Hi, welcome to today's lesson.

We're gonna be thinking all about reverse motion linkages today.

My name is Mr. Brown, and I'll be going through this activity and this lesson with you, and I hope you're gonna have a lot of fun.

We are going to be thinking about how to make reverse motion linkages, understanding what levers are, understanding what linkages are, some of the key vocabulary, and we'll have some practical side as well today.

Today's learning outcome.

Today's learning outcome, as I've already previously mentioned, is we're going to be making reverse motion linkages today.

We're also gonna be thinking about these keywords.

Now, we've got five keywords today, so a fair amount to get through, but I think it's really important that we understand all of these keywords, 'cause that will give us the knowledge to be able to help us make reverse motion linkages later on.

So, the first keyword.

Mechanism, set of moving parts that make something happen.

A lever.

And that is a mechanism that creates movement.

A pivot.

And a pivot is a point around which an object moves or rotates.

A linkage.

A linkage is a mechanism which connects levers together.

And a reverse motion linkage.

And that's a linkage that creates movement in opposite directions.

This will all become very, very clear as we go through the slide deck.

Here are the learning cycles for today.

So, we've got three learning cycles.

So the first one is key features of levers.

The second one is key features of reverse motion linkages, so we're narrowing it down just looking at one.

And then lastly, we're gonna be making a reverse motion linkage.

Obviously, we're gonna be starting with lesson cycle one, and lesson cycle one is about key features of levers.

"What is a lever?" is the first question to maybe be thinking about.

Well, a lever is a mechanism that helps us move things.

So that's come direct from the keywords, if you remember looking back at that earlier in the lesson.

What I would like you to do now is just take a few seconds just to go through and have a look at this seesaw.

A seesaw is the type of lever, but I want you to think about how does it actually work.

So, with your peers, with your friends, can you just take a few minutes, a couple of minutes, just actually thinking about how does a seesaw actually work? Okay, hope you've had some really good, rich discussion.

We're gonna go through now about how a seesaw actually works.

So let's first of all think about the main sections of a seesaw.

The main sections, we've got the lever, that's that rigid bar.

Now, rigid means hard to bend, so it's gonna be very solid, a solid bar that's hard to bend.

And that's what sits over a fulcrum, or we call it a pivot point.

So a pivot point, sometimes called a fulcrum, but for these purposes, we're gonna call it a pivot point, and the bar sits on top of the pivot point and then moves up and down.

So the pivot point, that allows the lever to move up and down, but it could also mean for it to rotate.

And in some ways, it's actually rotating on that one pivot point.

And as Sam says there on the screen, the children on either side create the effort, and that makes each other go up and down.

So one person sits on one side, and the seesaw goes down on that side, another person sits on the other side, and that allows the seesaw to go down that side, with that motion of going up and down.

Quick check for understanding.

So on a lever, the fulcrum is, the point at which the lever is weakest, the point the lever pivots on, or the point where force is applied to the lever? Which do you think? Okay, you're right, it's the point that the lever pivots on.

So again, it's not where it's weakest, it's not where the force is applied, but it's where the lever pivots.

Okay, you can see here, there's a GIF of a seesaw, and you can see the different sections of the seesaw, it's a very simplistic drawing.

What I'd like you to do is just have a think about how it works, and all the different parts of the lever.

So here we've got a black box, a purple arrow, and we've got a triangle underneath.

We're gonna go through each one and label 'em so we know the clear parts of of levers.

So, underneath, is a pivot point, and then on the left, we have a load, that's the object to be moved.

And then the purple arrow is the force that makes the lever work.

So if you imagine being on a seesaw, you've got one person who's the load, that's on the left hand side, the black box, if you like, and then a second person comes on and applies force, they put their own weight and gravitational pull onto that seesaw, and that moves the load up.

And then, of course, it swaps around and goes the other way.

Now, levers can be classed in three different ways, and it all depends upon what is in the centre of that lever.

So, the first one to look at is a class one lever, and that's got the fulcrum or the pivot point, that's actually going to be in the middle.

So for example, again, going through all the different labelling that we've already gone through, the pivot point at the middle, a load on the left and the effort on the right.

Now, a class two lever has the load in the middle.

And if I show you the diagram and go talk through it, you can start to think about a real life example as I'm talking.

So we've got the pivot point, this time on the left, the load is in the centre, the effort is underneath, lifting it up, and this allows you to lift a heavy load.

Now, a real life example, you certainly wouldn't be using a triangular pivot point necessarily here, but you might be using a round one, in a wheelbarrow for example.

So wheelbarrow is the pivot point, and that's on the left-hand side.

The load is in the middle of the wheelbarrow, in the actual barrow part, and then that's lifted by the handles.

A class three lever, this time, has the effort in the middle.

So remember, class one had the pivot in the middle, class two had the the load in the middle, and class three had the effort in the middle.

And here you can see the pivot point on the left, the load on the right, and the effort in the middle.

And if you have a look at that picture, you can probably decide that that's gonna be something similar to a pair of tweezers, or a pair of kitchen tongs where you are trying to pick something up.

