Sports scientists also use hydraulic machine elements in their designs. Particularly when analysing the speed force on certain training equipment. As high forces can occur in the end positions, the Institute of Sports Science at the University of Tübingen relies on adjustable industrial shock absorbers to protect man and machine.


For over 180 years, the Tübingen Sports Institute has been a permanent fixture in the German university landscape. More than 50 scientists now research and teach on various key topics in the areas of performance, health and education. The spectrum ranges from talent development and the design of sports competitions to school education and individualised health promotion. Department III, which focuses on biomechanics, movement and training science, is headed by Professor Dr Veit Wank. Among other things, his team deals with the analysis and optimisation of sporting movement sequences. In training science research, the focus is on the diagnosis of strength abilities in individual sports. In addition, talented athletes from athletics association squads and teams receive performance diagnostics support.



Test device for assessing movement technique and speed forces

Various training devices have been developed at the institute for years for this purpose. The so-called "training and testing device for the impact throw" was primarily designed for the javelin throw and handball. The impact throw may no longer be so familiar, but many participants in national youth games have already had the impact ball in their hands. In handball, the impact throw is the basic technique for all throws, and in athletics the term "straight throw" is used as a synonym and basis for the javelin throw. In both cases, athletes build up an arc tension for the maximum acceleration distance. Through the active use and the associated thrust of the rear pressure leg in the throwing phase, the hip on the throwing arm side is brought forwards, which pretensions the upper body. This process and the conscious sequential use of the shoulder, elbow and throwing hand optimises the acceleration of the throwing implement. This movement technique maximises the final speed of the throwing implement, i.e. the ball or javelin, or in this case the throwing sled. The simultaneous observation of movement poses and the positions of the throwers in the video and the corresponding values for sled position, sled speed and acceleration make it easy to assess the movement technique and physical abilities, in particular the thrower's speed. The corresponding training device is primarily used in Tübingen for testing purposes. Professor Wank and his team use it to check the speed strength values. The sports scientist explains: "For athletes who have been in the squad for a long time, this also allows us to check whether the training content of the past weeks and months was chosen correctly. Because the measurements on the test and training device generate high inertial forces again and again due to the throwing movements, we need suitable damping solutions for braking in the upper and lower end positions that allow the system to be used for a long time and at the same time provide the greatest possible protection for our test subjects."


Design engineer chooses flexible dampers for inclined plane

After Professor Wank had already had good experiences with solutions from ACE Stoßdämpfer GmbH for a test and training device for measuring the performance of the thigh muscles, he turned to the specialists for damping solutions of all kinds from Langenfeld during the design phase of the training and test device for the impact throw. "I researched the modified leg press for isometric and dynamic leg extension movements on the internet and in the ACE catalogue. In the end position, masses of 25 kilograms to 200 kilograms, which are accelerated at speeds of approx. 3 to 5 metres per second, have to be braked at impact speeds of approx. 0.5 metres per second. Even if the MA64150 damper we tested at the time does not technically manage this range, the deceleration works well empirically. In the case of the damping of the forces during the impact throw, I also phoned ACE's customer service to confirm this," reports Professor Wank. The structure of this test machine essentially consists of an inclined plane constructed using linear rails with a linearly guided load carriage. Either a spear handle or a throwing ball can be mounted on this. The aim is to maximise the acceleration of the sled either from a standing position or with an initial movement along the plane, as in a competition throw. The distance covered by the sled is 4.5 metres long. Shortly before reaching the highest point of the construction and when returning to the starting position, the accelerated sledge is slowed down by an industrial shock absorber and then hurtles back down the inclined plane. The special feature of the design in Tübingen is that the plane can be continuously adjusted between angles of 0 degrees and 35 degrees to suit the specific requirements of the individual athletes. For example, a flat throwing angle is required for handball, while up to 35 degrees is required for the javelin throw. Compared to other solutions such as steel springs or rubber dampers, the components used by ACE are significantly higher quality and more durable. An experience that the sports scientist shares in the interview: "As with the deceleration of the leg extension movements, the adjustable dampers also work well when decelerating the throwing movements. In our design, we have installed a second damper for the return movement of the load carriage. This is slightly oversized, but initially tried cheap solutions with a kind of door stopper did not work, hence the larger investment. Although this is considerable for our budget, it is so solid that I invested in it with safety aspects and responsibility towards the test subjects in mind. As it turns out, it was a good decision. We have only tested the settings a little and the components have worked without any major effort or problems since then. However, the dampers are not used very frequently by industry standards, as the test devices are only used for studies, which happens around two to three times a year for periods of one to three weeks."


