KNEX Education Simple Machines Deluxe GEARS Teachers Manual
TEACHER’S
GUIDE
M
SIMPLE MACHINES DELUXE
GEARS
T
KNX 79520-V1-11/10
©2011 K’NEX Limited Partnership Group
and its licensors.
K’NEX is a trademark of K’NEX Limited Partnership Group.
Website: www.knexeducation.com
Email: abcknex@knex.com
Phone: 1-888-ABC-KNEX (USA/CAN only)
K’NEX Limited Partnership Group
P.O. Box 700
Hatfield, PA 19440-0700
USA
Table of Contents
Simple Machines Deluxe Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Standard Alignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
All About Gears
What is a Gear? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Key Words and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Key Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Student Reference Sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Spur Gears
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Sprocket Bicycle Gear
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Crown Gears
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Rack and Pinion Gears
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Worm and Worm Gear
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Planetary Gears
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Simple Transmission
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Car Window
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Lawnmower
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Eggbeater
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Food Mixer
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Differential
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Clock
Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Part & Model List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Introduction:
OVERVIEW
This Teacher’s Guide has been developed to support you as your students investigate the
K’NEX Education Simple Machines Deluxe Set. In conjunction with the K’NEX materials and
individual student journals, the information and resources here can be used to build your
students’ understanding of scientific concepts and channel their inquiries into active and
meaningful learning experiences.
SIMPLE MACHINES DELUXE
This K’NEX Education set is designed to introduce students to the scientific concepts
associated with simple machines. Students are provided with the opportunity to acquire skills
using a hands-on, inquiry based approach to information and concepts. Working cooperatively,
students are encouraged to interact with each other as they build, investigate, discuss and
evaluate scientific principles in action.
TEACHER’S GUIDE
Designed as a resource for the teacher, this guide provides a glossary of key terms and
definitions, includes an overview of the concepts associated with the different simple machines,
identifies student objectives for each investigation, and offers plans and scripts to successfully
present selected models and their associated activities.We have also provided Student Activity
and Reference Sheets. These comprise illustrations and definitions of some of the concepts
featured in the model building activities. Most lessons can be completed in 30 to 45 minutes.
We recommend that teachers review their curriculum and science education standards to
identify those activities that best support their academic needs.
STUDENT JOURNALS
It is expected that students will have journals available for recording information.They should
be encouraged to enter initial thought at the start of an inquiry – what they “think” will happen.
These initial thoughts many be amended, based upon their ongoing inquiry and analysis, until the
students feel comfortable about drawing conclusions. Their journal entries will help make a
connection between the models they have built, the experiments they have conducted, and how
this information is applied to the real-world machines they use on a regular basis.The journals
will also provide students with a place to practice making drawings and diagrams of systems.
Finally, the journals will serve as a method of assessment for the Simple Machines units. Journal
Checklists are also included in the Teacher’s Guide for each model and it’s associated activities.
4
Alignment with National Standards Grades K-4
The National Science Education Standards
Unifying Concepts
and Processes
Physical Science
Science and Technology
Reprinted with permission from National Science Education Standards, 2001 by the National Academy of Sciences,
Courtesy of the National Academies Press,Washington,D.C.
• Systems, order, and organization
• Evidence, models, and explanation
• Change, constancy, and measurement
• Form and function
• Properties of objects and materials
• Position and motion of objects
• Abilities of technological design
• Understandings about science and
technology
Alignment with National Standards Grades 5 -8
The National Science Education Standards
Unifying Concepts
and Processes
Physical Science
Science as Inquiry
Science and Technology
Reprinted with permission from National Science Education Standards, 2001 by the National Academy of Sciences,
Courtesy of the National Academies Press,Washington,D.C.
