How do the San Francisco cable cars work?
The cable car system starts with the engineering of a pulley and cable system originating in a power station at one end of the cablecar line. There, an electric motor turns a pulley on which is attached a metal cable approximately one inch in diameter. At the other end of the system, in another building, is another pulley. The cable moves incessantly, and the passenger car itself is equipped with a large pincer-type device which allows the driver to engage and disengage the perpetually moving cable, thereby moving the car or stopping the car (by disengaging and applying brakes). This physical arrangement allows the car to climb steep hills, since no wheels need to have friction with the roadway. The cars are equipped with metal wheels that run on metal tracks set in the roadway, with the cable running between them under the road surface and “grabbable” with the pincers through a perpetual slot. While this arrangement restricts where the cablecar can travel, it also provides pollution-free mass transportation in a metropolitan area.