Flat belt drives became common after the “Industrial Revolution,” when the early machine shops were driven by overhead line shafting originating from a central power source, such as a water wheel or steam engine. They were also used in agriculture and mining applications. The early machine tools were directly linked to and driven from an overhead pulley that ran at a continuous speed and was always running. The machine usually had three different pulley sizes attached to the work spindle for slow, medium, or high speed. When the machine operator required changing spindle speed using a piece of wood, he would have to ip the belt from one pulley to anther (a procedure not without its dangers).