KNEX Gears Simple Machines Teacher Guide

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Gears

Teacher’s Guide

GEARS

KNX 96166-V2

and its licensors.

’NEX Education is a Registered Trademark

of K’NEX Limited Partnership Group.

Conforms to the Requirements of ASTM

Standard Consumer Safety Specification

on Toy Safety, F963-03.

Manufactured under U.S. Patents 5,061,219;

5,199,919; 5,350,331; 5,137,486.

Other U.S. and foreign patents pending.

Protected by International Copyright.

CHOKE HAZARD - Small parts.

Not for children under 3 years.

A NOTE ABOUT SAFETY:

Safety is of primary concern in science and

technology classrooms. It is recommended that

you develop a set of rules that governs the safe,

proper use of K’NEX in your classroom. Safety,

as it relates to the use of the Rubber Bands

should be specifically addressed.

CAUTIONS:

Students should not overstretch or overwind their

Rubber Bands. Overstretching and overwinding

can cause the Rubber Band to snap and cause

personal injury. Any wear and tear or deterioration

of Rubber Bands should be reported immediately

to the teacher. Teachers and students should

inspect Rubber Bands for deterioration before

each experiment.

Caution students to keep hands and hair away from

all moving parts. Never put fingers in moving Gears

or other moving parts.

INTRODUCTION TO SIMPLE MACHINES

Introduction:

OVERVIEW

This Teacher’s Guide has been developed to support you as your students investigate the K’NEX Intro to Simple

Machines: Gears set. In conjunction with the K’NEX materials and individual student journals, the information and

resources included here can be used to build your students’ understanding of scientific concepts and channel their

inquiries into active and meaningful learning experiences.

K’NEX INTRO TO SIMPLE MACHINES: Gears

As part of a series, this K’NEX construction set is designed to introduce students to the scientific concepts associated

with gears. Students are provided with the opportunity to acquire skills using a hands-on, inquiry-based approach to

information and concepts. Working cooperatively, students are encouraged to interact with each other as they build,

investigate, discuss, and evaluate scientific principles in action.

TEACHER’S GUIDE

Designed as a resource for the teacher, this guide provides a glossary of key terms and definitions, includes an

overview of the concepts associated with gears, identifies student objectives for each investigation, and offers plans

and scripts to successfully present selected models and their associated activities. We have also provided a selection of

black line masters for your classroom use. These comprise illustrations and short definitions of some of the concepts

featured in the model building activities. Most investigations can be completed in 30 to 45 minutes. Each

investigation also includes a suggested extension activity, which may be used to further explore the concept that was

the focus of the investigation. We recommend that teachers review their curriculum and science education standards

to identify those activities that best support their academic needs.

STUDENT JOURNALS

It is expected that students will have journals available for recording observations and student responses. Students

should be encouraged to enter initial thoughts at the start of an inquiry, such as inferences about possible outcomes

or expository text describing what they already know about a concept or topic. Encourage students to revisit and

revise their initial thoughts frequently during each investigation, until they feel confident enough to draw one or more

conclusions. Students should feel comfortable consulting journal entries from other investigations within and

occasionally outside the unit of focus. Their journal entries will help them make connections between the models they

have built, the investigation they have conducted, and how this information is applied to real-world machines that

they may use in their daily lives. Journals provide students with a place to practice drawing and labeling diagrams of

systems, as well as providing a means of assessment for the Simple Machines unit. Journal Checklists are included in

the Teacher’s Guide for each model and the associated inquiry activities

TABLE OF CONTENTS

Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Key Terms & Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Key Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

The Crank Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-18

The Car Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-24

The Blender (with extension activities for the Eggbeater) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-30

The Stationary Bicycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31-34

Blackline Masters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35-40

NOTE: The K’NEX Intro to Simple Machines: Gears set also includes instructions for building models of a

Phonograph and a Chain Saw. These models can be used to reinforce concepts and to enhance the students’

understanding of the ways in which gear systems work.

INTRODUCTION TO SIMPLE MACHINES

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Wheels & Axles

Gears

Background Information

KEY TERMS and DEFINITIONS for the teacher.

The following is intended as a resource for the teacher. The age of the students, their abilities and prior knowledge,

and your curriculum requirements will determine which of these terms and definitions you introduce into your

classroom activities. These terms are not presented as a list that students copy and memorize. Rather, they should be

used to formalize and clarify the operational definitions your students develop during their investigations. Students

should be encouraged to use the appropriate terms in context as they write about their discoveries in their journals.

Simple Machine:

A simple machine is a device that transfers energy in a single motion. Simple machines make work easier by changing

the way in which work is done. A simple machine does not, however, reduce the amount of work that is needed to do

the job.

Force:

Any kind of push or pull applied to an object.

Effort:

The force that is applied to move a load or overcome a resistance (i.e. the force that is applied to do work.) The force

applied to a simple machine is called input or effort force.

Resistance:

The force exerted by an object against the effort force.

Work:

In science, work refers to the amount of force used to move a load (object) through a given distance. Work can be

defined as follows:

W = F x D

Where W = work

F = the force applied to an object

D = the distance through which the force is applied

NOTE: If an object does not move, work has not been done.

Gear:

A wheel with teeth around its outer rim.

Gear Train:

Two or more gears that interlock or mesh together form a gear train. As one gear turns, its teeth push against the

teeth of the adjacent gear causing the second gear to turn in the opposite direction.

OBJECTIVES

Students will:

. Investigate the characteristics of gear systems to understand how they work.

2. Describe the relationships between the parts of a gear system.

3. Construct different types of gear systems and demonstrate how they function.

4. Understand how differences in gear size within a system affect speed and force output.

5. Identify how rotational motion changes into linear motion using different gear systems.

6. Identify how the use of a gear system affects work in relation to force, distance, speed,

and direction.

7. Analyze objects/tools in terms of their application as gear systems.

w w w. k n e x e d u c a t i o n . c o m

INTRODUCTION TO SIMPLE MACHINES

Driver Gear:

The gear to which the effort force is applied. The driver gear transfers the effort force to the next gear in a gear

train, the driven gear.

riven Gear:

The gear that moves the load.

Idler Gear:

This gear makes those on either side of it rotate in the same direction.

Mechanical Advantage (MA):

(Appropriate for students whose Math skills allow them to understand and work with fractions.)

A mathematical calculation that indicates how many times a machine multiplies effort force or speed. For a gear

system, mechanical advantage can be calculated using the following formula:

Number of teeth on the driven gear

Number of teeth on the driver gear

Because the units (teeth) cancel each other out, mechanical advantage is always expressed as

a number without a unit.

For example: MA = 16 teeth

8 teeth

Gear Ratio

(Appropriate for students whose Math skills allow them to understand and work with fractions and ratios: generally

Grade 5 or above.)

A ratio of the speed of rotation of the driver gear in a gear train to that of the driven gear. It can be calculated by

comparing the number of teeth on the driven gear to the number of teeth on the driver gear in

the train.

Gear ratio = Number of teeth on driven gear (84) 6

Number of teeth on driver gear (14) 1

Sprocket

A toothed wheel on which a chain runs.

