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TEACHER’SGUIDE

SIMPLE MACHINES DELUXETM

GEARS

Simple Machines Deluxe Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Standard Alignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

All About GearsWhat is a Gear? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8KeyWords and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Key Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Student Reference Sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Spur GearsLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Sprocket Bicycle GearLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Crown GearsLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Rack and Pinion GearsLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Worm and Worm GearLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Planetary GearsLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Simple TransmissionLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Car WindowLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

LawnmowerLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

EggbeaterLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Food MixerLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

DifferentialLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

ClockLesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Student Activity Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Part & Model List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Table of Contents

4

OVERVIEW

This Teacher’s Guide has been developed to support you as your students investigate theK’NEX Education Simple Machines Deluxe Set. In conjunction with the K’NEX materials andindividual student journals, the information and resources here can be used to build yourstudents’ understanding of scientific concepts and channel their inquiries into active andmeaningful learning experiences.

SIMPLE MACHINES DELUXE

This K’NEX Education set is designed to introduce students to the scientific conceptsassociated with simple machines. Students are provided with the opportunity to acquire skillsusing 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 andevaluate scientific principles in action.

TEACHER’S GUIDE

Designed as a resource for the teacher, this guide provides a glossary of key terms anddefinitions, includes an overview of the concepts associated with the different simple machines,identifies student objectives for each investigation, and offers plans and scripts to successfullypresent selected models and their associated activities.We have also provided Student Activityand Reference Sheets. These comprise illustrations and definitions of some of the conceptsfeatured 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 toidentify those activities that best support their academic needs.

STUDENT JOURNALS

It is expected that students will have journals available for recording information.They shouldbe 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 thestudents feel comfortable about drawing conclusions. Their journal entries will help make aconnection between the models they have built, the experiments they have conducted, and howthis information is applied to the real-world machines they use on a regular basis.The journalswill 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. JournalChecklists are also included in theTeacher’s Guide for each model and it’s associated activities.

Introduction:

5

Alignment with National Standards Grades K-4

Reprinted with permission from National Science Education Standards, 2001 by the National Academy of Sciences,Courtesy of the National Academies Press,Washington, D.C.

The National Science Education Standards

Unifying Conceptsand Processes

Physical Science

Science and Technology

• 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 andtechnology

Alignment with National Standards Grades 5-8

Reprinted with permission from National Science Education Standards, 2001 by the National Academy of Sciences,Courtesy of the National Academies Press,Washington, D.C.

The National Science Education Standards

Unifying Conceptsand Processes

Physical Science

Science and Technology

• Systems, order, and organization• Evidence, models, and explanation• Change, constancy, and measurement• Form and function

• Motions and Forces• Transfer of Energy

• Abilities of technological design• Understandings about science andtechnology

Science as Inquiry • Abilities necessary to do scientific inquiry• Understanding about scientific inquiry

6

Alignment with Standards for Technological Literacy Grades 3-5

Abilities of a Technological World

Design

The Nature of Technology

Apply design process• Collecting information•Visualize a solution• Test and evaluate solutions• Improve a design

The Attributes of design• Requirements of design

Engineering Design• Engineering design process• Creativity and considering all ideas• Models

The role of troubleshooting, research anddevelopment, invention and innovation, andexperimentation in problem solving• Troubleshooting• Invention and innovation• Experimentation

Core Concepts of Technology• Systems• Processes• Requirements

Relationships among technologies• Technologies integrated

Used with permission of ITEEA (www.iteea.org)

Standards for Technological Literacy

7

Alignment with Standards for Technological Literacy Grades 6-8

Used with permission of ITEEA (www.iteea.org)

Standards for Technological Literacy

The Nature of Technology

Design

Abilities of a Technological World

Core Concepts of Technology• Systems• Processes• Requirements

Relationships among technologies• Interaction of systems• Knowledge from other fields of studyand technology

The Attributes of design• Design leads to useful products andsystems•There is no perfect design

Engineering Design• Brainstorming• Modeling, testing, evaluating, andmodifying

The role of troubleshooting, research anddevelopment, invention and innovation,and experimentation in problem solving• Troubleshooting• Invention and innovation• Experimentation

Apply design process• Indentify criteria and constraints• Test and evaluate• Make a product or system

8 Graphics courtesy of ClickArt® 65,000 Incredible Image PakTM; ©1996-97,T/Maker Co. knexeducation.com

All About

GEARS

Effort - the force that is applied to do work; thepush, pull, squeeze or lift provided to use gears tomove an object

Resistance- the force provided by the object onwhich one is trying to do work; the object worksagainst (pushes back) the effort

Mechanical Advantage (MA)-a mathematical calculation that reveals how manytimes easier a job is to do

MA greater than 1 shows that the gear systemmultiplied the effort force, but must move througha greater distance. MA less than 1 shows that thegear system requires greater effort force tooperate but the driven gear moves more quickly

Gear ratio- a mathematical relationship thatindicates the difference in the size of gears in agear system; the rate at which one gear turnsanother based on the number of teeth ordiameter of each gear

Diameter- the distance through the center of anobject; a straight line passing through the centerof a circle ended at the circumference

Work- the job being done while using the gears

Load - the object (weight) lifted or moved; providesresistance to the gears

Force- any kind of push or pull applied to an object

Bevel- an angle that is not a right angle; slanted

Key Words and Definitions

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 thetwo gears interlock, mesh or connect.

• Gears can change the amount of force, the direction and thespeed of rotation needed to do a job.

number of teeth(driven gear)

number of teeth(drive gear)MA= ÷

diameter(driven gear)

diameter(drive gear)MA=

or

÷

number of teeth(large gear)

number of teeth(small gear)

GearRatio= ÷

diameter(large gear)

diameter(small gear)MA=

or

÷

How do gears help you?• Gears can change the force needed to makesomething move and the speed it moves.

• One gear affects the way another gear movesbased on how the gears are configured inthe system.

• Many gears, working together in differentarrangements, allow a single machine to do workat both different speeds and directions.

• The Mechanical Advantage, or gear ratio, of a setof gears, is determined by ratios of: the number ofteeth; the diameters; the speeds of the two gears;and the amounts of force with which they turn.

Key Concepts

:1

:1

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How do gears affect force?• Gears can reduce the amount of force needed todo a job.

• A small gear requires less force to turn than a biggear but must be turned many times in order tomake the big gear turn once.

• When a small gear turns a big gear, theMechanical Advantage tells how many timeseasier your job is.

How do gears affect speed?• When using two gears of different sizes, the smallgear turns more quickly than the big gear.

• When a big gear turns a small gear, the gear ratiotells how many times faster the job is done.

How do gears affect direction?• When two gears are linked together, they turn inopposite directions and can make different partsof machines turn in opposite directions.

• Gears can change the angle of rotation whena gear on a vertical plane turns a gear on ahorizontal plane.

• Special gear systems can change circular motioninto back-and-forth motion.

What are spur gears?• Spur gears lie in the same plane and turn inopposite directions when meshed.

• Different-sized spur gears turn at differentspeeds and with different amounts of force.

What are sprocket gears?• Sprocket gears are a special type of spur gearsconsisting of two gears on the same plane, setapart from each other and linked by a chain.

• Sprocket gears turn in the same direction.

• Different-sized sprocket gears turn at differentspeeds and with different amounts of force.

What are crown gears?• Crown gears lie in different planes (at right anglesto each other) and turn in opposite directions.

• Different-sized crown gears turn at differentspeeds and with different amounts of force.

What are rack and pinion gears?• Rack and pinion gears consist of a toothed barand a toothed wheel.

• Rack and pinion gears change circular motioninto back-and-forth motion.

What are worm gears?• Worm gears consist of a spiral-edged cylindercalled the worm and a toothed wheel called theworm gear.

• A worm and its worm gear turn in differentdirections, at different speeds and with differentamounts of force.

• Worm gears change fast motion into slowmotion.

Key Concepts

REMEMBERSpecial types of gears can be used tochange the direction of circular motionand to gear up or down depending onthe need for speed.


How do gears help you?Gears can help you in three different ways.

ForceGears can change the force you need to makesomething move.When you turn a small gear, itcan make a big gear move.You have to turn it lotsof times to make the big gear turn around once,but the small gear doesn’t take much force toturn.

SpeedGears can change the speed that a machinemoves. If two gears are different sizes, the smallergear will turn faster thanthe larger gear.Many machines use gearsof different sizes to makecertain parts of themachine turn faster orslower than others.

DirectionGears can also change thedirection somethingmoves.When two gearsare linked together, they turn in opposite direc-tions and can make parts of machines turn in op-posite directions too. Gears can also be set upwhere one gear is lying flat, but it makes an up-right gear turn. Different arrangements of gearsmake it possible for machines to do work inmany different directions.

Getting Started

With GearsWhat 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 thetwo 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.

Here’s an example of how gearscan help.Imagine you work for a zoo.Your job is to build afeeder to adjust the meals for an elephant namedMoe. Moe eats whatever food is put out for him sohis intake must be watched closely or he’ll overeat.The zoo manager asked you to find a machine tofeed Moe specific amounts at the proper times. Im-possible? NO! Not with the help of gears.

Picture this.

You could design ahuge plate whichrotates in acircle. Alongthe outsideof the plate arelarge bowls with elephant-sized helpings for Moe’smeals.Your design puts only one bowl in Moe’sreach at a time. The speed the plate turns is con-trolled by a series of gears underneath the plate.This allows it to run at the right speed so Moe getsfed at the proper time without your help.

A Bright Idea!

Gears were a pretty modern invention. Conductresearch to find out about the earliest use of thissimple machine.

STUDENT REFERENCE SHEET

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How much do gears help you?Just by counting the gear’s teeth and dividing a few numbers, you canfind out how much gears make work easier or faster.

Count the number of teeth on your driven Gear and the number on your driveGear.

Divide the driven number by the drive number. The answer is theMechanicalAdvantage (MA), which tells you how many times easier your job is.

You can also figure out the MA by measuring the diameter of each Gear. Then, dividethe diameter of the driven Gear by the diameter of the drive Gear. Is your answerabout the same as your answer from Step 2?

You can use the gear ratio to tell you how many times faster something canmove when you use a big Gear to turn a small Gear. Divide the number ofteeth on the big Gear by the number of teeth on thesmall Gear to get this ratio.

Gears let you use less forceImagine you want to turn a merry-go-round.A big gear with 500 teeth is attached to the plat-form where people ride. A smaller gear with 20teeth is attached to a motor.

A Mechanical Advantage of 25 means that themotor turns the small gear 25 times for one turnof the merry-go-round, but it takes 25 times lessforce than it would to turn the big gear itself.

The MA shows the number of times the gear sys-tem multiplies the effort force applied to the smallgear.

Gears give you speedImagine you are using a hand drill. You turn thecrank on the big gear, which has 60 teeth. Thesmall gear has 15 teeth.

The gear ratio is 4:1, which means that the drillbit turns four times faster than you turn thecrank since you are using a big gear to drive asmall gear. That helps you drill a hole quickly andeasily.

The gear ratio shows how many times faster thesmall gear turns when you apply the effort forceto the big gear.

