Hello there.

My name is Mrs. Dhami.

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

Now, the big question for today is what are levers and linkages? Now we're gonna explore this together.

We are going to look at lots of examples that you'll probably find around your own homes and some that you might find in schools as well.

So, hard hats on.

Let's get cracking.

Our outcome for today is we will be able to describe the function of levers and linkages using specific examples.

Our key keywords for today are fulcrum, which is a fixed pivot point, effort, which is our input force, load, our output force.

Mechanical advantage is when we make moving or lifting something easier, and I'll go into a bit more detail about that later.

And then linkages, which is a set of levers joined together to transfer and control motion.

Our lesson outline is going to follow two learning cycles today.

We're going to explore levers, and then we're going to go on to explore linkages.

So let's get started with exploring levers.

Now, I imagine lots of you have either opened a tin of paint or a tin of syrup using a screwdriver or using the end of a spoon like this.

Now what you might not realise is that what you are actually doing is you're creating a lever.

So let's find out what a lever is.

So a lever is a rigid, stiff bar that turns around a fulcrum.

levers have three changeable elements.

So let's identify them here.

The fulcrum, as we said, as one of our keywords, is a fixed pivot point to move around.

So that's the edge of the tin there.

The effort is the input force and the effort in this example is going through the handle of the screwdriver.

The load is the output force.

So the load in this example is the lid of the tin.

So a lever is a very simple way to gain a mechanical advantage.

Remember, mechanical advantage is one of our key words.

It's to make moving or lifting something easier.

You probably wouldn't get the lid of this tin off without using the screwdriver or the end of a spoon.

So the example of opening a tin of paint is actually an example of a class one lever.

Now we can define a class one lever as the fulcrum being positioned anywhere between the load and the effort.

Now we know that the tin of paint is obviously an example of this, but other examples include a seesaw and a pair of scissors.

Notice, have a little look at each of those.

Notice where that fulcrum is.

It's in between the load and effort on each one.

As we have just said, first class levers can provide a mechanical advantage by amplifying the force.

So they make a job easier to do time for a quick check-in.

The scissors use a first class lever mechanism.

On the picture, I would like you to label the fulcrum, the load, and the effort.

Think back to the tin of paint that might help you.

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

Fantastic, well done if you've got load for where the scissors are cutting fulcrum for that pivot point in between, and then effort in two places.

Now, I must just add a little bit here.

Scissors can also be called a double first class lever.

Due to the effort being exerted in two places, that's a little bit different to the tin where you just exerted it in one place to open the tin by putting the force on the handle of the screwdriver.

Whereas with a pair of scissors, you put the effort in two places.

So this is an example of a first class lever when it is at what we call equilibrium.

Now, that means that the load equals the effort and it balances.

So we can clearly see that there's four little penguins which are balancing the load of the large penguin.

Okay, so they're in what we call equilibrium.

So my question to you is, what could you change to make the little penguins lift the larger penguin without adding more little penguins? Have a little think.

Chat to the person next to you.

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

Okay, so Alex says, "You could move the position of the fulcrum closer to the large penguin to give more mechanical advantage to the smaller ones." I wonder if you worked that out with your partner and got the same answer as Alex.

Hopefully.

Now you may have had the opportunity at school to cut out some metal using tin snips.

We do this at our school, and we put the tin snips into a vice so that all the effort can be pushed down on that one handle of the tin snips.

However, some of my students still find this really, really difficult.

So my question to you is, what could you do to make this easier, but without increasing the effort? What do you think I do in my classroom? Have a little chat with the person next to you.

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

So Andeep is right.

Andeep says, "You could make that handle longer," and that is exactly what we do in our classroom.

We put some tubular metal onto the top handle to make the handle longer where we put the effort in.

And I'm gonna explain that a bit more on the next slide.

Making the handle longer increases what we call the arm length from the fulcrum.

Remember, fulcrum being that pivot point that increases the mechanical advantage.

