Gears are mechanisms used to transfer motion from one shaft to another. From automobiles to machinery : All products use gears to transfer motion. Different types of gear has different applications. For Example, spur gears are used to transfer motion between parallel shafts. Whereas Rack and Pinion gears are used to covert rotational motion into linear motion. In this article we will talk about types of gear and their applications.
Types of Gear
According to type of motion gear transfer from one shaft to another. Gears are classified in following types. Each gear type has different applications.
Spur gears have teeth parallel to the gear axis. They are used to transmit power between parallel shafts.
- Simple in construction and easy to manufacture.
- Low Cost and high efficiency.
- Various gear ratio can be achieved.
- Automobiles and bicycle.
- Mechanical Clocks etc
Helical gears have teeth inclined to the gear axis. For the same width, helical gear teeth are longer than spur gears. Therefore they can transfer more power between parallel shafts compared to spur gears.
- Higher load carrying capacity and contact ratio compared to spur gears.
- Smoother and quite than spur gears.
- Good precision rating.
- Lower efficiency compared to spur gears.
- Helix angle also add axial thrust on the shaft.
They are used to transfer very high speeds and loads between parallel shaft. Some of examples of helical gear applications include but not limited to:
- Automotive gearboxes.
- Printing and other machinery
- Conveyors and elevators
- Factory Automation etc.
Herringbone and Double Helical Gear
They are double helical gears with opposite helical teeth. Double Helical gear have groove in the middle between the teeth. Whereas Herringbone gear does not have groove.
Both gear types are used to transfer power between parallel shafts. Compared to helical gear they offer an advantage of balancing axial thrust in both directions.
- Reduced axial force
- Smoother transmission and engagement
- Reduced noise
- Self centering capability
- High load capacity
- Difficult to manufacture
- High Cost.
Herringbone gears have high load carrying capacity applications. Therefore they are used in Differentials and heavy machinery.
Rack and Pinion
A rack is a cylindrical gear with infinite radius. Whereas pinion is a spur gear. They are used to convert rotational motion into linear motion.
Since rack is a gear with infinite length. Which is not possible in real world. Therefore rack and pinion gears can not transfer continuous motion. They are used to transfer transnational motion.
Rack and Pinion Gear applications includes :
- Convert car steering wheel rotation into side motion of wheels.
- Lifting Mechanisms
- Shaper machine.
Bevel gears has a cone surface and its teeth are cut along that cone surface. They are further classified in following two types.
1) Straight Bevel Gear
Straight bevel gears transfer power between perpendicular shafts.
- Operate under high speeds and high loads.
- Good precision rating.
- Difficult to manufacture
2) Spiral Bevel Gear
Spiral bevel gears transfer power between perpendicular shafts. They have applications similar to straight bevel gears.
- Higher load carrying capacity compared to straight bevel gear
- Smooth Operation
- Lower efficiency compared to straight bevel gear.
Bevel gear are used for right angle motion transfer at higher velocity ratios. Some of bevel gear applications includes :
- Machine Tools : Lathe and milling Machine.
- Garden Equipment.
- Positioning Equipment
- Automotive differentials and right angle drives etc.
Worm and Worm Wheel
Worm and worm wheel consists of a worm (similar to a screw) and a worm gear (Helical gear). They are used in right-angle skew shafts. These gears have a sliding contact. To reduce friction worm is manufactured in hard material whereas worm wheel is manufactured in soft material.
- Gear engagement occurs without any shock.
- Compact Drives
- Quieter operation
- High reduction ratios (8 to 400)
- Considerable amount of heat is produced due to Friction.
- Low Efficiency (from 90% to 40 %)
- Higher speed ratio gears are non-reversible.
- Lubrication is required for heat dissipation and for improving the efficiency.
Worm and Worm wheel gear has application in devices both at home and in heavy machinery. Some of its applications includes:
- Elevators and Lifts
- Tuning Instruments : Guitar
- Of Road Vehicles
Spiral Gears are also known as crossed helical gears with high helix angle. They are used to transmit power between two non-intersecting non-parallel shafts.
- Poor precision rating
They are used for low load and low speed application such as instruments, sewing machine etc.
A Hypoid Gear is a type of spiral bevel gear whose axis does not intersect with the axis of the meshing gear. The shape of a hypoid gear is a revolved hyperboloid. In Another words pitch surface of the hypoid gear is a hyperbolic surface.
Hypoid gears are typically used in rear-drive automobile drive trains. Buy now these gears are replaced by spiral gears. But these gears are still common in large vehicles because they can transfer large torque.
Internal Gears transmits power between parallel shafts. In this bigger gears have teeth on the inner periphery and both driver and driven gear runs in same direction.
- Very Compact
- Not recommended for precision meshes because of design, fabrication, and
Internal gears has applications involving planetary gear drives (Planetary, solar and star) and gear couplings.
To sum up, various gears are available to transfer various motions. For Example, spur gears are used to transfer motion between parallel shafts. Whereas Rack and Pinion gears are used to covert rotational motion into linear motion. We suggest you to read this article on Gear Terminology (Basic Terms used in gears) and Gear Ratio Calculations.
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