Chain and Sprocket

The driver system used to transmit rotary motion from a driver axle to a driven axle. The links of the chain mesh

with the teeth on a sprocket.

KEY CONCEPTS

The following summarizes some of the key

concepts associated with gears and is offered here

as a resource for the teacher. You may find some

of this information helpful as you prepare your

classroom activities using the K’NEX Intro to

Simple Machines: Gears set.

Gears are used to transfer motion and force

from one location to another. These may be

transferred directly through physical contact

between gears in a gear train or transferred

over a distance by a chain or belt that

connects two or more gears.

= MA

= 2

= = 6:1

Fig. 1

Gear: A wheel with teeth around its outer rim.

GEARS

INTRODUCTION TO SIMPLE MACHINES

In order to work, the teeth on gears must interlock or be connected by a chain or belt. A simple

gear train comprises two or more meshed gears with only one meshed gear on each axle.

The gear wheel to which the effort is applied is called the driver gear. In the K’NEX Crank Fan model,

the driver gear is the gear that is attached to the crank axle. The driver gear transmits turning forces

to the driven (or follower) gear causing it to rotate in the opposite direction.

The force applied to the driver gear is the effort force or input force; the driven gear produces the output force.

Key fact about simple gear trains: In a simple gear train with two gears of the same size, the driven gear turns at

the same speed as the driver gear, but in the opposite direction.

Gear systems may make work easier:

Gear systems can make work easier by making things easier to move. They can do this in the following ways:

Transfer motion and force from one location to another. When a twisting force, known as torque, is

applied to the driver gear, its teeth transfer force and motion to the teeth of the adjacent driven gear. An

example of this application is found in a salad spinner.

Effort

Load

Driver Gear Driven Gear

Idler Gear

Gear train with an odd number of gears.

Change the direction of rotational motion. Adjacent gears in a gear train spin in opposite directions relative

to each other. In gear trains made up of odd numbers of gears, however, the direction of rotational motion of

the driven gear is the same as the direction of rotational motion of the driver gear. Examples of this use can

be found in an eggbeater and in the mechanism of a clock.

Fig. 2

Fig. 3

GEARS

Multiply the force applied to do a job. Using different sized gears in a gear train or sprockets wrapped by a

chain, affects the output force of the driven gear. A small gear driving a larger gear multiplies force at the

expense of speed.

Change the output speed of a system. Using

different sized gears in a gear train or

sprockets wrapped by a chain, affects the

output speed of the driven gear.

• Speeding Up.

A large driver gear turning a small driven gear increases the turning speed of the axle attached to

the driven gear.

(Appropriate for use with students whose Math skills allow them to understand and work with

fractions and ratios.)

For example: An 84-tooth driver gear will make 1 complete turn for every 6 turns made by a 14-

tooth driven gear. In this case the gear ratio of 1:6 indicates that the output speed is 6 times faster

than the input speed. This is called gearing up. Gearing up will increase the speed of rotation but

decrease the force.

Number of teeth on driven gear 24

Number of teeth on driver gear 8

When mechanical advantage is greater than 1,

effort force is multiplied by the gear system.

= = 3MA =

Fig. 4

(

Appropriate for use with students whose Math skills allow

them to understand and work with fractions and ratios.)

GEARS

INTRODUCTION TO SIMPLE MACHINES

• Slowing Down.

A small driver gear turning a large driven gear slows the turning speed of the axle attached

to the driven gear.

For example: A 14-tooth driver gear will make 6 complete turns for every 1 turn made by an

84-tooth driven gear. This ratio of 6:1 indicates that the input speed of the small driver gear is

6 times faster than the output speed of the large driven gear. This is called gearing down.

Gearing down will decrease the speed of rotation, but increase the force.

Types of Gears

Spur Gears: These gears lie in

the same plane and turn in opposite

directions when meshed. Different

sized spur gears turn at different

speeds and with different amounts

of force.

Sprocket Gears: A special type

of spur gear consisting of two gears

on the same plane, set apart from

each other and linked by a chain.

Sprocket gears turn in the same

direction. Different size sprocket

gears turn at different speeds and

with different amounts of force.

If they are the same size they turn

at the same speed and with the

same force.

REMEMBER: When driving a car, you shift UP through the gears (1st, 2nd, 3rd, 4th) to go faster and shift

DOWN through the gears (4th, 3rd, 2nd, 1st) to go slower.

GEARS

Crown Gears: These gears lie in planes at right angles to each other. Different sized crown gears turn at

different speeds and with different amounts of force.

Rack and Pinion Gears: These gears

consist of a toothed bar and a toothed

wheel. Rack and pinion gears change

circular motion into linear motion.

Worm Gears: These gears consist of a spiral edged cylinder called the worm and a toothed wheel called

the worm gear. A worm and its worm gear turn in different directions, at different speeds and with

different amounts of force. The worm gear turns more slowly than the worm. Worm gears generally slow

down motion.

Useful Web sites: http://science.howstuffworks.com/gear.htm

Don’t be deterred by the first paragraph, which you may feel is too difficult for your students – if you

continue through the site and follow some of the links you will discover some very helpful animations.

GEARS

INTRODUCTION TO SIMPLE MACHINES

The Crank Fan:

An example of the use of a spur gear system.

Crank Fan

PROCEDURE

Introduction

If this is the students’ first experience with gears, you may want to demonstrate the transfer of energy from one

object to another. Using two large rubber balls, have a student roll one ball into the other. Ask the students to

describe their observations. Use the following questions to help them identify what took place:

What did the first ball do to the second ball?

When was the exact moment that the pushing

took place?

What was transferred from one ball to the other?

Distribute 2 gears to each student. Encourage them to think about how they would describe a gear and to

explore how gears fit together.

Begin the lesson by discussing and expanding what the

students have discovered about their gears. You may

choose to accept their operational definition for how the

gears operate, or formalize the terms they use in

describing the gears and how they fit together.

OBJECTIVES

Students will:

1. Understand and describe the transfer of motion through a spur gear system.

2. Investigate the relationship between gear size, speed of rotation, and force.

MATERIALS

Each student group will need:

- 1 K’NEX Gears Building Set with Building

Instructions booklet

- Masking Tape

- Dot stickers (optional)

- Student Journals

You will need:

- Pictures and examples of different spur gear systems.

(Suggestions: music box; electric fan; hand-held can

opener; gear operated toy.)

- K’NEX gears for students to examine before they begin the

building activity. (Remove a sufficient number of gears

from each K’NEX Introduction to Simple Machines: Gears

set so that each student has access to 2 gears.)

- 2 large rubber balls (optional.)

- Cardboard and Popsicle sticks (optional)

NOTE: As described below, this activity may take more than 45 minutes.

The first ball pushed the second ball.

The first ball pushed the second ball when

the two balls came into contact.

Gears are wheels with teeth around their

outer rim. The teeth of one gear fit between

(mesh with) the teeth on the other gear.

Motion, energy, force.

GEARS

Explain that gears are simple machines

that transfer energy in the form of

motion from one location to another.

se a child’s gear toy or a gear train

that you construct from cardboard to

demonstrate what happens when you

rotate one gear that is in contact with a

second gear.