This makes it easier to cut through the metal without having to increase the effort.

So if ever you are struggling with a pair of tin snips, get out a bit of tubular metal, pop it onto the handle, and increase your arm length.

Time for a check-in.

What does mechanical advantage mean? A, making something heavier, B, moving objects faster, C, making, moving, or lifting something easier, Or D, increasing the size of an object.

Have a think.

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

Well done if you got C.

Creating a mechanical advantage means we make moving or lifting something easier, just like that longer handle with the tin snips.

Let's take a look at class two levers.

Now have a little look at the diagram.

Take note.

The fulcrum is no longer in the middle in comparison to a class one lever, we have the load in the middle instead now.

So the definition of a class two lever is when the load is positioned anywhere between the fulcrum and the effort.

Example, products of these are the wheelbarrow and the nutcracker.

Now second class levers are common in tools and machines designed to reduce the effort needed for heavy lifting, such as the wheelbarrow, or squeezing such as the nutcracker.

Let's check in.

The wheelbarrow uses a second class lever mechanism.

On the picture, I would like you to label the fulcrum, load, and effort.

Have a go.

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

Fantastic if you've got A as the load.

That's whatever's going inside the wheelbarrow.

B, the effort where you are lifting up those handles.

And C, the fulcrum, which is the wheel, which is the pivot point.

Well done.

Onto class three levers.

Have a little look at the diagram.

Notice what is now in the middle.

Yes, you're right.

It is effort.

So class three levers, we can define them as the effort is positioned anywhere between the fulcrum and the load.

And some example products here are tweezers and tongs.

Now third class leavers are useful for tasks, sorry, tasks requiring control, accuracy, and precision.

So tweezers, you often want to use those to pluck tiny fine hairs out.

And tongs, you often want to avoid getting the tomato out of the salad.

So yes, they are for control, accuracy, and precision.

Okay, let's take a quick check-in, which diagram below is an example of a third class lever.

Think about where all the bits and bobs are positioned.

Have a think.

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

Well done if you manage to get B.

B is our third class lever, and the reason why is because the effort is in between the fulcrum and the load.

Task A then.

the picture below shows a pair of kitchen tongs.

Kitchen tongs use a lever mechanism.

So question one, which class lever does the kitchen tongs use and why? And then part two, I'd like you to label the picture to show the fulcrum, effort, and load.

Come back to me when you've had a good go.

Let's take a look at your answers.

Hopefully you identified that the kitchen tongs are an example of a third class lever.

This is because tongs require precision and accuracy.

Part two is labelling the fulcrum, effort, and load.

Hopefully you got load as A, fulcrum as B, and effort as C.

Well done if you got those correct.

The picture shows a tin of paint being opened with a flat head screwdriver.

The screwdriver acts as a lever.

So for part three, I'd like you to identify which class lever the screwdriver represents.

Part four, label fulcrum, effort, and load on a simple sketch of the lever.

And lastly, for part five, what could be changed to the screwdriver to increase the mechanical advantage? And I'd like you to sketch out your answer.

Good luck.

Have a go.

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

So let's take a little look at your answers.

Hopefully, for part three.

You identified that the flat head screwdriver is an example of a first class lever.

What a mouthful.

Then for part four, I wanted you to create a little sketch.

And on that sketch, I hope that you have the load as the lid to the painting, the fulcrum for the edge of the tin, and then obviously the effort coming from the handle of the screwdriver.

Then for part five, I asked you, how do you increase the mechanical advantage? And the answer here is that you can increase the arm length of the screwdriver, and that would be great if you've managed to show that on a little sketch and identified what the arm length is, as you can see on my picture on the bottom right, if you've got any of this slightly wrong, use a bit of time to adapt your sketches and well done if you got it right.

Onto our second learning cycle, which is exploring linkages.

Now just before we start linkages, it will be really useful to quickly recap the four different types of motion.

So have a little think chat to the person next to you.

What are all four of these motions called? Have a think.

