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Red arrows indicate which way force is applied to the gear rack. The rack and pawl are both restricted to only linear movement (not shown). A ratchet (occasionally spelled rachet ) is a mechanical device that allows continuous linear or rotary motion in only one direction while preventing motion in the opposite direction.
A simple machine is a mechanical device that changes the direction or magnitude of a force. [1] In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. [2] Usually the term refers to the six classical simple machines that were defined by Renaissance scientists: [3] [4 ...
3-wheeled handcar or velocipede on a railroad track Preserved railroad velocipede on exhibit at the Toronto Railway Historical Association. A handcar (also known as a pump trolley, pump car, rail push trolley, push-trolley, jigger, Kalamazoo, [1] velocipede, or draisine) is a railroad car powered by its passengers or by people pushing the car from behind.
Geared machines use worm gears to control mechanical movement of elevator cars by "rolling" steel hoist ropes over a drive sheave which is attached to a gearbox driven by a high-speed motor. These machines are generally the best option for basement or overhead traction use for speeds up to 3 m/s (500 ft/min). [50]
The hand axe is the first example of a wedge, the oldest of the six classic simple machines, from which most machines are based. The second oldest simple machine was the inclined plane (ramp), [6] which has been used since prehistoric times to move heavy objects. [7] [8] The other four simple machines were invented in the ancient Near East. [9]
Most weight machines have levers or pins to customize the seat height and range of motion, so don’t hesitate to consult the machine’s diagram or ask a gym staff member for help if needed.
A crane is a machine used to move materials both vertically and horizontally, utilizing a system of a boom, hoist, wire ropes or chains, and sheaves for lifting and relocating heavy objects within the swing of its boom. The device uses one or more simple machines, such as the lever and pulley, to create mechanical advantage to do its work.
The Song Shi description of the gears in Yan Su's chariot, and the numbers of teeth on them, suggests that it worked this way, without a third road wheel. The gear ratios would have been correct if the pointing doll was attached directly to the large horizontal gear wheel, and the track-width of the chariot equalled the diameter of the road wheels.