Abstract: An pneumatic tensioner apparatus is disclosed, the apparatus including: a main drive belt; a chuck assembly, suspended from the main drive belt, having a spinning member and a drive contact portion; a first frictional drive belt in a first track, the first frictional drive belt in contact with the drive contact portion operative to spin the chuck assembly; and a first tension adjusting device having at least one pneumatic tension adjustment member operative to apply pressure to the first frictional drive belt tangentially to the drive contact portion.