Lesson video

Hello, my name's Mrs. Fletcher and I'm here to help you with this design and technology lesson today.

Today's lesson is called Pulley Systems and it's part of the Pulleys and Gears Electric Vehicles Unit.

In this lesson, we'll get to see how a pulley system works and how we might be able to use it to build a prototype electric vehicle.

So let's have a look at what we'll be learning about today.

The outcome of today's lesson is: I can create and understand movement with pulleys.

So I'll be going to be looking in detail at how a pulley system works and how we can use that as part of a prototype electric vehicle.

So by the end of this lesson, you'll be able to understand how a pulley system works, but also explain it and use it in your own type of system as well.

There are some keywords and phrases that we need to look at that we're going to see in today's lesson, so let's have a look at those to start with.

So first of all, we've got the phrase design specification, and this means a list of things that a product must have or do.

So we're going to be coming up with our own design specification for an electric vehicle in this lesson.

Then we've got that word pulley, and that describes a simple mechanism whereby a belt moves around a grooved wheel.

So we're going to see how that works in this lesson.

We've got the word movement, which means changing place or direction.

We've got the word rotation, which means moving in a circular motion.

And then we've got the word direction, so that means the way something is going or the way it's pointing.

So those are all words we're going to be using to describe how a pulley system works today.

Today's lesson is going to be split into two parts.

First of all, we're going to be looking at a design specification for an electric vehicle and the things that we would need in order to make that.

And then we're going to be looking at pulleys in particular because that's an going to be an essential part of the electric vehicle that we're going to be making.

So let's get started with the design specification part of the lesson.

Electric vehicles have become much more common in recent years as people have become more aware of the damage that travel can cause to the planet.

Emissions, that's the gases and smoke that come from diesel and petrol engines, contribute to air pollution on the planet.

And because a lot of the vehicles that we use have these types of engines, including cars, trains, and aeroplanes , it's is becoming quite a big problem.

Electric trains and trams and buses have replaced some of the older, more polluting vehicles in recent years.

And you may have seen trams in different cities that run on electricity, which is supplied by cables which are overhead.

You can see them in that picture there.

Electric scooters and bikes have also become more popular as a way of people moving around in a more sustainable way, so that's something else you may have seen people using.

Electric vehicles are powered by electricity, which is stored in batteries, which are sometimes called cells.

The batteries have to be recharged when the power runs out, and this is usually done by plugging it into a mains power supply, so that's the electricity that we have in buildings.

So you may have seen some cars like this one here plugged into the electricity of a building in order to charge up, ready to go.

You also see charges now in some petrol stations and some supermarkets as well.

Car engineers are working on new designs and ideas to make travel more sustainable in the future.

So that means it's going to cause less damage to the planet in the future.

They are using models and prototypes to explore different ideas.

It's not always possible to build a whole car to see how it will work and how it will look, so they use much smaller models and prototypes to help them try out different design ideas.

Simple electrical circuits, including cells, motors, and switches, can be used to power those prototypes, so there are much smaller version of an electrical circuit that would be used in a larger electric vehicle, but they can use it on a smaller scale to make small models and prototypes and so can we.

A local car manufacturing company would like to see some brand new ideas for electric vehicles that we may see in the future, and this is something you could help them with.

Some of our Oak pupils are keen to have a go at this task as well.

Sam is thinking that she could design a prototype vehicle that has a brand new shape, so she can think about the shape of vehicles in the future, and she could even make her prototype out of recycled materials, which would means that even the prototype will not impact the environment too much.

Jacob is thinking differently.

He's thinking that he might have a look at the size or number of wheels that a vehicle has and look at how that affects its movement.

So he's thinking about changing that aspect of a vehicle for a future design.

Now, all of these things that they'll need to consider are part of the design specifications.

So that's the list of things that the vehicle must have in order to function as we want it to.

So is it true or false that the components of an electric vehicle will be included in a design specification? Is that true or false? Pause video and have a think.

Welcome back.

What did you think? Of course it is true, and that is because design specifications list the things that a product must have or do in its design, so those components of the vehicle are an important part of the design specification.

Well done if you got that right.

A simple vehicle has these components: So if we're going to be building a simple electric vehicle as our prototype, we'll need these parts on it as well.

We'll need wheels and axles.

We'll need a switch.

We'll need a pulley system.

We'll need a chassis, which is a frame of a vehicle.

We'll need a motor, and we'll need a battery pack as a power source.

So all of those things are part of the electric vehicle system that we will need to build a prototype.

A quick check then.

So on that simple electric system that we would use on a vehicle, which part would transfer movement from the motor to the axle? So thinking about what makes the axle move, makes the axle rotate.

Is it the switch? Is it a cell? Is it the chassis or is it the pulley? Pause the video and have a think.

Welcome back.