• Systems, order, and organization
• Evidence, models, and explanation
• Change, constancy, and measurement
• Form and function
• Motions and Forces
• Transfer of Energy
• Abilities necessary to do scientific inquiry
• Understanding about scientific inquiry
• Abilities of technological design
• Understandings about science and
technology
5
Alignment with Standards for Technological Literacy Grades 3-5
Standards for Technological Literacy
The Nature of Technology
Design
Core Concepts of Technology
• Systems
• Processes
• Requirements
Relationships among technologies
• Technologies integrated
The Attributes of design
• Requirements of design
Engineering Design
• Engineering design process
• Creativity and considering all ideas
• Models
The role of troubleshooting, research and
development, invention and innovation, and
experimentation in problem solving
• Troubleshooting
• Invention and innovation
• Experimentation
Abilities of a Technological World
Used with permission of ITEEA (www.iteea.org)
6
Apply design process
• Collecting information
• Visualize a solution
• Test and evaluate solutions
• Improve a design
Alignment with Standards for Technological Literacy Grades 6 -8
Standards for Technological Literacy
The Nature of Technology
Design
Core Concepts of Technology
• Systems
• Processes
• Requirements
Relationships among technologies
• Interaction of systems
• Knowledge from other fields of study
and technology
The Attributes of design
• Design leads to useful products and
systems
• There is no perfect design
Engineering Design
• Brainstorming
• Modeling, testing, evaluating, and
modifying
The role of troubleshooting, research and
development, invention and innovation,
and experimentation in problem solving
• Troubleshooting
• Invention and innovation
• Experimentation
Abilities of a Technological World
Used with permission of ITEEA (www.iteea.org)
Apply design process
• Indentify criteria and constraints
• Test and evaluate
• Make a product or system
7
All About
GEARS
What is a Gear?
• A gear is a wheel with teeth along its outer edge.
• One gear can make another gear turn when the teeth of the
two gears interlock, mesh or connect.
• Gears can change the amount of force, the direction and the
speed of rotation needed to do a job.
Key Words and Definitions
Effort - the force that is applied to do work; the
push, pull, squeeze or lift provided to use gears to
move an object
Resistance - the force provided by the object on
which one is trying to do work; the object works
against (pushes back) the effort
Mechanical Advantage (MA) -
a mathematical calculation that reveals how many
times easier a job is to do
MA greater than 1 shows that the gear system
multiplied the effort force, but must move through
a greater distance. MA less than 1 shows that the
gear system requires greater effort force to
operate but the driven gear moves more quickly
MA =
number of teeth
(driven gear)
number of teeth
÷
(drive gear)
or
MA =
diameter
(driven gear)
diameter
÷
(drive gear)
Gear ratio - a mathematical relationship that
indicates the difference in the size of gears in a
gear system; the rate at which one gear turns
another based on the number of teeth or
diameter of each gear
Gear
Ratio
number of teeth
=
(large gear)
number of teeth
÷
(small gear)
or
MA =
Diameter - the distance through the center of an
object; a straight line passing through the center
of a circle ended at the circumference
Work - the job being done while using the gears
Load - the object (weight) lifted or moved; provides
resistance to the gears
Force -
Bevel - an angle that is not a right angle; slanted
diameter
(large gear)
any kind of push or pull applied to an object
diameter
÷
(small gear)
:1
:1
Key Concepts
How do gears help you?
• Gears can change the force needed to make
something move and the speed it moves.
• One gear affects the way another gear moves
based on how the gears are configured in
the system.
8
Graphics courtesy of ClickArt® 65,000 Incredible Image PakTM; ©1996-97,T/Maker Co. knexeducat io n. co m
• Many gears, working together in different
arrangements, allow a single machine to do work
at both different speeds and directions.
•
The Mechanical Advantage, or gear ratio, of a set
of gears, is determined by ratios of: the number of
teeth; the diameters; the speeds of the two gears;
and the amounts of force with which they turn.
Key Concepts
How do gears affect force?
• Gears can reduce the amount of force needed to
do a job.
• A small gear requires less force to turn than a big
gear but must be turned many times in order to
make the big gear turn once.
• When a small gear turns a big gear, the
Mechanical Advantage tells how many times
easier your job is.
How do gears affect speed?
• When using two gears of different sizes, the small
gear turns more quickly than the big gear.
• When a big gear turns a small gear, the gear ratio
tells how many times faster the job is done.
How do gears affect direction?
• When two gears are linked together, they turn in
opposite directions and can make different parts
of machines turn in opposite directions.
• Gears can change the angle of rotation when
a gear on a vertical plane turns a gear on a
horizontal plane.
• Special gear systems can change circular motion
into back-and-forth motion.
What are spur gears?
• Spur gears lie in the same plane and turn in
opposite directions when meshed.
• Different-sized spur gears turn at different
speeds and with different amounts of force.
What are sprocket gears?
• Sprocket gears are a special type of spur gears
consisting of two gears on the same plane, set
apart from each other and linked by a chain.
• Sprocket gears turn in the same direction.