Check for understanding now.

The force that we use to make the lever work, is it called the load, the effort, or the fulcrum? Have a think and decide which one you think is correct.

Okay, hopefully you got the answer right.

And the answer is effort.

The effort is the force that we use to make the lever work.

Well done.

Now we're onto Task A, and the examples that I've already used in some ways of the different levers that we've been looking at, the class one, the class two, the class three, there's some real life examples there.

So I haven't really spoken too much about scissors, but there's some levers there that work together, and I want you to start thinking about all of the different loads, efforts, and the pivots of where they would be on the levers.

So, two different parts to this task.

I want you to take the picture of the scissors, and I'd like you to label the scissors of where the pivot point is, where the load is, and where the effort is, and what type of lever actually it is.

Now when you're stating which lever, sorry, which type of lever, which class of lever you actually know it is, I'd like you to just write down or state why you know, or how you know.

So it could be, "I know that this is a class two lever because.

." for example.

Right, I'm gonna let you get on, and I'll see you soon.

Well done, everybody.

Let's go through the feedback for Task A.

As you can see from this picture, you can see where the effort is, that's where the two handles are being pushed together.

We have the pivot point in the centre, and then we have the load, which is in-between where the two blades are.

And this is a class one lever, and we know that because the pivot point is in the middle, and a pair of scissors is made up of two levers joined at the fulcrum, or pivot point.

Second one, the wheelbarrow, you can see here the pivot point is where the wheel is, the load is in the barrow, and the effort is used to lift up the wheelbarrow.

And this is a class two lever because the load is in the middle.

Lastly, the third one is a pair of tweezers.

Now, the pivot point is on the right-hand side, and this time the effort is in the centre, and the load is on the left-hand side, and this is a class three lever, because the effort is in the middle.

Onto learning cycle two.

So, key features of reverse motion linkages.

First thing we need to talk about is what are linkages.

So levers can be joined to create linkage mechanisms, and they use pivot points to join the levers together.

Now, there's different types of linkages which create different types of movements.

Check for understanding about what I've just said there.

So, true or false, linkages do not contain any levers.

Is that true or false? That's right, it's false.

They do contain levers, because a linkage needs levers to create movement.

Now, one type of linkage is called a reverse motion linkage, and we've been talking about that already.

So to talk about what a reverse motion linkage is, and if you look carefully at that diagram there, it will all become very clear about how this works, it has one fixed pivot, which we're gonna talk about a little bit in a moment, around which the linkage rotates.

And if you see that, that's the red one in the centre.

So that red one is a fixed pivot.

Now, a fixed pivot means that it's not going to be moving.

However, the movement, as you can see from those green arrows, is going to go left or right depending upon which way it's being pulled.

So as the top lever on the top-left is pulled, the bottom lever on the bottom right-hand side goes in the opposite direction.

That's why we call it a reverse motion linkage.

So we've got two loose pivots, and you can see there, those are the green circles there.

Now those, that is what allows the linkage to actually move.

If those were fixed, then there wouldn't be any movement.

In fact, if only one of them was fixed, then there wouldn't be any movement either.

Now, when we say fixed pivot, we do mean that it will still allow movement around it, but it's not going to move.

And I'll show you exactly how it moves in a moment.

Because before we go any further, I want to talk about inputs and outputs of mechanisms, 'cause we're gonna relate this to what you've already learned about reverse motion linkages.

So the input is a movement that starts a mechanism, and the output is what happens because of that input.

So, going back to the the seesaw, which is a very simple mechanism, the input is someone, is the force being applied, and the output is that the load is lifted.

So when we think about that with a reverse motion linkage, here is the input and the output.

So the input, on the top-left, is being pulled to the left, and the output, it's actually the lever on the bottom right-hand side, moves to the right.

So hopefully you can be able to see about input and output, and how that links to reverse motion linkages.

If you also have a look very carefully at the motion within this GIF, it's not also that it goes left and right, but it does also go up and down slightly as well.

So, have a look at this example.

We've got two fixed pivots and one loose pivot.

What do you think might actually happen? That's right, if we change the pivots, we then change the whole linkage itself.

Now, changing the pivots does change the type of movement, and if you see that there's two fixed pivots, there's not gonna be any movement.

You could argue that that bottom lever might fall down, and might still allow some movement, but there's no movement of the whole linkage, it might just be that one lever.

So the linkage itself is not going to be moving at all, because it will need those pivots to actually move.

Check for understanding.

A reverse motion linkage uses one fixed pivot and one loose pivot, one fixed pivot and two loose pivots, or two fixed pivots and two loose pivots? Have a think.

What do you think is the answer? Well done.

That's right.

It's got one fixed pivot and two loose pivots.

Sometimes we can add them together, but actually, usually, reverse motion linkage has one fixed pivot and two loose pivots.

Certainly in the examples that we've looked at, it does have that.

Here's an example of a reverse motion linkage in action.

So this is push chair, and how that folds up uses the same sorts of linkage that we're talking about today, a reverse motion linkage.

Task B.

Let's go through Task B.

