Many of the early sewing machines were powered by a treadle mechanism. The treadle was operated by pressing down on it with a foot, or both feet, to cause a rocking movement. This movement spins a large wheel on the treadle frame, connected by a thin leather belt to a smaller driving wheels on the sewing machine.A treadle sewing machine flywheel mad of cast iron. It is three tangent circles within a larger circle.3treadle sewing-machine flywheel