ABSTRACT
One of the oldest and, at the same time, most ingeneous applications of a screw is the Archimedes' screw for lifting water. As the screw is rotated, each thread of the screw transports a certain amount of water. Theoretically there is no limit to the height the water can be lifted other than manufacturing capabilities of long length and the required torque on the input shaft. A metal strip or square rod may be twisted to make a long-lead thread, ideal for transforming linear into rotary motion. Note that the number of turns or dwell of the output gear is easily altered by changing the twist of the strip. The worm drives the wheel, which also acts as a nut. The rotation of the nut lowers or lifts the jack, which is prevented from rotating by a screw that fits into a keyway in the jack. The worm and worm wheel drive decreases the input torque.
