Introduction of Gears and Friction Wheel
Introduction of gears: The slip and creep in the belt or rope drives is a common phenomenon, in the transmission of motion or power between two shafts. The effect of slip is to reduce the velocity ratio of the drive. In precision machine, in which a definite velocity ratio is importance (as in watch mechanism, special purpose machines..etc), the only positive drive is by means of gears or toothed wheels.
Kinematically, the motion and power transmitted by gears is equivalent to that transmitted by friction wheels or discs in contact with sufficient friction between them. In order to understand motion transmitted by two toothed wheels, let us consider the two discs placed together as shown in the above figure
When one of the discs is rotated, the other disc will be rotate as long as the tangential force exerted by the driving disc does not exceed the maximum frictional resistance between the two discs. But when the tangential force exceeds the frictional resistance, slipping will take place between the two discs. Thus the friction drive is not positive a drive, beyond certain limit.
Gears are machine elements that transmit motion by means of successively engaging teeth. The gear teeth act like small levers. Gears are highly efficient (nearly 95%) due to primarily rolling contact between the teeth, thus the motion transmitted is considered as positive.
Gears essentially allow positive engagement between teeth so high forces can be transmitted while still undergoing essentially rolling contact. Gears do not depend on friction and do best when friction is minimized.
Some common places that gears can normally be found are:
|Printing machinery parts||Newspaper Industry||Book binding machines|
|Rotary die cutting machines||Plastics machinery builders||Injection molding machinery|
|Blow molding machinery||Motorcycle Transmissions (street and race applications)||Heavy earth moving to personal vehicles|
|Agricultural equipment||Polymer pumps||High volume water pumps for municipalities|
|High volume vacuum pumps||Turbo boosters for automotive applications||Marine applications|
|Boat out drives||Special offshore racing drive systems||Canning and bottling machinery builders|
|Hoists and Cranes||Commercial and Military operations||Military off-road vehicles|
|Automotive prototype and reproduction||Low volume automotive production||Stamping presses|
|Diesel engine builders||Special gear box builders||Many different special machine tool builders|