A gear train is formed by mounting gears on a frame so that the teeth of the gears engage. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, this provides a smooth transmission of rotation from one gear to the next.
The transmission of rotation between contacting toothed wheels can be traced back to the Antikythera mechanism of Greece and the South Pointing Chariot of China. Illustrations by the renaissance scientist Georgius Agricola show gear trains with cylindrical teeth. The implementation of the involute tooth yielded a standard gear design that provides a constant speed ratio.
Some important features of gears and gear trains are:
- The ratio of the pitch circles of mating gears defines the speed ratio and the mechanical advantage of the gear set.
- A planetary gear train provides high gear reduction in a compact package.
- It is possible to design gear teeth for gears that are non-circular, yet still transmit torque smoothly.
- The speed ratios of chain and belt drives are computed in the same way as gear ratios. See bicycle gearing.
... Types of gear trains include Simple gear train Compound gear train Epicyclic gear train Reverted gear train ...
... Factors affecting the amount backlash required in a gear train include errors in profile, pitch, tooth thickness, helix angle and center distance, and runout ... created by cutting the teeth deeper into the gears than the ideal depth ... backlash is by increasing the center distances between the gears ...
... coiled spring or a suspended weight, transmitted through the timepiece's gear train ... The escapement releases the tooth of a gear, which therefore changes from a "locked" state to a "drive" state until the opposite arm strikes another tooth on the gear, which locks the gear again ... A clock's tick is the sound of the gear train stopping as the escapement locks ...
... The engine, rotating at only a few hundred revolutions per minute, drives a reduction gear train ... The gear train drives an ascending chain lift to lift ball weights to a top track from which they load onto a drive chain providing the driving force to the clock while ... The engine-driven gear train drives the lower sprocket of a vertical link-chain (similar to a bicycle chain), with a lift of about four feet ...
... A gear train, called the going train, which has the dual function of transmitting the force of the mainspring to the balance wheel and adding up the ... A separate part of the gear train, called the keyless work, allows the user to wind the mainspring and enables the hands to be moved to set the time ... wheel vibrating by giving it a push with each swing, and allowing the clock's gears to advance or 'escape' by a set amount with each swing ...
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