Hello and welcome to today's Design and Technology lesson.

My name's Mrs. Fletcher, and I'm here to guide you through today's lesson.

Now, today's lesson is called Cam Mechanisms, and it's part of the Cams: automata unit.

This unit builds on work you may already have done on: wheels and axles, gears and pulleys, and joining and cutting different materials.

So let's have a look at what we're going to be learning about today.

So the outcome for today's lesson is I can identify how cams create movement.

So we're going to be looking in detail at the cam mechanism itself and how making changes to that can create different types of movement in the products that they're used in.

Now you're going to get to do some practical work in today's lesson as well, because we're going to make a prototype so we can explore how the mechanisms work in more detail.

Now, there are some keywords that we're going to need to use in today's lesson.

So let's have a look at them together to make sure we know what they mean.

So we've got the word cam, which describes the mechanism that changes one type of movement into another type of movement.

So we're gonna be exploring how that works.

We've got the word rotary, which describe movement that goes around in a circle.

We've got the word linear, which describes movement in a straight line.

We've got the word reciprocating, which you may have heard before.

Let's repeat that to your partner.

Reciprocating.

Well done.

And that describes a backwards and forwards movement in a straight line, just like we see in a slider.

You may have seen that in previous lessons.

And then we've got the word oscillating.

You may have heard that one before.

Repeat that one to your partner.

Oscillating.

Well done.

And that describes movement back and forth along a curved path.

So not in a straight line anymore, on a curved path.

So much like you see in a swing or in the pendulum of a clock, it's kind of a curved path that it's following.

So those are the keywords we're gonna be using today.

So let's have a look what we're going to be learning about.

So the lesson's going to be split into three parts today.

So first we're going to look at the cam mechanisms themselves.

Then we're going to look at how those cams create movements, particularly different types of movements.

And then we're going to be making that prototype cam, which will give us a hands-on look at how they work.

So let's get started with the cam mechanisms. So a cam is a simple mechanism that converts one type of movement into another type.

So it starts off as one type and it ends up as a different type of movement.

Cams usually convert rotary motion, so that was that movement that goes around in a circle, into linear motion, which was movement that goes around in a straight line.

A cam is made up of three main parts.

You can see on this diagram here, we're gonna look at the three main parts that make up a cam mechanism.

So at the bottom there, we've got the cam itself, and that's like a disc shape that can come in a different shapes and is rotated round on an axle.

So just the way you've seen a wheel and axle in the past, this rotates around on the axle and it uses a crank, which is a type of handle to rotate it.

Then above that we've got the follower, and this sits above the cam and it's affected by the rotation of the cam.

So it's affected by the movement of the cam disc underneath it.

And then we've got the slide, which holds up that follower in place, allowing the movement to be repeated over and over again in exactly the same way.

So let's have a quick check.

What does a cam turn rotary motion into? Does it turn it into circular motion, linear motion, or a sliding motion? Pause the video.

Have a think.

Well, welcome back.

Well done if you said that a cam turns rotary motion into linear motion.

Well done.

So a cam is designed to repeat the same movement over and over again.

So that's the purpose of a cam mechanism, to repeat that movement over and over again.

And when a linear movement is repeated like that, that's when we call it a reciprocating motion.

So that word reciprocating from our keywords means repeating the same movement over and over again.

A reciprocating motion can be up and down, like we can see in that little gif there, or side to side.

Cams can be found in lots of different products that we find in everyday life, like sewing machines, carousels that we see at the fair.

And even lots of different types of toys have cam mechanisms in them.

In all of those examples, rotary motion is being turned into a reciprocating motion.

So the rotary motion is in one part of the product and it's turned into a reciprocating motion, that's a repeated motion, in another part of the product.

So if we look at the sewing machine as an example.

So here we've got an old fashioned sewing machine.

You could see on old fashioned sewing machines, the handle that the user had to turn around and around.

So that's the rotary motion that we are talking about.

And that rotary motion is converted into the reciprocating linear motion of the needle going up and down.

So we can see it quite clearly on an old fashioned sewing machine.

It works the same way on a modern sewing machine, but you can't see all of that mechanism.

So the rotary motion is hidden inside.

The rotary component is hidden inside the sewing machine and it's driven by electricity.

But we've still got the same input of a rotary motion and output of that linear up and down movement of the needle that's used for the sewing.

A carousel or a merry-go-round converts the rotary motion of the base.

So the base of the carousel is going around and around in a circle.

It converts that into a reciprocating motion.

That repeated motion of the horse is moving up and down.

So that's how it works in a carousel.

That rotating base converts into a movement, a reciprocating movement up and down, of the horses.