1

2

1 2

3

MA= Diameter of driven Gear - Diameter of drive Gear:

MA=500- 20MA=25

:Gear Ratio =60 -15 1Gear Ratio =4 1

:

What’s the

Mechanical Advantage?

4

Gear Ratio = Number of teeth on big Gear - Number of teeth on small Gear :1:

MA = Number of teeth on driven Gear - Number of teeth on drive Gear:

::



What are

Spur Gears?

Spur gears are sets of gears that work together bybeing set in the same position. The teeth on the edgeof one gear mesh with the teeth on the other gear.When you turn one gear, the other gear turns in theopposite direction.

Spur gears can be the same size or different sizes. If thesizes are different, the gears will turn at different speedsand with different amounts of force.

Here’s an example.Spur gears inside a wristwatch make the handsturn.When you wind the watch, you wind up aspring that powers the gears. Small and largespur gears work together to make the handsturn at different rates, so you can tell the time.

How do spur gears help you?Spur gears of different sizes can help you bymaking parts of a machine turn at differentrates.When a small gear and a large gear worktogether, the small gear turns faster than thelarge gear. Its circumference is smaller, so itdoesn’t have as far to go to make onecomplete turn.

In a wristwatch, small and large gears worktogether to make the second hand turn a fullcircle within a minute; the minute hand turn afull circle within an hour and the hour handturn a full circle within twelve hours.

Different-sized spur gears also turn with dif-ferent amounts of force.These gears can helpyou when you use a machine that requiresextra force to do a job.


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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 iseasy to recognize. It’s the spiral part you turn to makethe jaws of the wrench come together. The worm gearmight not be so easy to identify. It has a toothed edgealong the bottom of its moving jaw. (You can just imagineit’s the edge of a big wheel!)

How do worm gears help you?Worm gears help by letting you turn part of a machineat one speed while you make another part of themachine turn at a much slower or faster speed.Worm gears can do this, because the worm has to makea full turn to make the worm gear move ahead by justone tooth. As a result, the worm turns much morequickly than the worm gear.

When you turn the worm on the crescent wrench, theworm gear turns slowly. It makes the movable jaw ofthe wrench move just a tiny bit–maybe a fraction of amillimeter. Being able to make such tiny movements letsyou adjust the wrench just the right amount.

Since the worm and worm gear move at differentspeeds, 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 eachtrace out a circle as they turn, the two circles are atright angles to each other.


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 theother gear. Both gears turn in the same direction.The teeth on sprocket gears are specially shapedto fit between the pegs or notches on a chain.

What are

Sprocket Gears?



Here’s an example.A bicycle uses sprocket gears to turn the backwheel. You push the pedals, making the pedal gearturn. The chain, which is wrapped around bothgears, then makes the back gear turn. The backgear turns the wheel and off you go!

How do sprocket gearshelp you?A special feature of sprocket gears is that they letyou spread your turning action over a distance.You don’t need to place the gears right next toeach other in order for them to work together.In a bicycle, it helps to have the gears separated, soyou have room for your feet to turn the pedals andto fit the big rear wheel next to the back gear.

Two sprocket gears connected by a chain move inthe same direction. Both gears turn clockwise orboth turn counterclockwise. That’s helpful in abicycle. Otherwise, you’d have to pedal backwardsto make the bike go forward!

Sprocket gears can vary in size. Like other spurgears, they can turn at different speeds and withdifferent amounts of force. As a result, the pedalgear turns at a different speed than the gearattached to the wheel.

Here’s an example.A hand drill has a crank to turn and a shaft thatholds the drill bit. When you turn the crank, thedrill bit spins to drill a hole. The drill’s crown gearshelp you drill straight down while turning the crankon the side of the drill.

How do crown gears help you?Crown gears make different parts of machines turnin different directions. On a hand drill, the crank isconnected to an upright gear.With the crank inthis position, your hand can easily turn it. If the drillhad a crank that turned around the drill’s shaft, itwould probably make the drill wobble as it turnedand the drill would be difficult to hold.

Like spur gears, crown gears can be different sizes.Then, the crown gears will turn at different speedsand with different amounts of force, in the sameway that spur gears do.

Crown gears are gears that work together but,unlike spur gears, they are not set in the sameposition. Instead, a pair of crown gears lie at angles toeach other – usually at right angles. One gear mightbe upright, while the other lays flat. Another namefor crown gears is bevel gears. They are called bevelgears because the word bevel means “slanted.”

Graphics courtesy of ClickArt® 65,000 Incredible Image PakTM; ©1996-97,T/Maker Co.knexeducation.com

What are

Crown Gears?


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Graphics courtesy of ClickArt® 65,000 Incredible Image PakTM; ©1996-97,T/Maker Co. knexeducation.com16

Here’s an example.Inside a car, rack and pinion gears control the waythe car turns. The car’s steering wheel is connectedto a pinion gear that turns round and round. Itmoves the rack, which turns the front wheels tothe right or left, allowing the car to turn.

How do rack and pinion gearshelp you?Rack and pinion gears let you change round-and-round motion into back-and-forth motion.These gears make it easy to steer a car.You canturn the wheel a little to make the car angle to theright or left, or turn it a lot to make a sharp turn.Imagine trying to steer if you didn’t have rack andpinion gears.You’d have to shift the wheels in someother way- perhaps with a lever. Rack and piniongears sure make things easier!

Rack and pinion gears have their own special shape andtheir own kind of movement. The rack is a long, toothedbar which moves back and forth.The pinion is a toothedwheel which rotates.

What are Rack

and Pinion Gears?



Every wheel and axle has a job to doA salad spinner provides a great demonstration of spur gears. Count and compare the number of turnsof the salad spinner handle to the number of turns of the basket. Note that the spinner makes workeasier, because the basket spins fast enough to make the water fly away from the lettuce, but you don’thave to turn the crank very fast.

Journal Check

� Explanation for how spur

gears function

� Explanation of 1:1 and 6:1 gear

ratios based on observations

� Force measurements and compar

isons

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 betw

een

spur gear size and their functiona

l

advantage(s)

� Explanation of the relationship be

tween

spur gear arrangement and applie

d force

Materials-K’NEX Rubber Band Scale-small weight, such as cup ofpennies or green Rods-string-extra K’NEX pieces

• Identify a spur gear

• Demonstrate how spur gears function

• Explain the advantage offered by spur gears of differ-ent gear ratios and their effect on force and speed

• Measure applied forces using a Rubber Band Scale and determineMechanical Advantage

• Determine if spur gears change force, speed or direction

• Practice creative design utilizing spur gears

• Compare and contrast spur gears with other gears

Objectives

The Spur Gears Lesson Plan Lesson Length: 30-45 minutes

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1 Build the 1:1 Spur Gear model. Mark eachGear near the rim with a small piece of tape.Turn the crank for the top Gear one full turnand observe the model.Which way does eachGear move? How many turns did the bottomGear make? This Spur Gear model has a oneto one (1:1) gear ratio. Based on your obser-vation, what does this mean? (Refer to the“What’s the Mechanical Advantage” ReferenceSheet for help.)

2 a. Hang a cup with small weights (green Rods,pennies, etc.) from the crank on the lowerGear.Turn the top crank to lift the weight.Feel how much force it takes to do this.Connect the K’NEX Rubber Band Scale tothe end of the top Gear’s crank. Measure theamount of force used to lift the weight.Record your findings.b. Next, hang the weight from the crank forthe top Gear.Turn the lower crank and feelthe force used to lift the weight. Do you usethe same amount of force to lift the weightnow?Measure the force used to lift the weight inthis position. Record your findings. Comparethe measurements. Did the amount of forceused differ?Why or why not?Write a para-graph explaining your results.

3 a. Build the 6:1 Spur Gear model. Repeat Ac-tivity 1, turning the crank for the yellow Gear.How many turns did the blue Gear make forone turn of the yellow Gear? Based on yourobservation, what is the gear ratio for thismodel?Why would you need to use spurgears that have different ratios?b. Repeat Activity 2, testing the weight oneach crank.Which Gear requires less force tolift the weight?What are other benefits tousing this Gear arrangement?

4 Using K’NEX, build a hand cranked fan thatuses spur gears to turn at different speeds.Make blades for your fan from cardboard orposter board. Crank the fan and feel the coolbreeze!

1 1 Two adjacent spur Gears turn in opposite di-rections. For the 1:1 Spur Gear, the bottomGear makes one turn as the top Gear makesa single turn. A 1:1 gear ratio means that twospur gears are the same size and they turn atthe same rate.

2. To lift weights with the 1:1 Spur Gear, youneed to apply the same force whether youattach the weight to the top or bottom Gearbecause the two Gears are the same size.Same size gears turn with the same amountof force.a. For the 6:1 Spur Gear, the small Gear turnssix times for each turn of the large Gear.When spur gears differ in size, the smallerone turns faster.b. Using the 6:1 Spur Gear, you need to applyless force to the small Gear when the weightis attached to the large Gear.The large Gearturns more slowly, but with more force,so you don’t need to supply so much forceyourself.This arrangement changes the direction thecrank rotates.

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3

QUESTIONS ANSWERS

4


Every gear has a job to doSpur gears lie one behind the other. By turning one spur gear,you can make another gear move.When you use a salad spinnerto dry a head of lettuce, you are using spur gears.These gearsare inside the lid and they connect the handle to the basketwhere you put the lettuce.When you turn the handle, thebasket turns much faster than the handle turns.The watergoes flying into the outer bowl and your lettuce is dry, thanksto spur gears!

1 Build the 1:1 Spur Gear model. Mark eachGear near the rim with a small piece oftape.Turn the crank for the top Gear onefull turn and observe the model.Whichway does each Gear move? How manyturns did the bottom Gear make? ThisSpur Gear model has a one to one (1:1)gear ratio. Based on your observation,what does this mean? (Refer to the “What’sthe Mechanical Advantage” ReferenceSheet for help.)

2 a. Hang a cup with small weights (greenRods, pennies, etc.) from the crank on thelower Gear.Turn the top crank to lift theweight. Feel how much force it takes todo this.

Connect the K’NEX Rubber Band Scale tothe end of the top Gear’s crank. Measurethe amount of force used to lift the weight.Record your findings.

b. Next, hang the weight from the crankfor the top Gear.Turn the lower crank andfeel the force used to lift the weight.Do you use the same amount of forceto lift the weight now?

Measure the force used to lift the weightin this position. Record your findings.Compare the measurements. Did theamount of force used differ?Why orwhy not?Write a paragraph explainingyour results.

3 a. Build the 6:1 Spur Gear model. RepeatActivity 1, turning the crank for the yellowGear. How many turns did the blue Gearmake for one turn of the yellow Gear?Based on your observation, what is thegear ratio for this model?Why would youneed to use spur gears that have differentratios?

b. Repeat Activity 2, testing the weight oneach crank.Which Gear requires less forceto lift the weight?What are other benefitsto using this Gear arrangement?

4 Using K’NEX, build a hand cranked fanthat uses spur gears to turn at differentspeeds. Make blades for your fan fromcardboard or poster board. Crank the fanand feel the cool breeze!

