Strong Pneumatics

A little history

Even as early as the third century BC, Greek mathematician and inventor Ctesibius was experimenting with compressed air and the exciting possibilities it offers. He was the first person to develop machines operated using compressed air, such as a catapult that used compressed air to slingshot balls and spears. Heron of Alexandria created a very famous compressed air machine. It generated compressed air using an altar fire, causing the huge temple doors to open as though moved by an invisible hand.

The heat of the altar fire warmed the air in a pressure vessel which was half filled with water. When air is heated, it expands and air pressure increases. The expanding air needed more space, so it forced the water out of the pressure vessel and into a water container. The container grew heavier and sank down, opening the doors.

Pneumatic energy has been used in drive and control technology in industrial applications since the early 20th century. Pneumatic equipment is used in construction and agricultural machinery, for instance to drive hammers and drills. Pneumatic suction and pneumatic pressure are also used in conveyor technology, for instance in mills to suction grain and to transport flour. We even find pneumatics in the music industry, for instance in organ building. The keys of a pianola, a self-playing piano, are controlled pneumatically. Pneumatics has applications in the automotive industry, the textile and food industries, electrical engineering - even in space, as well as in many areas of our everyday lives.

What advantages do pneumatic machines have?

The advantages of pneumatic machines are...

Compressed air can be stored
Compressed air can be transported across long distances by pipes and tubes or in containers designed for this purpose
Compressed air is clean and does not create any contamination
Movements can be carried out quickly using compressed air
Pneumatic cylinders can be used to execute many different movements without complex mechanics
They are explosion-safe

We will explain these advantages and lots of other interesting information to you in the Strong Pneumatics building set. In addition, we will show you how pneumatic components function. We will explain the individual components step by step, and show you how they work. In addition, the building set includes lots of different example models that illustrate how pneumatics are used.

A pneumatic system consists of five sub-systems.

Compressed air generation
Compressed air distribution
Compressed air preparation
Generating movement using a pneumatic cylinder
Controlling the movement via valves

Compressed air can be generated using a compressor or air pump and stored in compressed air tanks and other pressure vessels.

The diaphragm pump as compressor

The fischertechnik compressor is a diaphragm pump. It provides the compressed air you need to control the individual models. In industrial applications, this is called a compressed air source.

Functionality:
A diaphragm pump consists of two chambers separated by a diaphragm, which is where the name of the component comes from. In one of the chambers, the elastic diaphragm is moved up and down by a piston and a tappet. The diaphragm is pulled back on the downward stroke, and air is suctioned in through the intake valve in the second chamber. The diaphragm pushes the air out of the pump head via the outlet valve on the piston's downward stroke.

Note:
The overpressure generated by the compressor is approx. 0.7 to 0.8 bar. The diaphragm pump is maintenance-free. It is important that you use a 9 V alkaline battery as the power supply for the compressor. Of course, the fischertechnik Battery Set is even better, since it has much more power than the 9 V block, lasts much longer, and can be recharged again and again.

Compressed air distribution
The blue hoses are used to transport the compressed air. They move the compressed air to where it is needed. You can install the air lines from the compressor to the valves and cylinders.

Compressed air preparation
To ensure that pneumatic components work correctly in industrial applications, the compressed air must be properly prepared. The air must be filtered, cooled, and dehumidified for this purpose, and any oil in the air must be removed. However, this is not required for the models in the Strong Pneumatics building set.

The diaphragm pump as a compressor

Your fischertechnik compressor is a diaphragm pump. It supplies you with the compressed air you need to control the individual models. In industry, this is referred to as the compressed air source.

How it works:
A diaphragm pump consists of two chambers separated by a diaphragm, hence the name of the component. In one, the elastic diaphragm is moved up and down by a piston and an eccentric. On the downstroke, the diaphragm is pulled back and air is drawn into the second chamber through the inlet valve. On the upward stroke of the piston, the diaphragm forces the air out of the pump head through the outlet valve.

Notice:
The overpressure generated by the compressor is approximately 0.7 to 0.8 bar. The diaphragm pump is maintenance-free. It is important that you use a 9 V alkaline battery as power supply for the compressor. Even better, of course, is the fischertechnik Accu Set, which has much more power than the 9 V block, lasts much longer and can be recharged again and again.

Compressed air distribution
The blue hoses are the means of transporting compressed air. They transport the compressed air to where it is needed. You can lay the air lines from the compressor to the valves and cylinders.

Compressed air preparation
In order for pneumatic components to function properly in industry, it is important that the compressed air is appropriately processed. For this purpose, the air must be filtered, cooled, dehumidified and, if present, the oil must be removed. However, this is not necessary with the models of the Strong Pneumatics modular system.

Pneumatic cylinders

We use pneumatic cylinders to generate movements using air. We generally differentiate between “single acting” and “dual acting” cylinders. There are two different sizes of pneumatic cylinders in the Strong Pneumatics building set, each with the same “dual acting” function.

