But it works! That is far better than most of us - I disconnected my test loops to facilitate new skylight installations September a year ago - still haven't re-connected. But all of my Challengers ran well at some point in ancient history.
Rocker - 2-rail articulated models are always connected just like the real thing - one engine is rigidly connected to boiler and firebox, the other to a tongue and slider arrangement.
And generally, a Mallet will have larger cylinders on the articulating engine. The UP Challengers are "Simple Articulated."