What did you think? Well done if you said it was the pulley.

So that pulley system that's attached to the motor and the axle transfers that movement from the moving motor to help it turn that axle and wheel as well.

Well done if you got that right.

So time for a task then in this first part of the lesson.

So you are going to be writing the design specification to make a prototype for the manufacturing company for your new design for a new vehicle.

In small groups, you're going to share some ideas for an electric vehicle prototype design.

So you're going to think about what you might change about an existing vehicle design in order to make it different for the future.

So I'd like our Oak pupils, while thinking about changing the shape or changing the number or size of wheels, you can discuss what you might be thinking about changing for your design, and you're going to use this design specification here to help you.

So these are the things you need to think about: You need to think about the function, so that's what will your prototype show.

So what's new about the design that your prototype will help you to show? You're going to think about the user, so how will they operate the vehicle? That means how will they start and stop your prototype vehicle.

So we're thinking about the prototype, not the actual vehicle.

Think about the performance, so that's what type of circuit switch and wheels you're going to use in order to make your prototype vehicle work.

Think about the aesthetic, so what will it look like, your finished vehicle? Will you change the shape? Will it look different to a typical car we see today? Think about the materials you're going to use to make your prototype.

So it may not be the same materials you would choose to make the actual finished car or that the car manufacturers would use to make the actual car.

It's the materials you're going to use to make your prototype to show how your new design will work.

And you can also consider the environment, just like Sam did, in your prototype.

So think about how you can reduce, reuse and recycle materials to make your prototype vehicle as well.

So all of your ideas are to do with the prototype to show the car manufacturing company your new ideas.

Pause the video while you have a go at this task and come back when you're done.

Welcome back.

How did you get on? Well, Sam and Jacob have been discussing further their ideas that they had earlier for their new vehicles of the future.

Sam was concentrating on new vehicle shape and she's decided that the chassis, that's the frame of her vehicle, will be narrow at the front and wider at the back because she's thinking about where the batteries are going to be stored on her vehicle.

So she's going to make it a bit wider at the back for that reason.

Jacob is thinking about using a pulley to rotate the axles, but he will try and use different size wheels.

The smaller ones might go at the front of his vehicle and he might use larger ones at the back.

So they're thinking about how they can use that pulley system in their design, but the other things that they might change as well.

Well done to those pupils and well done if you manage to get that part of the task done as well.

So now it's time to move on to the second part of the lesson.

This is where we'll look at that pulley system and those pulleys in a little bit more detail so we can see how we can apply them to our prototype vehicles.

A pulley system is a simple mechanism used for lifting objects and driving movement.

So some commonplace that we see this type of system is in flag poles.

So where we pull the rope, that rope system is help moving the flag up the pole, which is also attached to the same rope moving around the pulley wheel.

We see it on cranes, which are used to lower and lift heavy objects.

And we see it's on sailboats, so again, that pulling of the rope lifts those sails up into the air and it uses the pulley system to help them do that.

And a pulley system includes at least one pulley wheel, so they can be more than one, but needs at least one wheel to make it work.

And it needs either a rope or a chain or some kind of belt to transfer the movement from the pulley wheel into whatever it's lifting or moving.

A pulley system transfers rotary motion, so that's that circular turning motion from the pulley wheel through the belt to create movement.

So you can see here the belt's attached to a pulley wheel on one side, and in this case a pulley wheel on the other side.

And you can see it in action there.

As one of those wheels is turned, the belt helps it to turn the second wheel as well.

So the movement of that first wheel is transferred through the belt to the second wheel, you can see in that model there.

The belt has to fit into a groove on the pulley wheel to hold it in place.

So whether it's a belt or a chain or a rope, it fits into a groove in the wheel.

So the wheels are not flat.

They have a groove or a dip in them, which that rope or belt can fit inside of so it doesn't slip off.

A pulley system can be operated manually.

That means by hand, so thinking about those flag poles or the sailboat rigging, or they can be driven by a motor.

So here's the manual version where we pull on the rope and that uses the pulley wheel to lift or move something else.

Or it can be driven here like this with a motor.

So the motor turns and that turns the belt, which turns the pulley wheel, which can then turn or lift something else in turn.

The belt controls the direction of the movement, so the way it's going to move.

If the belt is crossed like this between the pulley wheel and what it's connected to, then the direction of the movement is reversed.

So you can see in this second model here that the belt's been crossed over.

So where the wheel is turning in a clockwise direction, the movement that's being transferred to the opposite wheel means that that is travelling in the anticlockwise direction.

So by crossing that belt, we've changed the direction of the output, the movement that comes outta that system.

Which of these diagrams then shows the correct movement of a pulley.

So remember, we thinking about the crossed and uncrossed belts, how that affects the movement.

So we are looking at diagram A shows the left pulley moving in anti-clockwise, the right pulley moving in a clockwise direction.