Distribute pieces of tape or dot stickers. Instruct students to place a small piece of tape (or dot sticker) on each

of the two K’NEX gears they used earlier so they can observe the direction that the gears move. Ask students to

lay the gears on a piece of paper on their desk and to mesh the gear teeth together. Ask one student to put a

pencil point in the hole on each gear to hold them in place while the other student turns one gear.

Ask the students how they are able to

move only one gear and cause the

second gear to also move.

Encourage the students to see how many gears they can put together into a gear train. They should sketch and

label the direction of rotation of each gear.

This is an excellent opportunity to introduce formal terms that the students should use during their

experiments with gears. This activity lends itself to the introduction of driver gear, driven (or follower) gear,

and gear train.

Ask the students to describe in which

direction each of their gears turned.

Ask the students to think of other examples of gears used in their daily lives. Many students will identify the

gears on bicycles. This will give you the opportunity to explain that there are several different types of gear

systems and that the type used will depend on the job that needs to be done. For example, the gear system on a

bicycle is different from the gear system in a can opener.

Pass a hand-held can opener around the room. Allow the students time to explore the gear mechanism.

Encourage the students to brainstorm a list of other objects that use gear systems. Record these on the board.

Be prepared to show examples if the students are not aware of any gear systems.

Suggestion: Use circles of cardboard and carefully glue

Popsicle sticks to them to represent gears. Make sure that the

Popsicle sticks are evenly spaced around the circles. It is

easier to make a pair of gears that are the same size than

ears that have different numbers of teeth. Mount the gears

to a larger piece of cardboard with pushpins, making sure

that they mesh and rotate easily.

As one wheel turns, its teeth push against those on the other

gear wheel. See diagram below.

If the first gear wheel is turning in one direction, it will push

the second gear wheel in the opposite direction.

GEARS

INTRODUCTION TO SIMPLE MACHINES

You may wish to introduce the concept of motion and

use formal terms to describe the types of motions the

students used in the previous activity. Some of the terms

you may want to include are: input motion (the

students’ hands turning the first gear), output motion

(the movement of the second gear caused by the input

motion), rotational motion (turning about a point),

linear (straight-line) motion. (Provide the students

with an example of linear motion as a comparison to

rotational motion.)

Divide the class into groups made up of 2 to 3 students.

Inquiry Activity: How is motion transferred through a spur gear system?

Use the following guidelines and script to help the students explore the function of a spur gear system.

Steps

1. (a) When the models are completed, allow the students time to explore. Ask them to locate and identify the

gears. They should watch the gear mechanism in operation as they turn the crank.

(b) Encourage the students to identify

any additional simple machines with

which they are familiar and that may

be present in their fan models.

Motion refers to an object’s change

of position over time in relation to a

reference point.

Building Activity

Distribute a K’NEX Gears building set to each group. Ask the students to open the materials and locate the

Building Instructions booklet. If the class has not used K’NEX building materials, review the Building Tips

page, particularly the information about the purple connectors. Allow the students some time to explore the

materials – it is crucial that they grasp the building concept at this stage so that frustrations are avoided later.

Make sure the students return the gears handed out in the earlier part of the lesson to their set.

Provide some basic guidelines for keeping track of all the pieces in the set so that they will be available for

future use. Remind students that they will need about 5 minutes at the end of the class period for clean up.

Explain that they will build a model of a crank fan that uses a gear system to turn the fan blades. Direct their

attention to the photo of an electric fan on Page 2 of the Building Instructions booklet or have an actual

example for display in the classroom.

Ask students to build the model according to the instructions booklet.

Building Tip:

To prevent the 2 red axles from coming loose in their housing we recommend adding gray connectors. (These are

the small clips – approximately 2.5 cms. long - with one closed, circular end through which a rod may pass and

one open end into which a rod can be snapped.) They should be added in the following locations:

1. At the free end of the upper fan blade axle.

2. On either side of the existing gray connectors on the lower or crank axle.

If your class has already completed the wheel and axle

investigations, this is an ideal opportunity to facilitate a

quick review of this simple machine.

Crank Fan

GEARS

(b) Encourage the students to give names to the various parts of their model. You can then formalize these and

ask them to label their diagram appropriately. Labeled parts will include:

Crank, driver gear, driven gear, and fan blades.

3. The students should respond in their journals to the following:

• Does the fan have moving parts?

List the moving parts in your journal.

• Describe how the moving parts

that you listed above are

connected to each other.

• Describe the input motion - the

motion they use when they

operate the crank.

• Describe the motion of the gears.

• Draw arrows on your diagram to

show the direction each part

moves as you operate the fan.

xle or shaft

Overlapping

circles represent

gears meshing

it together and that they are in line with one another. Remind students of their earlier investigation where

they used the gears in line with each other as the gears lay flat on the table. Explain that in this arrangement,

known as a spur gear system, the gears fit together, or mesh, along the same line or in the same plane. In this

model the gears are arranged one above the other. You may have to ask students to turn the model on its side

so they can see that the gears are in line with each other as they were in the previous activity.

2. (a) Ask the students to draw a diagram of the crank fan in their journals. The gears can be represented

symbolically – there is no need for the students to attempt to draw every tooth in the gear wheels.

For example:

The crank is connected to the driver gear by an axle. The

teeth on the driver gear mesh with the teeth on the driven

gear, which is connected to the fan blades by an axle.

Crank, driver gear, driven gear, fan blades.

The gears turn or rotate.

The input motion is circular or rotational. They turn their

hand in a circle.

GEARS

INTRODUCTION TO SIMPLE MACHINES

4. Ask the students to attach a small piece of masking tape to the edge of one fan blade and

ask them to select a reference point so they can keep track of the fan blade as it rotates.

Encourage them to turn the crank.

(a) Ask the students to turn the crank to make one rotation. Have them continue turning the crank but they

should vary the speed at which it is turned.

Ask them how they can make the

fan turn faster/slower.

(b) Suggest that they mark the two

gear wheels with either a dot

sticker or with a pencil mark. The

marks should be made at the point

where the two gears mesh. Then

ask them to make one slow turn

of the crank. What do they notice?

journals the sizes of the two

gears - driver and driven – used

in the model.

(d) Do they think there could be a

relationship between the size of

the gears and their findings to

(b) above?

(e) Ask the students to turn the

crank one additional turn, but

this time, ask them to notice how

far the fan blades travel. One

student should count the number

of times the blade with the

masking tape passes the selected

reference point, while the other

should focus on making just one

full turn with the crank.

(f) How easy/hard is it to turn the

crank with this gear arrangement?

(g) Ask them to summarize what their

observations show concerning the

distance the two gears and the fan

blades turn with one rotation of

the crank.

Students should observe that the speed of the fan was entirely

dependent upon the speed at which the crank was turned.

The students should be helped to understand that these two

gears, that are the same size and meshed together, rotate at

the same speed even though they are on different axles.

Note: This will generate subjective responses, but will help

the students make comparisons when they explore other

gear arrangements for the model.