The blue piston rod is movable and the cylinder is sealed. If you blow air into the cylinder through one of the two hose connections, the piston rod will move. If you blow on the other side, the piston will fall back. This means the piston can work actively in both directions. The connection you use to extend the piston rod is called connection A, and the connection for retracting it is called connection B. Since the piston rod of the cylinder can be retracted and extended using air, the cylinder is called a “dual-acting cylinder”. Complete an experiment to see this in practice.

Experiment:

Join a piece of the blue hose to connection A of a cylinder, then join it to the hose connection on the compressor, which is already connected to the battery holder. When you switch the compressor on, the piston rod will extend. Since it is a dual acting cylinder, the piston will retract once again when you join the hose to connection B and feed in compressed air once again using the compressor.
However, as noted above there are also “single acting cylinders”. In these cylinders, the piston rod can only move in one direction. A spring is often used to move the cylinder in the other direction.
Complete another experiment to show that you can compress air.

Experiment:

Now, extend the piston of the cylinder once again by joining your blue hose, which is connected to the compressor, with connection A once again and feeding in compressed air. After the piston rod has extended, switch the hose connection to B, and hold connection A closed using your finger.

Observe:

The piston rod can only be pressed in a short way. Do you know why?

Explanation:

Since you are holding air connection A closed with your finger, the air in the cylinder cannot escape. However, the air can be compressed. Because of this, you can push the piston rod in slightly. The more air is compressed, the greater the pressure in the cylinder will be. You can measure this pressure using a manometer. The unit for pressure is “bar” or “Pascal”. You can also calculate the amount of pressure. The formula for calculating pressure is:

Pressure = Force/area, or p = F/A

As this formula shows, the amount of pressure is dependent on how much force you exercise on the round surface in the cylinder.

As you can see from your experiments, it is fairly difficult to keep switching the hose connections around. Valves do this work for you, as we will explain in more detail in the next section.

Valves

In pneumatic systems, valves have the job of controlling the air flow to a pneumatic cylinder so that the cylinder either extends or retracts. A valve can be operated mechanically, electrically, pneumatically or manually.
The Strong Pneumatics building set contains manual valves. Each of these valves has four connections:

The centre connection is used to feed compressed air from the compressor. The left or right nozzles control the compressed air to the connection or connection of the cylinder. The connection on the bottom of the valve is used for venting. The air that returns from the cylinder escapes through this valve. Complete the following experiment to test out the function of the valve.

Experiment:

Connect the compressor, which is already joined to the battery holder, with one of your valves. To do so, take a piece of the blue hose and attach it to the hose connection of the compressor, and connection P on the valve. Leave the other connections open. Set the blue switch on the manual valve to the centre position and switch the compressor on.

Observe:

Nothing happens.

Explanation:

When you set the switch of the manual valve to the centre position, the connections are closed and the air cannot get through.

Next experiment:

Now, turn the switch on the valve to the right and switch the compressor back on again. As you do so, continue tapping the free nozzles A and B with your finger. Do the same once you have turned the valve switch to the left.

Observe:

The air will always flow through connection A when you turn the blue switch on the valve to the right, and through connection B when you turn the switch to the left.

Explanation:

The image helps you understand how air flows through the valve when you turn the switch in the different directions. The blue line is the compressed air flowing through the valve. The black lines show how the air that returns from the cylinder will flow.

The valve has four connections and three switching positions (centre – left – right). Because of this, the valve is called a 4/3 way valve in pneumatics.

Exhaust throttle

Have you ever stood on a garden hose in the yard? Or got a kink in your hose? If so, then you probably noticed that less water came out of the hose all of a sudden. But why is that? The kink in the hose means water has less space to flow. It is throttled, and moves more slowly. The same thing happens in pneumatics when the air in the transport medium, in our case the blue hose, is restricted and has less space to move through.

You might be asking yourself why we would want to do something like that?
Throttling the air allows us to carry out the different movements more slowly and in a more controlled manner.
Industrial pneumatic systems are generally operated with a pressure between 6 and 8 bar. This allows pneumatic cylinders to be extended very fast and with a large amount of power if needed. Often, a powerful movement is needed, but it needs to be slow and controlled. A movement that is too fast could endanger machine components, workpieces being handled, or even people.
The compressed air is throttled to move the cylinder more slowly. We allow less air to flow through a hose or line in a certain amount of time, by simply restricting the diameter of the line.

Experiment

Build the functional model and complete the following experiments:

Do not throttle the exhaust by only screwing the blue hose into the housing far enough so that it is not compressed. Observe how quickly the cylinder extends or retracts.
Now, throttle the exhaust bit by bit by screwing the blue screw in step by step. Continue to observe the cylinder. What do you notice?

As you can see, the exhaust throttle helps you adjust the extension or retraction speed of the cylinder.

