After reading this thread I checked one of my Atlas O NE-6 cabooses. First picture shows pitting on one of the thumbtacks that evidently had been making intermittent contact with the middle rail. The clearance between the thumbtack and rail was very small and slight downward pressure on the coupler caused it to contact the middle rail. I slightly loosened the coupler drawbar (larger phillips) pivot screw, removed the truck (smaller phillips) pivot screw, and gently pulled the truck out from beneath the car. I then turned the car upright and tightened the slotted upper drawbar screw. I retightened the coupler drawbar pivot screw and reinstalled the truck pivot screw. The thumbtack now has about 3/32-inch clearance from the rail and does not deflect when slight downward pressure is applied – same as at the other end of the car.
Note: the coupler drawbar pivot screw has a spring underneath, so release it carefully, although the screw does not have to be removed to do the repair.
MELGAR
