When building a layout, we sometimes forget to just stop and run trains on it. I finally decided to take the time to see what would run on the helix. I decided to stop at 12 passenger cars and a tender (or extra box car on diesels), because I didn’t want to pick them off the floor, or start loosing traction tires. In all the trains was over 15 feet long. The biggest surprises were the Lionel engines Polar Express, Hogwarts, and RI 5100, because these are all single motors. The MTHs RK PRR GG1, CSX Dash 8, PRR F3, and Williams Amtrak FP45 seemed to have plenty of power to spare for some more cars.