Name: Arabela Grace C. Aguilar
CYS: BET-MT-2B
Understanding Gear and Gear Nomenclature
Types of Gear
Spur Gear
Bevel Gear / Mitre
Gear / Crown Gear
Applications
Spur gears are gear wheels with straight teeth
that are mounted on parallel shafts. These
gears are designed to mesh with each other,
transferring rotational motion and torque
between the shafts. The teeth of spur gears are
evenly spaced and cut straight across the
gear’s face.
 Automotive Industry
 Robotics
 Industrial Machinery
 Clocks and watches
 Home appliances
Bevel gears are of the intersecting axes/shafts
type, so their connection is done on vertical
inclination. Their shape is conical, and their
teeth can be either straight, or spiraled for
quieter operation. Although the 90 degrees of
angle between the interconnected axis isn’t
mandatory, they are typically found in this
arrangement and have the exact same number
of teeth so as the rotation speed between the
two is the same. This type of bevel gears is
called a miter gear, and it is used in cases
where speed modifications are not required.
Any other angle and difference in the number
of the teeth is simply called a bevel gear
arrangement.
 Automotive industry
 Marine industry
 Power tools
Advantages
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Disadvantages
Simple and compact
design
Cost-effective to
manufacture
High efficiency in
power transmission
Wide range of sizes
and ratios available
Easy to maintain and
replace
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Efficient power
transmission at varying
angles
Ability to transmit
motion between
intersecting shafts
Versatility in handling
different speed ratios
Smooth and quiet
operation
Widely available in
various sizes and
configurations
Suitable for
intersecting shafts
at a 90-degree
angle
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Generates high noise
levels
Limited to parallel
shaft arrangements
Prone to axial thrust
and backlash
Requires proper
lubrication for smooth
operation
May experience
increased wear and
tear
Complex design and
manufacturing
process
Higher cost
compared to spur
gears
Requires proper
alignment for
optimal performance
Limited loadcarrying capacity
Increased
complexity for
maintenance and
repair
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Helical Gear
Heavy machinery
Robotics
Printing Passes
Hand Tools
Helical gears are gear wheels with angled teeth
that are cut in a helix shape around the gear’s
circumference. Unlike spur gears with straight
teeth, helical gears have a twisted tooth profile
that allows for smoother engagement and
quieter operation.
 Automotive industry
 Machinery and equipment
 Robotics and automation
 Aerospace industry
 Power generation
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Compact and spacesaving design
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Limited speed ratios
compared to other
gear types
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Smooth and quiet
operation
Increased loadcarrying capacity
Higher efficiency
due to greater
contact area
Improved torque
transmission
Better resistance to
shock and impact
loads
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Higher axial thrust
compared to spur
gears
More complex
design and
manufacturing
process
Require proper
alignment for
optimal performance
Slightly lower
mechanical
efficiency compared
to spur gears
Increased cost
compared to spur
gears
More complex
design and
manufacturing
Higher
manufacturing costs
Limited availability
of specialized
machinery for
production
Requires precise
alignment during
assembly
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Double Helical Gear
Double helical gears are gear wheels that
feature two sets of teeth with a V-shaped
groove in the middle, forming a unique
herringbone pattern. This design allows for
improved load distribution, reduced axial thrust,
and enhanced performance compared to
traditional helical gears.
 Heavy machinery and equipment
 Oil and gas industry
 Power generation
 Marine propulsion
 Gear boxes and transmissions
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Reduced axial thrust
Improved load
distribution
Increased loadcarrying capacity
Smoother operation
and reduced noise and
vibration
Enhanced durability
and resistance to wear
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Worm Gear
Internal Gear
Hypoid Gear
A worm gear consists of a cylindrical gear
called a worm and a toothed wheel known as a
worm wheel or worm gear. The worm has a
helical thread that meshes with the teeth of the
worm wheel. This unique configuration allows
the worm gear to convert rotational motion
between non-intersecting and perpendicular
shafts.
 Automotive Industry
 Conveyor Systems
 Lifts and Elevators
 Machine Tools
 Packaging Machinery
Internal gears are gear wheels with teeth
positioned on the inner surface of the gear rim.
Unlike external gears where the teeth are on
the outer surface, internal gears have teeth
facing inward. They are designed to mesh with
external gears, allowing for smooth and
efficient power transmission between parallel
or concentric shafts.
