People started to use the first bearings, i.e. components that reduce friction, already in antiquity. And their development is still going on. Experts in tribology from the Faculty of Mechanical Engineering of the Brno University of Technology are working on modern hydrostatic bearings. They have figured out how to make bearings up to 20% more energy-efficient. The improved technology could be used in large machine tools, theatre turntables or the world's largest telescopes. The latter are to be studied by doctoral student Jan Foltýn, who is now leaving for Chile.

"In layman's terms, we can imagine a hydrostatic bearing as two pieces of iron or steel with grooves milled into them, into which oil is blown under pressure. The lubricant separates the surfaces, so they seem to levitate on the liquid," explains researcher Michal Michalec from the Institute of Machine and Industrial Design at the Faculty of Mechanical Engineering.

Today, hydrostatic bearings are used wherever precise and smooth movement is needed. "It can be a small lathe or a huge structure, such as theatre turntables or astronomical telescopes. Hydrostatic bearings feature very low friction, even at low speeds, and almost no or no wear when functioning properly. Thanks to this, the movement of the device is very smooth, which is essential, for example, in telescopes, because they contain very precise optical devices in which shocks and vibrations must be avoided. The machining centres appreciate their high rigidity, thanks to which we can achieve more precise machining," explains Michalec.

In the laboratory at the Faculty of Mechanical Engineering, there is a two-metre large experimental bearing, which the researchers constructed as a miniature of a much larger, twenty-metre bearing. "If you want to spin such a thing on a rolling mount, you need enormous forces. When using a hydrostatic bearing, significantly smaller forces are required, because the resistance is generated only in the liquid film and at low speeds the coefficient of friction can be up to a thousand times lower," adds Michalec.

This technology is used to build the world's largest hydrostatic bearings, such as those found at the European Southern Observatory in Chile. This array of telescopes and other facilities in remote parts of the Atacama Desert in South America includes four Very Large Telescopes (VLT) used for observation of the most distant objects in the Universe. Not far away, on Cerro Armazones, is ELT (Extremely Large Telescope) – the world's largest telescope.

When observing the Universe, the VLT rotates on hydrostatic bearings with a diameter of 20 metres. Jan Foltýn, a doctoral student of tribology, is now also going to spend 6 months in the observatory. "I will be involved in the engineering team that is responsible for the operation of the telescope's hydrostatic bearing. I am really curious about the experience because these are currently the largest bearings in the world. We only know the problems that may occur in connection with these bearing only from model situations. Now I'm going to see it directly," says Foltýn, who started to study this field due to his desire to design large machines. "I've always been attracted to mining equipment, machinery and telescopes. The VLT weighs hundreds of tonnes, so the bearing is extremely loaded," he adds.

The issue of such large bearings is even further complicated by the fact that it is virtually impossible to produce and assemble them in a single piece. "So we have to deal not only with the accuracy of their manufacturing but also with their setting. They must be in a perfect plane, with allowed deviation only in the order of a few hundredths millimetres. Another challenge is to ensure constant functionality of the bearings even when their load changes. A hydrostatic bearing must be able to react to this, which a conventional bearing cannot do. That is why we try to design it in a way that it can adapt to changes in load, for example. The solution involves sensors and hydraulic modifications that can respond to a new situation by changing the flow of lubricant or adjusting the thickness of the lubricating film," says Foltýn. Just to give you an idea: in the case of the currently built largest telescope in the world, the ELT, whose bearing will have a diameter of 50 metres, we are talking about a lubricating film thickness of around 50 micrometres.

Telescopes represent the icing on the cake, though. The development efforts of engineers from BUT can also be used in classic industrial companies. "In general, we focus on the improvement of these bearings in terms of efficiency, safety and accuracy. We have already been able to find out how to design the bearing to make it even more efficient based on a parametric study. We have found that if we change their shape, we can reduce energy consumption by about twenty per cent. And this is not a little saving," says Michalec, adding that they want to continue their research, ideally in cooperation with companies in the field. "We don't want to perform research without application, we want to see our technology used in practice," he concludes.