Leavitt-Riedler Pumping Engine at Chestnut Hill Pumping Station in Massachusetts, USA. The left side is one of the three shafts from of the steam engine. The vertical rod with six-foot stroke from the engine pushes up and down, driving the horizontal shaft connected to the flywheel (right) as well as rocking the crank. The horizontal rod (the left-most rod) is driven from the horizontal shaft pull and push the crank backward and forward. The combined action of the two rods rocks the crank, driving an inclined pump plunger (not seen in this photo).