Here is a perimeter marble run around my sons 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.
Go to the following link for more information on the building of this track:
www instructables com/id/Kinetic-Marble-Track-Ar ound-The-