Have you ever looked underneath a car? It looks very complicated and there are all sorts of pieces and parts, each with their own job to do. We are going to focus on two of the main parts in a vehicle which allow it to move.
There is no specified Technology Design Process in this chapter, but the focus is on Technology and systems. In Gr. 6 in Earth and Beyond, learners will follow a Design Process and design and make a car to move on the Moon or Mars. They will revise some of the concepts that they learnt here about wheels and axles.
Wheels and axles
All vehicles have wheels. Most cars have 4 wheels, while some have only 3 wheels, and yet others have many more. Trucks and buses have many wheels while some trailers or bicycles only have 2 wheels.
Why do you think wheels are round? Why will a square or a triangular wheel not work?
Wheels need to be round in order to roll. A square or triangle wheel will not roll.
How did wheels and axles develop?
In the past, before the wheel was invented, it was very difficult to move things around. People would try to drag heaving objects along the ground using ropes, or else they had to carry things, but this was very inefficient! As a result, people started to experiment with ways of making it easier to transport goods and heavy objects.
The pyramids in Egypt were built long before modern transport (including trucks) was invented.
The pyramids are very high structures made of stone.
The Egyptians were very clever in finding ways to move very heavy objects. They used logs that were laid down like in the picture. The heavy objects were placed on them, rolling them creating movement like in the picture.
Egyptians pulling heavy stone blocks along logs
You can demonstrate this by using pencils and placing a bunch of pencils next to each other. Then put a heavy object on top of the pencils and push it along. As the object moves the pencils underneath it move too.
The Egyptians used this method to move the massive blocks of stone to build their pyramids. But, there were still many problems with using logs cut from trees.
Can you think of any problems of using logs to try move very heavy objects? Discuss with your friends around you and write your answers below.
Logs not of the same size or length. Needed a lot of logs and then had to move logs as well.
This can be demonstrated by using different shapes and sizes of pencils and pens.
Later on, people started to cut the logs into short pieces so that they were the same size. Each piece was like a wooden disc. The wooden disc could not stand up by itself so people attached a wooden pole between two of the wooden discs. The wooden pole was the first axle, and we still use axles to this day. That is how the first wheel and axle was developed!
People could then balance goods on the axle and use this simple machine to pull or push objects along. However, this wooden disc wheel was still very heavy! To make it lighter, the wheel was changed to a round frame with spokes, like a wagon wheel. This made it much lighter and easier to move. Since then, the wheel has advanced a lot. Think of the shiny metal and rubber wheels you see on cars today!
A wagon wheel (left) and the modern rubber and metal rimmed wheel we have today (right)
How do wheels and axles help us?
Humans have built many machines to help make their tasks easier. A wheel and axle is a simple machine. It makes it easier to move a load; to transport things and people.
It is much easier to move a heavy bag on a wheelbarrow rather than carry it by hand.
A wheel and axle is made up of a wheel (large cylinder) joined onto an axle (which is a small cylinder).
Label the two wheels and the axle in the following diagram.
Wheels and axle
When we think of wheels and axles, we think of cars and other vehicles that we see all around us that have wheels.
A wagon wheel and axle
However, there are many examples of objects and machines that use wheels and axles:
rolling pin,
windmill,
fan,
egg beater,
door knob, and
bicycle wheels.
Identifying vehicles with wheels
Find pictures of three of the above examples. Look in old magazines and newspapers at home, or on the internet for pictures. Paste the pictures in below and label the axle and the wheel in each picture.
Explain carefully how a door knob is a wheel and axle machine.
A door knob has a large cylinder on the outside, attached to a small cylinder on the inside. It is easier to turn the large cylinder than the small cylinder with your hands.
Let's make a simple wheel and axle mechanism to understand how it works.
Asimple wheel and axle machine
MATERIALS:
2chairs
broom handle
string
bucket with handle
masking tape
scissors
ruler
INSTRUCTIONS:
Place the chairs back to back, about 30 cm apart. Rest the broom handle across the back of the chairs.
Tie a 50 cm length of string to the bucket handle.
Tape the free end of the string to the middle of the broom handle.
Place a few marbles or some other light objects in the bucket.
Turn the broom handle with your hands to raise the bucket into the air. Turn it back the other way to return the bucket to the ground.
Tape the ruler straight up and down the broom handle near one end.
Use the ruler, which acts as a wheel, to turn the broom handle and lift the pail.
QUESTIONS:
Could you lift the bucket by turning the broom handle with your hands?
Yes
Was it easier to lift the bucket when you turned the broom handle using the ruler?
Yes
Replace the ruler with a stick that is longer than the ruler and use the stick to turn the broom. Was it easier to lift the bucket using the long stick?
Yes, the longer the ruler or stick the easier it was to lift the bucket.
Identify the axle in the setup.
The broom handle is the axle.
Identify the wheel in the setup.
The ruler or long stick is the wheel.
Write a conclusion to summarise what you learnt in this activity.
We could lift the bucket by turning the broom handle. It was much easier to lift the bucket when we used the ruler. Our hand had to move further when we used the ruler, but it was easier and the bucket felt lighter. We made a simple wheel and axle machine to make it easier to lift the bucket.
Now, let's put two axles and four wheels together to make a simple tractor!
Making a trailer with wheels and axles
MATERIALS:
cardboard
two pencils
a small box
scissors
INSTRUCTIONS:
Cut out four circles of the same size from the cardboard. You can use a lid from a bottle or a cup to trace around to get circles which are all the same.