Come back to me when you an answer.

So for A, hopefully you've got rotary, which is motion in a continuous circle.

For part B, hopefully you've got oscillating, which is motion going in the shape of an arc.

Part C, which is linear motion, in a straight line.

And then part D is reciprocating motion, which can either be forwards and backwards or up and down.

Well done if you got those right.

Time for a quick check, which image below represents oscillating motion.

Just think we've just defined what all the motions are.

What is oscillating motion? Image A is a fan, image B is a bike wheel, and image C is a playground swing.

Have a think.

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

Okay, well done if you've got the playground swing.

The playground swing, the motion is moving in the shape of an arc, which is that definition of oscillating.

onto linkages.

So what are linkages? Linkages are a set of levers joined together.

Now, linkages can change the direction of a force, and you can see the Hoberman sphere here.

You might have one of these getting smaller and getting larger.

And linkages can also change the magnitude, the size or amount of a force.

And they can also transform one type of motion into another motion.

And you'll see the gif on the right that is the metal guillotine in one of my workshops.

That is absolutely brilliant for cutting up pieces of metal, and those linkages there help to change the size of the force so that I can actually get through the metal.

We are now going to explore a variety of different linkages and we're gonna start with the lazy tong linkage.

What a great name.

So the lazy tong linkage is made up of interlinked arms that allow the product to contract, see the bottom left, and then consequently expand.

Now, the beauty of the lazy tong linkage is that there are no fixed pivots.

That means that the product is not anchored to a fixed point.

So the whole product can expand up, and the whole product can contract, and that is due to moving pivots, which are those green circles that you can see on the diagrams. Now the best product example of that has to be the folding clothes horse.

Now you might have one of these at home.

You can see it starts off as a nice compact product and quickly is lifted up into a much larger product in which you fold, can hang your clothes.

But it's great because when it's not in use, you can hide it away behind a sofa or somewhere where it's not going to be seen.

Onto the reverse motion linkage.

Now, first of all, have a little look at the diagram and note where the input and the output are.

Okay, so if the input is pulled, then the output is pushed.

So the input and output move in opposite directions to each other.

Let's explain that a little bit more.

Can you now find the pink circle? Now that is the fixed pivot.

That is a stationary point which the linkage rotates around.

Now find the green points, the green circles.

Got them? Yeah, they are the moving pivots.

So they change position as the linkage moves, and this enables the input and the output to move in their opposite directions.

A brilliant example of a reverse motion linkage is a foldable push chair.

And if you have a little look at the diagram beneath and the gif, you'll see that pushchair managing to fold into something compact.

So reverse motion linkages allow products to open and close, enabling products to be compact.

Quick check then.

What is false about a reverse motion linkage? Is it A, enables products to become compact, B, input and output move in opposite directions, or C, transfer rotary to linear motion? Remember, I'm looking for the false answer or answers.

Have a think.

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

Okay, well done if you found C was false.

A reverse motion linkage does not transfer rotary to linear motion.

Well then if you've got that one false.

Let's move on to the parallel motion linkage.

Now, in a parallel motion linkage, the input and output motion move in the same direction as each other.

Let's really let that sink in.

Let's look at the diagram.

Notice the input and the output at the bottom, and notice the arrow head is going in the same direction, input, output, same direction.

And a brilliant product to show that is a toolbox.

So you can see it on the left hand side, it's all closed, and then you pull to open it, and the direction that your hand is moving to open it is the same direction that the toolbox also opens.

Next we have the bell crank linkage.

So the input motion moves the output motion by 90 degrees.

Notice again the diagram.

Look at the arrows.

The input is going that way.

The output is going 90 degrees in comparison to the input.

Now, the best example for that are bicycle brakes.

Bicycle breaks are pressed on the handlebars, which are then translated 90 degrees onto the brake pads.

Time for a quick check then.

Which linkage in the diagrams below enable the input and output motions to move in the same direction as each other.

