What is gear
A gear is a rotating circular machine part which used to transmit rotation and power from one shaft to another. In gear drives, gear wheels, which are also referred to as cogwheels toothed wheels, or simply gear, engage with each other and thus transfer the revolution and torque of the input shaft to the desired value on the output shaft. The speed reduction depends on the different number of teeth between the respective pairs of gears.
What is gear drive
- A gear is a toothed where the teeth are machined on the outer edge of a cylinder or a cone
- Gear is mounted on the shafts with a key
- There are two gears installed, one on each of the driving and driven shaft
- So teeth of one gear are meshed with the teeth of the other gear
- The rotation of the gear will cause rotation of the other in the opposite direction
Types of gear and gear drive
1- Spur gear
2-helical gear
3-bevel gear
4-rank and pinion gear
5- Worm gear
Spur Gear
Spur gears are used to transmit the power in the same plane or when the drive and driven shaft are parallel to each other. In this type of gear, teeth are cut equal to the axis of the shafts.
- Teeth are straight and parallel manner to the axis of the shaft
- Transmits power in parallel shaft
- There will be no axial force
- Used for low-power transmission
- Used in the center lathe to transmit motion from the main spindle to the lead screw
Helical Gear
The helical gear teeth are cut at an angle from the axis of it. It used in industries due to less wear and tear. It is also used to transmit power in parallel shafts.
- Teeth are cut at an angle related to the axis of rotation
- Used to transmit power between two shafts aligned in parallel
- It runs more silently than a super gear
- There will be axial force/thrust force
- Widely used in automobile vehicles
- The helix angle ranges from 20 degrees to 35 degrees
Bevel Gear
The bevel gear is used to transmit power between perpendiculars. The driving shaft and driven shaft make a right angle with each other.
- The bevel gear are used to transmit motion between shaft at various angle to each other
- Teeth may be straight or spiral
- When two bevel gear transmit motion at right angle, is called miter gear
Rank and Pinion Gear
In rack and pinion gear, teeth are cut on straight rectilinear geometry known as rack and one spur gear known as pinion. This gear is used in the steering system of automobiles.
- The rack and pinion can convert rotary into movement and vice versa.
- The rack and pinion are used in the drilling machine, vernier height gauge, and lathe transverse mechanism.
Worm Gear
The worm gear is used to transmit the power in a non-intersecting shaft which makes a right angle. In this type of arrangement, the driving gear is a screw gear and the driven gear is a helical gear or gear with spiral teeth.
- These are used to transmit motion at right angle to the axis of motion at different planes
- These are widely used for speed reduction purpose
Advantage of Gears
1-Positive drives because no slip
2-High transmission deficiency
3-High velocity possible, even up to 60:1
4-Used for low, medium and high power transmission
5-Compact compared to belt and chain drive
6-Velocity ratio will remain constant throughout
7-Easy to install
Disadvantages of Gears
1-Require lubrication
2- At very high speed, Produce nice and vibration
3- Manufacturing of gears is costly
4- Not suitable for shafts having large center distance
5- The large number of gear wheels in gear trains increased the weight of machine
Gear Terminology
It is calculation depends on certain factors, some basic terminologies are discussed in this blog:
Pitch Circle: It is the imaginary circle which by rolling action gives the same motion as the actual gear.
Pitch Circle Diameter: This represents the diameter of the pitch circle, which is commonly used to define the size of the gear.so It is also called pitch diameter.
Base Circle: It is a section from the in-volute section of the tooth that is generated.
Pitch Point: It is a typical point of intersection between two pitch circles.
Addendum: It denotes the radial distance of a tooth from the pitch circle to the highest of the tooth
Dedendum: It represents the radial distance of a tooth from the pitch circle to the base of the tooth
Circular Pitch: The distance measured on the circumference of the pitch circle from the point of one tooth to the corresponding point on the next tooth. It is usually indicated by PC. Pc=IID1/T1+IID2/T2
Diametrical Pitch: It is the proportion of number of the teeth to the pitch circle diameter in measure millimeters. It is indicated by Pd
- Pd=T/D
- Where T= Number of teeth and
- D= Pitch circle diameter
Types of gear failure
The diffrents modes of failure of gear teeth and their possible remedies to avoid the dailure are follows
Here we are discuss some main gear failure
- Bending Failure
- Pitting
- Scoring
- Abrasive wear
- Corrosive wear
Bending Failure:
Each gear tooth functions as a cantilever. If the combined repetitive dynamic load acting on the gear tooth is greater than the beam strength of the gear tooth, the gear tooth will bend and fail, i.e
In order to this kind of problem, we adjust the size and width of the gear is adjusted so that the beam strength is greater than the dynamic load.
