Robotx
Rolling
along
Six Simple Machines
The Wheel and Axle
Written by Gerry Bailey
Illustrated by Mike Spoor
The two robots are usually
very, very busy in
their workshop…
Meet
RobbO
2
and
RobbEE
The Robotx.
…making all kinds of useful
(and not so useful) machines…
3
A machine is…
…machines like this…
A machine is a tool used to make
work easier. It allows us to push,
pull or lift a heavy or difficult
weight much further than we
could by ourselves.
and this…
and this.
and this…
4
The six simple machines are an
important part of every kind of
machine. Some have just one part
that moves, while others are made
up of two or more parts. They are:
• the wheel and axle
• the wedge • the pulley
• the lever • the screw
• the inclined plane In this book we will learn all about
the wheel and axle – and the
Robotx will help us.
5
This morning, there is a delivery.
It’s all the gear
that RobbO
needs to build his
new whizz-fizz
machine.
So much stuff!
6
It’s RobbEE’s job to carry it all
into the workshop. Whew, it’s
hard work. He gets so tired he
has to stop and recharge a lot.
7
‘Hurry,’ says RobbO,
who is impatient to get
started on his new
invention.
‘RobbEE,’ says RobbO.
‘You can make things a lot
easier if you use the wheels.’
RobbEE tries carrying
several boxes at a time.
But they’re too heavy.
He tries dragging them and pushing
them, but gets just as run-down.
8
‘Of course!’ says RobbEE (who
had forgotten all about them).
‘I’ll use some wheels.’
9
‘Here,’ says RobbO, who knows just
what to do. ‘You need to use a
wheel and axle.
First you connect each
wheel with a rod called
an axle.
‘Now you join the axles with a long
plank. Then fix a box seat over the
plank.’
‘These go in the front.
‘Then you
connect two
more wheels to
another axle.
These go at
the back.
10
RobbO has made a cart.
11
Now RobbEE can pile the cart
high and it’s easy to pull it
along.
Wheels and friction
Friction happens when two
things rub together. The
amount of friction created
depends on the weight of
the load and the surface
over which it is moving.
direction of motion
Friction makes things
slow down because it
pulls in the opposite
direction to the
direction the object
is moving.
force of friction
After a few loads, the job is finished.
12
Wheels reduce friction. They need a little friction to
grip the ground as they roll forward but they make
moving a load much easier and faster.
13
RobbO tells RobbEE they can
have fun with the cart. They
can use it like a soap-box
racer to run downhill.
First he adds a seat to the
back of the cart. Then he
attaches the front axle with
a screw so the axle can turn.
Now RobbO can steer his cart.
To turn right he pulls the righthand cord. To turn left he pulls
the left-hand cord.
It’s lots of fun
riding downhill
together.
Finally he adds a cord to
each end of the axle.
14
15
The spinning wheel
The Robotx take
a break. RobbO
tells his friend
a story about a
spinning wheel.
16
This made Arachne angry
too, and she challenged
Athena to a spinning
contest. The goddess
instantly threw off her
disguise and accepted
the challenge.
Athena had to admit that
Arachne was good but she
wanted to punish her for
her pride.
Long ago there lived a beautiful young woman called
Arachne. Not only was she beautiful but she was an
expert spinner at her wheel. In time Arachne became
conceited. She even claimed she could spin better
than the goddess Athena!
So Athena told Arachne
that as she loved to spin and
weave she would live forever
in her yarn. And with that
the goddess turned the
shocked girl into a spider.
This made Athena angry. Disguised as an old woman
she visited Arachne and told her that a mortal could
never compete with a goddess.
And since that time all
spiders have had to live
in the webs they spin.
17
Wheels and axles
A wheel and axle can be used to move
an object from place to place, to
drive a machine or to create power.
Windmills are used
to make power or to
pump water out of
the ground.
These huge train wheels are
are powered by electricity,
either from wires above the
train or from a rail that runs
under the train.
An ancient way of using
a wheel and axle was the
water wheel. Huge wheels
with buckets round the
edge were used to lift
water out of a river.
A propeller is a kind of wheel
with blades. It is attached
to the back of a boat. It
pushes the boat through
the water as it spins.
18
Stop taps close off the
pipes when they turn.
Roller skates
allow you to
glide over the ground
much more quickly
than walking.
19
Funtime wheels
RobbO knows where there is a large
wheel and axle they can have fun
with. It’s the roundabout in the park.
A roundabout is a wheel that lies on
its side. It spins on an axle that’s
fixed in an upright position.
20
A Ferris wheel is a
huge wheel with seats
around its edge. It
turns very slowly on
an axle. People sit in
the seats for an
exciting ride.
