I believe you're looking for a gantry; it's what I'm wanting eventually.

http://www.synthx.com/btw/crane.htm

They have plans with different weight ratings and the material lists to correspond to get you there.

We have a locally fabbed one at work for our main mechanical room.

http://www.walkablecommunities.org/

Democracy is two wolves and a lamb voting on what to have for dinner. Liberty is a well-armed lamb contesting the vote.

**ubi apis- ibi salus**