PLTW VR AR Gear Mechanisms

Automation and
Robotics

Gear Mechanisms

Hanshaw Middle School

Open Ended

What was the most interesting thing you learned in the history of robots history?

What do a guitar, a bicycle, an
eggbeater, and a sewing
machine have in common?

Introduction

They all use gears to
increase, decrease, or
redirect power.

What is the
purpose of a
mechanism?

A mechanism is a device that
transmits motion so that motion
is different than the input.

It can be used to change the
direction, speed/force ,type of
motion.

Another word used for force is
torque.

Torque is simply any force that is twists.

Multiple Choice

A mechanism is?

• A push or pull on an object.

• Information fed into a system.

• The part of a machine that contains two or more pieces arranged so that the motion of one compels the motion of the others.

• A toothed wheel that works with others to alter the relation between the speed of an engine and the speed of the driven parts.

A simple gear train is a
mechanism that consists of two or more interconnected gears.

Simple gear trains are useful in transferring energy from one part of a system to another. The number of teeth and size of the gear impact the way in which
the energy is transferred.

Generally, to
increase speed, the
input (drive) gear
needs to have more
teeth than the
output (driven) gear.
To increase torque,
the driven gear
needs to have more
teeth. The speed
and torque are
constant if the gears
have the same
number of teeth.

Multiple Choice

A gear is?

• A push or pull on an object.

• Information fed into a system.

• The part of a machine that contains two or more pieces arranged so that the motion of one compels the motion of the others.

• A toothed wheel that works with others to alter the relation between the speed of an engine and the speed of the driven parts.

Gears come in all sizes. A mechanical
wind-up watch has very small gears,
while the gears used to lift a bridge to
allow ships to pass underneath are huge.
Different gear configurations are used for
different purposes.

The gear that is attached to the motor is the drive(r) gear, also known
as the input.

The gear that moves as a result of the drive gear moving is the driven
gear, also known as the output.

In a simple gear train, if the drive gear is
moving clockwise the driven gear will move
counterclockwise and vice-versa.

Driving Gears and Driven Gears

Balanced gears are when both the drive(r) gear and driven gear have
the same number of teeth.

Their will not be an increase in speed
or power in balanced gears. Instead
you will have a change in direction
only.

Balanced Gears

When the input gear, or drive gear, is larger than the output gear it is
called gearing up.

Their will be an increase in speed and a change in direction. Because of
the increase in speed, there will be a decrease in torque.

Gear Up

When the input gear, or drive gear, is smaller than the output gear it is
called gearing down.

Their will be an increase in torque and a change in direction. Because of
the increase in torque, there will be a decrease in speed.

Gear Down

Multiple Choice

What type of gear mechanism is this?

• Balanced

• Gear Down

• Gear up

Multiple Choice

What type of gear mechanism is this?

Would you expect more torque or speed from this type of gear mechanism?

• Gear Up - Increased Speed

• Gear Down - Increased Torque

• Gear Up - Increased Torque

• Gear Down - Increased Speed

Multiple Choice

What type of gear mechanism is this?

Would you expect it to have more torque or speed?

• Gear Up - Torque Advantage

• Gear Down - Speed Advantage

• Balanced - no Mechanical Advantage

• Gear Down - Torque Advantage

Multiple Choice

What happens to speed when you increase torque?

• It increases

• It stays the same

• It decreases

• It is not affected.

Multiple Choice

The ratio of the speed of the driving member of a gear train to that of the driven member.

• Torque

• Gear Ratios

• Rotary Motion

• Output

Multiple Choice

A 36 tooth driving gear (connected to the motor) is moving a 12 tooth driven gear. What is the gear ratio?... It has a speed advantage.

• 3:1

• 1:3

• 3:3

• 1:1

Multiple Choice

Looking at the picture, what is the gear ratio?

The arrow indicates how the motor is turning the gear.

• 4 : 6

• 6 : 4

• 2 : 3

• 3 : 2

Multiple Choice

What is the gear ratio with a driving gear with 40 teeth and a driven gear with 8 teeth?

Make sure ratio is reduced to lowest terms

• 8 : 40

• 1 : 5

• 5 : 1

• 40 : 8

Multiple Choice

The input gear has 6 teeth.

The output gear has 48 teeth. The gear ratio is...

Make sure ratio is reduced to lowest terms

• 1 : 8

• 8 : 1

• 6 : 48

• 48 : 6

Multiple Choice

# of teeth output gear = 30

# of teeth input gear = 60

What is the gear ratio (in lowest terms)?

• 1 : 2

• 30 : 60

• 2 : 1

• 60 : 30

An idler gear is a gear wheel that is inserted between two or more other
gear wheels. All gears in between the Driving Gear and the Driven Gear
that only transmit power are known as Idler Gears.

The purpose of using an idler gear is to have the drive gear and the
driven gear move in the same direction or to provide spacing of drive
shafts.

Idler Gears

Idler Gears have NO EFFECT on Gear
Ratio or Gear Reduction, regardless of
the number of teeth they have.

All three photos to the right have the
same gear ratio, as only the driving
gear and driven gear have an affect on
the amount of speed or torque.

All three gear trains to the right have
an increase in power, or torque.

Idler Gears

Explanation Slide...

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Explanation Slide...

​

Multiple Choice

Identify the type of gear from the last slide. Gear B is a??

• Idler Gear

• Drive gear

• Driven Gear

• alternate gear

Open Ended

Reflect on your learning.

Why do you think it is important to know what gear ratios increase torque or speed?

Why is it important to know the exact ratio of the gear train?