So I want you to have a picture of a reverse motion linkage, and I would like you to label the correct pivot points, but also add a movement arrow.

So, adding the arrows to show where the movement is.

So, remember, we need to see the loose pivots, the fixed pivot, and the movement.

The picture there, hopefully, will give you some guidance as well about how to actually complete this.

But that's not just the only part of this task, the second part of the task is also that, in your own words, I'd like you to explain how the reverse motion linkage works.

And if you could use the words input and output, that will really add to the explanation.

Right, I'm gonna let you get on, and I look forward to coming back to you in a few minutes.

Well done, everybody.

Hopefully, your diagram looks something similar to this.

So we have the movement arrows, where it's going left and right, 'cause of course it could go either direction.

And the green whole circles are the loose pivots, and the red one is the fixed pivot.

Well done.

Now, as for an explanation, here is a very simple explanation about it, and yours might well look something similar to this.

Reverse motion linkages change the direction of the input so the output goes in the opposite direction.

The loose pivots move with the direction, and the fixed pivot forces the change of direction.

So, of course, we're thinking very carefully about how the fixed pivot is right in the centre there, and the loose pivots just rotate around it, but also helping the movement themselves as well.

Onto learning cycle three.

And we're going to be making a reverse motion linkage now.

Here are the materials you're going to need to make the linkage.

So, we've got a pencil, strips of card, card from a cereal box, scissors, split pin, and sticky tack.

We'll be talking about why we need sticky tack in a moment, but just a little discussion about the strips of card.

There is a worksheet where you can photocopy these onto card, or alternatively, you can make your own strips of card too.

The worksheet's quite useful, because we've already put holes there, or put circles where the holes for the pivots will be.

Some of them may be used, some of them might not be used, but all become clear later today.

Check for understanding.

Thinking about all the different materials and tools that we need for this activity, which of them will we not need? Is it scissors, a hacksaw, or split pins? That's correct.

It's hacksaw.

We're not gonna be needing a junior hacksaw for this activity today, but we will be using scissors, and we will be using split pins, or paper fasteners.

I told you we're going to be talking about why we needed sticky tack.

Well, this is just a really useful way of putting a pilot hole within a piece of card.

So you may notice that these strips of card, if we just try to push a hole through, let's say for example with a pencil, sometimes that can be quite difficult, because it can bend the card, it might not make an accurate pilot hole, and also it could actually hurt your fingertips if you're trying to do it in a difficult situation.

Using sticky tack is much easier.

If you put the sticky tack underneath the strip of card, and then push the pencil through the card into the sticky tack, first of all, it makes a nice, clear pilot hole, but also it's much easier to use, and also safer for you to use.

So whilst we're not going to be including the sticky tack within the actual linkage, we're using it as a tool to help us make a pilot hole.

Here are the stages of making the reverse motion linkage.

So the first one is to prepare the holes carefully, and we can use the sticky tack, as we've just spoken about.

And if you have a look at the three levers that are there, we've got two levers that have just got one hole, and then we've got one lever that's actually got three holes.

So do just check that you've got that correct.

We then add them together with the loose pivots.

So we've got two loose pivots that we've created using the split pins.

And then, lastly, we attach it to the card, and that creates the fixed pivot in the centre.

Check for understanding.

Which of these are gonna be used as pivots in this activity? Is it card, split pins, or scissors? That's correct.

We're gonna use split pins as our pivots.

And on to Task C, make the reverse motion linkage.

What I would like you to do now is just have a look at the success criteria, we are gonna have all the resources out on the materials.

And when you are making this, remember to include two loose pivots, one fixed pivot.

Remember to create the hole safely, using the sticky tack method that we talked about earlier, and then attach the linkage to another piece of card.

When we talk about another piece of card, what we are talking about here is just a piece of scrap card, so back of a cereal box card, that's quite a nice thickness, because it's not too thick, so you can get the pivot holes through quite easily.

And we just don't want to waste too many resources, because this is just a prototype, this is to allow you to get to use these materials and just explore how all of the different linkages work.

Okay, I'm gonna stop talking now.

I'd like you to get on with it, and I look forward to seeing what you've actually done.

Well done.

Well done, everybody.

I'm sure you have fun exploring, and making sure that you've been very careful whilst making your reverse motion linkage, and that you've got this reverse motion linkage working as your prototype.

Let's go through the success criteria once again.

So making sure that we've included two loose pivots, one fixed pivot, we've created the hole safely, and we've attached the linkage to another piece of card.

Let's go through the summary of the lesson.

So this lesson has been about levers and reverse motion linkages.

So we now know that levers are rigid bars that create movement by turning on a pivot point.

We know that linkages are systems that create movement using levers, and we've also worked out that reverse motion linkages use a fixed pivot to change the direction of the input so that the output goes the opposite way.

But quite a lot of key vocabulary today.

But all of this is really rich knowledge for you to understand linkages.

Right, well done.

Thank you for being with me today.

I hope you've enjoyed the lesson, and that you've learned a great deal, and that we've got all of those key words into our vocabulary.

Well done.

I look forward to working with you next time.