Gears are mechanical devices that transfer torque and motion or set mechanical motion in action through the engagement of other gears, a shaft or a series of parts. Gears interlock with one another and turn together with the help of evenly cut teeth. Teeth allow different sized and shaped gears to interlock with one another.
Gear applications are quite diverse and highly customizable; they appear anywhere that an application requires speed reduction, speed increase, power transmission, motion transmission or force reduction.The relationship between gear size and speed is called “speed ratio,” or alternatively, “gear ratio.” Gear ratio can be calculated using a gear’s number of teeth. For example, two interlocking gears that have 60 teeth and 30 teeth, respectively, have a gear ratio of 2:1.
The world of industrial gears is quite varied. Some common ones include: spur gears, sprockets, planetary gears, bevel gears, spline gears, helical gears, rack and pinion spur gears, rear end gears, worm gears and differential gears. The spur gear, also called a straight-cut gear, is the simplest type of gear available. Straight-sided along the gear wheel’s axis, with straight teeth in line with the axis, spur gears are frequently used as sprockets. Sprockets are thin gears with easy-locking teeth that lock into roller chains, like bike gears. They’re used for non-slip pulley power transmission.
Other types of spur gears transmit motion and torque laterally through compatibility with other parallel aligned gears. Such gears are main components in planetary gears. Planetary gears, also called epicyclic gear trains, are used in complex applications that require smooth torque transmission, such as drivetrains and automotive transmissions.
The spur gear used by planetary gears is called a “sun spur,” which is surrounded by three-plus exterior gears called “planet gears.” Bevel gears are conically shaped, allowing them to interlock with other gears perpendicularly, making them useful for rear end wheel torque applications.
Bevel gears have either straight or curved teeth, in which case they are called spiral bevel gears. Curved teeth are helpful for speed reduction of process machines like packaging machinery, textile looms, material handling systems and conveyor systems. Spline gears are either cylindrical or rod-shaped with straight teeth that allow them to transmit motion laterally by fitting inside internal devices or gears.
When manufacturers design industrial gears, they choose teeth numbers and gear ratios with the knowledge that these determine a gear’s durability and strength, as well as the speed, function and control the gear will wield within a larger assembly. To help gears withstand wear and tear, they may also use a variety of cutting techniques, such as gear hobbing.
To increase or reduce a shaft’s rotational speed, manufacturers join differently sized gears. These gears may be made from any number of materials, depending on their application requirements. Most are made from metals or hard plastics. Demanding automotive applications, for example, engage hard metals like copper, brass, steel and, occasionally, titanium. In contrast, machinery applications that require lightweight components often utilize water-resistant plastics like polycarbonate and nylon. Also, to extend and improve the working life of gear systems, gears generally use some form of lubrication. Well-maintained gears yield great results.