• Different-sized sprocket gears turn at different
speeds and with different amounts of force.
What are crown gears?
• Crown gears lie in different planes (at right angles
to each other) and turn in opposite directions.
• Different-sized crown gears turn at different
speeds and with different amounts of force.
What are rack and pinion gears?
• Rack and pinion gears consist of a toothed bar
and a toothed wheel.
• Rack and pinion gears change circular motion
into back-and-forth motion.
What are worm gears?
• Worm gears consist of a spiral-edged cylinder
called the worm and a toothed wheel called the
worm gear.
• A worm and its worm gear turn in different
directions, at different speeds and with different
amounts of force.
• Worm gears change fast motion into slow
motion.
REMEMBER
Special types of gears can be used to
change the direction of circular motion
and to gear up or down depending on
the need for speed.
1-88 8- AB C- KNEX
9
STUDENT REFERENCE SHEET
Gettin
g Started
With Gears
What is a gear?
A gear is a wheel with teeth along its outer edge.
•
One gear can make another gear turn when the teeth of the
•
two gears interlock, mesh or connect.
Gears can make work easier by letting you use less force to do a job.
•
Some gears let you move a gear in one direction by turning another gear in a different direction.
•
Other gears help by changing the speed of the turning parts.
•
How do gears help you?
Gears can help you in three different ways.
Force
Gears can change the force you need to make
something move.When you turn a small gear, it
can make a big gear move. You have to turn it lots
of times to make the big gear turn around once,
but the small gear doesn’t take much force to
turn.
Speed
Gears can change the speed that a machine
moves. If two gears are different sizes, the smaller
gear will turn faster than
the larger gear.
Many machines use gears
of different sizes to make
certain parts of the
machine turn faster or
slower than others.
Direction
Gears can also change the
direction something
moves.When two gears
are linked together, they turn in opposite directions and can make parts of machines turn in opposite directions too. Gears can also be set up
where one gear is lying flat, but it makes an upright gear turn. Different arrangements of gears
make it possible for machines to do work in
many different directions.
Here’s an example of how gears
can help.
Imagine you work for a zoo. Your job is to build a
feeder to adjust the meals for an elephant named
Moe. Moe eats whatever food is put out for him so
his intake must be watched closely or he’ll overeat.
The zoo manager asked you to find a machine to
feed Moe specific amounts at the proper times. Impossible? NO! Not with the help of gears.
Picture this.
You could design a
huge plate which
rotates in a
circle. Along
the outside
of the plate are
large bowls with elephant-sized helpings for Moe’s
meals. Your design puts only one bowl in Moe’s
reach at a time. The speed the plate turns is controlled by a series of gears underneath the plate.
This allows it to run at the right speed so Moe gets
fed at the proper time without your help.
A Bright Idea!
Gears were a pretty modern invention. Conduct
research to find out about the earliest use of this
simple machine.
10
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STUDENT REFERENCE SHEET
What’s the
vantage?
al A
Mec
han
ic
How much do gears help you?
Just by counting the gear’s teeth and dividing a few numbers, you can
find out how much gears make work easier or faster.
Count the number of teeth on your driven Gear and the number on your drive
1
Gear.
2
Divide the driven number by the drive number. The answer is the Mechanical
Advantage (MA), which tells you how many times easier your job is.
d
MA = Number of teeth on driven Gear - Number of teeth on drive Gear
3
You can also figure out the MA by measuring the diameter of each Gear. Then, divide
the diameter of the driven Gear by the diameter of the drive Gear. Is your answer
about the same as your answer from Step 2?
MA= Diameter of driven Gear- Diameter of drive Gear
4
You can use the gear ratio to tell you how many times faster something can
move when you use a big Gear to turn a small Gear. Divide the number of
teeth on the big Gear by the number of teeth on the
small Gear to get this ratio.
:
Gear Ratio = Number of teeth on big Gear - Number of teeth on small Gear :1
Gears let you use less force
1
Imagine you want to turn a merry-go-round.
A big gear with 500 teeth is attached to the platform where people ride. A smaller gear with 20
teeth is attached to a motor.
MA=500-20
:
:
:
Gears give you speed
2
Imagine you are using a hand drill. You turn the
crank on the big gear, which has 60 teeth. The
small gear has 15 teeth.
