Hydraulic Learning

The reason our kits are called SUPERCHARGED is because they come with loads of additional learning. I don’t want to just create kids that teach kids to follow instructions., they get enough of that already. Instead I want to give the kids a starting place from which they can springboard into loads of awesome learning so they can start their own journey of innovation, engineering and problem solving. The kit comes with 10 learning points, several of which have small spin off projects associated with them including plans to build a digger attachment and a problem solving challenge that will get your brain thinking and have your fine motor skills tested!

Project 1 – 4 Bar Linkage

Hydraulic Arm Kit - 4 bar linkage
What’s this all about then? Well the long pieces that allow the arm to move up and down in the Hydraulic arm kit are officially known a ‘Four Bar Linkage’. It’s a funny name but basically it means there are four sections which are all pinned together. If you hold one steady and move one of the other pieces, the ones opposite each other remain parallel IF they are the same length just like in this GIF below

The sections don’t have to be straight, just look at the ones in the kit, they have a kink in them to allow a greater range of movement. If you’ve already built the kit, try moving the arm up and down and watch what happens to the arms as the claw lifts up and down.

THE PROJECT – Make yourself a simple 4 bar linkage and explore what happens when you make bits longer or shorter

Get 4 split pins, or nails, or pencils – basically something to act as a pivot.

Then cut 4 straight pieces of card and pierce a hole in the end of each one.

Connect them together with the pivots, hold one part steady and articulate the others.


  • What happens? How does it move? Does it do what you expected?
  • Do the arms touch one another and do they prevent the arm moving as much as you thought?
  • What happens if one of the pieces is made longer or shorter?
  • What happens if you keep the length between the pivots the same but change the shape?


Ever played with an Angle-poise lamp? They use a combination of linkages, springs and stiff pivots to allow the lamp head to be positioned wherever you want it to be.

Vice grips have a 4 bar linkage that is adjustable using a screw that allows you to grip different sized objects.


Project 2 – Basic Gears

Gears are fascinating and somehow quite magical when they’re moving together. There are all kinds of different types of gear wheels but all of them have some form of teeth that mesh together. This means that when one of them rotates, the teeth will push on the teeth of the other gear and force it to rotate too.

In the case of the hydraulic arm kit, gears are used in a number of different places for different effects.

Project 3 – I Beam

You could make the legs of the kit strong by adding layers and layers of card to make it solid BUT this isn’t an efficient use of materials either physically or financially. Now, imagine a metal ruler, it’s really bendy BUT if you rotate it 90 degrees, you’ve effectively multiplied the thickness 15 times! If you had a machine it would still be possible to bend it but it’s significantly stronger.

Now imagine combining three of those thin, strong parts together and seam welding them ( or glueing them) together. That’s why the legs are so stiff and strong. For the same cross sectional area, an I-Beam is far and away stronger and stiffer than a solid bar. Enclosing the legs at either end mean that it’s even stiffer and stronger.

Also, bear in mind, that the card is made of thin layers of card, ones that would be floppy and wobbly if you flapped them in the air!

Project 4 – Hydraulics

Who doesn’t love Hydraulics?! From enormous cranes lifting stuff high into the sky to dumper trucks lifting up their load seemingly from no where – watching these pistons do their thing is fantastic! Do this, lift your hydraulic arm right up to the top then let go of the levers and watch it slowly return to its lower position – notice how it moves slowly and steadily downwards. The reason for this is the friction on the seals inside the pistons, and the increased pressure placed on the water as it passes though the tubing, this tries to fight against gravity but eventually gravity overcomes these forces pulling the arm gracefully down to rest!

In this kit our pistons are made using medicine syringes but without the needles. A piston is basically a tube with a small hole at one end and a plunger inside that can move up and down. The magic happens when you start to connect these pistons together with tubing. Then you can start to move, lift , twist, turn and manipulate objects.

So why are Hydraulics useful?

Well there are tons of reasons that hydraulics are fantastic , lets list them out below:

  • They are useful for moving energy or effort form one place to another

When someone is driving a car and they put their foot on the brake, what they are literally doing is pushing a piston which drives the hydraulic fluid through the tube into the brake caliper which pushes the brake discs against the brake discs. It’s quite long but an aeroplane is even longer!  A lot of the flaps on the wings are operated by hydraulic pistons as the forces are so great.

  • They can help convert a small input force into a much larger output force

The tubes are not filled with air they are filled with water. (In real life they use hydraulic fluid which doesn’t rot the pipes or evaporate like water can)Water is very nearly in-compressible – try it! get some water and squash in in your hands, it will squirt out everywhere! The same happens in the pistons but when you push one of them, the water can’t expand so instead it moves down through the tubing and pushes the plunger at the other end. The pressure is equal throughout the system but you can increase or decrease the force it creates by making the plungers bigger or smaller in diameter. There’s some clever maths behind this which you can explore if you would like below. Put simply, if you double the area of your output piston, you double the force but reduce the distance it travels.

  • Its really easy to see if the system is leaking

Because the system relies on fluid inside, if it’s leaking you’ll be able to find the source easily and just as easily repair it

  • Fewer moving parts there’s less to go wrong

With gears and pulleys and bearings etc there’s lots of different parts to potentially break. Hydraulic systems on the other hand are relatively simple with less to go wrong.

  • They can lift massively heavy items

Because the fluid is nearly in-compressible, it’s a great system for lifting very heavy items.