Now, we want to observe what we just learned on some models we can build ourselves. In the real world, these would often be operated with pneumatic energy. To do so, let's build the models one by one and do one or two experiments on each one to better understand how everything works.

Scissors lift

Lift tables are used to help lift heavy loads. They are primarily used to load workpieces. Such platform lifts consist of a base frame that the load can be placed on top of. Scissors of the same length are attached to it. These scissors move an axis at their centre that is also attached to the base frame.

To correctly understand the structure of the scissors list, build the first model as described in the building instructions.

Scissors lift – task 1:

After you have connected the compressor and installed the hoses as described in the building instructions, turn the blue switch on the valve to the right. What happens? The scissors lift moves up. But why?
Since you connected the hoses in your model so that nozzle A of your valve feeds the compressed air to connection A of the cylinder, the piston of the cylinder extends. This extension pushes the centre axis of the lift table to the right, straightening the scissors and pushing them up.
You can move the platform lift back down by turning the valve on the left side and retracting the piston of the cylinder once again.

Scissors lift – task 2:

But what happens if the scissors lift has a bigger load to carry, such as a cup or a book? Can you still move the platform lift upward? Try to find out how much weight you can place on your platform lift so that it can still lift the weight straight up. Enter the values in the following table.

Scissors lift – task 3:

Do you know how the platform lift can lift even heavier weights? Think about how to increase the lifting capacity of this scissors lift.

Solution:

If the force of one cylinder is not sufficient to lift heavier loads, then add a second pneumatic cylinder.
Install the second cylinder in the platform lift as described in the building instructions and connect it according to the hose diagram shown there.
Repeat scissors lift task 2 with your new model, and analyse what has changed.

In the “Pneumatic cylinders” section, you learned that the effective force depends on the pressure and the area on which the pressure acts (round area in the cylinder). Since the pressure that the compressor generates is constant, we have to increase the size of the area on which the pressure acts. We do so by using two cylinders. This means that the pressure will be acting on twice the area (two round cylinder areas). This also doubles the force and thereby the weight that you can lift. This means we can generate more force through more area.

Clamping device

Do you have a vice at home? It is a great way to clamp parts that you want to work on. File, drill, or just press together. It's a very practical tool to have, although you do have to crank it for a while. As you can see, we could use a pneumatic solution.

Clamping device – task 1:

Develop and build your own pneumatic clamping device with one cylinder (without building instructions). Do you have an idea how it could work? If not, you can find our suggestion in the building instructions.
After you built the model, you probably switched on the compressor and turned the switch on the valve.

Switch to the right = clamp

Switch in centre position = hold clamped

Switch to the left = release clamp

If you have switched the compressor back off again, you can correctly clamp a workpiece in your pneumatic clamping device in task 2 (block 30).

Clamping device – task 2:

Compressor is switched off.

Turn the valve switch to the centre position
Insert the workpiece.
Switch on the compressor
Turn the valve switch to the right
Turn the valve switch to the centre position
Switch the compressor off

Now, your workpiece is pneumatically clamped for processing.

You might ask: “Why should I move the switch to the centre position?”
Every pneumatic connection and every line loses a little bit of air. In the centre position, the line to the compressor is disconnected and the compressed air loss from it is reduced.

To open the clamping device on the first model all the way, you would have to turn the compressor back on. This is time-consuming, don’t you think? In the first model, your compressor was connected directly to the centre connection of the manual valve without an air reservoir. In our next model, we will install two air reservoirs. This means that the compressed air for this model will not be fed directly from the compressor to the manual valve, but rather to the other cylinders. These cylinders are then filled with compressed air and store it.
Now, add two cylinders to your simple model as air reservoirs. If you don't know how exactly to add the air reservoirs to your model, use the building instructions.

After you have converted your model, insert your workpiece (block) into the clamping device. Turn the switch on the manual valve to the centre position. Switch the compressor on and watch how the pistons in the cylinder move upward while they fill with compressed air. If the compressor makes a constant humming noise, it has built up enough pressure and you can switch it back off.
Now comes the moment when your conversion pays off.

Clamping device – task 3:

The valve switch is in centre position, pressure accumulator is filled and the compressor is switched off.

Insert the workpiece
Turn the valve switch to the right
Turn the valve switch to the centre position --> workpiece is clamped
To release it, you simply have to turn the valve switch to the left

Observe:

Did you notice the difference from the first model? The cylinder is completely retracted during releasing, without switching the compressor on again. You can even clamp and release the workpiece a second time. Do you know why?

Explanation:

Your compressor can store additional air volume in the two cylinders as a reserve, then deliver it to the clamping cylinders as needed.
All of these topics and experiments have taught you a bit more about the world of pneumatics. As you can see, pneumatics is a very interesting and useful field. In the next section, you can try out the toy models in the Strong Pneumatics building set.

The power of compressed air