In this type of gear teeth are cut parallel to the axis of the shafts so when is meshes with another spur gear it transmit the power in parallel shaft and when it connects with the helical gear it will transmit power at an angle from the driving axis.
On the helical gears teeth are cut at an angle from the axis of it. It has cylindrical roller with helicoid teeth. The main advantage of helical gears is that they work with less noise and vibration because the load is distributed on the full helix as compared to spur gears.
It also has less wear and tear due to which they are widely used in industries. It also used for transmit power in parallel shaft but sometime they are used to transmit power in non-parallel shaft also.
In the helical gears if the pinion driving gear is cut with right handed teeth then the gear driven gear is cut with left handed of in opposite direction. This gear has both right and left handed teeth on one gear.
This gear is use to provide additional shear area on gear which further required for higher torque transmission.
This is same as helical. This gear is used to transmit power between perpendiculars. The driving shaft and driven shaft makes a right angle with each other and both the axis of shaft meets each other at one point.
This gear has helical or spiral teeth on a conical shaped geometry and meshes with the same gear. For true driving enthusiasts, nothing can beat the feeling of a perfectly timed shift on a good old manual. The ubiquitous automatic is by far the most common transmission on the road today. Though the behind-the-scenes action is quite complicated, all the driver has to do is select from the familiar P-R-N-D-L choices on the gear selector. The advantage is, of course, a simplified driving experience and a gentle learning curve.
The trade-off for the driving simplicity is mechanical complexity, which makes the automatic more prone to failure and pricier to fix. Some late-model cars are equipped with transmissions boasting eight or even nine forward gears.
The CVT offers a similar driving experience to an automatic, but operates using a completely different mechanism. Their biggest drawback may be a subjective one — the driving experience. Screw : Screw gears, also called crossed helical gears, are helical gears which are used for non-parallel, non-intersecting configurations. Unlike the helical gears used for parallel configurations, screw gears employ same-hand pairs rather than a right-hand and left-hand gear per pair.
These gears have relatively low load capacities and efficiency rates and are not suitable for high power transmission applications.
Bevel gears are cone-shaped gears with teeth placed along the conical surface. These gears are used to transmit motion and power between intersecting shafts in applications which require changes to the axis of rotation. Typically, bevel gears are employed for shaft configurations placed at degree angles, but configurations with lesser or greater angles are also manageable. There are several types of bevel gears available differentiated mainly by their tooth design.
The most commonly used of the bevel gear tooth designs due to its simplicity and, consequently, its ease of manufacturing, straight bevel teeth are designed such that when properly matched straight bevel gears come into contact with one another, their teeth engage together all at once rather than gradually.
As is the issue with spur gears, the engagement of straight bevel gear teeth results in high impact, increasing the level of noise produced and amount of stress experienced by the gear teeth, as well as reducing their durability and lifespan. In spiral bevel gears , the teeth are angled and curved to provide for more gradual tooth engagement and more tooth-to-tooth contact than with a straight bevel gear.
Like helical gears, spiral bevel gears are available with right-hand or left-hand angled teeth. As is also the case with helical gears, these gears are more complex and difficult to manufacture and, consequently, more expensive , but offer greater tooth strength, smoother operation, and lower levels of noise during operation than straight bevel gears.
Other than the types mentioned above, there are several other designs of bevel gears available including miter, crown, and hypoid gears. Miter : Miter gears are bevel gears which, when paired, have a gear ratio of This gear ratio is a result of pairing two miter gears with the same number of teeth. This type of bevel gear is used in applications which require a change only to the axis of rotation with speed remaining constant. Crown : Crown gears , also referred to as face gears , are cylindrical rather than conical bevel gears with teeth cut or inserted perpendicular to the gear face.
Crown gears can be paired either with other bevel gears or, depending on the tooth design, spur gears. Hypoid : Originally developed for the automobile industry, hypoid gears , unlike the previously mentioned types, are a type of spiral bevel gear used for non-parallel, non-intersecting configurations. This design allows for components to be placed lower, allowing for more space in the sections above.
Employing curved and angled teeth similar to those used in spiral bevel gears, hypoid gears are even more complex and, consequently, more difficult and costly to manufacture. Worm gear pairs are comprised of a worm wheel—typically a cylindrical gear—paired with a worm —i. These gears are used to transmit motion and power between non-parallel, non-intersecting shafts. They offer large gear ratios and capabilities for substantial speed reduction while maintaining quiet and smooth operation.
