Movement No. 170 presents another form of centrifugal steam engine governor — a variation of the classic ball governor (No. 161) that eliminates the central slide on the spindle by using crossed arms and short links to directly actuate the valve-rod. Instead of separate upper and lower arms connected by linkages to a sliding collar, the governor arms in this design cross each other at a pivot point. Each arm carries a ball at its lower end and extends upward beyond the crossing point. As engine speed increases and centrifugal force swings the balls outward, the crossed-arm geometry causes the upper extensions of the arms to move inward and upward. Two short links connect these upper extensions directly to the valve-rod, translating the inward motion of the arm tops into a closing action on the regulating valve. This crossed-arm design is more compact and direct than the slide-collar arrangement, with fewer moving parts and a more immediate mechanical response to speed changes.
170. Another form of steam engine governor. Instead of the arms being connected with a slide working on a spindle, they cross each other and are elongated upward beyond the top thereof and connected with the valve-rod by two short links.