Hello there, my name is Mrs. Dhami.

Thank you for joining me for your design and technology lesson today.

Now the big question today is what are gears? We are going to be exploring this together.

We're going to be having a little look at some gears that you might find around daily life, be that inside the classroom or be that outside of the classroom.

So get your seatbelts on, let's get tracking.

So our outcome for today is, I can describe the function of gears using specific examples.

Our key words for today are gear, driver gear, driven gear, gear ratio, and rack and pinion.

Now I'm not gonna go through all of these now, I will go through them as we meet them throughout today's lesson.

But feel free to come back to this slide at any point.

We're gonna follow two learning cycles today.

First of all, we're gonna explore gears, and then we're going to move on to explain how gears can transfer motion.

So let's get going with exploring gears.

It will be really useful to recap these types of motion before we get going into our lesson.

So with a partner, with a friend, or tell me, what do each of these represent? Sorry, which types of motion do these represent? Come back to me when you've had a go.

Okay, so for A, hopefully you've got rotary, which is motion in a continuous circle, oscillating, for B, which is motion in the shape of an arc, linear for C, which is motion in a straight line, and D, reciprocating, which is motion either forwards and backwards or up and down.

Well done if you got those right.

So let's apply those types of motion to an actual product.

I want you to identify the motions when pedalling a bite and you've got the choice of rotary, oscillating, linear and reciprocating.

Come back to me when you've got an answer.

Okay, well done if you identified two, we've got rotary, with of course the wheels turning around and we have linear with the bike moving along the road in a straight line.

Well done if you got those right.

So let's start off with what is a gear? A gear, just like the diagram is a toothed wheel that normally connects to another gear.

Gears rotate to move, and they are usually used to change the direction, speed, or rotational force of a mechanism.

Take a little look at this GIF, How could you describe the motion of these gears? Pause the video.

Have a little chat with the person next to you and come back to me when you're ready.

So Aisha said, "They are going in opposite directions." She's absolutely right.

Jun says, "It is rotary motion." Again, he's absolutely right.

And lastly, Sofia said, "They are going at the same speed as each other." And again, she's totally right.

All three of those things that have been noticed are correct and hopefully you may have got all three or a couple of those.

So a simple gear train is when two gears are connected, just like the GIF that we saw on the previous slide.

They go in opposite directions to each other.

Let's have a quick check then.

Looking at these gears in the picture, which statements are true? A, they turn the same direction.

B, turn opposite directions.

C, turn at the same speed.

D, turn at different speeds.

Have a think.

Come back to me when you're ready.

Okay, well done if you noticed and found two things are true, they turn in opposite directions to each other and they turn at the same speed because they are the same size.

Well done if you got those correct.

Have a little look at the diagram.

I have two spanners here, but two different size banners.

If each span is turned at the same speed, which one will complete a full turn first? Have a little think.

Tell the person next to you.

Come back to me when you've got an answer.

Jacob says, "The smallest spanner as it has less distance to travel." He's absolutely right.

And it's the same with a gear.

The smaller the gear, the quicker it'll complete a rotation in comparison to the larger gear.

Now we often think the bigger the gear, the quicker something will go and it's actually the opposite.

The smaller the gear, the quicker it'll be able to complete a rotation in comparison to a larger one.

Different gears can have different names.

Now in this example, the large gear, we are going to call the driver gear 'cause that is going to provide our input motion.

Now that could be driven by hand, manually, by turning a handle or it could be driven by a motor.

The small gear in this example we would call the driven gear.

Now the driven gear provides the output motion and the driven gear is always driven by the driver gear.

Changing the size of gears can change the output speeds.

So let's have a little look at this example.

The driver gear on the left has 32 teeth, whereas the driven gear on the right has 16 teeth.

So the gear ratio, which again is another one of our keywords, is the comparison of teeth between two meshing gears, and this controls speed.

So the gear ratio is all to do with speed.

Let's have a little look at this in a bit more detail.

So in this example, the driver gear has 32 teeth and the driven gear has 16 teeth.

What do you notice about the gear ratio of this example? Jacob has an answer.

He says, "The driven gear has half the amount of teeth in comparison to the driver gear." But what does that mean? The driven gear completes two rotations in the time it takes the driver gear to complete one.