Students should notice that all the moving parts rotate once

with one turn of the crank.

BOTH gears make one complete rotation with one turn of

the crank.

The fan blades also make one complete turn with one turn of

the crank.

They are the same size.

Crank Fan

GEARS

NOTE: We recommend that 2 groups work together for Step 5 below. One group should build the model with the

large gear as the driver, and the other group should build the version of the model with the small gear as the

driver. Having both models available will make comparisons easier.

5. (a) Ask the students to speculate what they think will happen if they use

(i) a large gear wheel to drive a small gear wheel and

(ii) a small gear wheel to drive a large gear wheel.

They should make a note of their responses in their journals.

(b) Encourage the students to discover if their predictions were correct by rebuilding their models using two

gears that are different in size. They should use the diagrams on the right hand side of Page 3 of the

Building Instructions booklet as a guide.

compare the speed that the fan

turns, with the speed of the crank

when the big gear is attached to the

crank and the small gear is attached

to the fan blades.

(d) How easy/hard is it to turn the

crank with this arrangement

compared to when the gears were

the same size?

All their observations should be

recorded in their journals.

(e) Students should then compare the speed at which the fan turns with the speed of the crank, when the small

gear is attached to the crank axle and the big gear is attached to the fan blade’s axle.

(f) How easy/hard is it to turn the crank with this arrangement, compared to when the gears were (i) the same

size and (ii) the large gear was the driver?

Observations should be recorded

in their journals.

6. (a) Discuss their observations of gear systems using different sized gears.

(b) Ask the students if their observations support the prediction that they each wrote earlier. Encourage the

students to support their conclusions using evidence from their investigations.

Use the technique adopted in Step 4 - put a piece of masking

tape on one fan blade and observe where it is before a turn

of the crank and then notice how many times the tape

passes that same point when the crank is turned one time.

Students should observe that when the small gear drives the

big gear, the fan turns more slowly than the crank: it takes 6

turns of the crank for the fan blades to make 1 complete

rotation. The crank, however, is easier to turn than in either

of the other 2 gear arrangements.

Students should observe that when the big gear drives the

small gear, the fan turns more quickly than the crank: 1

turn of the crank results in approximately 6 turns of the fan

blades. The crank, however, is harder to turn than it was

when the model had both gears the same size.

GEARS

INTRODUCTION TO SIMPLE MACHINES

Applying The Idea

Review the findings of Step 3 with the class:

Did the crank and the gear on its

axle move at the same speed?

Did you notice the same results

when you used a smaller gear? A

larger gear?

When you operated the fan using two gears that were the same size, which of these statements was true?

The driver gear turned faster than the driven gear?

The driven gear turned faster than the driver gear?

They both turned at the same speed.

Ask the class to summarize these findings about the fan with the same sized gears by completing the

following sentences:

Gears that are on the same axle rotate at the

__________________ __________________

Gears that mesh and are the same size rotate at the

__________________ __________________

In this crank fan all the moving parts rotate at the

__________________ __________________

because the driver gear and the driven gear are the

__________________ __________________

Ask the students to record the

advantages and disadvantages of

the 2 different gear systems they

investigated in Step 4.

Encourage the students to discuss

situations where each gear system

would be most useful. Encourage

them to include “effort force,”

“driver gear,” and “driven gear” in

their responses.

They move at the same speed: one turn of the crank (wheel)

causes the gear on the same axle to rotate once.

Yes. Even when gears are a different size, if they are on the

same axle they will rotate at the same speed.

They turned at the same speed: one rotation of the driver

gear turned the driven gear through one rotation.

same speed

same speed; same size

Turning the crank was easier when the small gear turned

the large gear. However, the fan turned more slowly than

the crank. Although the crank was harder to turn when the

large gear turned the small gear, the fan blades turned

much faster than the crank.

Answers will vary. Possible answer: A small gear turning a

large gear would be most useful if the object that must be

turned is heavy. Turning a large, heavy object would need

less effort force when the driver gear is smaller than the

driven gear.

Crank Fan

GEARS

Extending The Idea

(Suggested grade levels are indicated.)

[Grades: 3-4.]

. Suggest that the students search the Internet for additional information about gear systems. They could

conduct a Google

search using the key word: “gear.”

[Grade: 5.]

2. (a) Remind the students that they used a crude measurement to compare the input and output speeds of the

gear wheels when they completed Steps 4(e), 5(c), and 5(e). Explain that what they discovered was a simple

Gear Ratio.

(b) Explain that a more accurate approach is to compare results by counting the number of teeth on each gear

wheel. Write the equation for the Gear Ratio on the blackboard, dry board, or overhead projector so that it is

visible from any location in the classroom.

Number of teeth on the driven (follower) gear

Number of teeth on the driver gear

For example: 14/84 gives a gear ratio of 1/6 or 1:6

Explain that a 1:6 gear ratio means that for every complete revolution of the driver gear, the driven gear makes

6 complete revolutions. Or, said another way: the output speed is faster than the input speed.

[Grades: 3-5.]

3. (a) Ask all the student groups to remove the fan blades from their crank fans and set them aside.

(b) Divide the groups so that half have crank fans in which the large gear is the driver gear and the small gear is

the driven gear. The remaining groups should have crank fans in which the smaller gear is the driver gear

and the larger gear is the driven gear. Students do not need to disassemble their fans. Simply have students

attach the crank to the appropriate shaft. (See diagrams below.) In order to watch the speed of rotation of

the second gear in the gear chain, students should attach a yellow connector to the end of that gear’s axle.

(This connector replaces the blades that, if used on the lower axle, will strike the tabletop unless the model

is pushed to the very edge.)

Gear Ratio =

Set-up one: Crank on upper axle. Put the

yellow connector on the end of the lower axle.

Set-up two: Crank on the lower axle. Put the

yellow connector on the end of the upper axle

where the blades used to be.

GEARS

INTRODUCTION TO SIMPLE MACHINES

[Grade: 5.]

ratio in their journals and describe, in their own words, what the gear ratio means in reference

to their crank fan.

(d) Encourage the students to tell you what is gained by using this gear train. If students need clarification, ask

them whether their fan turns quickly or slowly. You can then take this opportunity to help the students

understand they cannot use a machine to gain both speed and force. They can gain speed at the expense of

force or gain force at the expense of speed. If you decide to include this there is space provided in the chart

below for students to record their findings.

[Grade: 5.]

4. The groups should exchange fans and repeat Step (d) above.

[Grade: 5.]

5. Ask the students to organize their observations and conclusions regarding gears in a table or chart. (See

Journal Check below.) It may be helpful to provide a chart such as the one shown here.

[Grade 4-5.]

6. Ask the students to brainstorm

how they could change the design

of the crank fan so that the crank

and the fan turn in the same

direction. If necessary, hint that

they would have to add something

to the mechanism. This will

provide you with an opportunity

to introduce the concept of the

idler gear.

Allow students time to test their ideas.