Cams, like I say, can also be found in toys, particularly those where they've got parts that move when you push or pull them along.

So we have a rotary motion from the wheels, usually.

That's converted into reciprocating motion where another element of the toy moves up and down or side to side.

The rotary motion of the wheels usually makes another part of that toy move.

So cams can sometimes create a movement which travels backwards and forwards, along a curved path, and that's when we call it an oscillating motion.

So like we mentioned before, like on a swing, the same path is followed by the swing backwards and forwards along that curved path.

So just let's have a quick check of your understanding.

What does that word reciprocating mean? So we've used it a few times already.

What does the word reciprocating mean? Does it mean round in a circle? Does it mean swinging back and forth? Or does it mean a repeated linear movement? Pause the video and have a think.

Okay, welcome back.

What did you think then? What does reciprocating mean? Well done if you thought it was a repeated linear movement.

That's exactly right.

Well done.

So let's have a look now at a task.

So I want you to label the parts of the cam that we've just looked at.

So before we move on to looking at how they work, let's just make sure we know the parts of the cam really well.

So I've given you a clue by giving you the first letter of each of the three parts that I want you to label in this task.

So pause the video, have a go at labelling those three separate parts of the cam.

Okay, welcome back.

How did you get on? Did those first letters give you a clue? Let's have a look at the answer.

So you should have had: at the top there, the slide, in the middle, the follower, and then down at the bottom we have the cam disc itself.

So we should have labelled with those three words.

Well done if you got that right.

Okay, for the second part of your task now, I'd like you to fill in some missing words.

So I've got a word bank.

I've put a word bank at the bottom there for you with the words oscillating, rotary, reciprocating, and linear.

But I want you to put them in the right place in these sentences.

So the sentences say: A cam turns.

mm, motion into.

mm, motion.

So there's two missing words there.

Linear motion that's repeated over and over again is called.

mm, motion.

So we've got a missing word there.

And then movement that goes back and forth along a curved path is called.

mm, motion.

So we've got another missing word there.

So can you put those four missing words into the right place? Come back when you're finished.

Okay, welcome back.

How did you get on? Let's have a look if you managed to put those four words in the right place.

So a cam turns rotary motion into linear motion.

Linear motion that's repeated over and over again is called reciprocating motion, and movement that goes back and forth along a curved path is called oscillating motion.

So well done if you manage to get all of those words in the right place.

So we're gonna move on now to look at the next part of our learning about how cams create movement.

So now we know what parts a cam is made up of, now we can look at how they help to create the movements that they make in a product.

So the output movement of the follower, so that's the piece that was moving up and down in that mechanism, can be changed by changing the shape of the cam disc.

So the actual cam disc at the bottom can be shaped, the shape can be changed, the size can be changed, and the position of the follower, or the angle of the follower can also be changed.

So if we change any of those things, we'll get different types of movement.

So the cam, particular shape of the cam, can be any shape, but the most common ones that we see are these four.

So we usually see either an eccentric cam, an elliptical cam, a snail cam, or a pear cam.

So you can see the differences in those where centric cam is a circular shape with an off-center hole.

The elliptical cam is an elongated shape, so like a circular shape that's been compressed at the sides with a central hole.

We've got a snail-shaped cam named after the shape of a snail shell where it's mostly circular shaped, but it has that little lip on the end, which makes that slightly different shape.

And then we've got the pear shaped cam, which has a wider bottom and a narrower top, just like the shape of a pear.

So having those different shapes creates different movements.

So which one of those, quick check, was the excentric cam? So pause the video, have a think.

Well done if you said that it was C, that was the eccentric cam, the circular disc with the off-center hole.

So let's have a look at that eccentric cam in a bit more detail.

So here we have some images showing the up and down movement, that linear up and down movement of a follower on top of an eccentric cam.

So the cam turns on the axle, the hole in the cam is off-center, which creates a gradual change of distance between the cam and the follower.

If the hole was in the centre of that cam, there would be no change in distance, so that follower wouldn't move anywhere.

It would just, the circular disc would just move around and around, underneath and nothing would happen.

So by having that off-center hole, it means that the size of the cam changes as it moves around, which means the follower is pushed up and down on top of the disc.

So the follower rises and falls with a smooth constant motion.

So it moves up slowly and falls down slowly.

So we've got that constant smooth motion.

The larger the cam, so if we increase the size of the cam, the longer it will take to do a full rotation on the axle.

So this creates a much slower but larger movement.

So if we can see in these images, on the ordinary shaped cam there, we've got the highest point that it can move up to.

But if we increase the size of the cam, then that follower can move up to a higher point.

So it can make a much larger movement, but it will be slower because it will take longer to get around the full size of that cam disc.