One distinction of worm gear pairs is that the worm can turn the worm wheel, but, depending on the angle of the worm, the worm wheel may not be able to turn the worm. This characteristic is employed in equipment requiring self-locking mechanisms.
Some of the disadvantages of worm gears are the low transmission efficiency and the amount of friction generated between the worm wheel and worm gear which necessitates continuous lubrication. Rack and pinion gears are a pair of gears comprised of a gear rack and a cylindrical gear referred to as the pinion. The gear rack can be considered as a gear of infinite radius i. For either of these rack designs, rotational motion can be converted into linear motion or linear motion can be converted into rotational motion.
Some of the advantages of a rack and pinion gear pair are the simplicity of the design and the low cost of manufacturing and high load carrying capacities. Despite the advantages of this design, gears which employ this approach are also limited by it. For example, transmission cannot continue infinitely in one direction as motion is limited by the designated length of the gear rack.
Additionally, rack and pinion gears tend to have a greater amount of backlash i. Some of the common applications of rack and pinion gear pairs include the steering system of automobiles, transfer systems, and weighing scales.
Gears are employed in a variety of mechanical devices, and, consequently, several different types and designs are available. The suitability of each type of gear and its exact design for a motion or power transmission application is dependent on the specifications and requirements of the application. Some of the principal factors which may be considered when designing and choosing a gear include:.
Some of the operational conditions which may affect a gear are the amount of weight applied, noise and vibration produced, and friction and stress placed on the teeth, while some of the environmental conditions which may affect a gear include temperature, humidity, and sanitation and cleanliness. These conditions influence a variety of gear design factors, including the construction material, surface treatments, and lubricant type and lubrication method. Gears are available in a variety of construction materials—e.
For example:. However, grinding also increases the overall cost of production. There are several heat treatment services available for gears include surface hardening, tempering, normalizing, annealing, and carburizing.
If adequately and properly applied, gear lubricants can help to extend the overall lifespan of a gear by preventing or reducing the amount of stress and fatigue experienced by the gear body and teeth. However, both the optimal type of lubricant and lubrication method are dependent on the requirements and specifications of the application. Given the employment of the proper lubricant, some of the benefits include the reduction of friction between gear teeth, mitigation of heat generated, and lowering of the amount of noise and vibration produced during operation.
Once a suitable lubricant is selected, it must be properly applied. One interesting thing about helical gears is that if the angles of the gear teeth are correct, they can be mounted on perpendicular shafts, adjusting the rotation angle by 90 degrees.
Bevel gears are useful when the direction of a shaft's rotation needs to be changed. They are usually mounted on shafts that are 90 degrees apart, but can be designed to work at other angles as well. The teeth on bevel gears can be straight , spiral or hypoid. Straight bevel gear teeth actually have the same problem as straight spur gear teeth -- as each tooth engages, it impacts the corresponding tooth all at once.
Just as with spur gears, the solution to this problem is to curve the gear teeth. These spiral teeth engage just like helical teeth: the contact starts at one end of the gear and progressively spreads across the whole tooth. On straight and spiral bevel gears, the shafts must be perpendicular to each other, but they must also be in the same plane. If you were to extend the two shafts past the gears, they would intersect.
The hypoid gear , on the other hand, can engage with the axes in different planes. This feature is used in many car differentials. The ring gear of the differential and the input pinion gear are both hypoid. This allows the input pinion to be mounted lower than the axis of the ring gear.
Figure 7 shows the input pinion engaging the ring gear of the differential. Since the driveshaft of the car is connected to the input pinion, this also lowers the driveshaft. This means that the driveshaft doesn't intrude into the passenger compartment of the car as much, making more room for people and cargo. Worm gears are used when large gear reductions are needed. It is common for worm gears to have reductions of , and even up to or greater.
Many worm gears have an interesting property that no other gear set has: the worm can easily turn the gear, but the gear cannot turn the worm.
This is because the angle on the worm is so shallow that when the gear tries to spin it, the friction between the gear and the worm holds the worm in place.
This feature is useful for machines such as conveyor systems, in which the locking feature can act as a brake for the conveyor when the motor is not turning. One other very interesting usage of worm gears is in the Torsen differential , which is used on some high-performance cars and trucks. Rack and pinion gears are used to convert rotation into linear motion. A perfect example of this is the steering system on many cars.
The steering wheel rotates a gear which engages the rack.
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