Okay, welcome to today's lesson.

My name is Mr. Brown and I'll be going through the lesson with you today.

We're looking at two different types of linkages.

We're looking at parallel linkages and push-pull linkages today.

So we're talking about the differences, the similarities also, and thinking about linkages again in more detail.

Okay, what we're gonna start doing now, first of all, is we'll be looking at the lesson outcome.

Today's lesson outcome is to make parallel and push-pull linkages.

Obviously we'll go through all the different stages about what they are, and how they work, and then you are going to have the opportunity to actually make them as well.

The keywords today.

We've got four keywords.

The first one is parallel linkage.

So parallel linkage is a linkage that creates movement in the same direction using two pairs of levers.

We have input, something that goes into a system.

Output, something that comes out of a system and push-pull linkage.

And that's a linkage that uses short levers to push and pull three other levers in the same direction.

You'll be able to see and understand this as we go through the slide deck.

Here is the lesson outline.

So we've got a bit of a repeating theme here.

So first of all, we're going to be splitting the lesson into half and thinking about parallel linkages.

So we'll look at the key features of a parallel linkage and then you'll make a parallel linkage.

And then the second half of the lesson is also split into two where we're looking at the key features of a push-pull linkage, and then you'll be making push-pull linkage.

So there's four lesson cycles in all, and the first two we're looking at parallel linkages.

And the second two we're looking at push-pull linkages.

Obviously we're going to be starting with the first lesson cycle, and the first lesson cycle is looking at the key features of a parallel linkage.

The picture there shows you an example of a parallel linkage.

Now two pairs of levers work parallel or opposite to each other.

And if you have a look at that shape, it looks very similar to a parallelogram.

Also notice that we've got different pivots and we're going to be talking about those in a moment.

There we have one pair of parallel levers opposite each other, and there we have a second pair of parallel levers opposite each other.

Now this parallel linkage has got two fixed and two loose pivot points.

Now we can actually change those.

There are different types of parallel linkage, but we're just gonna look at this version for the moment.

You can notice that the fixed pivot points are the ones in red and the loose pivot points are the ones in green.

Check for understanding.

To create a movement within a parallel linkage, it must have either all loose pivots, fixed and loose pivots, or all fixed pivots? Which do you think? That's right.

It's gotta have fixed and loose pivots.

If it's all loose, then there's going to be some movement, but it's gonna be a bit all over the place, not really controlled.

If it's all fixed, then it's definitely not going to be moving whatsoever.

So to have a really good controlled movement, it needs to be fixed and also have loose pivots as well.

Now in a mechanisms we've got inputs and outputs.

So the input is the movement, which starts a mechanism, and the output is the movement that happens as a result of an input.

So if you have a look at that parallel linkage on the right there, you've got that the input is going in one direction, and the output is going in another direction.

And here is another parallel linkage with the opposite happening, as in an opposite movement, but the input is going in one direction, and the output is going in one direction.

So therefore we've always got the input in a parallel linkage creates output in the same direction.

Here's a gif which shows the movement of a parallel linkage, and you can see that it's got this side-to side type movement.

So the input always moves in the same direction as the output.

Check for understanding.

How does a parallel linkage move? Does it move side-to-side with the input and output being still? Does it move side-to-side with the input and output moving in the same direction? Or does it move side-to-side with the input and output moving in opposite directions? Which do you think is the correct answer? That's right, the movement is a side-to-side movement with the input and the output moving in the same direction.

Well done.

Now a real life use of a parallel linkage might be found in a toolbox, for example.

So the input would be the handles of a toolbox being pulled and they'll be pulled apart.

And the parallel linkages, the output of that means that it actually opens up the toolbox.

And if you have a look at where the parallel linkages are labelled there, you'll be able to see those are the metal bars that move.

And onto Task A.

So key features of a parallel linkage.

I want you to show that you understand the key features of a parallel linkage by labelling this parallel linkage with the correct pivot points.

Please can you make sure that you've added the loose pivots and you've labelled the loose pivots, you've labelled the fixed pivots, and of course you've also added the movement, so you've made sure that you've had some false arrows to show where the movement is within a parallel linkage.

Okay, I'm going to let you get on with that now and I look forward to giving you some feedback once you've completed.

Well done.

I'm sure you were able to label this accurately.