Gear Ratio =60 -15 1
Gear Ratio =4 1
:
:
:
MA=25
A Mechanical Advantage of 25 means that the
motor turns the small gear 25 times for one turn
of the merry-go-round, but it takes 25 times less
force than it would to turn the big gear itself.
The MA shows the number of times the gear system multiplies the effort force applied to the small
gear.
1-88 8- AB C- KNEX
The gear ratio is 4:1, which means that the drill
bit turns four times faster than you turn the
crank since you are using a big gear to drive a
small gear. That helps you drill a hole quickly and
easily.
The gear ratio shows how many times faster the
small gear turns when you apply the effort force
to the big gear.
11
STUDENT REFERENCE SHEET
What
are
Spur Gears?
Spur gears are sets of gears that work together by
being set in the same position. The teeth on the edge
of one gear mesh with the teeth on the other gear.
When you turn one gear, the other gear turns in the
opposite direction.
Spur gears can be the same size or different sizes. If the
sizes are different, the gears will turn at different speeds
and with different amounts of force.
Here’s an example.
Spur gears inside a wristwatch make the hands
turn. When you wind the watch, you wind up a
spring that powers the gears. Small and large
spur gears work together to make the hands
turn at different rates, so you can tell the time.
How do spur gears help you?
Spur gears of different sizes can help you by
making parts of a machine turn at different
rates. When a small gear and a large gear work
together, the small gear turns faster than the
large gear. Its circumference is smaller, so it
doesn’t have as far to go to make one
complete turn.
In a wristwatch, small and large gears work
together to make the second hand turn a full
circle within a minute; the minute hand turn a
full circle within an hour and the hour hand
turn a full circle within twelve hours.
Different-sized spur gears also turn with different amounts of force.These gears can help
you when you use a machine that requires
extra force to do a job.
12
Graphics courtesy of ClickArt® 65,000 Incredible Image PakTM; ©1996-97,T/Maker Co. knexeducat io n. co m
STUDENT REFERENCE SHEET
What
are
Worm Gears?
Worm gears have two different parts: a worm gear and a worm.
The worm gear looks like most other gears, a wheel with teeth.
The worm got its name because its tube-like shape resembles a
worm with a ridge that wraps around it in a spiral. This ridge
meshes with the teeth of the worm gear, and together, they turn.
The worm and the worm gear turn at different speeds, with
different amounts of force and in different directions.
Here’s an example.
A crescent wrench uses worm gears. The worm is
easy to recognize. It’s the spiral part you turn to make
the jaws of the wrench come together. The worm gear
might not be so easy to identify. It has a toothed edge
along the bottom of its moving jaw. (You can just imagine
it’s the edge of a big wheel!)
How do worm gears help you?
Worm gears help by letting you turn part of a machine
at one speed while you make another part of the
machine turn at a much slower or faster speed.
Worm gears can do this, because the worm has to make
a full turn to make the worm gear move ahead by just
one tooth. As a result, the worm turns much more
quickly than the worm gear.
When you turn the worm on the crescent wrench, the
worm gear turns slowly. It makes the movable jaw of
the wrench move just a tiny bit–maybe a fraction of a
millimeter. Being able to make such tiny movements lets
you adjust the wrench just the right amount.
Since the worm and worm gear move at different
speeds, they also move with different amounts of force.
The worm gear turns with more force than the worm.
A worm and its worm gear turn in different directions.
If you imagine that the worm and the worm gear each
trace out a circle as they turn, the two circles are at
right angles to each other.
1-88 8- AB C- KNEX
13
STUDENT REFERENCE SHEET
What
Sproc
Sprocket gears are special types of spur gears.
Two sprocket gears are set in the same position,
but they are placed a certain distance apart.
A chain wraps around the gears. By turning one gear,
you make the chain move and the chain turns the
other gear. Both gears turn in the same direction.
The teeth on sprocket gears are specially shaped
to fit between the pegs or notches on a chain.
ket
are
Gears?
Here’s an example.
A bicycle uses sprocket gears to turn the back
wheel. You push the pedals, making the pedal gear
turn. The chain, which is wrapped around both
gears, then makes the back gear turn. The back
gear turns the wheel and off you go!
How do sprocket gears
help you?
A special feature of sprocket gears is that they let
you spread your turning action over a distance.
You don’t need to place the gears right next to
each other in order for them to work together.
In a bicycle, it helps to have the gears separated, so
you have room for your feet to turn the pedals and
to fit the big rear wheel next to the back gear.