Here’s some images that explain what’s going on:

THE PROJECT – experiment with the parts to explore the difference between air filled and water filled systems

Firstly, connect up a tube and 2 syringes WITHOUT water inside. Try pushing the plunger and see what happens at the other end. Now, with some help, hold the second piston closed and squash the first piston – what happens? Can it still move? Did you notice anything about the temperature of the tubing or syringes?Have you ever tried pumping up a bicycle tyre? What happens to the pump? It gets warm doesn’t it! that’s because you’re doing work on the air, you’re adding energy to do it, compressing the air which forces the molecules closer together. This energy has to go somewhere and results in heat.

Now try the same thing with water in the tubes. Can you compress the liquid? If you keep pushing, you’re likely to spring a leak! That’s because the water is in-compressible and with the force you’re applying that delivers the same pressure to all parts of the system – if there’s a joint that’s not tight, the water will find it and it will burst open soaking you in the process!!

To explore more about Hydraulics there’s another kit a make that helps you build a bridge. You can find it here

Project 5 – Levers

Project 6 – Axle Support

Take a pencil and put it between you fingers. Now wobble it side to side and try with your other hand to prevent that from happening – you can’t! Take the same pencil and hold it in your fist, now try and wobble it – you can’t! You’ve effectively supported the pencil over 5 times the length. Now, you don’t need the material in between. It’s similar to the I-Beam, it’s a more efficient use of material to put the material where it’s needed, not where it’s not needed. Its the exact way that the main body of the Hydraulic arm kit is designed. The central pivot is supported by five 2mm thick sheets of card and consequently can’t wobble at all, only rotate or move up and down.


Project 7 – Grips

Have you heard of the phrase ‘butter fingers’? Well let’s assume that this robot arm was a proper piece of machinery, you wouldn’t want it dropping the items it was lifting accidentally would you? This is where grips or grippy material come in handy.

It comes down to two things, FRICTION and UNDERCUTS.

What’s a friction surface? Materials such as rubber, sand paper, carpet etc all cause much higher friction than much smoother surfaces like glass, silk, polished plastic etc.

But, you can lift something very slippery or shiny like glass for example if you either lift from the underside OR if you have something with a high friction surface.

Lifting from underneath works because all the weight of the object sits on top. So long as the object doesn’t topple to either side it will lift up just fine.

THE PROJECT – Explore different material properties using the jaws and a jar of jam

Now, experiment with different materials from around the house and attach hem onto the jaws and test them using something relatively heavy and shiny. I would suggest a jar of jam or something similar BUT make sure you put a towel down in case you drop the jam – you don’t want to be responsible for cleaning that up!!

How would you modify the design to make it more like a fork lift truck that that it could reach under objects to lift them up?


  • What material was the best and why?
  • Were these materials difficult to attach to the jaws? if so why?
  • Can you sort materials into two piles, high friction and low friction.? What do you notice about each of them?

Project 8 – Why Cardboard?

Literally my favourite material. Don’t get me wrong, I’ve worked with titanium, die cast aluminium, stainless steel and a multitude of different types of plastics BUT the very best way to get kids interested in engineering is cardboard.

Why? The obvious question, and yet there are so many obvious answers. It’s almost free! Every box and parcel delivered to your door, the cereal packets in your cupboards, the inside of your toilet rolls – they are literally giving you FREE materials to work with.

Not just that it’s cheap, it’s so incredibly versatile. I’ve created everything from gear systems, to full working cars, to masks, to ping pong ball launchers and visual models. Bend it one way it’s super curvy, bend it the other way it becomes very strong. Together with 6 eight year olds, we’ve made a bridge that all their parents were able to walk over!

The tools required to work with cardboard are cheap, highly accessible and easy to use and with those tools you can create almost anything.

Here’s a video I made a while ago showing the basics of cardboard…

Project 9  – The Tower of Hanoi

There’s loads of parts to this challenge. The first thing to do is to build yourself some boxes. Below you’ll find a link to a document to download and print. The document has plans to cut out and use to build the boxes AND it has the game sheet needed for the Tower of Hanoi Challenge. If you don’t have a printer, you can draw the template from scratch like I did and you can draw out the game sheet too.

Once you’ve got your boxes made, it’s time to play the game!

The challenge is to move the boxes from the pad at one end to the pad at the other end – sounds simple right? Well you need to do it in as few moves as possible AND you can only place a lower value box on top of a higher value box, oh and you can only move one box at a time. How many moves did you do it in?

Project 10- Digger Attachment

Hydraulic arm - digger attachment

I’ve spent the last 8 years working in R&D. You have to work fast, efficient and economically to get answers as soon as possible. It’s better to know that an idea won’t work sooner rather than wasting weeks, months or years in development. The single best way I’ve seen over the years is to make our design modular. How can you get 10 answers out of one test rig? How can you design something that is adaptable where neither concept is compromised?

This project is learning to work with someone else’s plans (Mine!). The design is already done BUT parts need to be made. It’s about learning to make decent quality parts, the right way out of card then assemble them correctly so that the device works.

If it doesn’t work the first time, that’s ok. Have another go! I’ve given the kids a starting point by supplying the linkages laser cut in the main kit. these are the hardest parts to make. I’ve also added an extra dowel in the kit to use for the pivot points.

Watch the video then download the plans.