Here's an example of something that you, of some feedback.

So we've got the loose pivots, those two green ones at the top, and then we have the fixed pivots, which are those two red ones at the bottom.

And the movement, as you can see, goes side-to-side.

Remember that the input and the output of a parallel linkage is in the same direction.

Good.

Now we're on to learning cycle two.

So we're going to actually be making a parallel linkage now.

Here's the equipment that you will need, and this, the equipment that we've got is a pencil.

We need some sticky tack, some split pins, scissors, card from a cereal box and strips of card.

The card from a cereal box is to be used to make your prototype, 'cause these are just prototypes, we're just getting used to knowing how these linkages work.

The strips of card could be photocopied onto card or you could use any other strips of card, and we've, I've got three holes designed onto those strips of card but that doesn't mean we're gonna be using them all.

and you'll be able to see that as we go through the stages of the making.

So this is the equipment that you're going to be needing to make the linkage.

So a little I do, you do.

So just to make a hole in the paper or card, place a sticky tack under the card, use a pencil to make a pilot hole.

Now it's your turn to go ahead and to practise this.

So using the sticky tap, sticky tack, the pencil and the card, what I would like you to do is to practise making a pilot hole.

Well done.

Remember, if the linkage doesn't run smoothly when you've added the split pin, what you can actually do is just turn the split pin slightly and that will loosen the hole to make it just the right size.

You don't want the hole to be too big, otherwise the split pin might get lost, or fall through, and the movement might be too big, but you also don't want it to be too tight so that there's no rotation allowed for the split pin.

Okay, good.

Well done.

As I mentioned earlier, this is the stages of making of a parallel linkage.

So the first thing that we do is to prepare the holes carefully, and if you have a look on the strips of card that are there, there are four strips of card, and each one has got a hole in the top and the bottom.

We are not using the holes in the centre this time.

Second stage would be to go through and to create the loose pivots.

And here we've got two loose pivots at the top, and then we've also still got our spare lever at the bottom.

And this spare lever is where we attach the fixed pivot to the backing card, whether that be a cereal box or a bit of scrap card.

You can see there that the two bottom ones are the fixed pivots and the two top ones are the loose pivots.

Check for understanding.

If the pivot is turning, isn't turning freely in the pivot hole, what can you do? You can either make the hole bigger with a pair of scissors.

Make the hole bigger by twisting the split pin, or make the hole bigger with a bigger pencil.

Now in some ways, you are always going to be able to make the pivot hole bigger using all three, but which is going to be the most effective? Good.

It's the second option.

Twisting the split pin.

Twisting the split pin just allows that little bit of freedom, and make sure that the split pin isn't in too big a hole.

A pair of scissors and a bigger pencil can often make too big a hole for the pivot.

Onto Task B.

So Task B is to make the parallel linkage and there's some success criteria there for you.

So can you make sure that you've included two fixed pivots, two loose pivots, created the holes safely, and attach the parallel linkage to another piece of card? You'll need to do that remember, to make sure that you've got your fixed pivots in place so that it actually moves.

Hopefully by the end of completing this, you would've understood how the parallel linkage works and you'll have a moving parallel linkage.

Right, I'm going to let you get on with this now and I look forward to seeing you when you've finished.

So off you go.

Welcome back.

Hope you had a lot of fun making that, and that you understand how a parallel linkage works.

You should have in front of you a parallel linkage that moves side-to-side, and we've got the input going in one direction, the output goes in exactly the same direction.

Let's go through the success criteria so you can check against your project that you've completed.

So have you got two moving pivots? Have you got two fixed pivots? Have you created holes safely? And have you attached the parallel linkage to another piece of card? If you've done all those things, what you should have in front of you is a working parallel linkage.

Well done.

We're onto learning cycle three now.

Key features of a push-pull linkage.

So we've covered parallel linkages, and what their key features are, and how to make them.

And now we're looking into key features of push-pull linkages before then making a push-pull linkage.

So this is a push-pull linkage, and it's called push-pull because there are short levers at the bottom, and they are pushed and pulled to create movement.

It looks fairly similar to the parallel linkage, but we're going to be talking about the differences and why you would choose one maybe over the other.

There you can see the short levers.

And we've got the two fixed, and four this time, loose pivots.

So you can see it is slightly different, but because there are more pivots on this example.

