 As with those systems it used a return crank on a driver (instead of the eccentrics used by the Stephenson valve gear).The return crank attached to the eccentric rod, which hung from a pivot close to the far end of the eccentric rod.This pivot attached to the end of the radius hanger, the other end of which attached to a link block which slid back and forth in a track curved in the same manner as the expansion link of a Walschaerts gear.