I've been slowly building an outdoor play area for my kids (4 energetic children aged from 2-11). One of my neighbors recently put a large number (~25) of wood posts out for the trash, and we saved the trash pickup guys some trouble and snagged them. The posts have about a 6" diameter, are well rounded, and are cut in fairly even lengths of about 3 feet long.
I've already bought some standard 2x4's and I'm going to put some of these posts into the ground as simple supports to turn 2x4's into balance beams.
I would like to to use some of the rest to turn them into "spinning" balance beams, or something along those lines. I'm not sure what might be the best way to do that. The rough picture in my head involves simply drilling a deep hole into both ends of a post, inserting a long bolt through a support post and into the hole (without securing it inside the post). That's probably not the best description, and probably won't work, but I also suspect that there might be some specialty bolt/joint/fasteners that are designed for this sort of movement and which will work much better anyway.
Are there any specialty "bolts" that might be dropped into both ends of a post and allow it to spin freely while supported from the ends? If not, is there any way I might fashion such a connection using common home-improvement store items?