The Spur Gears

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STUDENT ACTIVITY SHEET


Every gear has a job to doWhen riding multi-speed bikes, riders need to shift gears when riding uphill, downhill or into the wind.These riding conditions affect the amount of force that must be applied to the sprocket gears in order tokeep riding with a certain level of comfort and speed. (An illustration of a roller coaster’s starting climbwill also effectively demonstrate the use of sprocket gears.)

Journal Check

� Measurements of sprocket gear r

otations

and gear ratios

� Weight and forcemeasurements

� Descriptive comparison of the

feel and speed of the force requir

ed for

varying sprocketgear configuratio

ns

� Explanation of how force measureme

nts

support observations

� Description of why bicycles are b

est served

by sprocket gears

� Lists of other machines which use

sprocket gears

The Sprocket Bicycle Gear Lesson Plan

Materials-no special materials required

• Identify a sprocket gear• Demonstrate how sprocket gears function• Explain the advantages offered by sprocket gears of thesame and different gear ratios and their effect on forceand speed

• Measure applied forces with a Rubber Band Scale and determineMechanical Advantage• Determine if sprocket gears change force, speed or direction• Demonstrate the significance and advantage of gear ratios and force spreadover distance

• Compare and contrast sprocket gears with other gears• Determine the appropriateness of sprocket versus other gears used incertain machines

Objectives

Lesson Length: 30-45 minutes

21

a. Set up the Sprocket Bicycle Gear model withthe chain wrapped around the two sets of smallyellow Gears.Turn the pedal and count the num-ber of times theWheel turns. Record your an-swer.What is the gear ratio for these SprocketBicycle Gears?What is the Mechanical Advantage?(Refer to the “What’s the Mechanical Advantage”Reference Sheet.)b.Attach a cup with small weights to the gray Rodwith theWheel. Measure the force used to turnthe pedals with the K’NEX Rubber Band Scale.(Snap the orange Connector at the bottom of theScale to the blue Rod on the pedal.) Record yourresults.

2 a.Add extra links to the Chain.Wrap the Chainaround the set of small Gears and big Gears. Nowput the pedals on the axle with the small Gears.Put the wheel on the axle with the big Gears.How does it feel to turn the pedals?b. Repeat the process fromActivity 1. Comparethese results with your previous results.Whichset of Sprocket Bicycle Gears need more force tolift the weight?Why?

3 a. Now switch the pedals to the axle with the bigGears, and put theWheel on the axle with thesmall Gears.Turn the pedals. How does it feel?Does theWheel turn faster or slower?Why?b. Repeat the process fromActivity 1.

4 Compare all your results.Why are the gear com-binations described as high and low? How doyour force and speed measurements prove this?Which Gear arrangement lets you ride fast withthe least force? Explain.

6 Why are sprocket gears a good choice for abicycle? Make a list of machines that use sprocketgears. Explain why this gear system is the bestchoice for these machines.

1 1 a.The gear ratio for the set of small Sprocket Bi-cycle Gears is 1:1.They turn in the same direc-tion. The Mechanical Advantage is 1.

2 a. Students should find that they must turn thepedals (which are attached to the small Gears)about 2.5 turns for every turn of the wheel(which is attached to the large Gears).The pedalsturn easily, but the wheel doesn’t go very fast.b. Students will find that it takes less force to liftthe weight when turning the small Gears to makethe large Gears lift the weight.This arrangementhas a MA of 2.5.

3 a.They only need to turn the pedals (which areattached to the large Gears) less than one-half aturn (about 0.4 turn) for the wheel (which is at-tached to the small Gears) to turn once.The ped-als are harder to turn, but the wheel turns faster.b. Students will find that it takes more force to liftthe weight when turning the large Gears to makethe small Gears turn but the weight is lifted faster.This arrangement has a MA of 0.4.

4. With the K’NEX model set in low gear it’s easierto pedal faster because you don’t need to apply alot of force. However, you do not go very far be-cause the wheel does not turn very often.Withthe model in high gear, you must apply moreforce. It will be more difficult to turn the pedalsbut they will turn the wheel much more often, togo farther.The K’NEX model correlates to a real bicycle: thebicycle’s front gears are attached to the crankshaft,which the pedals turn.The back gears are attachedto the back wheel, so they turn with the wheel.

5. Sprocket gears make a good choice for a bicycle be-cause the chain makes the pedal gear turn in thesame direction as the wheel gear.The chain allowsthe pedal gear and the wheel gear to be separatedfrom each other so you have room for the pedalsand your legs.Students may have seen sprocket gears in chainsaws, chain hoists, garage door openers, barbecuerotisseries, movie projectors and cameras (thefilm acts as the “chain”).These machines usesprocket gears to move the chain or to turn agear some distance away.

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3

ANSWERS

5

QUESTIONS

4

4

5

1-888-ABC-KNEX


Every gear has a job to doSprocket gears are set apart from each other and areconnected by a chain. Many bikes have a set of sprocketgears which help you ride at an even pace, on any kind ofsurface. Sprocket gears also pull roller coaster cars up thefirst ramp of the ride.The chain has notches or pegs that fitaround the gears.When you turn one gear, the chain moves too, and it makesthe gear on the other end of the chain turn.These gears let you supply thepower in one place and have the power be used across a distance.

1 a. Set up the Sprocket Bicycle Gear modelwith the chain wrapped around the twosets of small yellow Gears.Turn the pedaland count the number of times theWheelturns. Record your answer.What is thegear ratio for these Sprocket BicycleGears?What is the Mechanical Advantage?(Refer to the “What’s the MechanicalAdvantage” Reference Sheet.)

b.Attach a cup with small weights to thegray Rod with theWheel. Measure theforce used to turn the pedals withthe K’NEX Rubber Band Scale. (Snapthe orange Connector at the bottom ofthe Scale to the blue Rod on the pedal.)Record your results.

2 a.Add extra links to the Chain.Wrap theChain around the set of small Gears andbig Gears. Now put the pedals on the axlewith the small Gears. Put the wheel on theaxle with the big Gears. How does it feelto turn the pedals?

b. Repeat the process fromActivity 1.Compare these results with your previousresults.Which set of Sprocket BicycleGears need more force to lift the weight?Why?

3 a. Now switch the pedals to the axle withthe big Gears, and put theWheel on theaxle with the small Gears.Turn the pedals.How does it feel? Does theWheel turnfaster or slower?Why?

b. Repeat the process fromActivity 1.

4 Compare all your results.Why are thegear combinations described as high andlow? How do your force and speedmeasurements prove this?Which Geararrangement lets you ride fast with theleast force? Explain.

6 Why are sprocket gears a good choice fora bicycle? Make a list of machines thatuse sprocket gears. Explain why this gearsystem is the best choice for thesemachines.

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5

The SprocketBicycle Gear



Every gear has a job to doCrown gears allow you to turn a gear in one direction, while making anothergear turn at a right angle. Help students see how the arrangement of crowngears can be useful. For example, in the case of a power drill, you don’t haveto get your hand near the sharp drill bit to tighten the screw.

Journal Check

� Description of how crown

gears work and the directions

they turn

� Description of the difference in

force and direction in various

model configurations

� Force measurements for crown

gear arrangements

� Gear ratios for sets of crown gea

rs

� Description of how crown gears can

do work in a newly designed

potter’s wheel

The Crown Gears Lesson Plan

Materials-tape-extra K’NEX piecesincluding a large Gear

Objectives • Identify a crown gear• Demonstrate how crown gears functio• Measure applied forces with a Rubber Band Scale anddetermine Mechanical Advantage

• Determine if crown gears change force, speed or direction• Infer the significance and advantage of crown gear ratios and theireffect on force and speed• Demonstrate the significance and advantages of using crown gears• Practice creative design to build a model which effectively utilizescrown gears

• Compare and contrast crown gears with other gears


24

Turn the crank to make your K’NEX CrownGears move.Which way does each Gear turn?How is their movement different from themovement of spur gears?

2 Use the K’NEX Rubber Band Scale to meas-ure the force used to lift a small weight withthe Crown Gears, like you did with the SpurGears. Record your findings. Did the CrownGears reduce the force needed to lift theweight?Why or why not?

3 a.Try replacing one small Gear in yourCrown Gears model with a big yellow Gear.You will have to change the stand so the bigGear will fit.

b. Use a small piece of tape to mark the topof each Gear.Turn the large Gears one turnand see how many times the small Gear turnsaround.

c.Again, use the Rubber Band Scale to meas-ure the force needed to lift the weight.Record your results and compare them tothe previous measurement. How did thisCrown Gear arrangement affect the amountof force used to do the work?Write a fewsentences explaining your findings.

d.What is the gear ratio for this set of CrownGears?What is the Mechanical Advantage?(Refer to the “What’s the Mechanical Advantage”Reference Sheet for help.) How can crowngears help you do work?

4. Imagine you make clay pots and you want tobuild a potter’s wheel that is powered by bikepedals. How might crown gears help you dothis? Using K’NEX, design and build thismodel.

1 1. When you turn the Crown Gears, one Gearturns clockwise and the other turns counter-clockwise, just as with spur gears.This may behard to see because the two Gears lie in dif-ferent planes. Look at the Crown Gears atthe inside “corner” where the two Gearsmesh.

2. Crown gears of the same size turn with thesame amount of force. If the crown gearshave the same gear ratio and MA as spurgears, they turn with the same amount offorce.

3 b.The small yellow Gear turns about 2.5times for each turn of the big Gear.

c.When turning the small Gear to lift theweight on the big Gear, the force needed tolift the weight was reduced due to the Me-chanical Advantage. However, the arrange-ment of the Gears does not have an effect onthe amount of force used.

d. Students will find that the big yellow Gearhas 84 teeth and the small yellow Gear has34 teeth.The equation to find the gear ratiois 84/34= 2.47:1.The MA will either be 2.47or 0.4 depending upon how they set up themodel. Note that this number is close totheir observed results.The “What’s the Me-chanical Advantage?” Reference Sheet will ex-plain more about the gear ratio.

Crown gears help do work by changing thedirection of the work.You can apply the forcein the direction that is easiest for you andhave the work take place in a different direc-tion.

4. To make a potter’s wheel turn using bike ped-als, you need to link a horizontal wheel witha vertical wheel.A horizontal surface isneeded to put the pot on, but you have toturn the bike pedals while you’re sitting up, sothey must work in a vertical plane. Any otherarrangement would have your pot sliding offan upright surface or you would have topedal while lying down.

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ANSWERSQUESTIONS

4

4

1-888-ABC-KNEX


Every gear has a job to doCrown gears meet at right angles, which means that onegear turns vertically (up and down) and meshes withanother gear which turns horizontally (side to side).Crown gears let you change the angle and motion you’returning.A little tool called a chuck key (pictured here at thetop) uses crown gears to help you tighten a power drill bit.You turn the key and the “jaws” of the drill come togetherto hold the bit in place.The gears are arranged this way sothe bit won’t poke you when you tighten it.

1. Turn the crank to make your K’NEXCrown Gears move.Which way does eachGear turn? How is their movementdifferent from the movement of spurgears?

2 Use the K’NEX Rubber Band Scale tomeasure the force used to lift a smallweight with the Crown Gears, like you didwith the Spur Gears. Record your findings.Did the Crown Gears reduce the forceneeded to lift the weight?Why orwhy not?

