Super helpful, man. *BUT* I'm still not quite seeing where all the extra length of the 7L axle goes, because when I initially slot it into the technic 1x2 brick, then follow it with all the things shown in your video, it still leaves about an inch of length sticking out. Maybe I have something longer than a 7L axle?
Screenshot shows what I ordered on bricklink! Seems like the axle should go back farther into the engine, but those funny white spoked half cylinders the set uses for the back half of each engine have nowhere for an axle to pass through.
Call me confused! Thanks again for the help!!