This means it moves double speed in comparison to the driver gear.

Let's have a little look at the maths behind it.

So my turn, the driver gear as we know, has 32 teeth, the driven gear has 16 teeth.

To work out the gear ratio, we have to divide the number of teeth of the driven gear by the number of teeth of the driver gear.

So that would be 16 divided by 32, which would give us a half.

That means the gear ratio is 1 per 2.

Your turn.

The driver gear has 32 teeth.

The driven gear has eight teeth.

Use my method to work that out.

Pause the video, come back to me when you've got an answer.

Okay, so hopefully you've had a bit of time.

We know the gear ratio is the number of teeth on the driven gear divided by the number of teeth on the driver gear.

In this instance, the gear ratio would be 8 divided by 32, which gives me a fraction of a quarter.

Therefore the gear ratio is 1 to 4.

So let's have a little look at what this means for us.

So in my example, the gear ratio came out as 1 to 2.

That means the driven gear turns twice as fast as the driver gear.

Now let's have a little look at your example.

The driver here stayed the same size, but the driven gear became smaller and your gear ratio came out as 1 to 4.

This means the driven gear turns four times as fast as the driver gear.

That was all by just making the driven gear smaller.

Andeep says, "Decreasing the size of the driven gear or increasing the size of the driver gear, increases the output speed of the driven gear." And you have just proved that using your gear ratios.

Now you may own or you may know somebody who owns a bike and you might have heard them talking about gears.

You might change the gears yourself if you own a bike.

Now bikes use a chain and sprocket system, where the gears, sprockets, are connected by a chain.

Take a little look at the bottom left hand picture.

It shows a variety of sized bike gears.

Now the chain is moved between those different size gears or sprockets to make different gear ratios and it changes the rotational force required.

Now this is important depending on what kind of terrain you're cycling on.

Let's look at this a little bit more closely.

So when you're going uphill on a bike, you usually use a lower gear, now that means if you look on the right hand side, the driver gear is small, that's your input gear and your driven gear, your output gear, is larger.

This means that the pedals are easier to turn, but you need to pedal more to create more rotations.

Therefore, the rotational force required is small and it makes it easier to go uphill.

Now the opposite is true for flat or downhill surfaces.

Let's take a look at the right to start with.

The driver gear, so the input gear is large, and the driven gear, the output gear is small.

This means you are using a higher gear, which means that it's harder to turn the pedals around, but the bike goes further with each pedal and less rotations.

So the rotational force required is larger, but because you're not going uphill, that is easier to do, therefore, you go a lot lot further.

Let's have a quick check in.

Which of these statements are false about a gear ratio? A, it affects the output speed of the gears.

B, they can be altered on a bike for different terrains.

And C, the larger the gear, the faster it rotates.

Which one is false? Have a think, come back to me when you're ready.

Fantastic, hopefully you identified that C is false.

The larger the gear, the faster it rotates, is false.

It's a common misconception.

If you think the smaller the gear, the quicker it can complete a full rotation in comparison to a large gear.

Well done if you identified the false one.

Have a little look at the GIF.

How could you describe the motion of these gears? Have a little think.

Come back to me when you're ready.

Aisha says, "The two big gears are going in the same direction as each other." A bit different to a few slides ago.

Sofia says, "The little gear in the middle is moving in the opposite direction to the larger gears." They're both correct.

The gear in the middle that Sofia has identified, we call the idler gear.

We're gonna go into a bit more detail on the next slide.

Have a little look at my diagram.

We've noticed the driver gear and the driven gear before, but now we have the idler gear in the middle.

So the driver gear turns the idler gear in the opposite direction, and you can see that with the arrows, the idler gear then turns the driven gear in the opposite direction to itself.

Again, notice the arrows.

This means that the driver and the driven gear rotate in the same direction.

And this is only because of the idler gear.

True or false? The role of the idler gear is to keep the driver and driven gear turning it in opposite directions to each other.

Have a little think based on what we've just learned.

Come back to me when you're ready.

Well done if you got false.

But why? The main role of an idler gear is to enable the driver and driven gear to turn in the same direction as each other.