We've got diagram B, which shows the crossed band and both of the pulleys moving in the same direction.

And then we've got diagram C where the band is not crossed, and both pulleys are moving in the same direction.

So which one of those is correct for the correct movement that the pulley would make? Pause the video and have a think.

Welcome back.

What did you think? Well done if you said C.

So if we look carefully at A, the band is uncrossed, so that means the wheels should be turning in the same direction.

Diagram B, the belt is crossed, which means the pulley wheels should not be moving in the same direction.

And diagram C shows the correct movement.

The band is uncrossed, which means the pulley wheels are moving in the same direction.

Well done if you got that right.

If the pulley wheels are different sizes, then the output speed will differ from the input speed.

So we've already had a look at how we can change the direction of the movement.

Now we're having a look at how we change the speed of the movement.

So you can see here we've got a small wheel on the left and it's linked to a much larger pulley wheel on the right.

And if we put that into operation, this is what it would look like on a pulley system.

And the larger pulley will turn much more slowly than the smaller pulley because it has a much bigger distance to rotate.

So it takes longer to fully turn than the smaller pulley.

So that means the smaller pulley is turning much quicker than that bigger pulley because it has a bigger distance to cover.

What does that mean then? Let's have a quick check.

A small pulley wheel will turn, mm, a larger pulley wheel.

So does a smaller pulley wheel turn slower than a larger pulley wheel? Does a small pulley wheel turn faster than a larger pulley wheel? Or does a small pulley wheel turn at the same speed as a large pulley wheel? Pause the video and have a think Welcome back.

What did you think? Well done if you said faster than.

So the small pulley wheel will turn faster than the large one because it has a much smaller distance to move, so it can do it much faster than the larger one.

Well done if you got that right.

Now, construction kits are a really good way of exploring these pulley systems, and they can be used to build quite simple pulley systems to rotate an axle.

So you can see here this example.

We've got two axles here that are being held in place by an axle holder, so that's to keep them in the right place.

Then we've got a pulley, which is attached to both axles by an elastic band, which is acting as the belt between those two pulleys.

So that's a simple pulley system that's been built using a construction kit.

And there's lots of different ways you could do that and lots of different ways you could explore different types and sizes of pulley using that.

And that leads us onto our second task in today's lesson.

So you're going to use construction kits to build a simple pulley system.

You can try changing the size of the pulleys, you can try changing the direction of the movement by crossing the belt, and you can observe the effect that each change has on your pulley system.

And this will help you to think about how you can use this in your electric vehicle prototype to change the movement of the vehicle and to change the direction that the vehicle is moving in as well.

Pause the video while you have a go at this task and come back when you're done.

Welcome back, how have you got on? So using those construction kits is a really good way of exploring how the pulley system works.

And now you've had a go at building one, the second part of the task is to show your pulley system to a partner and I want you to point out each part to them and explain how it works.

So this will show your understanding of the pulley system and it will help their understanding of the pulley system as well.

You can use these keywords to help you.

So can you show them where the pulley is, the belt, the axle, which part is rotating, which direction has been changed, which direction it's moving in, and the movement that you are creating as well.

So by pointing out and talking about all of those different elements of your pulley system, you can make sure you both fully understand how your pulley system is working.

Pause the video while you complete that task and come back when you're done.

Welcome back.

So having built your pulley system and explained it to your partner, you may have explained it a little bit like this: The pulleys are connected to the axles, so that's the placement where it needs to go in order to work.

The belt connects those two pulleys together, so in this case, you might have used elastic band to do that.

When you rotate one axle, it turns the pulley that's connected to that axle.

This moves the belt, which causes the second axle and pulley to rotate in the same direction.

So if your system is connected like Jacob's there, then both of those axles will move in the same direction.

If you were to cross the band, then you would've observed that the axles were moving in opposite directions.

And if you think about how that might work in a vehicle, do we want the wheels to be moving in opposite directions? So that's where it will help us to plan how we can use a pulley system in our electric vehicles.

So we've come to the end of the lesson today, and I've really enjoyed exploring the pulley systems with you and thinking about how we might incorporate those into an electric vehicle prototype model in the future.

We've learned that listing those main components, those main parts of a simple electric vehicle, can start us thinking about a design specification.

We've learned that construction kits are a really good way to explore pulley direction, a really good way to explore how the pulleys affect the movement.

And we've learned that the size of pulleys can affect the speed of rotation.

So that's particularly important if we're thinking about building an electric vehicle prototype.

We need to think about how those wheels are going to rotate.

We need them to rotate in the same direction, and we need them to rotate at a certain speed.

That means that the vehicle can be demonstrated accurately.

Thank you for joining me for today's lesson.

I hope to see you again in another lesson, but at least, goodbye from me for now.

Bye-bye.