boom. I can understand that a single one is easy just a screw and motor, but how can I make a second section extend out again?

Also what motors are you using for these type of things? I can't seem to fins anything small enough.

[Finster]

I think this video explains the concept you are looking for.
http://www.youtube.com/watch?v=yInMEfrQWwA

Hope this helps.

[Muddydisco]

Yeah that's one way but I'm not going to have gravity to help bring it back together. It's a recovery boom so not vertical more like 45 degrees max. I'm also working it 1:12 so space will be tight.

[Finster]

Ok maybe this is better, its from a Liebherrr Crane Brochure. Just simplify it for fewer sections.

http://i298.photobucket.com/albums/mm244/Finsterbaby101/forum_post/telescopic_boom_zps62bb1b9c.png (http://s298.photobucket.com/user/Finsterbaby101/media/forum_post/telescopic_boom_zps62bb1b9c.png.html)