Here you go. Theses are the parts to build the 28" tracks on that robot.
Main drive, sprockets, shafts and track: mtdcanada.com/partscatalogue/winter/pg45.pdf
And here is where they can be purchased: mtdcanada.com/yardman/yardma … winter.asp
http://i138.photobucket.com/albums/q253/gfisher2002/robots/Belt.jpg
http://i138.photobucket.com/albums/q253/gfisher2002/robots/Sprocket.jpg
http://i138.photobucket.com/albums/q253/gfisher2002/robots/MainDrive.jpg
http://i138.photobucket.com/albums/q253/gfisher2002/robots/MainDrive2.jpg