Gears are same size

Large driver gear moving

small driven gear

Small driver gear moving

large driven gear

GEAR TRAIN FAN SPEED GEAR RATIO INCREASED OUTPUT

SPEED VS. CRANK SPEED (APPROXIMATE) SPEED OR INCREASED

OUTPUT FORCE

The crank and fan would turn in the same direction if a

third gear – an idler gear - were added to the gear train

between the driver and driven gears.

Crank Fan

GEARS

JOURNAL CHECK:

Students should keep individual journals to record their findings. The following are examples of the types of

tems that could appear in each student’s journal:

✔

iagram of crank fan including labels and arrows.

✔

Record of student observations.

✔

Predictions.

✔

Conclusions.

✔

A table such as the one shown below that summarizes their findings.

Gears are same size.

Large driver gear moving

small driven gear.

Small driver gear moving

large driven gear.

Fan speed equals

crank speed.

Fan speed is greater

than crank speed.

Fan speed is slower

than crank speed.

1:1

1:6

6:1

No change.

Increased output speed.

Increased output force.

GEAR TRAIN FAN SPEED GEAR RATIO INCREASED OUTPUT

SPEED VS. CRANK SPEED (APPROXIMATE) SPEED OR INCREASED

OUTPUT FORCE

GEARS

INTRODUCTION TO SIMPLE MACHINES

The Car Window:

An example of a spur gear system used to convert

rotational motion into linear motion.

Car Window

PROCEDURE

Introduction

If your students have explored the

CRANK FAN model, ask them to tell

you how motion was transferred

through the fan system.

Remind the students that a spur gear

system was used to change the speed

and direction the blades of the fan

turned. Ask students to describe a spur

gear system and how the gear ratio of

the system affects the motion of the

fan. Encourage students to use “gear

train” in their answers.

Explain that they will discover, as they build

an operating car window, that not all gear

systems using spur gears result in

rotational output motion. But, before they

begin their inquiry they should each

imagine they have to explain how to operate

a car window to a time traveler from 1776.

Ask one or two students to provide

directions for opening the car window. If

the students tell you to, “Push the button,”

explain that using a button is a quite recent

design modification and that there are still

many cars on the road that require more

work from the window operator.

OBJECTIVES

Students will:

1. Construct and understand the mechanism of a model system representing a real-life object.

2. Observe how rotational motion is converted into linear motion using a spur gear system.

3. Explore spur gears as a means to multiplying output force.

MATERIALS

Each student group will need:

- 1 K’NEX Intro to Simple Machines: Gears set

with Building Instructions booklet

- Dot stickers or small pieces of tape

- Student Journals

The rotational motion of the turning crank was transferred

through the rotational motion of the gears causing the fan

blades to turn.

In a spur gear system, the gears are meshed and turn in the

same plane. How fast or slow the fan turns relative to the

crank depends on the arrangement of different sized gears

in the gear train. Also, since the spur gear system in the fan

contains two gears, the fan blades turn in the opposite

direction to the force applied to the crank handle.

Suggest they look at the photo on Page 4 of the Building

Instructions booklet.

GEARS

Ask the students to tell you what you

mean by ‘work.’

Explain that opening a window has usually required you to manually wind the window up or down. [Go through the

motion of winding a window up and then winding it down.] Ask students to identify the type of motion that was

needed to turn the handle of the car window. (Rotational). Explain that this rotational motion is the input motion.

Help the students to understand that

regardless of whether you push a

button or wind the handle, the output

motion—the motion of the window—is

the same. Ask them to identify the

window’s motion.

Tell the students they will be exploring the mechanism that makes a car window move. As part of this inquiry

they will discover how a spur gear system can change rotational motion into linear motion.

Divide the class into groups made up of 2 to 3 students.

Students should provide an appropriate definition similar to

the one provided in the list of Key Terms and Definitions on

Page 3 of this Guide.

Up and down or Linear.

Building Activity

Distribute a K’NEX Intro to Simple Machines: Gears set to each group.

Ask the students to turn to Page 4 and 5 of the Building Instructions booklet and construct the model of

the CAR WINDOW. If time is a concern, we recommend that one student complete Steps 1-5 while another

group member is completing Steps 6-9. If groups comprise more than two students, have a third student

complete Steps 10-12 while the others are building their portions of the model. Students should be ready to

help each other assemble parts of the model. For example, joining Step 4 to Steps 1, 2 and 3 may require

more than one pair of hands.

Building Tip:

In Step 3, pay particular attention to the placement of the blue rod (with the free end) within the white connector.

Inquiry Activity: How can gears convert rotational motion into linear motion?

Steps

1. (a) When the students have completed

the models, allow them some time

to explore. Ask them to locate and

identify (i) the gear trains in their

models and (ii) the types of simple

machines used to make up

their models.

(b) Each group should investigate exactly how the mechanism works. On the board, provide some guidelines

for their investigations and discussions:

• How does the mechanism work?

• Which parts move?

• What type of movement is applied to the blue crank (the input movement)?

Spur gear, wheel and axle, lever.

GEARS

INTRODUCTION TO SIMPLE MACHINES

• Describe the movement of the window (the output movement.)

• Why is a small gear wheel used as the driver to turn a large driven gear?

• How can you control the speed of the output motion?

• Why does the crank turn many times but the window rises only slowly?

Students should record their initial thoughts in their journals.

2. As a class activity, review the steps that occur from applying the effort force to the handle, to the raising

of the window. Ask volunteers to describe, step-by-step, what takes place and use the following to start

the description:

“ Turning the crank counterclockwise causes the……”

Record the steps on the board.

Review their other thoughts, recorded in 1(b), as a class activity.

3. Review the ways simple machines can make work easier – they multiply the force applied or they increase

the distance (speed) the resistance moves. Remind them that force and distance cannot both be increased

at the same time.

You may wish to complete the next activity as a class.

4. (a) Lower the car window all the way and then turn the blue crank one full turn to raise the window.

(i) When you turn the crank

through one full turn how

far does the first 14-tooth tan

gear turn? You may want to

mark a starting point with a

pencil or a dot sticker on the

gear wheel and count how

many teeth it moves as you

turn the crank.

Students should record their answers in a table such the one shown below. (DATA TABLE 1).

(ii) How far does the 34-tooth

yellow gear that meshes with

the tan gear turn? Record your

answer in the table.

(iii)Based on the observations

recorded in (i) and (ii)

above, which moves faster -

the driver gear or the

driven gear?

(iv) [For Grade 5 only:]

Using your knowledge of

gear ratios, what is gained,

or multiplied, as the effort

force moves through the

first gear train?

(v) How is force transferred to

the second gear train?

How are these two gear

trains connected?

This rotates through approximately 14-teeth – a little less

than half a turn.

Students should reason that the driven gear turns more

slowly than the driver gear. Therefore, if speed is lost, then

the system has multiplied force.

Force is transferred along the axle that connects the large

gear of the first gear train with the small gear of the second

gear train.

Driver gear.

This gear makes 1 complete rotation.