 Gearboxes and transmissions
 Robotics
 Machine tools
 Printing presses
 Wind turbines
Hypoid gears are gear wheels that have offset
axes and non-intersecting shafts. Unlike bevel
gears, which have intersecting axes, hypoid
gears have a slight offset between the axes of
the driving and driven gears. This unique
design allows for efficient power transmission
between non-parallel shafts, while also
providing compactness and versatility.
 Automotive industry
 Power tools and machinery
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High gear reduction
ratio
Compact design
Precise motion control
Self-locking capability
High shock load
resistance
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Compact design
High torque
transmission
Smooth and quiet
operation
Efficient power
transmission
Suitable for compact
spaces
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Efficient power
transmission between
non-parallel shafts
Compact and versatile
design
Ability to handle high
torque and heavy
loads
Smooth and reliable
motion control
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Lower efficiency
compared to other
gear types
Limited speed
capabilities
Increased friction and
heat generation
Limited applications
due to specific
requirements
Potential for backlash
Complex
manufacturing process
Limited gear ratio
options
Higher manufacturing
costs
Requires precise
alignment
More challenging
maintenance
Complex design and
manufacturing process
Requires proper
lubrication for optimal
performance
Limited availability of
specialized
manufacturing
equipment
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Harmonic Drive
Gears
Planetary Gear
Robotics and automation
Construction and mining equipment
Wind turbines
Harmonic drive gears, also known as strain
wave gears, are a type of mechanical gear
system that delivers high precision, excellent
torque capacity, and zero backlash. These
gears consist of three main components:
Circular Spline, Flex spline, Wave Generator.
 Robotics
 Aerospace
 Medical Devices
 Automation
 Optics
Planetary gears are at the heart of modern
engineering and are used in basic plant
machinery to electric vehicles. These are also
known as epicyclic gears, consist of
two gears so that the center of one gear rotates
around the center of the other.
 These gears are commonly used to
improve torque in robots.
 In addition, it is also used in printing
presses to reduce the speed of the rollers.
 It is used in packaging machines for
reproducible products in industries.
 Furthermore, it is also useful in drives such
as wheel drive, track drive, conveyor, slew
drive, hoist drive, and winch drive.
 They are also used in pumps, coil tubing
injectors and cutter head drives.
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High Precision
Zero Backlash
Compact Size
High Torque Capacity
Durability
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It provides a more
compact unit operating
about a common
central axis.
The gear and gear
housings are
comparatively smaller
in overall dimensions.
These gear set is more
flexible compared to a
normal gear set.
These types of gear
trains occupy less
pace.
This gear has
high gear ratio and
more torque.
It is usually compact in
size.
Instead of having the
load on only one pair
of gears, it is
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Requires precise
alignment during
assembly
Complex
Manufacturing
Limited Flexibility
Sensitivity
Overloads
Higher Cost
to
The general cost of a
planetary gear system
will be higher than
a conventional
gearbox.
The design and
manufacture of
planetary gears are
quite complex and
difficult.
Determining the
efficiency of a
planetary gear system
would be challenging.
The gear system
requires the gearing to
be precise, so it is
quite difficult.
Some types of
planetary gearing
arrangements make
distributed over
several gear wheels.
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more noise during
operation.
To ignore any
additional gearing, the
driving member and
the driven member
must converge.
Gear Nomenclature
 Pitch cylinder: These are imaginary cylinder or friction cylinder
which are imagined rolling together pure rolling motion transmit the
motion.
 Pitch Circle: This is the circle corresponding to the pitch cylinder
that is shown in a normal plane to the Axis.
 Pitch Diameter: It is the diameter of pitch circle.
 Pitch Surface: It is the surface of pitch cylinder.
 Pitch point: It is the point where the two-pitch circle meets.
 Circular pitch: It is denoted by P.
 Diametrical Pitch: It is the ratio of no. of teeth to the pitch
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diameter.
Diametrical Pitch: It is the ratio of no. of teeth to the pitch diameter.
Module: It is the ratio of the pitch diameter to the no. of teeth. pitch diameter should be in mm.
Gear Ratio: It is the ratio of no. of teeth of gears (Driver) to the no. of teeth of a pinion (driven).
Velocity Ratio: It is the ratio of the Angular velocity of the follower (pinion) to the Angular speed of driver (gear).
Addendum Circle: The circle touching the tip of the teeth.
Addendum: It is Radial distance of the tooth above the circle. Normally its value is equal to 1 module
Dedendum Circle: It is the circle that passes through the bottom of the teeth circle are parallel to the pitch circle
Dedendum: It is the Radial Distance measured from the pitch circle to the Roots of the teeth. Its value is generally
more than Addendum. Its value is 1 .157m
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Clearance: The difference between Addendum and Dedendum Radially.