Well done if you got that right.

Now I wonder whether you might recognise this piece of equipment.

It's one of my favourites in my workshop.

It's called a rolling mill, and it's either used to reduce the thickness of a piece of metal, or you can use it to roll a pattern into the surface of a piece of metal.

It's great for jewellery making.

Now if you notice I have put some little arrows on.

So the idler gear is actually the driver gear in this instance because you can see my hand there turning the idler gear.

So I've labelled the other gears as gear 1 and gear 2.

So the idler gear ensures gear 1 and gear 2 move in the same direction as each other.

This is because gear 1 and gear 2 are being used to change the difference between the rollers.

So if you've got a piece of metal, you have to change, increase the distance between the rollers, whereas if it's a thin piece of metal, you're going to decrease the distance between the rollers.

Therefore, it's really important that both gear 1 and gear 2 move in the same direction that can only be achieved with an idler gear.

So let's now apply that wonderful knowledge that you have just learned in our task.

Question one, how will increasing the size of the driven gear affect the speed of the output? And you can use this diagram to help you.

Number two, if the driver gear has 27 teeth and the driven gear has nine teeth, calculate the gear ratio.

That can be found a few slides ago.

Number three, what does this gear ratio tell you about the speed of the gears? What's the effect? And number four, what is the function of the idler gear in this diagram? Have a go, come back to me.

Good luck.

Let's take a look at your answers.

Number one, increasing the size of the driven gear will decrease the output speed of the driven gear, as it changes the gear ratio.

Take a note of that 'cause lots of people get that wrong and think it's the other way round.

Part two, gear ratio.

Now hopefully you remember the equation where we say the number of teeth on the driven gear divided by the number of teeth on the driver gear.

That gives us a fraction of 9 over 27, which we can then simplify to 1 over 3, which then gives our gear ratio as 1 to 3.

Part three.

What does this actually mean? This means that the output speed of the driven gear is three times quicker than that of the driver gear.

Quite impressive, really? Part four, the idler gear ensures that the driver gear and the driven gear turn in the same direction as each other, which is important for lots of different products.

Right, let's move on.

So the image below shows part of a bike gear system.

Making reference to gear ratio, I would like you to explain how bikes use gears differently to travel uphill and along flat surfaces.

Good luck, have a go.

Rejoin me when you're ready.

So let's have a little look at a model answer.

Gears make cycling easier by letting you adjust the gear ratio based on the terrain.

For starting out or climbing hills, use a low gear, which means a small front gear and a large rear gear.

This makes it easier to turn the pedals and push the bike uphill, but you won't go as far with each pedal.

For going fast on flat roads, ooh, that was difficult to say, for going fast on flat roads use a high gear, so a large front gear and a small rear gear.

This means the pedals are harder to push, but the bike moves further with each pedal turn, helping you gain speed.

By adjusting the gear ratio, you can cycle more efficiently and handle different terrains with less effort.

Hopefully you got something similar or on the lines to that, if you didn't, use this to adjust your answers.

Well done folks.

We've completed our first learning cycle where we have explored a variety of gears.

We're now gonna use that knowledge to explain how gears can transfer motion.

So keep all that knowledge at the top of your head, ready for the next part.

Let's get cracking.

Hopefully you've all seen and hopefully used one of these hand drills before.

You're now gonna watch a video of the hand drill being operated.

Whilst you watch it, I want you to think about how you could describe the motion of the gears that you can see.

Let's take a look.

Notice the large gear being turned by the hand and notice the two smaller gears being turned by the larger gear.

Have a little look and notice the difference in speeds between the large gear and the smaller gear.

What can you notice? Let's take a look at what we noticed.

Aisha says, "There are two small gears moving at a different angle to the large gear." Did you notice that? Sofia says, "The little gears are moving more quickly than the large gear." Hopefully you were able to see these things.

If not, have another little look at the video.

Now this diagram represents what you have just seen in the video.

So we have the driver gear at the bottom, which is the same gear that was being turned by hand.

And then the two smaller gears were the driven gears.

Now we turn, we turn, we call this a bevel gear.

So bevel gears transmit rotary motion through 90 degrees.

