Movement No. 159 is a modification of Movement No. 158, replacing the rigid connecting-rod with a cord and pulley arrangement to convert treadle motion into disk rotation. The foot treadle pivots at one end and is pressed down by the operator. Instead of a connecting-rod, a flexible cord is attached to the treadle and runs up and over a pulley, then wraps around the axle or rim of the rotating disk. As the treadle is pressed down, the cord is pulled, which unwinds from the disk’s axle and causes the disk to rotate. A return spring or the weight of the treadle lifts it back up for the next stroke. The substitution of a cord and pulley for the connecting-rod offers a simpler and more flexible arrangement — the cord can change direction easily around the pulley, allowing the treadle and disk to be positioned at different angles or distances from each other. This variation was used in early spinning wheels, grinding tools, and other foot-powered devices where a direct rigid linkage was inconvenient.
159. A modification of 158, a cord and pulley being substituted for the connecting rod.