Let's have a look at an elliptical cam now.

So this works in a slightly different way.

So it still turns around on the axle, but as the widest part of that elongated shape reaches the top, that's when the follower is pushed up and then the follower moves back down as that point moves away, and it moves across the wider part of that elongated shape.

So it spends longer in the lower position because the surface area of that wider part is much bigger than the narrower part.

On a snail cam, we've got a much different, a much more different movement.

And that's because of that lip on the snail cam.

So it still turns on the axle, but a snail cam only works in one direction.

So you can only use it in one way.

It will only work in one direction.

And as the point of the spiral reaches the top, so that's that top of that lip, the follower is pushed, that's when the follower is pushed up.

And then as that point moves away, if you look in the second image there, you can see that the follower makes a sudden drop back down.

So it falls off the edge of that lip.

So we don't have a constant smooth movement like we did with the eccentric cam.

We have a smooth movement up to the top and then a sudden drop as it falls back down into position.

You can see here on this little video of a cam mechanism using a snail cam and you can track the movement of the follower.

The follower is the metal part in this image, and as it reaches the top of that lip, it's in a smooth movement up, but then as it reaches the top, it then suddenly drops back down and starts the movement over again.

So let's have a look at the pear cam now.

So a slightly different movement in the pear cam.

It still turns on the axle, but as the pointed end of the cam, so that narrower part of the cam reaches the top, that's when the follower is pushed up to its highest point.

And when that point moves away, the follower lowers back down.

And there's a short pause with a pear cam because the follower spends quite a long time in that lower position because it's got that elongated, wider base at the bottom, it spends much longer time travelling around that part, or following that part than it does in the narrow part.

So you get a pause before the follower moves back up again.

So a quick check of our understanding.

What happens to the follower when the widest part of the cam reaches the top? So what's happening to the follower when the widest part reaches the top? Does it drop down suddenly? Does it move up? Does it move down or does it stop? Pause the video, have a think.

Okay, what do you think? What happens to the follower when the widest part of the cam reaches the top of the axle? Well done if you said it moves up.

As that cam moves up into position, the follower is pushed up into a higher position.

Okay, time for a task now.

So let's show our learning by matching up the cam names to the picture of that cam and the description.

So one has already been done for you.

The snail name has been matched to the snail picture and matched to the description that says a spiral shape known for its drop motion.

So that first one's been done.

Can you match the next three and come back when you've done? Welcome back.

So how did you get on? Did you manage to match all three of those other cams to their name, picture and description? Let's have a look what we should have had.

So the eccentric cam was the bottom picture, and that was matched to a circular shape with an off-center hole.

The second one was the pear cam matched to the picture at the top, and that description was an elongated shape that's wider at one end.

And then the last one was the ellipse-shaped cam, which was the second one in the pictures, and that was the top description of an elongated shape with a central hole.

Well done if you managed to match all those, you're doing really well.

Okay, so time for the final part of our lesson now.

So this is where you get to get practical and make your own prototype cam.

So this is going to help us see how those cams work, especially how those different shape cams have different effects on the movement of the follower.

So let's have a look at how we're going to do that.

So in order to test the effects of the different cams on the movement of the followers, we can make a prototype cam mechanism.

And a prototype is a word we use to describe a model or a mock up to test how something works.

So it's not a finished product, it's just a model to show how something works for us to test something.

So we can make a prototype cam using these materials and tools.

So you might need to pause to get these things ready.

You're going to need a split pin, some sticky tack, a pencil, make sure it's sharp, some recycled card, cereal boxes are really good for this.

That's the type of card that would work really well.

A lollipop stick, a glue stick, some thin card, and some thick corrugated card.

So the type of card you get on cardboard boxes.

So pause the video and get all of those things ready.

Okay, so before we start, let's just quickly test your knowledge of what a prototype was.

What is a prototype? Is it a drawing? Is it an idea? Is it a model or a mock-up? Or is it a finished product? Pause the video, have a think.

Well done if you said it was a model or a mock-up.

It is.

Exactly.

It's something to test a product before we make the final thing.

Okay, so I'm going to go through the steps of how we are going to make a prototype cam today, and then you can pause.

or go back and have a look at each step by itself as you make it.

So step number one, you're going to need the piece of recycled card with the old cereal box or something similar.

You need to cut out a fairly large square piece of that or rectangular piece of that.

That's gonna act as the base of your mechanism.

You're then going to need to cut out two rectangles from the thick card.

So from that corrugated card, the thick card, and we're going to place the lollipop stick down on that rectangular recycled card, the base.

You're not going to glue that, that's just going to sit there for a moment.

And then you're going to glue the two thick pieces of card either side of the lollipop stick.

