The hydraulic system: the basic idea

How does a hydraulic system work?

Pascal's principle

The basic idea of any hydraulic system is very simple: the pressure applied at a given point is transmitted with the same intensity to every point in that same point by means of an incompressible fluid (for example oil or water). The following diagram shows the simplest hydraulic system: it consists of two pistons and an oil pipe connecting them.

If we apply a downward force to one piston (the one on the left in this case), this force is transmitted to the second piston through the oil in the tube with the same intensity. Since the oil is incompressible, the downward force we apply to one piston is very efficient, so that almost all of the force produced is transmitted to the second piston through the oil in the tube.

Advantages of a hydraulic system

The nice thing about hydraulic systems is that it is very easy to multiply (or divide) the force applied in the system. In a hydraulic system, all we do is change the size of a piston and cylinder relative to each other, as shown in the following diagram:

The piston on the right has a surface area nine times greater than the piston on the left. If we apply downward force to the piston on the left, it will move 9 cm for every 1 cm that the piston on the right moves, and the force will be multiplied by 9 on the piston on the right.

To determine the multiplication factor, we need to know the size of the piston. Suppose the piston on the left is 2 cm in diameter (radius 1 cm), while the one on the right is 6 cm in diameter (radius 3 cm). The area of the two pistons is Pi * r2. Therefore the area of the piston on the left is 3.14, while the area of the one on the right is 28.26. As a result, we get that the piston on the right is 9 times larger than the piston on the left. This means that any force applied to the piston on the left will be nine times greater on the one on the right. So if we apply a downward force of 100 kg to the piston on the left, an upward force of 900 kg will appear on the piston on the right. The only drawback is that we will have to lower the piston on the left 9 cm to raise the piston on the right 1 cm.

Example of hydraulic system

Car brakes are a good example of a basic piston driven by a hydraulic system. When you press the brake pedal, you are pushing the piston into the master brake cylinder (which is responsible for providing pressure to the two brake circuits in the car). The pressure exerted on this piston, acting on the fluid, is transmitted to four other pistons (one on each wheel) that operate the brakes to stop the car by pressing the brake pads against the brake rotor.

In most hydraulic systems, hydraulic cylinders and pistons are connected through valves to a pump that delivers oil at very high pressure.

Source: howstuffworks.com

What do we mean by hydraulics?

What do we mean by hydraulics?

It is the application of fluid mechanics in engineering to build devices that work with liquids (usually water or oil). Hydraulics solves problems such as the flow of fluids through open conduits or channels and the design of reservoirs, pumps and turbines. Its foundation is Pascal's principle , which states that the pressure applied at one point in a fluid is transmitted with the same intensity to each point in the same. Blaise Pascal, philosopher and scientist, formulated in 1647 the principle that bears his name, with very important applications in hydraulics.

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21 comments

    1. Hello Victor,

      Thank you for your comment. We are glad to know that you found the blog helpful! We hope that other people will find the content of our blog useful, just like you.
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  1. This information has been very, very useful to me. I really need someone to explain it so clearly! Thanks! 🙂

  2. Hello, I want to know about the comfort of the hydraulic lift. I have been told that the start is more abrupt than one with the motor up.

  3. Bernoulli's principle is widely used in underground mining, especially in muddy terrain, either to evacuate stagnant water or extract gold. In Colombian mining in the northern area of Antioquia, this principle is known as "elevator."

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