Two sprocket gears connected by a chain move in
the same direction. Both gears turn clockwise or
both turn counterclockwise. That’s helpful in a
bicycle. Otherwise, you’d have to pedal backwards
to make the bike go forward!
Sprocket gears can vary in size. Like other spur
gears, they can turn at different speeds and with
different amounts of force. As a result, the pedal
gear turns at a different speed than the gear
attached to the wheel.
14
Graphics courtesy of ClickArt® 65,000 Incredible Image PakTM; ©1996-97,T/Maker Co. knexeducat io n. co m
STUDENT REFERENCE SHEET
What
rown
C
Crown gears are gears that work together but,
unlike spur gears, they are not set in the same
position. Instead, a pair of crown gears lie at angles to
each other–usually at right angles. One gear might
be upright, while the other lays flat. Another name
for crown gears is bevel gears. They are called bevel
gears because the word bevel means “slanted.”
are
Gears?
Here’s an example.
A hand drill has a crank to turn and a shaft that
holds the drill bit. When you turn the crank, the
drill bit spins to drill a hole. The drill’s crown gears
help you drill straight down while turning the crank
on the side of the drill.
How do crown gears help you?
Crown gears make different parts of machines turn
in different directions. On a hand drill, the crank is
connected to an upright gear. With the crank in
this position, your hand can easily turn it. If the drill
had a crank that turned around the drill’s shaft, it
would probably make the drill wobble as it turned
and the drill would be difficult to hold.
Like spur gears, crown gears can be different sizes.
Then, the crown gears will turn at different speeds
and with different amounts of force, in the same
way that spur gears do.
1-88 8- AB C- KNEX
Graphics courtesy of ClickArt® 65,000 Incredible Image PakTM; ©1996-97,T/Maker Co.
knexeducat io n. co m
15
STUDENT REFERENCE SHEET
k
What
are R
ac
and Pinion
Gears?
Rack and pinion gears have their own special shape and
their own kind of movement. The rack is a long, toothed
bar which moves back and forth.The pinion is a toothed
wheel which rotates.
Here’s an example.
Inside a car, rack and pinion gears control the way
the car turns. The car’s steering wheel is connected
to a pinion gear that turns round and round. It
moves the rack, which turns the front wheels to
the right or left, allowing the car to turn.
How do rack and pinion gears
help you?
Rack and pinion gears let you change round-andround motion into back-and-forth motion.
These gears make it easy to steer a car.You can
turn the wheel a little to make the car angle to the
right or left, or turn it a lot to make a sharp turn.
Imagine trying to steer if you didn’t have rack and
pinion gears.You’d have to shift the wheels in some
other way - perhaps with a lever. Rack and pinion
gears sure make things easier!
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Graphics courtesy of ClickArt® 65,000 Incredible Image PakTM; ©1996-97,T/Maker Co. knexeducat io n. co m
The Spur Gears Lesson Plan
Lesson Length:
30-45 minutes
Object
• Measure applied forces using a Rubber Band Scale and determine
Mechanical Advantage
• Determine if spur gears change force, speed or direction
• Practice creative design utilizing spur gears
• Compare and contrast spur gears with other gears
ives
• Identify a spur gear
• Demonstrate how spur gears function
• Explain the advantage offered by spur gears of different gear ratios and their effect on force and speed
Materials
-K’NEX Rubber Band Scale
-small weight, such as cup of
pennies or green Rods
-string
-extra K’NEX pieces
Every wheel and axle has a job to do
A salad spinner provides a great demonstration of spur gears. Count and compare the number of turns
of the salad spinner handle to the number of turns of the basket. Note that the spinner makes work
easier, because the basket spins fast enough to make the water fly away from the lettuce, but you don’t
have to turn the crank very fast.
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Graphics courtesy of ClickArt® 65,000 Incredible Image PakTM; ©1996-97,T/Maker Co. knexeducat io n. co m
Journal
Explanati
✓
ar
ge
Explanation
✓
ratios based on observations
Force measurements and comparisons
✓
for 1:1 and 6:1 gear ratios
Explanatory paragraph for results
✓
of tests on 1:1 and 6:1 Spur
Gear models
Description of the difference between
✓
spur gear size and their functional
advantage(s)
Explanation of the relationship between
✓
spur gear arrangement and applied force
Check
on for how
s function
1 and 6:1 ge
of 1:
spur
ar
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