Dampers permanently stable, linear rails not at first

The industrial shock absorbers used in Tübingen are part of ACE's MAGNUM series. Since its market launch in 2000, this has been regarded as the reference class for medium sizes in industrial shock absorber technology. These hydraulic machine elements absorb the forces of moving masses over the entire stroke in the shortest possible time and convert the kinetic energy into heat, which is dissipated to the outside environment. Designed for continuous use in industry, users benefit from robustness and durability thanks to a sophisticated sealing package, hardened guide bearings and an integrated fixed stop. Compact sizes and extended mass ranges compared to previous solutions give designers more leeway in terms of damper size and machine performance utilisation. A special feature of this series is the optional availability of self-adjusting or adjustable types with M33, M45 and M64 threads. Professor Wank and his team in Tübingen also make use of the adjustability on the front and bottom sides on the MA4575EUM dampers used for the throwing analyses. Due to the total sled weights to be moved between 1.7 kilograms and a maximum of 25 kilograms and acceleration speeds of up to 13 metres per second in the measurements on the training and test device for the impact throw, only adjustable types were considered. Looking back, the sports scientist and designer reports: "I relied on my instincts with regard to the possible adjustment values on the ACE shock absorbers and in the end I probably had a good hand with trial and error. In any case, we are happy with the solution. We never had any problems with the dampers, they were somewhere else entirely. With the throwing test device, we had to replace the initially installed and not exactly cheap linear rails with a very expensive version after just one trial. With the first rails, the balls came out of the bearings. They simply couldn't cope with the high speeds during the impact analysis. The new ones have been working ever since, although we mainly use loads of 1.7 kilograms to 5 kilograms for our analyses, so that everything can still be considered under the term high-speed force."

High energy absorption and integrated noise protection

In addition to the sealing technology with diaphragm reservoir, the solid body without a retaining ring is responsible for the stability of the shock absorbers described here, which prevents leaks and absorbs over 50 per cent more energy than other shock absorber designs. The fact that the MAGNUM types have an even more compact design than previous ACE models proves to be an advantage, especially for ever smaller machines in automation. With a stroke of 73.9 millimetres, these dampers are suitable for decelerating effective masses in the range between 70 kilograms and up to 15,000 kilograms, with the energy absorption for rebound-free and linear deceleration per stroke reaching a value of up to 1,300 Newton metres. In industrial applications, values of 146,000 newton metres per hour can be achieved in continuous operation, whereby this value can be increased even further with an oil tank for the purpose of heat dissipation of the fluids and almost doubled when using an oil circuit. A wide range of accessories and connection parts ensures simple integration into existing designs and a wide range of possible applications. For example, all of the MAGNUMs installed by Professor Wank in Tübingen are used with special impact heads made of polyurethane. This leads to noise reductions of up to 7 decibels during the intensive leg extension and throwing tests and, in combination with the damping properties that are gentle on man and machine, can be described as a great success, as can the overall design. Professor Wank sums up: "In our analyses, the time courses of carriage travel, carriage speed and acceleration are relevant. We are not interested in the deceleration process in terms of performance diagnostics, it just has to work, i.e. the energy has to be dissipated without causing damage to the device." This has worked well so far.


Predictable quality: ACE industrial shock absorbers of the MAGNUM type

The secret of the success of these industrial shock absorbers is hidden inside. Whether as self-adjusting or adjustable elements, whether made of steel or stainless steel, the components in this series are equipped with state-of-the-art damping technology. Equipped with a hardened guide bearing and an integrated fixed stop, they impress with their long service life even in the most difficult environments. An important advantage for design engineers is their high energy absorption in a compact design, whereby they are available with threads in sizes M33, M45 and M64 as well as with a wide range of connection parts and accessories, depending on the version.