Pilling:
It is surface fatigue failure that occurs due to many repetitions of hertz contact stress. The failure occurs when the surface contact stress is higher than the endurance limit of the material. The failure started with the formation of pits which regularly to grow resulting in the rupture of the tooth surface.
In order to avoid the pitting, the dynamic load between the gear teeth is lower than the strength which can cause wear on the gear tooth.
Scoring:
The excessive heat is created when there is too much surface pressure, high speed or the supply of lubricant breaks down. It is a stick-slip phenomenon in which ultimate shearing and welding take place rapidly at high spots.
This type of failure can be avoided by properly designing the parameters such as speed, pressure, and proper flow of the lubrication so that the temperature at the rubbing faces is within the permissible limits.
Abrasive Wear:
The foreign particles in the lubricants such as dirt, dust or burr enter between the tooth and damage the form of the tooth.
This type of failure can be avoided by providing filters for the lubricating oil by using high-viscosity lubricant oil which enables the formation of thicker oil film and hence allows easy passage of such particles without harming the gear surface.
Corrosive Wear:
The corrosion of the tooth surface is mainly caused due to the presence of corrosive elements such as additives present in the lubricating oils.
In order to avoid this type of wear, proper anti corrosive should be used.
What is Gear coupling
Gear coupling belongs to the category of flexible coupling that is capable of transmitting very high torque. Constructional gear coupling utilizes the advantage of gear engineering; practically the coupling is a completed gear assembly.
A gear coupling is a mechanical device designed to transmit torque between two shafts that are not collinear. The two couplings typically consist of two flexible joints one fixed to each shaft.
Function of gear coupling
- The fundamental role of a gear coupling is to provide a mechanical link between two rotating shafts.
- They utilize gear engagement to transfer power and torque between the connected shafts. Hence, gear coupling is a mechanical device that transmits torque between two shafts by using gears
- The maximum degree of misalignment permissible in gear coupling is from 0.5 Degree to 1.5 Degrees. This varies with the size of the coupling used.
Parts of gear coupling
Hubs:
- The teeth of Gear hubs are crowned and are formed using the involute system.
- The amount of crowing and backlash valves are so chosen to ensure the best results in torque transmission, greater flexibility, and smooth operation.
Sleeves:
- The internal teeth of the sleeves are produced to ensure the correct profile
- The coupling sleeves are joined together with high tensile steel bolts ( class 8.8 IS: 1367 ) fitted using a gasket in between them.
“O”-Ring:
- The setting of a special “O” Ring at the ends of coupling hubs prevents leakage of lubricants and entry of dust and prevents the outside air and moisture.
- The “o” ring can also withstand high degrees of temperature up to 120 degrees C.
Seal Carriers:
- Seal carriers have been provided for size from FGC 11 to FGC 19 to facilitate inspection and replacement of “O” rings without disturbing the alignment.
- The teeth of gear hubs are crowned and are generated by in-volute system
Types of gear coupling
Two types of gear coupling
1-Full gear coupling
2-Half gear coupling ( Half gear half rigid )
Full gear coupling: A full gear coupling has a tooth hub which is fixed in both drive and driven shaft, and sleeves which has internal teeth meshing with the hub.
Half gear coupling ( Half gear half rigid ): A half-gear coupling consists of a toothed hub on the driven shaft paired with an internally geared sleeve and the driver shaft has a rigid hub.
The rigid hub is secured to the sleeve on the driven shaft using bolts.
Advantage of gear coupling
- Moderate misalignment capacity( parallel, angular, axial)
- Exceptional torsional stiffness
- Very high torque density
- High torque at high speeds.
FAQs
What is gear?
Answer: A gear is a rotating circular machine part which used to transmit rotation and power from one shaft to another
What is gear coupling?
Answer: Gear coupling belongs to the category of flexible coupling that is capable of transmitting very high torque.
How many types of gear coupling?
Answer: Two types of gear coupling 1-Full gear coupling and 2-Half gear coupling ( Half gear half rigid )
What are the main components of a gear coupling?
Answer: Two gear hubs are main components of a gear coupling with an elastomeric or metallic flexible element.
Conclusion
We hope that we have cleared all yours questions about gears. If you have any queries about the “GEARS” you can contact directly in my contact us page. Thanks for reading.
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