They are used in hand drills, just like what we've just seen in the video, and they're also used in food hand mixers.

Quick check-in.

Bevel gears transmit rotary motion through how many degrees, was it, 45, 90 or 180? Have a quick check.

Come back to me when you're ready.

Well done if you've got 90 degrees, they do, they transmit rotary motion through 90 degrees.

Have a little look at the video, the little GIF on your screen.

How could you describe the motion of what you can see? Have a chat with the person next to you or tell me, come back to me when you're ready.

So Aisha says, "There is a rotary gear," and she's absolutely right, can you see that turning around in a circle, "and it's producing linear motion." And again, she's right.

Notice that bit moving up.

That is your linear motion.

So my next question is, where is this mechanism found? And I'm pointing it out using the arrow and I've zoomed out on this little gear.

Turn to the person next to you.

Have a little think.

Come back to me when you're ready.

Sofia says, "This is a canal lock; it is filling the lock with water." And she's absolutely right.

This is a little video that I took myself in the pouring rain so that you could have a little look at some of these types of motion.

So let's have a little look at how canal locks work.

A canal lock is an example of what we call a rack and pinion mechanism.

It uses a gear to change the rotary motion to linear motion on a rack.

And let's have a little look at a diagram that's a nice zoom in of this.

You've got the gear at the top, which we call a pinion, and then you've got the rack at the bottom and you can see that very clearly on the canal lock.

It's used to open and close the gates on the canal lock to let the water through so that the boats can move through.

Let's test our knowledge.

A rack and pinion mechanism transfers rotary motion into which type of motion? Have a think.

Come back to me when you've got your answer.

Fantastic, well done if you've got the word linear, the pinion is the circular gear producing rotary motion, and this transfers into linear motion along the rack.

Now this is a GIF of one of the pillar drills in one of my workshops.

And as you can see, the handle is being turned and that table is moving up the rack.

Now you can't see the pinion, but the pinion is inside just where that handle is being turned.

And that is enabling the heavy metal table to move up the rack.

So pillar drills often use a rack and pinion mechanism.

Not all of them, but some of them do.

Have a little look next time you're in your workshop to see whether your pillar drill uses a rack and pinion mechanism.

Onto task B.

Now the image below shows a toy handheld whisk.

It's actually my children's, don't tell them I've nicked it.

So what I'd like you to do is, number one, I would like you to name the type of gear used in the whisk.

Number two, explain why this type of gear is suitable in a whisk.

And number three, name the type of motion created by this mechanism.

Good luck.

Have a go.

Join me back when you're ready.

So hopefully you recognise That it's a bevel gear used in the handheld whisk.

Number two, bevel gears transmit rotary motion through 90 degrees.

This means that the handle can be turned at a comfortable angle in comparison to the output of the movement in the whisk.

And then lastly, rotary motion, which is then transferred at a 90 angle into subsequent rotary motion again.

Well done if you got those right.

So the image shows a rack railway, rack railways allow trains to move up steep inclines.

What I'd like you to do is for question four, name the type of gear that is likely to be used.

Number five, sketch the gear.

And number six, describe how motion is transferred using these gears.

Good luck.

Have a go.

Join me back when you're ready.

Well done if you identified that it was a rack and pinion mechanism.

Now for part five, I asked you to draw the rack and pinion mechanism.

Extra points though if you managed to label the rack and the gear too.

Well done.

And then number six, it was to identify how the motion was transferred.

So the pinion is a circular gear on the train that rolls up or down the linear track on the steep incline to move the train up or down.

The pinion allows rotary motion to be converted into linear motion.

Well done if you managed to get those right.

So that brings our lesson to a close.

Well done with all your hard work today.

Let's summarise what we have found out.

A gear is a toothed wheel that rotates and normally connects to another.

Changing the size of gears can change speeds.

Output speeds can be increased or decreased by adjusting the gear ratio.

An idler gear allows the driver and driven gear to turn in the same direction.

Bevel gears transmit rotary motion through 90 degrees, and a rack and pinion uses a gear to change rotary motion to linear motion on a rack.

Well done folks.

Well done for all of your hard work.

Have a fab rest of your day and hopefully see you soon for another lesson.

Take good care, bye bye bye.