3 a.Try replacing one small Gear in yourCrown Gears model with a big yellowGear.You will have to change the standso the big Gear will fit.

b. Use a small piece of tape to mark thetop of each Gear.Turn the large Gears oneturn and see how many times the smallGear turns around.

c.Again, use the Rubber Band Scale tomeasure the force needed to lift theweight. Record your results and comparethem to the previous measurement. Howdid this Crown Gear arrangement affectthe amount of force used to do the work?Write a few sentences explaining yourfindings.

d.What is the gear ratio for this set ofCrown Gears?What is the MechanicalAdvantage? (Refer to the “What’s theMechanical Advantage” ReferenceSheet for help.) How can crown gearshelp you do work?

4. Imagine you make clay pots and you wantto build a potter’s wheel that is poweredby bike pedals. How might crown gearshelp you do this? Using K’NEX, designand build this model.

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1

Chuck KeyThe Crown Gears



Every gear has a job to doRack and pinion gears differ from other gears because they allow you to achieve back-and-forthmotion, rather than just circular motion. One common example in real-life is rack and pinionsteering in cars.The steering wheel is attached to the pinion, which moves a rack connectedto the front wheels. Its back-and-forth motion makes thewheels turn right or left.

Journal Check

� Explanation of how rack and pinion

gears function

� Measurements for distance the ra

ck

travels

� Comparative measurements (rati

os) for

turning the pinion and its relation

ship to

rack movement

� Illustration of design for rack and

pinion

invention

� Description of how cog railways wor

k

The Rack and Pinion Gears Lesson Plan

Materials-ruler-ping-pong ball or K’NEX ball-extra K’NEX pieces

Objectives • Identify a rack and pinion gear• Demonstrate how rack and pinion gears function• Explain and demonstrate the advantages offered byrack and pinion gears and their effect on forceand speed

• Determine if rack and pinion gears change force, speed or direction• Identify how rack and pinion gears are used in everyday life• Practice creative design to build a model which utilizes rack and piniongears

• Investigate cog railway systems and how they utilize rack and piniongears

• Compare and contrast rack and pinion gears with other gears


27

1. Turn the crank on your K’NEX Rack andPinion Gears one-half turn. How far does therack move? Use a ruler to measure thedistance and record your results.

2 Redesign the Rack and Pinion Gears using awhite Connector and eight white Rods forthe pinion. Spread the teeth on your rack tofit the spacing on the pinion and lengthen therack track.

Try turning the crank one-half turn. Measureand record how far this rack moves.WhichRack and Pinion set moves its rack farther?Which moves faster?Write a sentence de-scribing how the size of the pinion affects thedistance the rack moves.

3. Move the rack all the way to the left and resta small ball on the red Rods at the right.Turnthe pinion so the rack moves the ball alongthe Rods.Then, try moving other objectsalong the Rods, either horizontally or at aslant. Create a handy or a fun invention thatuses rack and pinion gears. Make a drawingand write a description of your invention. Fora real challenge, build it using K’NEX.

4 a. A cog railway brings train cars straight upa steep mountain slope, instead of travelingup a winding mountain path. Rack and piniongears help keep the cog railway car fromslipping down the mountain. Investigatecog railways.

b. Build a cog railway system out of K’NEX.How do the rack and pinion gears in a cograilway work differently from those in otherrack and pinion gear systems, like a car?

5. Rack and pinion systems are used to connectthe front wheels and the steering columns insome cars. Investigate vehicles which use thisgear system and build a K’NEX vehicle ofyour own design with a rack and pinionsteering system.

1 1. Turning the crank on the Rack and PinionGears one-half turn causes the rack to moveabout 7 cms.

2. After the Rack and Pinion is modified, forone-half turn of the pinion, the rack moves10 cms.The rack moves faster when thelarger pinion is used. Students might expresshow the size of the pinion affects the distancethe rack moves by stating: “The larger thepinion, the farther the rack moves for eachturn of the pinion.”

3. Students answers will vary. Everyday objectsthat must be moved back and forth are agood place to begin thinking of rack and pin-ion examples. Gears might be used to helpyou pass a pepper shaker across the table orto push a cassette tape into a tape player.

4 a. Cog railways are used in mountainousareas, such as the mountains of the North-east and the Rockies.The Mt.WashingtonCog Railway was built in 1869 as a tourist at-traction and is still used today. It uses a steamengine with two pinion gears on its under-side. To move the train up the steep moun-tainside, the pinion gears grip the rack thatlies between the rails in the center of thetrain track.

b. In a cog railway system, the car moves upbecause the pinions turn and grip the rack,which is stationary.The Rack and PinionGears model is an example of how the rackand pinion works in a car.The pinion turnswhile staying in one place and it causes therack to move back and forth.

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3

ANSWERS

5

QUESTIONS

4

4

1-888-ABC-KNEX


Every gear has a job to doRack and pinion gears have two parts: the rack, which is a barwith teeth and the pinion, which is a round gear.The rack movesback and forth and the pinion turns in circles.An ice creamscooper uses rack and pinion gears.After you’ve scooped upsome ice cream, you push with your thumb against the rack.It slides over, turns the pinion, and out pops a round scoop ofice cream.

1. Turn the crank on your K’NEX Rack andPinion Gears one-half turn. How far doesthe rack move? Use a ruler to measurethe distance and record your results.

2 Redesign the Rack and Pinion Gears usinga white Connector and eight white Rodsfor the pinion. Spread the teeth on yourrack to fit the spacing on the pinion andlengthen the rack track.

Try turning the crank one-half turn.Measure and record how far this rackmoves.Which Rack and Pinion set movesits rack farther?Which moves faster?Write a sentence describing how the sizeof the pinion affects the distance the rackmoves.

3. Move the rack all the way to the left andrest a small ball on the red Rods at theright.Turn the pinion so the rack movesthe ball along the Rods.Then, try movingother objects along the Rods, eitherhorizontally or at a slant. Create a handy

or a fun invention that uses rack andpinion gears. Make a drawing and write adescription of your invention. For a realchallenge, build it using K’NEX.

4 a. A cog railway brings train cars straightup a steep mountain slope, instead oftraveling up a winding mountain path.Rack and pinion gears help keep the cograilway car from slipping down themountain. Investigate cog railways.

b. Build a cog railway system out of K’NEX.How do the rack and pinion gears in a cograilway work differently from those inother rack and pinion gear systems, like acar?

5. Rack and pinion systems are used toconnect the front wheels and the steeringcolumns in some cars. Investigate vehicleswhich use this gear system and build aK’NEX vehicle of your own design witha rack and pinion steering system.

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The Rack andPinion Gears



Every gear has a job to doWhen a garden hose is turned on full power the water comes spraying out fast. If you connect thehose to a sprinkler, you can use the power of the water to make the sprinkler move.The fast-movingwater turns a small turbine inside the sprinkler, which rotates the worm.The worm turns the wormgear, which is connected to parts that move the sprinkler arm slowly back and forth.

Journal Check

� Explanation of how a worm and

worm gear function

� Illustration of thedirection worms

and worm gears turn

� Number of rotations of theWorm

Gear in one minute

� Number of teethon theWorm Gear

� Number of turnsof theWorm to

that of theWormGear

The Worm and Worm Gear Lesson Plan

Materials-stopwatch or clockwith second hand

Objectives • Identify a worm and worm gear

• Demonstrate how a worm and worm gear function

• Explain the advantages offered by worm gears and theireffect on force and speed

• Determine if worm gears change force, speed or direction

• Practice basic math skills

• Compare and contrast worm gears with other gears


30

1. Carefully, or with the help of an adult,start yourWorm Gear model by pluggingthe cord into the gray K’NEX Motor.Watch theWorm and theWorm Gearturn.Which way do they move? Draw apicture with arrows to show the directionthat each part turns.

2 a.Watch theWorm turn.You can see thatit spins very fast! Then, watch theWormGear turn and have a partner help youcount the number of times it turns in 60seconds.Mark one spot with tape or amarker so you can easily tell when theWorm Gear makes a full rotation. Dividethe number of turns by 60.Your answerwill be the number of turns theWormGear makes per second.Write downyour answer.b. Next, count and record the number ofteeth on theWorm Gear.c. Every time theWorm turns one fullturn, theWorm Gear moves ahead thedistance of only one small tooth. For theWorm Gear to make one full turn, theWorm has to turn the same number oftimes as the number of teeth on theWorm Gear.That means theWormturns fast! To find out how fast, try thismultiplication problem.

Your answer will be the number of turnsthe worm makes per second.That’s fast!

1 * CAUTION: Supervise students whenthey use the K’NEX Motor. Plug thetransformer into the wall yourself and letthem connect the small plug to the Motor.Make sure the Motor is not used nearwater and that students have dry handswhen handling the plug.

1. Worm gears change the direction ofmotion. Like bevel or crown gears, theworm turns in one plane and the wormgear in a plane at right angles to that ofthe worm.To help students visualize thismotion, ask them to look head on at theWorm, to see it as a wheel.Then, theyshould see that the two “wheels” — theWorm and theWorm Gear — are at rightangles to each other.Their drawingsshould reflect this arrangement.Theymight draw axles through the wheels tobetter reflect the right angle.

2 a.TheWorm moves so fast it’s almostimpossible to count the turns. However,theWorm Gear moves slowly enoughthat they can count how many turnsit makes in a minute. Use this observationto reinforce the idea that worm gears canbe used to reduce speed (or increasespeed, if the worm gear makes the wormturn). Students will probably find that theWorm Gear turns about 90 times in 60seconds or about 1.5 times per second.b.TheWorm Gear has 50 teeth.c.The number of turns theWorm makesper second is: 1.5 turns per second x 50teeth per turn = 75 turns per second.Note that this speed is much faster thanthe 1.5 turns per second of theWorm Gear.

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ANSWERSQUESTIONS

Number of turnsper second X

Number of wormgear teeth

1-888-ABC-KNEX

WARNING: Important note: Be extremelycareful whenever using electrical devices.Teachers should monitor student activities at alltimes, and should examine devices before use.


Every gear has a job to doLike all gears, a worm gear is a wheel with teeth. However, unlikeother gears, a worm gear is not turned by another gear. Instead, it isturned by a worm – a rod with a spiral edge that resembles a screw.Every time the worm makes one full turn, the worm gear moves aheadjust a tiny distance – the width of one worm gear tooth!

When you turn the worm slowly, the worm gear turns at a much slowerpace.Worm gears are used in things which need to move very slowly, likea lawn sprinkler, or in very small movements, like tightening a spotlight soit shines in precisely the right spot.

1. Carefully, or with the help of an adult, startyourWorm Gear model by plugging thecord into the gray K’NEX Motor.WatchtheWorm and theWorm Gear turn.Which way do they move? Draw a picturewith arrows to show the direction thateach part turns.

2 a.Watch theWorm turn.You can see thatit spins very fast! Then, watch theWormGear turn and have a partner help youcount the number of times it turns in 60seconds.Mark one spot with tape or amarker so you can easily tell when theWorm Gear makes a full rotation. Dividethe number of turns by 60.Your answer

will be the number of turns theWormGear makes per second.Write downyour answer.

b. Next, count and record the numberof teeth on theWorm Gear.

c. Every time theWorm turns one full turn,theWorm Gear moves ahead the distanceof only one small tooth. For theWormGear to make one full turn, theWorm hasto turn the same number of times as thenumber of teeth on theWorm Gear.Thatmeans theWorm turns fast! To find outhow fast, try this multiplication problem.