So these are gonna act as the slides.

So the lollipop stick's going to be our follower, and those two thick pieces of card are going to be the slides.

So you need to make sure that they are very close to the lollipop stick but not touching.

We don't want them to stop that lollipop stick from moving when we come to activate the mechanism later on.

When you've done that, you're going to cut a thin strip of rectangular card out of the thin card, and this is gonna make a bridge.

So the bridge is going to be glued across the lollipop stick and the slides that we've made already, you can see in the picture, and it's gonna be glued at either end.

So we don't want to put glue all the way along.

It doesn't need to stick to the slides or the lollipop stick, it just needs to be glued to the background card.

So it makes like a bridge that crosses over the mechanism, and that's to keep that follower in place to stop it from falling out.

Step number three, we're going to need to pierce a hole.

So we're gonna need to do this safely.

So you're going to pierce a hole about three centimetres below that lollipop stick and the thick card that we've already stuck down.

And to do that safely, you need to put the sticky tack underneath your base card and use your sharp pencil to push a hole through the top of that card.

So roughly about three centimetres underneath the lollipop stick.

When you've done that, I want you to cut out some different cam shapes from the very thick card.

So you may even need to stick two pieces of thick card together if you need to make it a little bit thicker.

Start with the four shapes that we've already looked at.

So make yourself an eccentric cam, an ellipse cam, a snail cam, or a pear-shaped cam.

Make sure the holes are in the correct place.

We need to pierce holes in those cams as well.

You may need to look back to make sure you've got the hole in the right place.

And you're going to use your split pin to attach it through the hole in that base card to put the cam in position.

And the cam should be able to move around freely.

And we're going to look at how that will affect the follower in a moment.

So quick check before you get going.

Which part of the cam mechanism is the lollipop stick going to be? Which part is it going to be? The slide, the follower, the cam or the axle? Pause the video, have a think.

Okay, what do you think? Well done if you said the follower.

So the lollipop stick is going to act as the follower, the part of the mechanism that is going to move up and down in that linear motion.

Okay, so this is your task then, to have a look at those steps again and make your own cam prototype.

So you're going to make sure that you've got two strips of thick card either side of the lollipop stick.

Make sure that lollipop stick is not stuck down.

You're going to make a thin, rectangular strip of card to bridge across those parts that you've just done.

You're going to make a hole about three centimetres directly underneath the lollipop stick using our safe method.

And we are going to make a selection of cam discs out of the thick corrugated card to act as our cam disc.

So make a selection of different shapes that you could use in this task.

Pause the video, go back to the steps that you need and come back when you've finished.

Okay, how did you get on? Did you manage to make yourself a working prototype cam? Let's have a look at what you should have to make it work.

So you should have two strips of thick card either side of a lollipop stick.

The lollipop stick should not be stuck down.

You should have one strip of thin card that bridges across those thick strips and the lollipop stick.

You should have a hole that was made safely using your pencil and sticky tack about three centimetres underneath the lollipop stick.

And you should have a selection of thick card cams to test, and those are going to be attached using your split pin to the base card of the mechanism.

So some top tips to make this work.

If you hold the card at an angle, this will allow the lollipop stick to fall in the correct place.

So if you hold it slightly at an angle, not straight up and not flat on the table, it needs to be at a slight angle.

If you move the cams with your fingers quite slowly, that will allow the lollipop stick to follow the shape of the cams. So if you do it too quickly, the lollipop stick will not be able to follow that shape as easily.

You may need to make some adjustments to make this work properly.

So you may need to adjust your cam discs if they're too big, you might need to cut them down, and if they're not big enough, you might need to make them bigger.

You might need to change the position of the hole either in the cam or in the base of your mechanism.

You might need to make those tweaks to make it work properly.

But hopefully you manage to get yourself a working prototype.

So we're coming to the end of the lesson now.

So let's have a quick summary of what it is that we have been learning about today.

So we've been thinking about those cam mechanisms. And cams are mechanisms that usually convert rotary motion into linear motion.

And rotary motion is a movement that goes around in a circle.

We also looked at an oscillating motion.

So that's movement that goes back and forth along a path, but it's not in a straight line.

So we're thinking about the swings or maybe a pendulum on a clock that moves in that back and forth motion, but not in a straight line.

When it was in a straight line, that's when we refer to it as that reciprocating motion that repeated backwards and forwards motion like we see on a slider.

So the repeated motion is a reciprocating motion.

So that's it for today's learning.

I've had fun.

I hope you've had fun too.

And I hope you come back to join me for another lesson in this unit on making the cams: automata, where we can see these mechanisms actually put into practise in a real working product.

I hope to see you then, but goodbye for now.

Thank you for joining me today.