What is Gear

A gear is a rotating circular machine part having incising or,in the case of a cog or bull gear, inserting teeth (called a cog) which meshes with another (compatible) toothed part to transmit (convert) torque and speed.The fundamentals behind how gears work are similar to the fundamentals of a lever.A gear may also be informally called a cog.Gearing can change the speed, torque and direction of a power source.Different sized gears create torque variations that create mechanical advantages through their gear ratios and can therefore be considered simple machines.The rotational speed and torque of the two meshing gears differ proportionally to their diameters.The teeth on the two meshing gears have the same shape.Two or more meshing gears working in sequence are called a gear train or transmission.The gears in a transmission are similar to the wheels in a crossed pulley system.One advantage of gears is that the teeth of the gears prevent slipping.

In transmissions with multiple gear ratios such as bicycles,motorcycles,and automobiles the term "gear" (such as "first gear") refers to the gear ratio rather than the actual physical gear.The term describes similar devices, even when the gear ratio is continuous rather than discrete, or when the device actually contains no gears, such as a continuously variable transmission (CVT).Sometimes a CVT is called a "continuously variable transmission."Additionally, a gear can mesh with a linear toothed part called a rack, producing linear motion instead of rotation (circular motion).For an example, see rack and pinion.

Etymology

The word gear probably comes from Old Norse gørvi (plural gørvar) "clothing, equipment", related to gøra, gørva, meaning "to make, build, build; set in order, prepare, a common verb in Old Norse,"used in everything from writing books to serving meat".In this case, the meaning of "a cog in a mechanism" is first attested to the 1520s; the specific mechanical meaning of "a part for which a motor transmits motion" is from 1814 ; until 1888 referring specifically to vehicles (bicycles, automobiles, etc.).Cogs are teeth on a wheel. From Middle English cogge ← Old Norse (compare Norse kugg ('cog'), Swedish kugg, kugge ('gear, tooth')), from Proto-Germanic *kuggō (compare Dutch kogge ('cogboat') ), German Kock), from Proto-Indo-European *gugā ('hump, ball') (compare Lithuanian gugà ('saddle, hump, hill'), from PIE *gēw-('curved, arched ').First used c.1300 in the sense of "a wheel with teeth or cogs"; late 14th century, "teeth on a wheel"; gears, early 15th century. Historically, gears were made of wood and Teeth that are not made of metal, technically a gear consists of a series of wooden teeth that sit around a mortise wheel, each tooth forming a special "through" mortise and tenon joint.Wheels can be made of wood, cast iron, or other materials Made.Wooden cogs were previously used for large metal gears that could not be cut, when the shape of the cast teeth wasn't even roughly correct, or the size of the wheel made fabrication impractical.The gears are usually made of maple.In 1967, the Thompson Manufacturing Company of Lancaster, New Hampshire was still very much alive, supplying tens of thousands of maple gear teeth a year, mostly for paper mills and mills, some dating back over 100 years.Since a wooden tooth functions exactly the same as a cast or machined metal tooth, the term was extended to apply to both, and the distinction has generally been lost.

Comparison with drive mechanisms

In precision machines,such as watches, that rely on precise speed ratios, a defined gear-to-gear ratio provides an advantage over other transmissions such as traction drives and V-belts.Gears also have an advantage over other drives in reducing the number of parts required when the drive and driven are close together.The downside is that the gears are more expensive to manufacture and their lubrication requirements can add to hourly operating costs.