Originally THING 1 was equipped with o-rings, one in the front(in place of a drive bar) and one in the rear. Both were balanced to give a seesaw action, but I had to scrap it. The o-rings worked perfectly for about 30 seconds until they stretched out to far and the A-bar clattered against the housing. I was trying to compensate for the yaw that occurs with the A-bar/cam system.