622’s tender coupling is a sandwich of phosphor bronze and styrene. The two layers of bronze carry track power from the two sides of the engine to the two sides of the tender through a mind-bending arrangement of layers and folds. Seriously, it is such a puzzle that I wasn’t certain I would have the left side of the tender hooked up to the left side of the locomotive until I tested it with a meter. Phew!
The sandwich is deliberately separated slightly at the ends to provide a springiness and maintain a positive contact with the various frame components. Two lengths of .03″ plastic rod pass through all the layers to try to ensure they don’t come apart to cause an intermittent short one day.
Pembroke:87 