This is the only freelance locomotive Aster has released, and the first of two locomotives driven by oscillating cylinders. (GER/OUEST/ETAT 0-6-0 is the other.) This one is even more unique in that both oscillators are single acting. In order to keep them 180 degrees out of phase, but the side rods 90 degrees out of phase so they won't lock up, there is a 90 degree return crank on the front driver of the left side. Thus, with the return crank in place, the cylinders are 180 degrees out of phase, and the connecting rods are 90 degrees out of phase... one cylinder always in a power stroke, no binding of the side rods. It also incorporates a fire tube boiler with curved tubes the carry the hot combustion gases from the vertical wick tubes through the smokebox. The tubes are so short that the gases will travel into the smokebox and out the stack unassisted; I've never seen anybody in Yokohama use a blower to fire one up.