Car Window

GEARS

Type of gear (driver/driven)

Result of 1 rotation of the blue crank

on the gears

Fastest gear

Force gained

14-tooth tan gear

Driver

1 complete rotation (through all

14 teeth)

✔

34-tooth yellow gear

Driven

Just under one half of a rotation

(through 14 teeth)

Speed lost as the force is transferred

✔

DATA TABLE 1

1st Gear Train

(b) Place a mark/dot sticker on one tooth of the second 14-tooth tan gear (this shares the same axle as the

34-tooth yellow gear.) Try to place the mark on the tan gear so that it lines up with the one you placed on

the yellow gear.

(i) Turn the blue crank through

1 full turn and notice how far

the tan and yellow gears turn.

You can count the number of

teeth the gear moves through,

or you may want to consider

the movement in terms of the

hands on the clock. For

example the gear moves from

9 o’clock to 2 o’clock. Students

should record their answers

in a table such the one

shown below.

(ii) Given that the yellow and

tan gears are different sizes,

how do you explain your

findings for (i) above?

Students should notice that both gears move through a little

less than half a full rotation.

Help the students to see that although these two gears are

different sizes, they turn through the same proportion of a

circle because they are on the same axle.

GEARS

INTRODUCTION TO SIMPLE MACHINES

blue crank 1 full turn to raise the window. Watch the large 82-tooth yellow gear and count

the number of teeth through which it rotates.

(i) How much does it turn? In

comparison to the other

gears how fast does it rotate?

(ii) What is gained by using the

second gear train with the

large 82-tooth gear?

d. (i) Describe how the window is

moved by the second gear train.

(ii) How is the motion of the window

different from the motion of the

crank and the gears?

5. Ask students to consider how

using thicker glass would affect

the design of the car window

mechanism.

It rotates through approximately 6-7 teeth, or nearly one

twelfth (1/12) of a complete rotation – a very small distance.

It is a slowly moving gear wheel.

Students should reason that the driven gear turns more

slowly than the driver gear. Therefore, if speed is lost, then

force is multiplied.

The window is attached to the large gear’s axle in the second

gear train by levers. When the large gear moves, force is

transferred along the levers causing the window to be raised

or lowered.

Students should infer that using thicker glass means that the

window would be heavier. Therefore, the gear trains or levers

would need to be changed to have a greater output force.

It is linear; the crank and the gears rotate.

Type of gear (driver/driven)

Result of 1 rotation of the blue crank

on the gears

Fastest gear

Force gained

14-tooth tan gear

Driver

Slightly less than one-half (1/2) a

full rotation (through 6-7 teeth.)

✔

82-tooth yellow gear

Driven

Approximately one-twelfth (1/12) of

a full rotation (through 6-7 teeth.)

Speed lost as the force is transferred

✔

DATA TABLE 2

2nd Gear Train

Car Window

GEARS

Applying The Idea

Ask the students to draw a diagram of the car window model in their journals. They should label the following:

rank, driver gear, driven gear, and lever. Their diagrams should indicate two driver gears and two driven gears.

tudents should draw arrows on their diagrams to show the direction of motion of each moving part as the

crank turns to raise the window.

Students should describe how the mechanism works in their journals using the step-by-step process they

identified in the class discussion.

Students should complete the following sentence:

“As energy is transferred through the machine,

__________________ is lost but __________________

is gained.”

Ask the students to brainstorm:

Why it is important for a car window to move slowly?

How is the car window system in a family car made safe so that passengers are protected from injury?

Extending The Idea

[Grade: 5]

1. Ask students to calculate the mechanical advantage of EACH gear train. Use the following directions:

(i) Count the number of teeth on the driven gear.

(ii) Count the number of teeth on

the driver gear.

(iii) Divide the number of teeth

on the driven gear by the

number of teeth on the

driver gear.

[Grade: 5]

2. Ask the students if their calculations of mechanical advantage support their earlier inference, in Inquiry

questions 4a(iv) and 4c(ii), that force was gained using these two gear trains.

Remind students that when MA is greater than 1, force is

multiplied. MA of the first gear train equals 2.4. MA of the

second gear train equals 5.8.

speed; force.

JOURNAL CHECK:

✔

Diagram of car window including labels and arrows

✔

A record of student observations as indicated by responses to questions in Steps 1(b) and 3.

✔

Completed data tables.

✔

An explanation of the transfer of force or motion through the machine to the window.

✔

Inferences describing how changing the properties of the window would affect the mechanism used

to raise it.

GEARS

INTRODUCTION TO SIMPLE MACHINES

The Blender:

An example of a crown gear system.

Blender

PROCEDURE

Introduction

Ask the students to describe how

motion was transferred through a

spur gear system.

If your students have completed the

CRANK FAN activity, review how a spur

gear system can make work easier by

changing output speed or multiplying

output force. Help the students

understand that they cannot use a

machine to gain both speed and force.

Explain that there is always a trade-off

when they use a simple machine. They

can gain speed at the expense of force

or gain force at the expense of speed.

Ask the students to describe what is

gained when a gear system uses the

same sized gears in a gear train.

Explain that a spur gear system is just one type of gear arrangement. Tell the students that they will explore the

gear mechanism used in a blender. The arrangement of gears in a blender differs from that used in a crank fan.

Their model blender will be hand operated.

NOTE: In Extending the Idea you will find building and associated activities for the EGGBEATER model.

(See Pages 10 and 11 of the Building Instructions booklet.)

OBJECTIVES

Students will:

1. Construct and investigate the mechanism of a model system that represents a

real-life object.

2. Observe how rotational motion is transferred from one plane to another using a crown

gear system.

MATERIALS

Each student group will need:

- 1 K’NEX Gears Building Set with Building

Instructions booklet

- Student Journals

You will need:

- A blender + food for demonstration purposes

Force and motion are transferred from one gear to another

along the same plane.

Students should remember from the Crank Fan activity that

when gears are the same size, neither speed nor force is

gained. You can use this opportunity to explain to them that

some machines use gears that are the same size in order to

change the direction of rotation.

GEARS

Demonstrate how a real blender works and discuss:

The different jobs that a blender does.

How some blenders use different speeds to cut, chop, beat, or homogenize foods.

Using the K’NEX Blender as an example, demonstrate on the board how to make simple labeled drawings of gear

ystems, using arrows to show the direction in which the gears turn. Emphasize that it is unnecessary to draw

every gear tooth – they can be shown symbolically.

Divide the class into groups made up of 2 to 3 students.

Building Activity

Distribute a K’NEX Gears building set to each group. Ask the students to turn to Pages 6 and 7 of the

Building Instructions booklet and construct the BLENDER. To save time, we suggest that one student builds

Steps 1-4 while another group member completes Steps 6-8.

Inquiry Activity: How does this machine change the direction of the effort force?

Steps

1. When the models are completed,

allow the students time to explore.

Encourage them to locate and

identify the gear train. Ask them

to identify which types of simple

machines were used to make up

their models.

2. Ask the students to draw a diagram of the blender in their journals. The following parts should be clearly

labeled: crank, driver gear, driven gear, and chopper. Write these terms on the board.

Ask the students to draw arrows on their diagrams to show the direction of motion of each moving part as the

crank turns.

3. Help the students understand how their model works by asking them to investigate the following:

(a) Where is the effort force applied?