A fairground
roundabout is a wheel
that spins on an axle
in an upright position.
21
In the toolbox
Doorknob
These tools don’t look like
wheels at all. But they all use wheel
and axle movements to do their work.
The round doorknob is a wheel.
An axle connects it to
another knob on the other
side of the door. When you
turn the knob, the axle
turns and moves back the
latch that keeps the door shut.
Screwdriver
The handle of a screwdriver acts
as the wheel. When you
turn it, the wheel turns the
axle. That’s the shaft bit, with
a flat piece at the end.
Carpenter’s brace
A carpenter’s brace has a bent
handle. It turns in a large
circle like a wheel. The
axle is the drill bit, which is
turned in a smaller circle.
22
Spanner
A spanner doesn’t look like
a wheel and axle, but when it
is attached to a bolt,
the bolt becomes
the axle. When you
turn the spanner
it acts as the wheel,
turning the bolt to
tighten its hold.
23
RobbO’s
Science Workshop
All the robots have gathered at
the workshop to learn about the
wheel and axle.
The wheel and axle is a
simple machine that helps
you turn things. The axle
goes through the centre
of the wheel and when it
is turned, the wheel turns
too.
24
This is how it works. The
radius of the wheel – that’s the
measurement across the wheel –
is larger than the radius of
the axle.
When you turn a doorknob, the
larger turning movement on
the knob is matched by a much
smaller, but more powerful,
turning movement in the axle.
This makes it easier to open
the door.
Friction
The wheel-and-axle machine helps
you overcome the force called
friction. Friction slows things down
when one rough surface rubs against
another. It even happens when an
object moves through
air, through gas or
through water.
Friction makes
objects heat
up too.
25
Two simple machines
working together
A bicycle uses two kinds of
simple machine. It has three
sets of wheel and axle, as
well as another kind of simple
machine called a lever.
lever
A lever is attached to each
of the handlebars. When
you squeeze the lever
shut, it pulls a cable.
cable
brake blocks
Two of the wheels are the big
ones at the front and back
that have spokes.
chain wheel
The third is the chain wheel. When you
turn the pedals, the axle turns the
chain wheel and this moves the chain
and makes the back wheels turn.
26
The cable is attached to brake blocks and
these grip the sides of the wheel and slow
the wheel down using friction.
27
Wheels turning wheels
Sometimes wheels have notches,
called cogs, cut around their edge.
Wheels like this are called gears.
Each gear fits into another,
passing the turning movement
on from gear to gear.
Gears are also
used to change
the direction of
wheels, as well as the
speed at which they move.
28
turns
clockwise
Inside a mechanical clock, there
are gears that turn the hands and
show the time of day.
turns
anti-clockwise
29
Build a Super-Cycle
Then RobbO puts all the wheel and
axle ideas together and builds a
Super-Cycle-Time Machine. It’s
his most useful invention yet!
30
RobbO turns the pedals.
The pedals turn the gears,
which turn the chain,
which turns the
hands of
the clock.
31
Arachne 16
Athena 16
axle 5, 10, 11, 14, 18,
20, 21, 22, 23, 24,
25, 26, 30
bicycle 26
blade 18
boat 18
bolt 23
brake block 27
cable 27
carpenter’s brace 22
cart 11, 12, 14, 15
chain wheel 26
clock 29
cog 28
cord 14, 15
doorknob 23, 24
drill 22
Index
electricity 19
Ferris wheel 21
friction 13, 25, 27
force 13, 25
gear 28, 29, 31
handle 22
handlebars 27
invention 8, 30
latch 23
lever 26, 27
load 13
machine 6, 18, 24, 26, 30
pedal 26, 31
propeller 18
pull 5,
pulley 5
push 5,
radius 24
rod 10
roller skate 19
roundabout 20, 21
screw 5, 14
screwdriver 22
spanner 23
spider 17
spinning wheel 16
spoke 26
stop tap 19
tool 5,
train 19
water wheel 18
wedge 5
weight 5, 13
wheel 5, 9, 10, 12, 13, 16, 18,
19, 20, 21, 22, 23, 24, 26,
27, 28
windmill 19
workshop 3, 7
Photo credits
All images are Shutterstock.com unless otherwise stated.
Pg 18 – (l) Eldin (r) OPIS Zagreb
Pg 19 – (tl) Thomas Barrat (tr) Alexander Kuguchin
(bl) aodaodaodaod (br) J Helgason
Pg 21 – (t) Chubykin Arkady (b) Jason Benz Bennee
Pg 29 - Voronin76
32
Copyright © 2013
BrambleKids Ltd.
All rights reserved.
ISBN 978-1-909711-49-5