Which do you think are push-pull linkages? There might be more than one correct answer.

So have a little look and decide which one you think are push-pull linkages.

Well done.

A and C are push-pull linkages.

C is just a rotated version of A.

And B, hopefully you recognise parallel linkage from the earlier learning cycles.

Now with the push-pull linkage, the input creates movement in the same way as the output.

And so of course there are real reasons why this is very similar to parallel linkage.

The input will be pushed, on this example, pushed from the left hand side and then the output pushes to the right hand side as well.

And there you've got a gif that actually shows you that inaction.

Another check for understanding.

What happens to the input and output movements on a push-pull linkage? So do they move in the opposite directions? Do they move apart or do they move in the same direction? What do you think? That's correct.

They move in the same direction.

Just like the parallel linkage.

Task C.

So we're looking at the key features of a push-pull linkage.

What I would like you to do is to look at this picture and label with the correct pivot points.

So label the correct loose pivots, label the fixed pivots, and then also I'd like you to label the movement in which direction do the parts move.

Remember, this one has got a fixed pivot in the centre of the two vertical levers.

I'm going to let you get on with this now and I look forward to giving you some feedback when you're finished.

Welcome back, well done.

We've got two fixed pivots, four loose pivots, as you can see from this feedback slide.

And we've got the movement moving from side-to-side.

Now you could, you might have put some false arrows and some movement arrows in the bottom as well with the short levers where they move side-to-side and that'd be absolutely fine, but you, so long as you've got the movements going in a side-to-side type motion.

We are now onto the last learning cycle today, which is taking our knowledge of the key features of push-pull linkage, and you're now going to be making a push-pull linkage.

Here's the equipment that you're going to need.

And the equipment is pretty much exactly the same as what we had for the parallel linkage.

We need a pencil, card from a cereal box, strips of card, sticky tack, split pins, and scissors.

Which two items from the equipment list do you need to create a hole for a pivot hole, pivot point? So is it that you need pencil and scissors? Scissors and sticky tack? Or sticky tack and pencil? Which combination is the best combination to make a pilot hole for a pivot point? Yes, correct, it's a sticky tack and pencil.

And we looked into how that actually works, didn't we earlier on in the lesson? And making sure that we've tried very carefully to use a sticky tack to make a an accurate pilot hole, but also a safer way of making a pilot hole.

Now with the push-pull linkage, we've got four card levers, but what we need is we need two short ones.

So we take one of those longer levers and we actually cut it in half as you can see from that diagram.

So just to create a short strip of card, use a pair of scissors and cut it in half.

Now the push-pull linkage, and this check for understanding, needs how many levers? Does it need? five long levers? Three long and two short? Or two long, and three short levers? Which do you think we need today? That's correct.

We need three long levers and we need two short levers.

Here's the stages of making a push-pull linkage.

So we prepare the holes carefully, and again, just like the parallel linkage, we're gonna use four long levers, and they're going to need a hole at the top and at the bottom, but some will need, or two will need, a hole in the centre as well.

We are gonna then create the loose pivots and put those together.

And remember to cut one linkage in half because that's going to be making our short levers, and then we use the fixed pivots to actually attach it to the card.

Now it's your turn.

So can you go and make the push-pull linkage including four, that's four loose pivots, two fixed pivots, creating the holes safely as ever, and attaching the push-pull linkage to another piece of card.

I'm going to let you get on with this practical activity.

I hope you're going to enjoy it, and I look forward to getting back to you and giving you some feedback once you've completed.

So off you go.

Go ahead, enjoy.

And I look forward to finding out about how successful your push-pull linkage is when you're finished.

Right, well done.

Let's go through the success criteria again.

Hopefully you included four loose pivots, two fixed pivots, you created holes safely and you attached the push-pull linkage to another piece of card.

Well done.

You should now have a push-pull linkage in front of you.

And let's go through the summary of today's lesson on parallel and push-pull linkages.

So a parallel linkage contains fixed pivots, and allows a movement backwards and forwards and side-to-side, and a push-pull linkage also does this and allows the input and output levers to move in the same direction.

Thank you ever so much for being with me today.

I hope you understand how parallel and push-pull linkages are similar but also different, and that you've got two working prototypes.

Look forward to working with you again.

In the meantime, thank you very much.