Your answer will be the number of turnsthe worm makes per second.That’s fast!

1

2


Number of turnsper second X

Number of wormgear teeth

The Worm andWorm Gear



Every gear has a job to doAn automatic transmission in a car uses planetary gears.When you hand crank the K’NEX PlanetaryGears model, you act like the motor in a car.The wheel on the model is like one of the car’s wheels.Make a connection between the way the model works and the way a car works: the car motor keepsturning whether the car is moving or stopped and the car uses different gear ratios totravel at different speeds.

Journal Check

� Explanation of how the Planetary Ge

ars

function

� Description of why planetary gear

components areaptly named

� Comparative measurements for t

he

rotation of the planet and annulus

gears

� Measurements with different Plan

etary

Gear components locked in place

� Force measurements for each

gear arrangement

� Explanation as towhy gear arrange

ments

affect force

The Planetary Gears Lesson Plan

Materials-K’NEX Rubber Band Scale-small weight such as a cupof pennies

Objectives • Identify a planetary gear and its various components

• Demonstrate how planetary gears function

• Experiment with the Planetary Gears to determinethe effects on force and speed

• Measure and compare the applied forces required for different plane-tary gear configurations with a Rubber Band Scale

• Explain and demonstrate the advantages offered by planetary gears

• Determine if planetary gears change force, speed or direction

• Compare and contrast a planetary gear with other gears


331-888-ABC-KNEX

1 a.Turn the crank on your Planetary Gears model.You’re acting as a motor, keeping the axle turning.Asyou turn, watch the Gears move.Which pieces serveas the sun, planet and annulus gears?Write down thename of each Gear, and describe the size, color,location and role each plays.

b.Write a paragraph telling why both the sun andplanet gears are suitably named.

2 a. Experiment with locking different Gears in place tosee how the speed of the wheel changes. First, lock theplanet and annulus gears together.Turn the crank andwatch how fast the wheel turns. How many turns doesthe wheel make for every turn of the crank?

b. Now, lock the annulus gear in place by putting on the“brake” (pull up on the yellow Rod attached to thegreen Connector on the base).Turn the crank. Howfast does the wheel spin now? How many turns does itmake each time you turn the crank?

c. Next, release the brake on the annulus gear and holdthe yellow Rods that surround the main axle.This willkeep the planet gears from “orbiting” the sun gear.How fast does the wheel turn now?Whicharrangement spins the wheel the fastest?Why?

3 Measure the force needed to lift a weight withdifferent arrangements of the Planetary Gears.Attach asmall weight to one end of the axle for the PlanetaryGears and a K’NEX Rubber Band Scale to the other.Turn the crank. Record and compare your measure-ments. How much force is used to lift the weight witheach arrangement of the gears?Which one uses themost force? The least force?Why?

1 1 a. Planetary Gears are more complicated than many ofthe other gear and simple machine models.A presentation which demonstrates that planetarygears use different gear ratios, all within a compact setof gears, will make this concept easier to grasp.

The yellow Gear is the sun gear; the blue Gears arethe planet gears; the green Gear is the annulus gear.

b. Students answers will vary but should include: thesun gear is central, like the sun in our solar system; theplanet gears “orbit” or revolve around the sun gearand each planet gear also turns on its axis (axle) asplanets do; annulus means ring and the annulus gearprovides a ring or border around the sun and planetgears so the whole system can work together.

2 a.To lock the planet and annulus gears together,students must push one of the blue Rods that servesas an axle for a blue Gear through a hole on the greenGear. In this arrangement, all of the Gears are lockedup. Everything turns only with the main axle. Since thecrank and the wheel are on the same axle, they areturning at the same rate.This makes the wheel turnone full turn for every turn of the crank.The wheelturns at the same rate as the motor.

b.When the annulus gear is locked in place, the blueplanet Gears orbit the yellow sun Gear throughout theinside of the green Gear.The entire planetary geargroup (the Rods and Connectors in the middle of themodels to which the blue Gears are attached) alsoturns. In this position, the crank must be turned about2 times to make the wheel go around once.This gearcombination makes the wheel go more slowly than themotor.

c.When holding the planetary gear group, the annulusgear (green Gear) turns but the wheel does not moveat all.The blue Gears spin on their own axles due tothe turning of the green Gear but the planetary geargroup is not able to orbit the sun.When the planetgears are kept from orbiting, the wheel will not turn atall.This arrangement lets the motor “idle” — or keeprunning while the wheel is stopped.The crank makesabout two turns for one full turn of the annulus gear.

3. With the arrangement from Step 2a, the machine is ac-tually behaving like a wheel and axle since the Gearsare all locked up.This arrangement uses the most forceto lift the weight.The arrangement from Step 2b usesthe least force to lift the weight.The arrangement fromStep 2c does not lift the weight at all since the wheeldoes not move.

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ANSWERSQUESTIONS

3


Every gear has a job to doA set of planetary gears includes a central sun gear that connectswith planet gears that are equally spaced around it. An outerannulus gear (“annulus” means ring) meshes with the outsideedge of the planet gears.The sun gear and the annulus gear are onthe same axle.

This special grouping of gears lets some of the gears turn while othersare locked in place.This way, you can make different combinations ofgears turn.This gives you different gear ratios and the ability to performdifferent tasks. Planetary gears are also useful when you want one partof a machine to turn while another part stops.

1 a.Turn the crank on your Planetary Gearsmodel.You’re acting as a motor, keepingthe axle turning.As you turn, watch theGears move.Which pieces serve as thesun, planet and annulus gears?Write downthe name of each Gear, and describe thesize, color, location and role each plays.

b.Write a paragraph telling why both thesun and planet gears are suitably named.

2 a. Experiment with locking different Gearsin place to see how the speed of the wheelchanges. First, lock the planet and annulusgears together.Turn the crank and watchhow fast the wheel turns. How many turnsdoes the wheel make for every turn of thecrank?

b. Now, lock the annulus gear in place byputting on the “brake” (pull up on theyellow Rod attached to the greenConnector on the base).Turn the crank.

How fast does the wheel spin now? Howmany turns does it make each time youturn the crank?

c. Next, release the brake on the annulusgear and hold the yellow Rods thatsurround the main axle.This will keep theplanet gears from “orbiting” the sun gear.How fast does the wheel turn now?Whicharrangement spins the wheel the fastest?Why?

3 Measure the force needed to lift a weightwith different arrangements of thePlanetary Gears.Attach a small weight toone end of the axle for the PlanetaryGears and a K’NEX Rubber Band Scale tothe other.Turn the crank. Record andcompare your measurements. How muchforce is used to lift the weight with eacharrangement of the gears?Which one usesthe most force? The least force?Why?

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23

The PlanetaryGears



Every gear has a job to doThe K’NEX SimpleTransmission model illustrates, in a simplified way, how a manual transmission works. (An automatictransmission works on a different system.) A description of cars with manual gearshifts will yield information abouthow the transmission allows the car to be driven forward or in reverse and how the driver moves the gearshift tomake the car change gears.The sounds the car makes when gears are shifted—a slower or faster whirring sound as the enginechanges speeds—may prove to be helpful.

Journal Check

� Description of how the SimpleTransm

ission

works and how the Gears link up

� Explanation of which gearshift pla

cement

turns faster andwhy

� Identification andexplanation of th

e three

different gear positions and their

proper names

� Description of what happens whe

n gearing

is switched quickly

� List of other machines which use

a

transmission

� Description of what the modified

K’NEX

model does

The Simple Transmission Lesson Plan

Materials-no special materials required

Objectives • Identify a simple transmission and its components

• Demonstrate how a simple transmission functions

• Explain how work is done by gears within a simpletransmission

• Determine if the gears within a transmission change force, speedor direction

• Infer uses of a transmission in other machines

• Modify the SimpleTransmission to create an invention which utilizesthe different transmission settings


36

1a. Carefully, or with the help of an adult, plugthe cord into the gray K’NEX Motor of yourTransmission model.The yellow Rod is thegearshift. Start with the gearshift in themiddle position and then move it to the rightor left so the different Gears link up.Writedown what you observe.

b.Which makes the shaft turn faster – shiftingthe Gears to the right or to the left?Explain why.

c.This SimpleTransmission has threepositions: first gear, second gear and neutral.These are also referred to as high gear, lowgear and neutral. Match the gear names toeach other.Then match those to the actualK’NEX SimpleTransmission model.Which doyou think is which and why?What does theTransmission do when it is in neutral?

2. Try switching fast from neutral into high gear.What happens? How is this like what happensin a car, when the driver accidentally switchesfrom the lowest gear to the highest gear orvice versa?

3. Besides cars, what other machines do youthink might use a transmission? Alter yourmodel to create an invention that uses allthree transmission settings.What does yourcreation do?

1 * CAUTION: Supervise students when theyuse the K’NEX Motor. Plug the transformerinto the wall yourself and let them connectthe small plug to the Motor. Make sure theMotor is not used near water and thatstudents have dry hands when handlingthe plug.

1 a.The center gearshift position leaves theupper shaft in “neutral” — the Motor is stillrunning, but it isn’t driving anything. Shifting tothe right makes the upper shaft turn at lowspeed, while shifting to the left makes it turnat high speed.

b.With the gray Motor in front of you, shiftingto the left makes the shaft turn faster.This isbecause a large Gear turns a small Gear.The small Gear can turn several times foreach turn of the large Gear, so it moves at afaster speed.

c.A manual transmission in a car has moregear combinations than the K’NEX SimpleTransmission. In a car, the gears for slowdriving are called first gear or low gear.Second gear, third gear, and fourth gear areused for medium, fast, and very fast driving.When theTransmission is in neutral, theMotor continues to run but it is not drivinganything; the upper shaft does not turn at all.

2. When you switch the SimpleTransmissionfrom neutral to high gear, the Gears maygrind together, because the top Gear has tocatch up with the lower Gear that is alreadymoving.This is similar to what happens in acar when shifting from neutral or low gearinto the highest gear.A car’s gears will makethe same grinding noise as the K’NEX model.

3. Students might build attachments on theupper shaft of theTransmission model tomake a multi-speed fan, blender or anotherinvention.

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3

ANSWERSQUESTIONS

1-888-ABC-KNEX



Every gear has a job to doA car can creep along at a low speed or it can zoomdown the road. If you could see inside the car’s enginewhile you were driving, you would see that the enginedoesn’t have a wide range of speeds.Actually, it justturns fast all the time. Gears are what help the enginemove the car at different speeds.A system of gears,working together, make up the car’s transmission,which drives the car’s engine.