Full Depth: It is the sum of Addendum and Dedendum.
Working Depth: As we know tooths penetrates tooth space means It is the addition of the Addendum of Driver’s
Driven when meshed.
Space width: It is the width of tooth space along the pitch circle.
Tooth thickness: Thickness of tooth of gear measured along the pitch circle.
Backlash: Difference between tooth space and tooth Thickness.
Flank: It is the surface of the tooth between the pitch circle and bottom.
Face: It is the surface of the tooth between the top land & pitch circle.
Pressure line: The driver exerts a force on the drive and this force will be along a line this is called a line of action.
Pressure Angle: The angle between the common tangent to the pitch circle and the pressure line. It is called a
pressure angle or angle of obliquity.
Path of contact: It is the locus of the point of contact from the beginning of Engagement to the end of the
Engagement (CD)
Arc of contact: The locus of the point on the pitch circle from the beginning of Engagement to the end of the Driver
and driven meshing together is called arc of contact.
Practical Application
The use of wind power as a renewable energy source is expanding
quickly. Knowing the inner workings of wind turbines is crucial to fully
appreciate the contribution they make to a more sustainable future. A
wind turbine’s gearbox is an integral part of the machine, as it is
responsible for transmitting mechanical energy from the blades to the
generator to produce electricity.
Wind Turbine Gear Design
The efficiency and longevity of a wind turbine system depend heavily
on the design of the gears used in the turbines. The four most common
types of gears found in wind turbines are spur gears, helical gears,
bevel gears, and planetary gears.
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Spur gears are the most common and simplest design in wind turbines. To transmit force, their straight teeth mesh
with another gear. However, they produce a lot of noise and cannot be used in any situation that requires speed.
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Helical gears are more effective than spur gears, making less noise and enabling faster speeds thanks to their
angled teeth. Frequently, they are found in wind turbines.
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Bevel gears are used to transmit power between two shafts that are not parallel. Wind turbine pitch and yaw
control systems often use them.
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Planetary gears have sun gear in the center that is surrounded by planetary gears that revolve around it. Highpower wind turbines frequently use them to increase the torque output of the gearbox.
Load capacity, efficiency, durability, and noise are all crucial factors in wind turbine gear design. Gearbox parts need to be
strong enough to withstand the torque applied by the rotor and efficient enough to transfer that power to the generator.
The gearbox needs to be sturdy enough to last the wind turbines expected 20 years of operation.
The shaft, bearings, lubrication, and cooling systems are the backbone of a gearbox for a wind turbine. The shaft and
bearings link the gearbox to the rotor and generator, allowing for effortless rotation. Gearboxes require lubrication and
cooling to alleviate friction and wear, and to dissipate heat generated by the gears and other moving parts.
Wind Turbine Gear Application
Power transfer from the rotor to the generator is the main purpose of the gears in wind turbines. The generator requires a
much higher speed, typically around 1500 RPM, whereas the rotor rotates at a low speed, typically between 10 and 20
revolutions per minute (RPM). The gearbox efficiently converts wind energy into electrical power by increasing the rotor’s
rotational speed to match the generator’s speed.
Wind turbine gears are also used in pitch and yaw control systems, in addition to power transmission. Pitch control adjusts
the angle of the turbine blades to optimize their angle of attack to the wind, while yaw control ensures that the turbine is
always facing the wind. These systems often use bevel gears to transmit power between the control mechanisms and the
turbine blades.
Offshore wind turbines present additional challenges for wind turbine gear design. The harsh marine environment can
cause corrosion and erosion, and the turbines must be able to withstand extreme weather conditions, including high winds
and waves. Offshore wind turbines can generate more energy than onshore turbines, making them appealing to countries
with limited land.
Citations and References:
Arshad, B. (2024, October 24). Types of gears | Advantages, disadvantages and uses |. Engineers Guidebook.
https://engineersguidebook.com/types-of-gears-addvantages-disadvantages/
Kumar, E. A. (2021, March 10). Spur Gear: Definition, Types, Terminology, Advantages, Disadvantages,
Application [Notes with PDF]. THEMECHANICALENGINEERING.COM.
https://themechanicalengineering.com/spur-gear/
Mike. (2023, March 17). Wind Turbine Gears: design and applications. Extruder Gearbox Repair.
https://extrudergearbox.net/wind-turbine-gears-design-andapplications/#:~:text=Wind%20Turbine%20Gear%20Design%201%20Spur%20gears%20are,by%20planetary%20ge
ars%20that%20revolve%20around%20it.%20