Make a hole in the centre of each circle and in the bottom 4 corners of your box.
To find the centre of the wheel, use a ruler to draw diameter lines across the middle.
A diameter line is the longest straight line you can draw across a circle. Where diameters cross, that is the centre.
A wheel is a circle. Find the centre by drawing some diameters. In this example the centre is the red dot.
Push a pencil through the middle of one circle and through a corner of the box.
Push the pencil through to the other hole on the other side of the box.
Then attach another circle on the end of the pencil poking out of the side of the box.
Repeat this for the other 2 wheels.
You know have a simple tractor like in the picture below.
Put an object in the box and push your vehicle along the floor.
QUESTIONS:
Can you see the wheels turning on the axle and how the axles connect the wheels?
Yes
Which part of the vehicle that you made is the axle?
The pencils are the axles.
Different ways to make wheels and axles
This section shows different ways of making wheels and axles using materials which are easily obtainable. First go through some of the ways to make wheels and axles, and finally the last activity is to experiment with different materials and evaluate which set ups work best.
We are now going to experiment with different ways of making wheels and axles and finding out the best materials to use.
There are two ways to let wheels turn on an axle. One way is to have the axle fixed to the body, and the wheels are free to turn on the axle. The other way is to have the wheels fixed to the axle and the axle turns in a bigger tube called the bearing. The bearing is the hollow tube that the axle goes through. The bearing must be bigger than the axle so that the axle can turn easily.
You can use plastic straws or the barrel of an old ball-point pen to make a bearing for an axle. The picture shows you two ways to fix the bearings onto the body.
Two ways to fix the bearing onto the body
What are the two ways used in the picture to fix the bearing onto the body.
tape and glue
What are some materials that you could use to make the axle in the above picture?
Smaller straws, dowel sticks, sosatie sticks, etc.
You can also use plastic sign-board or strong corrugated cardboard to make a body with wheels. Can you see how the axle goes through the holes in the cardboard?
The board makes bearings for the axles which are fixed to the wheels. The axles turn in the holes.
The next picture shows you the other way to let the wheels turn. This time the axle remains fixed and the wheels turn on the axle. The axle is fastened to a wooden body with cable clips. Cable clips fasten telephone cables to walls. Can you see the blown up version of a cable clip? The clips may hold the axle tightly, so the wheels must be free to rotate.
How the cable clips can hold an axleA clip to hold telephone cables to the wall
Making and evaluating different wheels and axles.
This activity does not follow a Technology Design process with all the steps, but does involve investigating, making and evaluating different objects to make wheels and axles and then using their best option to make an improved tractor from what they first made in the beginning of this chapter.. Ask learners to collect the materials for wheels and axles from home beforehand - tell them to also use their imaginations when looking for different materials to use. You will also need to supply some of the materials below.
MATERIALS:
things to collect for wheels: shoe-polish tins, the lids of bottles, cut out cardboard circles.
things to collect for axles: sosatie sticks, stiff plastic straws, wooden dowel sticks, aluminium rods, nails or wire, or the school may have plastic rods from a supplier.
scissors
glue
tape
pencils and crayons
a small box
Things you can use for wheels and axles.
INSTRUCTIONS:
Bring the different materials that you have collected to make wheels and axles to class.
You must now experiment with the different materials that you have to make wheels and axles. Attach the setup to the small box to test the wheels and axles.
Remember what you learnt about how to attach axles to the box and experiment with these different methods as well (Hint: Bearings!)
Experiment with different sized wheels and find the best option.
Once you have tested and evaluated the different setups you have made to see whether they move easily, select the best option and make an improved tractor from the simple tractor you made at the beginning of this chapter with the pencils.
Evaluate how far your improved tractor can go if you give it a push with an object in the small box.
Set up a mini competition to see whose tractor can go the furthest after giving it one push and it is carrying an object (such as the board duster, or some other small, fairly light object). Use a tape measure to record how far each learner's tractor went.
QUESTIONS:
Make a drawing of your final design for your improved tractor below. Remember to label the different materials that you used.
Which material did you decide was the best to use for the wheels and why?
Learner dependent answer. Make sure they provide a reason for the chosen material.
What did you decide to use for the axles and why?
Learner dependent answer. Make sure they provide a reason for the chosen material.
How did you attach the wheels to the axle in your final design?
Learner dependent answer
How far could your tractor travel (while carrying an object) after you gave it a push?
Learner dependent answer
How would you improve your design if you had to do it again?
This is a learner dependent answer but the teacher needs to check that learners evaluate their designs.
Many vehicles are machines that use wheels and axles.
Wheels and axles are used to help vehicles move more easily.
List four different vehicles that make use of wheels and axles in order to move.
Car, truck, bicycle, pram, motor bike, trolley, etc.
When Jojo was experimenting with making wheels, he decided to use bottle lids. Look at the picture below. He decided that glueing two lids together was better than one lid. Explain why you think Jojo did this.
Jojo glued two lids together.
Jojo did this because one lid was probably unstable and wobbled, whereas two lids are more stable and do not wobble.
When Jojo made the axles for his tractor, it looked like this underneath:
The axles under Jojo's tractor
What is wrong with these axles and how do you think the tractor will move? What should Jojo do to improve his design?
The one axle is skew which will make the tractor move in a curve to the one side. He should improve the design by making the axles parallel to each other and perpendicular to the side of the tractor. (Perhaps explain the words parallel and perpendicular to your class by drawing pictures on the board)
