Here is a perimeter marble run around this kids room The track runs around the entire room near the ceiling. The supports are walnut and a majority of the tracks and other parts are birch. Gear motors are run by "AA" battery packs. The marbles are 1 inch diameter.
[ame="http://www.youtube.com/watch?v=RTxmTTisThY"]YouTube - Perimeter Marble Run RBS[/ame]
[ame="http://www.youtube.com/watch?v=RTxmTTisThY"]YouTube - Perimeter Marble Run RBS[/ame]