Fundamentals of Pneumatics

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• In this presentation you will
• identify how gears can be used to change the axis
  of rotation in a mechanism

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In this presentation you will discover the
different types of gears that are used to change
the axis of rotation in a mechanical system.
You will see different types of bevel gears and
identify where they are most likely to be used.
You will also see how rack-and-pinion and worm
gears operate.
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Bevel Gears
Bevel gears are primarily used to transfer power
between intersecting shafts, where the axis of
rotation of two shafts are at 90 degrees to each
other.
The teeth of these gears are formed on a conical
surface.
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Types of Bevel Gears
Standard bevel gears have teeth that are cut
straight. The teeth point toward the apex of the
cone on which they are machined.
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Spiral bevel gears have teeth that have been cut
on a curve.
The larger surface contact area makes for a
smoother, quieter running system, much like
helical gears.
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Hypoid bevel gears are a special type of spiral
gear that will allow non-intersecting,
non-parallel shafts to mesh.
Hypoid gears are stronger, operate more quietly,
and can be used for higher reduction ratios than
spiral bevel gears.
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1
Question
Bevel gears are primarily used to transfer power
between parallel shafts. Is this true or false?
Answer True or False.
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Bevel Gear Applications
Standard bevel gears are mainly used in low speed
(less than 500 rpm) applications. At high speeds
they become noisy. They are typically used in
applications such as hand drills.
Spiral bevel gears are typically used for high
speed (greater than 500 rpm) and performance
applications, where low noise and vibration
levels are important. They are typically used in
transmission systems.
Hypoid bevel gears are also used in high
performance applications, but are more expensive
to produce. They are typically used in
transmission systems.
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2
Question
Which type of bevel gear is typically used in low
speed applications?
A) Standard
B) Spiral
C) Hypoid
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Worm Gears
Worm gears resemble screws, and can be used to
drive gear wheels (spur gears or helical gears).
They allow two non-intersecting shafts at right
angles to mesh with each other.
Worm drives provide a large reduction in speed.
For one rotation of the worm gear, the gear wheel
moves by a distance of one tooth.
They are typically used in gearboxes, where large
reductions in speed, for example 3001, are
required.
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Question
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A worm gear is driving a gear wheel that has 20
teeth. How far will the gear wheel turn, if the
worm gear rotates 5 times? Enter your answer in
degrees.
Enter your answer and press SEND.
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Rack-and-pinion Gears
The rack-and-pinion is typically used to turn
rotary motion into linear (straight line) motion,
or vice versa.
Racks are simply straight gears.
The pinion is usually a spur gear that meshes
with the rack.
As the pinion turns, the rack moves in a lateral
direction.
The rack-and-pinion is typically used in
automotive steering systems.
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Question
The rack-and-pinion is typically used in
automotive steering systems, and converts rotary
motion into linear motion. Is this true or false?
Answer True or False.
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Gear Ratios
Driven
The gear ratio of a bevel gear system is
calculated in the same way as for a simple gear
train.
Driver
With a worm system, the worm gear is equivalent
to a single tooth gear.
If the spur gear has 90 teeth, then the gear
ratio is
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Summary
You should now be aware of

• which types of gear can change the axis of
  rotation in a mechanism
• how to calculate gear ratios for bevel gears and
  worm gear systems

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