1 a. Carefully, or with the help of an adult,plug the cord into the gray K’NEX Motorof yourTransmission model.The yellowRod is the gearshift. Start with thegearshift in the middle position and thenmove it to the right or left so the differentGears link up.Write down what youobserve.

b.Which makes the shaft turn faster –shifting the Gears to the right or to theleft? Explain why.

c.This SimpleTransmission has threepositions: first gear, second gear andneutral.These are also referred to as high

gear, low gear and neutral. Match the gearnames to each other.Then match those tothe actual K’NEX SimpleTransmissionmodel.Which do you think is which andwhy?What does theTransmission do whenit is in neutral?

2. Try switching fast from neutral into highgear.What happens? How is this like whathappens in a car, when the driveraccidentally switches from the lowest gearto the highest gear or vice versa?

3. Besides cars, what other machines do youthink might use a transmission? Alter yourmodel to create an invention that uses allthree transmission settings.What doesyour creation do?

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3

The SimpleTransmission




Every gear has a job to doWhen opening and closing the window on a car, the mechanisms that do the work are contained insidethe car door. It may be difficult to picture the movement of the gears inside the door—but it wouldresemble the K’NEX CarWindow.The gears are configured somewhat differently,but the window works in basically the same way.The K’NEXCarWindow operates by hand crank andmost windows today are electric and usea switch lever to open and close.

Journal Check

� Identification of gear type used in

CarWindow

� Revolutions of different Gears an

d

resulting gear ratios and MAs

� Calculations of gear ratios

� Comparison of Gears and ratio fu

nction

� Description of Gear function if G

ear

configuration was reversed

� Assessment of rack and pinion gea

r

configuration in the CarWindow

The Car Window Lesson Plan

Materials-tape-extra K’NEX pieces

Objectives • Identify the type(s) of gear in a car window• Demonstrate how a car window functions• Calculate and explain the Mechanical Advantage ofthe gears in the CarWindow and their effect on forceand speed

• Compare and contrast gear revolutions• Infer rationale for gear configurations• Determine if the gears in a car window change force, speedor direction

• Apply knowledge of rack and pinion gear systems and determine if thissystem would work for a car window

• Design and build a model which utilizes rack and pinion gears


39

1. What kind of gears does the K’NEX CarWindow use: spur, crown, rack and pinion,worm or sprocket gears?

2. a. Lower the CarWindow all the way and thenturn the crank one full turn to raise thewindow.When you turn the crank one full turn,how much does the blue Gear turn? [Note: Becareful not to overwind the window or the blue Rodwill pop off!] How much does the yellow Gearturn?What is the Mechanical Advantage for thisgear system?

b. Now turn the crank one full turn again andwatch the blue Gear on the top axle (the Rodwith the yellow Gear). How much of a turndoes it make? How does this compare to theyellow Gear?

c.Turn the crank fully again and watch the greenGear. How much does it turn?What is the ratiobetween the blue and green Gears?What isthe MA?

d.Why does the CarWindow have thisarrangement of Gears?What would happento the CarWindow if the arrangement wasreversed? Explain.

3 The K’NEX CarWindow uses circular motionto make the window go up and down.Turn thehandle and observe how the Gears and the armthat holds the window work together.Wouldrack and pinion gears work well to raise andlower a car window? Make a drawing to showhow it might work.Then, build a K’NEX carwindow using rack and pinion gears.

1 1. The CarWindow uses two pairs of spur gears.Note that the Gears in each pair lie in the sameplane.

2 a. Since this blue Gear is on the same axle asthe crank, it turns once for one turn of thecrank.The yellow Gear makes a little less thanone-half turn.The Mechanical Advantage forthese Gears is 2.43.

b.The blue Gear on the top axle turns a littleless than half a turn when the crank turns a fullturn. It turns the same amount as the yellowGear. Help students see that even though theblue and yellow Gears are different sizes, theyturn the same amount because they are on thesame axle.The gear ratio is not a factor.

c.The green Gear only turns a very short dis-tance for a full turn of the crank.The gear ratiois 6:1.The MA is 6. In this case, the small Gearturns without needing to use a lot of force, butthe big Gear can only cover a short distance.This works out fine since the CarWindow onlyhas a short distance to move.

d.The gear ratio and MA greatly affect how theGears work together. Help students see thatthe combination of all these Gears makes itpossible for you to move the window just alittle without having to be very precise in yourturning action or providing a lot of effort. If thegear configuration was reversed, it would takemore effort to turn the crank and the windowwould move so quickly that you would have totake great care when turning or you coulddamage the window.

3. When designing a car window using rack andpinion gears, students will probably design avertical rack that pushes the window up.Asthey build, they might discover advantages ordisadvantages to using rack and pinion gears.They will need to consider where the windowcrank will be positioned on the door(preferably in a place where it could easily bereached!) and where the rack will move as thewindow goes up (possibly under the window oralong the side).

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3

3

ANSWERSQUESTIONS

1-888-ABC-KNEX


Every gear has a job to doMost cars today have automatic windows with levers whichyou push to open and close the car’s windows. Some carsstill have manual windows which operate by cranking awheel and axle on the inside of the car door. Regardless ofwhich system is used, the window moves up and down.How does this happen? Gears are the answer.A system ofgears inside the door shift an arm, which make the windowmove up or down.

1. What kind of gears does the K’NEX CarWindow use: spur, crown, rack and pinion,worm or sprocket gears?

2. a. Lower the CarWindow all the way andthen turn the crank one full turn to raisethe window.When you turn the crank onefull turn, how much does the blue Gearturn? (Note: Be careful not to overwind thewindow or the blue Rod will pop off!) Howmuch does the yellow Gear turn?What isthe Mechanical Advantage for this gearsystem?

b. Now turn the crank one full turn againand watch the blue Gear on the top axle(the Rod with the yellow Gear). Howmuch of a turn does it make? How doesthis compare to the yellow Gear?

c.Turn the crank fully again and watch thegreen Gear. How much does it turn?Whatis the ratio between the blue and greenGears?What is the MA?

d.Why does the CarWindow have thisarrangement of Gears?What wouldhappen to the CarWindow if thearrangement was reversed? Explain.

3 The K’NEX CarWindow uses circularmotion to make the window go up anddown.Turn the handle and observe howthe Gears and the arm that holds thewindow work together.Would rack andpinion gears work well to raise and lowera car window? Make a drawing to showhow it might work.Then, build a K’NEXcar window using rack and pinion gears.

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Window

The CarWindow



Journal Check

� Identification of the type of gears

in the

Lawnmower

� Explanation of how the spur gears fu

nction

� Calculations of gear ratios

� Comparison of the different gear

configurations and ratios

� Assessment of which gear arrange

ments

would be most effective and why

� Description of the scissor action o

f the

Lawnmower

The Lawnmower Lesson Plan

Materials-green tissue paper-scissors-tape-extra K’NEX pieces

Objectives • Identify the type(s) of gear used in a lawnmower

• Demonstrate how a lawnmower functions

• Explain the advantages offered by spur gears andtheir effect on force and speed

• Determine if the spur gears in the Lawnmower change force, speedor direction

• Calculate and demonstrate the significance and advantage ofgear ratios

Every gear has a job to doThis type of lawnmower is not used much anymore but surprisingly, most kids are familiar with it.The gears ina real push mower are not visible from the outside, which is typical of spur gears but they work in the sameway as the Gears in the K’NEX Lawnmower.The different speeds of the wheels and the rotating bladesgive a clue that gears are used.


42

1 a. Push your K’NEX Lawnmower across yourdesk and watch how the wheels and bladesturn.Which moves faster?

b. Count the number of teeth on the largeand small Gears that make the wheels turn.(Be sure to count the inside ring of teeth onthe green Gear, not the outside ring!) Thenfigure out the gear ratio by dividing the largenumber by the small number.This ratio tellsyou how much faster one gear turnscompared to the other when a large geardrives a small gear.

2. What kind of gears does the Lawnmower use:spur, crown, rack and pinion, worm orsprocket gears? How does the arrangementof Gears in the Lawnmower differ from othergear systems? Can you think of a differentarrangement which would work better? Ifyou can, build it. If not, use reference materi-als to learn more about lawnmowers and ex-plain why this is the best set up for thesegears.

3. Make some “grass” for your Lawnmower tomow.You can do this by cutting strips oftissue paper about 50 x 100 cm.Then, makeshort cuts into one of the long sides of eachstrip. Fold and tape the strips to a piece ofpaper so that the grass stands up.Then, mowthe lawn!Your Lawnmower may not cut, butwatch the way the blades of grass get sweptpast the cutting blade. Can you see the scis-sor action?Write a paragraph describing this.

1 1 a.The Lawnmower blades turn faster thanthe wheels.

b. Make sure to count the inner circle ofteeth on the large green Gear; it has 62 teeth.The small Gear has 14 teeth.The gear ratio isabout 4.4:1.You apply the effort to push theLawnmower but the green Gear turns theblue Gear fast so that the blades can turnquickly to cut the grass. Note that the largeyellow Gear just serves as the Lawnmower’sother wheel; it doesn’t connect to any otherGear.

2. The Lawnmower uses spur gears.The Gearsare arranged so that the small Gear runs onthe inner edge of the big Gear instead of theouter edge. Help students see that eventhough the arrangement is slightly differentfrom other spur gears they know, these gearsstill lie in the same plane, which is acharacteristic of spur gears.

Students answers will vary but should includelogical reasons to back up their ideas.Theywill likely determine that this is the mosteffective gear arrangement. It is convenient toline the gears up in the same plane and easierto perform the work in this plane also.Youare using the spur gears to apply your forceover a greater distance with more speed.

3. The best way to see how the Lawnmowerworks is by watching from the back of themower.The rotating blades sweep the grassto make it stand up and then the grass iscaught between a rotating blade and the fixedblade.The fixed blade actually does thecutting. Since the rotating blade is angled, itmoves across the fixed blade in the same waytwo scissor blades meet.

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3

3

ANSWERSQUESTIONS

1-888-ABC-KNEX


Every gear has a job to doAn old-fashioned lawnmower uses spinning blades to cutthe grass. As the blades whirl around, they catch the longgrass against a sharp blade that stays in one place at the backof the mower.The moving and fixed blades act like a scissorsto cut the grass. Inside the wheels, gears make the blades turnat the right speed.

1 a. Push your K’NEX Lawnmower acrossyour desk and watch how the wheels andblades turn.Which moves faster?

b. Count the number of teeth on the largeand small Gears that make the wheelsturn. (Be sure to count the inside ring ofteeth on the green Gear, not the outsidering!) Then figure out the gear ratio bydividing the large number by the smallnumber.This ratio tells you how muchfaster one gear turns compared to theother when a large gear drives a smallgear.

2. What kind of gears does the Lawnmoweruse: spur, crown, rack and pinion, wormor sprocket gears? How does thearrangement of Gears in the Lawnmowerdiffer from other gear systems? Can youthink of a different arrangement whichwould work better? If you can, build it.If not, use reference materials to learnmore about lawnmowers and explain whythis is the best set up for these gears.

3. Make some “grass” for your Lawnmowerto mow.You can do this by cutting strips oftissue paper about 50 x 100 cm.Then,make short cuts into one of the long sidesof each strip. Fold and tape the strips to apiece of paper so that the grass stands up.Then, mow the lawn!Your Lawnmowermay not cut, but watch the way the bladesof grass get swept past the cutting blade.Can you see the scissor action?Write aparagraph describing this.

