Rotary steam engines were found to be more suitable than beam engines because the steady speed of the heavy flywheel gave a predictable pause between reversals of direction, whereas pistons acting directly on the rods, even when controlled by a cataract governor, could surprise the passenger by irregular waits, longer or shorter. In Cornwall only the Wheal Reeth man engine, Godolphin, (where a pumping engine was converted to this new use) was powered by a piston acting directly on the rods. When not in use for the man engine, it was an advantage that a rotary engine could also be used to power a whim.