Gear system, wheel and axle. The gear train in this model

uses a crown gear; we recommend that you allow the

students time to investigate its characteristics before

discussing it formally with the class.

The effort force is applied to the crank.

Gear Wheel

Axle

GEARS

INTRODUCTION TO SIMPLE MACHINES

(b) What type of motion is the input

motion (or effort force)?

place? What type of motion is it?

(d) Compare input and output motions.

How are these motions the same?

How are these motions different?

(e) Observe and describe the motion

of each moving part. Is the part

rotating in a vertical plane or a

horizontal plane?

(f) Try to identify where the motion

changes from moving in a vertical

(up and down) plane to moving in a

horizontal (or flat) plane.

(g) Ask the students to investigate and

discuss with their team members:

(i) How they can control the speed

of the output movement.

(ii) Why the crank rotates at

the same speed as the

cutting blades.

(iii) Whether or not the

mechanism will be easier

to turn without the

crank handle.

4. Ask the students whether this gear

system increases speed or changes

the direction of motion. They

should record their observations

in their journals.

The output motion happens at the chopping blades.

The output motion is also a rotational motion.

The driver and the driven gear wheels have the same

number of teeth and rotate at the same speed. The crank is

directly connected to the driver while the cutting blades are

directly connected to the driven gear.

If your students have studied the wheel and axle they will

be familiar with the fact that it is easier to turn the wheel

(crank handle) than it is to turn the axle.

Students should notice that the gear system changes the

direction of motion.

Crank: vertical; 1st gear: vertical; 2nd gear: horizontal;

blades: vertical.

They are the same in that they are both rotational motions.

They are different in that they rotate in opposite directions.

Also, the chopper blades rotate in a horizontal plane. The

crank turns in an up and down [vertical] plane. If your

students are not familiar with the concept of planes, you

may accept their operational description of the relationship

between the gears. Students may say one gear is flat and

the other is on its edge.

The input motion is a rotational motion.

Adjust the speed at which they turn the crank.

Blender

GEARS

Applying The Idea

Explain to the students that they have been exploring a crown gear system. Ask them to take one of the spare

gear wheels from the set and suggest a reason why the name “crown” is used. If necessary demonstrate to the

students how the yellow gears have teeth that are set at 90-degrees to the surface of the gear. Looked at from its

side the gear resembles a crown. These teeth mesh with those on the rim of a second gear to give a 90-degree

hange in direction. Recommend that the students make a note about the name of this gear in their journals.

Calling on volunteers, review with the class the way in which energy is transferred from one plane to another (or

through 90-degrees) using a crown gear.

Where is the effort applied?

What type of movement is the effort?

Why does the driver gear turn?

What name is given to this particular driver gear?

Does the driver gear lie in a vertical or

horizontal position?

How is the position of the driven gear different

from that of the driver?

How does the driver transfer energy to the driven gear?

Where is the output motion produced?

What type of output motion is it?

Students should be encouraged to include this information in their journals in their own words using

appropriate vocabulary.

They can also be encouraged to complete the following summary statement:

A crown gear can change the direction

of motion from _______________________

You may want to explore the benefits of using a crown gear system rather than a spur gear system with your

students in the following way:

To the crank.

Rotational motion.

Crown gear.

Vertical.

The crank turns the axle; the driver gear is

on the same axle and turns also.

Its teeth mesh with the driven gear so that

when it turns so does the driven gear.

Answers will vary: one plane to another; a

vertical to a horizontal plane; some may

state that it changes it through 90-degrees.

The driven gear lies in a horizontal plane.

At the blades.

Rotational motion.

GEARS

INTRODUCTION TO SIMPLE MACHINES

Blender

1. Review their findings - a crown gear system helps do work by changing the direction of

motion. This means that the effort force can be applied in the direction that is easiest and

have the work take place in a different direction.

2. Ask them to compare the space taken up with a crown gear system and a spur gear system. The students

should recognize that a crown gear system could produce a more compact arrangement.

Ask the students to record these benefits in their journals using appropriate vocabulary.

Extending The Idea

Ask students whether or not they think that the same principles of gear ratios, speed, and force that they

observed in spur gear systems also applies to crown gear systems. Have the students write their predictions in

their journals.

Direct the students’ attention to the building instructions for the EGGBEATER on Pages 10 and 11 of the

Building Instruction booklet. Discuss some of the features of an eggbeater’s design – the need for a fast output

speed from the beaters to mix the eggs faster and more efficiently than by using a fork, for example.

What other machine have they studied

that must operate at high speed?

Could a similar gear system and mechanism be used to operate an eggbeater?

1. Ask the students if they can interpret how this machine works using only the building instruction

diagrams on Pages 10 and 11.

Use questioning strategies to determine student understanding:

(a) Look at the diagrams and identify the parts that move and suggest what their function might be.

(b) Suggest how the moving parts are joined together to create a change in direction.

(d) Identify the driver and driven gears.

(e) What is the direction of rotation of the driver and driven gears?

(f) Describe how the eggbeater gears are arranged differently from the crank fan gears.

(g) Will the handle rotate at the same speed as the beaters?

(h) Do the beaters turn in the same direction?

(i) Will the mechanism be easy or difficult to turn if the handle is removed?

2. The students should be given time to record their ideas in their journals.

3. Allow students time to build and investigate the K’NEX EGGBEATER.

4. (a) Ask the students to explain the movements and function of the mechanism they have investigated.

(b) How did their interpretation of the drawings differ from what they found when they built the model?

prepared to explain their answer.

Crank fan.

GEARS

JOURNAL CHECK:

✔

dentification of the gear mechanism.

✔

Diagram of the blender, including labels and arrows.

✔

Record of student observations as indicated by responses to questions in Step 3.

✔

Identification of the relative motions of moving parts.

✔

Identification of the change in direction of motion and force.

✔

How did the crown gear get its name?

✔

Benefits of using a crown gear system to change the direction of motion.

NOTES:

__________________________________________________________________________________________________

GEARS

INTRODUCTION TO SIMPLE MACHINES

The Stationary Bike:

An example of a chain and sprocket system.

Stationary Bike

PROCEDURE

Introduction

Review with the students how gears are

connected and how energy/motion is

transferred through a spur gear system.

Remind students that a spur gear

system makes work easier by changing

the output speed or multiplying the

output force. Remind students that

they cannot use a machine to gain both

speed and force. There is always a

trade-off when you use a simple

machine. They can gain speed at the

expense of force or multiply force at the

expense of speed. Ask the students to

tell you what is gained, if anything,

when a gear system uses gears of the

same size in a gear train.

Explain that a spur gear system is just one type of gear arrangement. Tell the students that they will explore

another type of gear system, one in which the gears DO NOT touch. The system they will investigate is one that

is used in a stationary bicycle.

OBJECTIVES

Students will:

1. Build and investigate the mechanism of a model system that represents a real-life object.

2. Observe how motion and force are transmitted through a distance using a chain and

sprocket system.

MATERIALS

Each student group will need:

- 1 K’NEX Intro To Simple Machines:

Gears set with Building Instructions booklet

- Student Journals

You will need:

- A bicycle (optional)

Students should remember that when gears are the same

size, neither speed nor force is gained. Your gain is that

you may be able to change the direction of motion.

