I have the bass drum mount, the L-arm, carriage bolt and the down tube/post. The u-bolt and down tube mounts do not have any ratchet or stops to keep the tom and L-arm from rotating on the carriage bolt (x-axis) . The L-arm does not twist in the u-bolt, the U-bolt turns around the carriage bolt sideways like a clock arm. Maybe a lock ring or ratchet is broken off or worn off???
The L-arm is fine and knurling is good, but I would replace with modern style L rod for the tom mount if the post to u-clamp can be solved.
[IMG]http://i836.photobucket.com/albums/zz285/sea_nettle2009/Vintage%20Drum/Slide1.jpg[/IMG]