Let's take a look at the diagrams. Have a think, perhaps speak to the person next to you, come back to me when you've got an answer, and we'll have a little look.

Okay, well done if you manage to get C.

C is an example of a parallel motion linkage where the input and output motions both move in the same direction.

Well done if you got that right.

Next up is the crank and slider linkage.

Now, crank and slider linkages change rotary motion into reciprocating motion.

Let's just quickly recap, rotary being continuous motion in a circle and reciprocating being motion forwards and backwards or up and down.

So the crank is held on a fixed pivot.

Note that on the diagram.

The connecting rod, the green part, is held onto both the crank and the slider with moving pivots that allow the slider to be pushed along a path.

Now the best example of that is the reciprocating motion of a needle in a sewing machine.

Next step is the treadle linkage.

Now, the treadle linkage changes rotary motion, motion in a continuous circle, into oscillating motion.

And if you remember, oscillating was motion moving in the shape of an arc.

So the crank and treadle are held on separate fixed pivots.

The connecting rod is held onto both the crank and the treadle with the moving pivots.

And the best example of this are windscreen wipers on vehicles.

Time for a quick check.

Which of the following statements about a treadle linkage is false? So we have A, there are two fixed pivots, B, there is A connecting rod, C, the output motion produced is reciprocating, and D, the crank produces rotary motion.

Have a think.

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

Well done if you got C.

The output motion produced is not reciprocating.

If you remember, it is oscillating in the shape of an arc.

Well done if you got that right.

Onto the first part of task B.

What I'd like you to do is fill in this chart.

So for each one of the linkages, I would like you to, A, name the linkage, and B, I'd like you to tell me about the direction of the input and output motion.

Think really carefully about this.

Think of the examples that we have used.

Come back to me when you've had a go.

Let's take a look at your answers then.

The first one, the one that looks like a Z, the name of the linkage is reverse motion.

And the direction of the input and output? The input and output move in opposite directions to each other.

Next one is an example of parallel motion, and this is where the input and output move in the same direction as each other.

Next one is an example of the bell crank linkage.

And if you remember, that was like the brakes on a bike.

The output is 90 degrees to the input motion.

Next one is the crank and slider, and that converts rotary to reciprocating.

Reciprocating going forwards and backwards in this instance.

And then lastly, treadle.

That converts rotary to oscillating.

Remember oscillating being motion in the shape of an arc.

Well then if you got those correct.

Next part of the task.

We can see in this image, it is a foldable clothes horse.

Now, a foldable clothes horse, as we know, uses linkages to fold away when not in use.

So for part two, I would like you to tell me what type of linkage is used in a foldable clothes horse.

Then part three, why is this type of linkage suitable for a clothes horse? And then I'd like you to draw and label the linkage in two different states, those being contracted and expanded.

Try your best, have a go.

Join me back when you've got some answers.

Let's take a little look at your answers then.

Hopefully, you've identified that the clothes workhorse is an example of the lazy tong linkage.

Then, next part, the reason why it's good for the clothes horse is because it allows the clothes horse to expand into full height, and then fold away so that it can be stored when it is not in use.

Great for hiding something away.

Part four, I asked you to draw it contracted and expanded.

So you can see, bottom left, that is the lazy tong linkage contracted.

And then on the right, that is the lazy tong linkage expanded.

Hopefully, you got the change in size there and hopefully you have labelled those correctly.

Well done with all your hard work with that.

That brings us to the end of our lesson today.

Well done for all your hard work.

So let's summarise what we have found out.

So first of all, a lever is a very simple way to gain a mechanical advantage to make moving or lifting something easier.

Levers have three changeable elements on a bar, fulcrum, the pivot point to move around, effort, the input force, load, the output force.

And linkages are mechanisms that can change the magnitude, so the size or height of a force, change the direction of a force, or transform one type of motion into another motion.

Well done with all your hard work today.

I look forward to seeing you hopefully in another lesson.

Take good care.

Bye, bye, bye.