In a spur gear system, the gears are meshed and in line.

Force and motion are transferred from one gear to another

along this line. If your students are familiar with the term

“plane” you can explain that the force and energy are

transferred along the same plane.

GEARS

Discuss how the stationary bicycle’s design is based on a 2-wheel bicycle. If possible provide an example of a

bicycle for the students to investigate. Alternatively, ask the students to look at Pages 12 and 13 of the Building

Instructions booklet to interpret how they think the mechanism works.

Ask them questions about how the bicycle works and encourage them to use terms they already know that are

ssociated with a bicycle’s gear system:

Where does the power come from to drive the bicycle?

Which parts move and what are their functions?

How is the power transferred to the rear wheel?

How is the gear arrangement in this mechanism

different from the spur gear system they

have studied?

Responses to this question will give you the

opportunity to discuss the chain and sprocket

drive system.

Divide the class into groups made up of 2 to 3 students.

Building Activity

Distribute a K’NEX Gears set to each group.

Ask the students to turn to Pages 12 and 13 of the Building Instructions booklet and construct the model of

the STATIONARY BIKE. To save time, we suggest that one student completes Steps 1- 6 at the same time as

another group member completes Steps 7-11.

Inquiry Activity: How is motion and force transferred using a chain and

sprocket system?

Steps

1. (a) Following completion of the

construction phase, allow students

time to explore their models.

Encourage the students to identify

the parts of their model bicycle.

(b) Using the model as an example,

demonstrate on the chalkboard

how to make simple labeled

diagrams using arrows to show

the direction of movement. See

example to the right:

Foot power, via the pedals.

Various answers.

Chain.

The chain and sprocket drive system uses a

chain to transmit rotary power from a driver

axle to a driven axle. Sprockets are toothed

wheels on which a chain runs. They are placed

a certain distance apart but the chain links

mesh with the teeth on the sprocket so that

turning one gear moves the chain and thus

turns the second gear.

Chain Direction of

Movement

Sprocket

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INTRODUCTION TO SIMPLE MACHINES

the various parts of their model. You can then decide whether or not to formalize these.

The following terms may be helpful:

Sprocket, chain, pedal, drive mechanism, links, driver gear, driven gear,

driver axle, driven axle.

(d) Have the students draw arrows on their diagrams to show the direction each part moves as the pedals

are turned.

(e) Ask the students to compare the

direction of motion of the axle on

the driver gear with the direction

of motion of the axle on the

driven gear.

(f) Students should record all their observations.

2. Encourage the students to continue exploring the chain and sprocket mechanism as they answer the

questions below. Ask the students to record their responses.

(a) Where is the effort force applied?

What type of motion is the

input motion?

(b) Where does the output motion

take place? What type of

motion is it?

chain in this system?

(d) Describe the transfer of

energy/motion through your

stationary bike system. Start

at the pedals and end at the

rear wheel.

Applying The Idea

NOTE: It may be helpful to have a model of the crank fan available for comparison at this point in the lesson.

Ask the students to write one reason

why bicycles use a chain and sprocket

system rather than a spur gear system.

Remind them to use their crank fan

notes if they need a little refresher on

spur gears.

The effort force is applied to the pedals. The input motion is

a rotational or circular motion.

The output motion happens at the back wheel. The output

motion is also a rotational or circular motion.

The chain transfers energy/motion from the gear at the

pedals to the gear at the rear wheel.

Answers will vary. Possible answer: In a spur gear system,

the driven gear turns in the opposite direction to the driver

gear. To go forward, you would have to pedal backwards.

Turning the pedals transfers motion and its energy along

the driver axle to the sprocket at the front of the bike (driver

gear). As the front sprocket turns, motion is transferred to

the chain. The chain transfers that motion and its energy to

the rear sprocket (driven gear). The turning of the driven

gear turns the rear wheel.

Both axles turn in the same direction.

Stationary Bike

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JOURNAL CHECK:

The following should be recorded:

✔

Identification of the gear mechanism.

✔

Diagram of the stationary bicycle, including labels and arrows.

✔

Record of student observations as indicated by responses to questions in Step 2.

✔

Identification of relative motions of moving components.

✔

Description of the transfer of energy/motion through the bicycle system.

hen the students are finished, ask individual students to share their ideas with the class. Record student

responses on the board.

Review the list. Ask the students to think about other machines that transfer motion over a distance. Tell the

students that chains are not the only way to transfer motion over a distance. Encourage them to brainstorm a list

f other machines that use a sprocket system to transfer motion. They will need help with this and it may be a

good idea to have pictures of some of the machines listed below. You can then ask the students to work out where

the chain and sprocket system is found in them. Examples you could use:

The checkout counter at the grocery store - a checkout uses a conveyor system.

A roller coaster at an amusement park - a chain is used to pull the roller coaster up the first big hill.

An escalator in a department store.

Extending The Idea

[Grade: 5]

1. Remind students that the term

gear ratio refers to the number

times the driven gear turns relative

to the number of times the driver

gear turns. Ask the students to

estimate the gear ratio of their

stationary bike models.

[Grade: 5]

2. Ask students to explain why

ten-speed and mountain bikes use

several different sized gears.

Students should be able to conclude that the gear ratio is

1:1 based on the identical nature of the gears used.

Possible answers: Different combinations of gears provide

different gear ratios. Most will probably suggest that they

use different sized gears going up hills compared to riding

on flat streets.

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INTRODUCTION TO SIMPLE MACHINES

GEARS: Changing direction, speed,

and force…

A gear is a wheel with teeth along its outer rim.

Gears can:

Change the direction in which something moves.

Change the speed that something moves.

Change the force needed to make something move.

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GEARS: On the move…

Driver Gear

Driven Gear

DRIVER GEAR: The gear to which the effort force is applied.

DRIVEN GEAR: The gear connected (meshed) to the driver gear.

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INTRODUCTION TO SIMPLE MACHINES

GEAR TRAINS: Changing the direction

of rotation…

Two, or more, gears meshed together make up a gear train.

Meshed gears turn in opposite directions.

An idler gear makes the gears on either side of it turn in the

same direction.

Driver Gear

Driven Gear

Idler Gear

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CROWN GEARS: Changing planes…

A crown gear meshes at right angles (90-degrees) to another

gear and changes the direction of motion. One gear turns

vertically (up and down), while the other turns horizontally

(side to side).

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INTRODUCTION TO SIMPLE MACHINES

GEARS: Changing speed and force…

SPEEDING UP: A large driver gear makes a small

driven gear turn faster. This increases turning speed,

but reduces turning force.

SLOWING DOWN: A small driver gear makes a large

driven gear turn more slowly. This reduces turning

speed, but increases turning force.

Large driver

gear (slow)

Small driven

gear (fast)

Large driven

gear (slow)

Small driver

gear (fast)

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GEARS: Try this…

Which way will these gears turn?

(a) (b)

(e) (f)

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INTRODUCTION TO SIMPLE MACHINES