2

1 3

The Lawnmower



Every gear has a job to doBeating an egg with a fork in a bowl until it’s white and frothy is hard work.An eggbeater works muchbetter than the fork and makes the work much easier.The gears in a real eggbeater correspond withthe gears in the K’NEX model.The gears let you apply less force and beat the eggs in no time.

Journal Check

� Explanation andassessment of ho

w crown

gears function inthe Eggbeater

� Timing for bubble generation

with a spoon andEggbeater

� Assessment of the best tool for

the work

� Observation of the direction the

beaters

turn and how this affects theirwork

� Explanation of the best arrangeme

nt

for beaters

� Written and illustrated advertisemen

t for

the Eggbeater

The Eggbeater Lesson Plan

Materials-bowl or laundry tub-water-dish soap-spoon-colored markers-magazines and catalogs

Objectives • Identify the type(s) of gear used in an eggbeater

• Demonstrate how an eggbeater functions

• Explain the advantages offered by crown gears andtheir effect on force and speed

• Determine if the crown gears in the Eggbeaterchange force, speed or direction

• Experiment with the way the crown gears drive the Eggbeater

• Determine if the Eggbeater could be designed differently to bemore effective

• Design, write and illustrate an advertisement for the Eggbeater


451-888-ABC-KNEX

1. As you turn the crank on your Eggbeater,look at the direction the Gears turn.Would this tool work as well if it usedspur gears? Explain.

2 a. Fill a bowl or laundry tub about6 centimeters deep with water.Then, adda small amount of dish soap. Use a spoonto stir the mixture.Time how long it takesto cover the surface of the water withbubbles.b. Now, start over with new water andsoap.Try stirring the mixture with yourEggbeater. How long does it take to coverthe water surface with bubbles when youuse the Eggbeater?Which tool is best forthe job?Why?

3. Observe the rotating motion of thebeaters when you turn the crank.Do the beaters turn in the same oropposite directions? If the beaters turneddifferently, do you think they would workbetter?Why or why not? Explainyour answer.

4. Write an ad describing this handy,time-saving tool.Then illustrate and designan advertisement for your Eggbeater.

1 1. The arrangement of the crown gears(vertical and horizontal) and the two pairsof Gears make the beaters turn inopposite directions. Using spur gearswould probably not work as well becausethen you would have to do your turningin a horizontal plane, at the top of theEggbeater where you hold it, which wouldbe awkward.

2 The Eggbeater should allow students towhip up soap bubbles much faster thanthey could using a spoon.One reason forthis is because the large Gears attachedto the crank make the small Gears turnthe beaters very fast.Also, the twobeaters turning in opposite directionsmake the soapy water churn and mix well.

3. The beaters turn in opposite directions.If the beaters turned in the same direc-tion, the Eggbeater would still work buthaving them turn differently makes mixingfaster and easier. Encourage students toexperiment with the Eggbeater todetermine how they could make thebeaters turn in the same direction to seehow effective they are.

4. Have magazines or catalogs accessible tostudents so they can each get ideas abouthow to write advertisements for theirEggbeaters.Their ads might includeillustrations, recipes, quotes from “satisfiedcustomers” or even impressive technicaljargon. Encourage them to be creative andthink of other uses for the Eggbeater.

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33

ANSWERSQUESTIONS

44


Every gear has a job to doHave you ever tried to beat egg whites or pancake mixwith a fork? It takes a lot of time and energy to turnthe egg whites into fluffy foam and beat the lumps outof the pancake batter. Gears can make these jobseasier and faster.An eggbeater and a manual handmixer both use crown gears.The upright gears make iteasy for you to turn the crank.The other gears lay flat,so they can turn the beaters around and around in thebowl.

1. As you turn the crank on your Eggbeater,look at the direction the Gears turn.Would this tool work as well if it usedspur gears? Explain.

2 a. Fill a bowl or laundry tub about6 centimeters deep with water.Then, adda small amount of dish soap. Use a spoonto stir the mixture.Time how long it takesto cover the surface of the water withbubbles.

b. Now, start over with new water andsoap.Try stirring the mixture with yourEggbeater. How long does it take to cover

the water surface with bubbles when youuse the Eggbeater?Which tool is best forthe job?Why?

3. Observe the rotating motion of thebeaters when you turn the crank. Do thebeaters turn in the same or oppositedirections? If the beaters turned differently,do you think they would work better?Why or why not? Explain your answer.

4. Write an ad describing this handy, time-saving tool.Then illustrate and design anadvertisement for your Eggbeater.

2

1

3

4

The Eggbeater



Every gear has a job to doA real electric mixer turns its beaters very quickly in opposite directions. It can also work atdifferent speeds.When compared with an eggbeater, the two function in the same way but theelectric mixer has more power.

Journal Check

� Explanation of how theWorm andWorm

Gear do work

� Comparison of the Food Mixer a

nd the

Eggbeater

� Prediction and support regarding

the

speed of the beaters if gear sizes

were changed

� Explanation of why two beaters a

re

required in the mixer as opposed

to one

� Assessment of the effectiveness o

f the

beaters if they both turned in the

same direction

The Food Mixer Lesson Plan

Materials-bowl-jellybeans, two different colors

Objectives • Identify the type(s) of gears in a food mixer

• Demonstrate how a food mixer functions

• Explain the advantage offered by worm gears andtheir effect on force and speed

• Determine if the worm gears in the Food Mixer change force, speedor direction

• Compare and contrast machines which perform the same functionbut use different types of gears


48

1. With the help of an adult, start your FoodMixer by plugging the cord into the grayK’NEX Motor. How are the Gears in thismodel different from the Gears in theK’NEX Eggbeater model? Describe thedifference in writing.

2. If you changed the blue Gears on the shaftsof the beaters to larger Gears, would thebeaters turn faster, slower or at the samespeed? Predict what would happen.Writedown your prediction and then experi-ment to find out.

3. Try using your Food Mixer to stir up abowl of jelly beans. Put jelly beans of twodifferent colors in a bowl, with the colorsseparated on each side of the bowl.

Watch how the two beaters turn inopposite directions and mix the colorstogether.Then, remove one beater and trymixing with a single beater.Which wayworks better – using one or two beaters?Why? Explain your answer. If the beatersturned in the same direction, would theFood Mixer mix the jelly beans as well?Experiment with the Mixer design andfunction to find out.

1 * CAUTION: Supervise students when theyuse the K’NEX Motor. Plug the transformerinto the wall yourself and let them connectthe small plug to the Motor. Make sure theMotor is not used near water and thatstudents have dry hands when handlingthe plug.

1. In the Food Mixer, aWorm Gear turnsthe axle that holds the upright Gears; inthe Eggbeater, you turn the crank to turnthe upright gear axle.The horizontalGears (on the shafts of the beaters) turnthe same way in both models.

2. If you increase the diameter of the Gearsat the top of the beater shafts, the beaterswill turn more slowly. Encourage studentsto think about the problem and make aprediction before they experiment to findout the answer. Refer them to the“What’s the Mechanical Advantage?”Reference Sheet.

3. When students try mixing jellybeans, usetwo or more colors to really bring outthe mixing process. Have several studentsin a group watch as the colors mixtogether. Encourage them to see how thebeaters turning in opposite directionsreally churn up the jellybeans and mixthem better than a single beater does.

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ANSWERSQUESTIONS

1-888-ABC-KNEX



Every gear has a job to doWhen you make cookies, some ingredients make thebatter thick and hard to stir.An electric mixer makesstirring easier because its motor gives you extrapower. But you wouldn’t want the mixer’s beaters toturn as fast as the motor turns.Then you’d havecookie batter splattering out of the bowl and all overthe kitchen!Worm gears make the mixer’s beatersturn at a slower speed than the motor — just theright speed for mixing.

1. With the help of an adult, start your FoodMixer by plugging the cord into the grayK’NEX Motor. How are the Gears in thismodel different from the Gears in theK’NEX Eggbeater model? Describe thedifference in writing.

2. If you changed the blue Gears on the shaftsof the beaters to larger Gears, would thebeaters turn faster, slower or at the samespeed? Predict what would happen.Writedown your prediction and then experimentto find out.

3. Try using your Food Mixer to stir up abowl of jelly beans. Put jelly beans of twodifferent colors in a bowl, with the colorsseparated on each side of the bowl.

Watch how the two beaters turn inopposite directions and mix the colorstogether.Then, remove one beater and trymixing with a single beater.Which wayworks better – using one or two beaters?Why? Explain your answer. If the beatersturned in the same direction, would theFood Mixer mix the jelly beans as well?Experiment with the Mixer design andfunction to find out.

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The Food Mixer




Every gear has a job to doA good way to visualize the need for a differential is to imagine a marching band making a turn.The marchers on the inside of the curve don’t have far to go, so they take small steps and move slowly.The marchers on the outside of the curve must move faster to keep the rows of marchers lined up. In afront-wheel drive car, both front wheels are fixed to the axle, which is turned by the engine.(The rear wheels receive the power in a rear-wheel drive car.)The axle makes the wheels turn. Since bothwheels must be fixed to the axle, they mustuse a differential to be able to turn atdifferent speeds. Journal Chec

k

� Description of how the Axle model w

orks

and why

� Description of how the Axle with

Differential works and why

� Explanation of the movement of t

he

Gears in the Differential

� Description of the action of turnin

g with

the Differential

� List of other machines that might

benefit

from a differential

The Differential Lesson Plan

Materials-carpet, towel or other roughsurface

Objectives • Identify the type(s) of gear used in a differential

• Demonstrate how a differential functions

• Compare and contrast models with and withouta differential

• Understand the necessity of a differential in a vehicle

• Demonstrate how the planetary gears within a differential work

• Explain the advantage offered by these planetary gears and theireffect on force and speed

• Determine what other machines could benefit from a differential


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1. Build the Axle model, as shown in Figure A inthe instructions, and test it. Push it straightover a rough surface, like a carpet. Explainwhat happens. Push the model around a sharpturn.What do you notice? Describe whathappens when this model makes a turn.Whydoes this happen?

2 a. Now, build the Axle with Differential, asshown in figure B in the instructions. Roll theAxle with Differential straight over a roughsurface. Observe the cluster of Gears thatmake up the Differential.Which Gearsturn and which Gears don’t? Record yourobservations.

b. Continue to roll the Axle with Differentialalong and have it make a sharp turn.Watchthe cluster of Gears move as you make a turnwith the Axle with Differential.What do younotice about how the model turns now?Which Gears are working? How does thecluster of Gears affect the turning? Describethe action of turning a corner with the use ofthe Differential.

3. A differential is a complicated, yet very clevergearing machine.What machines, other than acar, could benefit from the use of a differentialgearing system?Work with a partner tobrainstorm a list of machines.

1 1. Students should see that the two big Gearsjust serve as wheels in this model.Try toprovide a carpeted surface on which to runthe models. If a carpet is not available, a towelcan make a good substitute.When studentstry to make a turn using the Axle model, theyshould feel a strain as one wheel lags behindthe other.They may notice that the wheel onthe outside of the turn may slip to keep upwith the inner wheel. In describing whathappens, they may just say that it’s hard tomake a tight turn.

2 a. Make it clear that the cluster of Gears inthe center of the model make up theDifferential.This gear system uses planetarygears with crown gears.The two yellowGears parallel to the wheels are the sungears.The two yellow Gears at right angles tothe sun gears are the planet gears.You maywant to put markings on the two sets ofgears in order to differentiate between them.Again, the two big Gears are not functioningas gears but only as wheels.

When students use the Axle with Differentialmodel to travel in a straight line, they shouldnotice that the sun gears turn on their axes,but the planet gears don’t turn on their axes(although they do move as part of theDifferential unit).

b. Explain that the Differential helps eachwheel turn independently at the right speed.Turning is much easier, one wheel travels at adifferent speed than the other and you canmake very tight turns with this model,compared to the Axle model.

When the wheels turn, the planet gears inthe Differential also turn — in oppositedirections.The sun gears move at the samerate as the wheels. One sun gear may turnslowly or hold still while the other sun gearturns quickly.

3. Students answers will vary.

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ANSWERSQUESTIONS

1-888-ABC-KNEX

3


Every gear has a job to doWhen a car makes a right turn around a corner, thewheels on the right side of the vehicle make a smallcurve near the curb, but the wheels on the left travel ina big curve.The left wheels have to travel farther thanthe right wheels, but all of the wheels do this action inthe same period of time.That means that the left wheelsactually have to go faster than the right. But how canthey go faster when the left and right wheels areattached to the same axle? A differential is a set of gearsthat lets the left and right wheels turn at differentspeeds.

1. Build the Axle model, as shown in Figure Ain the instructions, and test it. Push itstraight over a rough surface, like a carpet.Explain what happens. Push the modelaround a sharp turn.What do you notice?Describe what happens when this modelmakes a turn.Why does this happen?

2 a. Now, build the Axle with Differential,as shown in figure B in the instructions.Roll the Axle with Differential straightover a rough surface. Observe the clusterof Gears that make up the Differential.Which Gears turn and which Gears don’t?Record your observations.

b. Continue to roll the Axle withDifferential along and have it makea sharp turn.Watch the cluster of Gearsmove as you make a turn with the Axlewith Differential.What do you noticeabout how the model turns now?WhichGears are working? How does the clusterof Gears affect the turning? Describe theaction of turning a corner with the use ofthe Differential.

3. A differential is a complicated, yet veryclever gearing machine.What machines,other than a car, could benefit from theuse of a differential gearing system?Work with a partner to brainstorma list of machines.

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The Differential



Every gear has a job to doMechanical clocks have a complex arrangements of gears. Some clocks also have complicated gear sys-tems which mark the date or phases of the moon as well as the time. Clockmakers have a highly skilledjob which requires precision work to make sure the gears run correctly to read the correct time,all the time.

Journal Check

� Number of timesminute hand turn

s in a

full turn of hourhand

� Explanation of how the K’NEX Cloc

k

differs from a normal clock

� Explanation of how the gear configur

ations

affect the function of the Clock

� Description andeffects of modific

ations

made to gear configurations

� Creative story about the Clock

The Clock Lesson Plan

Materials-lightweight cardboard-scissors-masking tape-colored markers-extra K’NEX piecesincluding Gears

Objectives • Identify the type(s) of gear used in a clock

• Demonstrate how a clock functions

• Compare the functioning of the K’NEX Clock witha real clock

• Design a clock face for telling time and assess time telling features

• Determine how to tell time based on this Clock’s system mechanisms

• Modify the Clock to determine the effects of changing gearconfigurations

• Write a creative story about the effects of the Clock’s timing system


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1. Carefully, or with the help of an adult, plug thecord into the K’NEX Clock’s gray K’NEX Motorand let the Clock run.Watch how the Clockhands turn. How many times does the minutehand turn for each full turn of the hour hand?How is this Clock different from a normal clock?(Hint:A normal clock is a twelve-hour clock.Whatwould you call this one?)

2 a. Make a face for your Clock, with markings toshow the hours. Remember, it won’t be like anormal clock face! To do this, run your Clockuntil both hands are pointing straight up.Then,start your Clock, stopping it each time the minutehand points straight up. Make a mark where thehour hand points. Keep going until you havemarked the whole face.

b. Start your Clock and then pull the Motor plugout to stop it.Try telling what time your Clockshows. Remember, one turn of the hour hand stillstands for 60 minutes.Take turns with a friendrunning the clock and guessing the time.

3. Try changing the Gear configurations that are atwork inside the Clock. How do the differentGear combinations affect the speed and directionof the hands on the Clock. Describe the changesyou made to the Clock and how these changesaltered the way the Clock works.

4. Write a story about your unusual Clock.Youmight imagine that in a far off land, people use adifferent system for telling time or that you had adream in which time sped up. Share your storywith the class.

1 * CAUTION: Supervise students when they use theK’NEX Motor. Plug the transformer into the wallyourself and let them connect the small plug to theMotor. Make sure the Motor is not used near waterand that students have dry hands when handling theplug.

Use the Clock as a culminating activity. Reviewwhat students have learned about gears andassess their understanding by seeing if they canidentify the various gear systems within thismodel.

1. The minute hand on the K’NEX Clock turns36 times for every single turn of the hour hand,compared with 12 times for the minute hand of anormal clock.This could be called a 36-hourclock.

2 a.To make a clock face, students could cut out a12-centimeter cardboard circle with a5-centimeter hole in the center.The circle shouldthen be fitted over the clock’s hands to go behindthem.A little masking tape will help keep the facein place.To mark the clock face, students couldmark numerals 1 though 36 or they could repeat1 through 12 three times.Students may need assistance positioning theirgears so the hands point straight up to beginmarking the Clock’s face.Try disengaging theClock’s Gears by pushing the yellow Gears awayfrom their blue Gears, so the hands can spinfreely.b.To tell time with the K’NEX Clock, read thehour markings to tell the hour. Determine theminutes after the hour just as you would with anormal clock. For example, when the minute handpoints straight down, it’s 30 minutes past thehour.

3. Students answers will vary depending upon howthey reconfigure the Gears.All answers shouldreflect knowledge of the basic facts of each gearsystem that they utilize and their reasons forusing a particular gear system.

4. To get started writing stories, students mightthink of situations where time is important, suchas running a race or waiting for a special occasion.Their stories could put a twist on an everydaysituation by having time run at a different rate orby having a different way to tell time.

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ANSWERSQUESTIONS

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1-888-ABC-KNEX



Every gear has a job to doFace clocks – the kind of clocks with hands and a face withnumbers – have lots of gears which turn at different rates.The special combination of gears makes the minute, hour andsecond hands rotate at the right speeds. Many types of gears allwork together in a clock to make sure you are always on time!

1. Carefully, or with the help of an adult, plugthe cord into the K’NEX Clock’s grayK’NEX Motor and let the Clock run.Watch how the Clock hands turn. Howmany times does the minute hand turn foreach full turn of the hour hand? How isthis Clock different from a normal clock?(Hint: A normal clock is a twelve-hourclock. What would you call this one?)

2 a. Make a face for your Clock, withmarkings to show the hours. Remember,it won’t be like a normal clock face! To dothis, run your Clock until both hands arepointing straight up.Then, start your Clock,stopping it each time the minute handpoints straight up. Make a mark where thehour hand points. Keep going until youhave marked the whole face.

b. Start your Clock and then pull theMotor plug out to stop it.Try telling whattime your Clock shows. Remember, oneturn of the hour hand still stands for 60minutes.Take turns with a friend runningthe clock and guessing the time.

3. Try changing the Gear configurations thatare at work inside the Clock. How do thedifferent Gear combinations affect thespeed and direction of the hands on theClock. Describe the changes you made tothe Clock and how these changes alteredthe way the Clock works.

4. Write a story about your unusual Clock.You might imagine that in a far off land,people use a different system for tellingtime or that you had a dream in whichtime sped up. Share your story with theclass.

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The Clock



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GEARSPart & ModelList

Tan Connector 5 10 4 10 1 11 13 11 11 4 11 12 9 27

Gray Connector 1 0 0 8 2 4 5 6 0 4 6 2 8 10

Orange Connector 0 4 3 9 1 6 1 2 3 4 2 2 6 14

Lt Gray Connector 4 0 1 0 0 1 0 0 2 0 0 0 0 4

Red Connector 4 4 2 0 2 9 5 17 18 6 13 10 6 18

Green Connector 0 0 0 0 0 1 0 3 6 0 2 0 7 6

Yellow Connector 4 2 0 2 0 0 2 11 13 4 8 8 11 13

Blue Connector 8 0 4 4 4 4 3 3 4 4 4 0 4 8

White Connector 3 0 0 3 0 1 5 1 5 4 5 1 4 5

Purple Connector 16 12 12 4 12 4 13 11 12 8 12 12 14 16

Yel/Grn Female Hinge 0 0 0 0 0 0 0 2 2 0 0 0 0 2

Lt. Blue Male Hinge 0 0 0 0 0 0 2 2 2 0 0 0 2 2

Green Rod 6 0 8 10 0 8 12 25 26 18 24 10 28 28

White Rod 4 0 0 2 4 2 16 12 22 11 16 6 20 22

Blue Rod 20 6 9 5 12 8 18 19 16 1 5 15 19 21

Yellow Rod 7 7 4 3 1 7 3 13 14 0 0 10 10 14

Red Rod 4 7 2 5 1 4 0 5 5 6 8 5 1 8

Gray Rod 1 2 0 2 0 0 2 0 3 0 0 0 0 6

Med. Tire 0 1 0 0 0 1 0 0 0 0 0 0 0 1

Lge. Pulley 0 1 0 0 0 1 0 0 0 0 0 0 0 1

Motor Assembly 0 0 0 0 1 0 1 0 0 0 1 0 1 1

Adapter 0 0 0 0 1 0 1 0 0 0 1 0 1 1

Natural Worm Gear 0 0 0 0 1 0 1 0 0 0 1 0 1 1

Sm. Blue Gear (14) 1 0 0 0 0 2 2 2 1 2 2 0 2 2

Black Chain Link 0 28 0 0 0 0 0 0 0 0 0 0 0 28

Sm. Gray Gear (14) 0 0 0 0 0 0 0 0 0 0 0 0 3 3

Med. Yellow Gear (34) 2 4 2 0 0 1 2 1 0 2 4 4 4 4

Lt. Blue Spacer 34 28 0 42 12 14 22 12 11 7 30 27 42 42

Green Gear (84) 0 1 0 0 0 1 0 1 1 0 0 1 1 1

Lge.Yellow Gear (84) 1 1 0 0 0 0 0 0 1 0 0 1 1 1

Rubber Band #18 0 0 0 0 0 0 0 0 0 0 0 0 0 3

TOTALS PER MODEL 125 118 51 109 55 90 129 159 178 85 155 126 205 311

SPURGEARS

SPROCKET

BICYCLEGEAR

CROWNGEARS

RACK&PINION

GEARS

WORM&WORM

GEAR

PLANETARY

GEARS

SIMPLE

TRANSMISSION

CARWINDOW

LAWNMOWER

EGGBEATER

FOODMIXER

DIFFERENTIAL

CLOCK

TOTALPARTS

INGEARSSET

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