It all started with a master's thesis at the Faculty of Mechanical and Materials Engineering at Aalen University, supervised by Professor Dr. Tillmann Körner. His team was supported by ACE Stoßdämpfer GmbH. In keeping with the company name and starting out as a specialist for industrial shock absorbers, the Langenfeld-based company, which has been part of the Stabilus Group since 2016, has long since developed into a full-service provider in the fields of vibration and damping technology, speed control and safety products. Vibration control technology is playing an increasingly important role, and not just in mechanical engineering. Eliminating vibrations means noise reduction, longer service life, protection of people and machines and, in the case of the university project, even more accurate measurement results.

When developing a test rig for sintered gears to determine fatigue strength curves, the initial aim was to stabilize a 2.5 t construction during operation. Professor Körner's students initially relied on steel springs. However, it soon became clear that the vibrations caused by the motors were so strong that the sensitive measuring electronics could not provide any usable data. As a result, contact was established with ACE: "On the one hand, we are familiar with ACE's products and services through demonstrations and events that the company regularly holds on site. On the other hand, machine elements from ACE are frequently used in designs at our university," reports the professor. According to him, work could then be continued quickly and efficiently.

Principle sketch of sintered gear test rig HS Aalen. © Aalen University

Test bench at Aalen University successfully decoupled from vibrations
During his many years of research and teaching, Professor Körner has always attached great importance to a high degree of personal responsibility. As a result, one student was responsible for the design and construction of the test bench, while another was responsible for the assembly and commissioning of the test bench. It is built on a slotted plate and adapter plates for motors and gearboxes with slotted holes for fastening. This means that the spacing and arrangement of the components are variable. Only the bearing covers in the two gearboxes have to be adapted in order to test different gears with different center distances. The test bench, measuring 1500 x 3000 x 1700 mm, consists of two motors and the two gearboxes. One motor sets the speed, the other serves as a load or generator, see diagram 1.

Gearbox II contains the sintered gears to be tested and gearbox I contains the reverse ratio. The slotted plate is connected to the base of the table at five points. As the test bench is to be mobile, the control cabinet is attached to the base of the table using aluminum profiles. Damping elements are required to isolate the vibrations generated by the test stand from the control cabinet and the sensitive electronics. Due to the heavy weight of the grooved plate and the test set-up, which weighs around 2,500 kg, it was clear that these also had to be quite resilient.

One of the five rubber-metal insulators from ACE under the test bench. © Aalen University

For the ACE specialists called in to help, selecting the right vibration dampers was easy. They advised the students to test the SFM-52012-75 rubber-metal isolators instead of the previously installed steel springs. Designers can also achieve this result in a different way. After positive experiences in the field of shock absorbers and gas springs, ACE now also offers an online program for calculating, selecting and ordering vibration dampers. In just a few steps, interested parties can independently find the ideal machine mount for more than 2/3 of all typical design cases. The calculation tool is intuitive to use and also offers optimum visualization of a wide range of possible applications. After entering a few key data, the program quickly calculates the machine's center of gravity and thus the individual load on the support points, even offering a choice between alternative vibration damping products for the best price-performance ratio.

There are several reasons for choosing machine feet from ACE
In this case, the rubber-metal isolators would also have been the right choice online. Designed in three different sizes, these machine feet are suitable for load ranges from 20 to 1,000 kg. The largest SFM types are now used due to the mass of the test stand. For a solution with additional safety tolerance, the prospective mechanical engineers use a total of five of these components to decouple the vibrations. The versatile, robust and maintenance-free rubber-metal isolators can be installed immediately and are characterized by high tear-off resistance. They are made of galvanized metal, with neoprene used as a damping material on the inside. In their design, care was taken to ensure that their longitudinal rigidity is two and a half times higher than the vertical rigidity and that their transverse rigidity is 75% of the vertical rigidity. These features underline the robustness and variability of ACE isolators. The SFM type components also have a natural frequency of only 8 Hz under maximum load. In practice, it has been shown that they not only withstand the loads, but also isolate more than 80% of the vibrations at the rated number of motors.

Users can independently calculate more than 2/3 of all typical design cases in the shortest possible time and display the ideally suited machine mounting. © ACE Shock absorber GmbH

Three years after commissioning, the test bench is still running perfectly. It is currently being used to test different materials for gear wheels as part of a doctoral thesis. In the meantime, however, the doctoral student is traveling to the automotive industry supplier mentioned at the beginning: "The test bench has provided us with many valuable insights in the assessment of materials and processes for sintered gears in high-performance engines in recent years, also due to the perfect vibration isolation. However, it has become apparent that the motors of the test stand are simply too loud for parallel teaching operations. As the mobility of the test bench is an important factor in the concept, we decided to outsource it for further research work," explains Professor Körner.

The rubber-metal isolators are just one part of ACE Stoßdämpfer GmbH's portfolio in the field of vibration control technology © ACE Shock absorber GmbH

The mobile facility has thus found a new home at a leading European manufacturer in the field of series production of high-strength aluminum sintered components. This cooperation is perfect as the students can apply their challenging academic work directly to practical projects, enabling the automotive specialist to further advance its efforts to reduce CO2 emissions with the latest scientific findings through additional weight reductions. In addition to their use in mechanical engineering and under measuring and test benches, as in the case described here, ACE's SFM types are mainly used in industrial applications to isolate the vibrations of marine engines, diesel generators or other devices for power generation.

From now on, users can also make the ideal selection for machine mounts quickly and easily on the ACE Stoßdämpfer GmbH homepage in the Calculations around the clock menu. Whether rigid or elastic, tear-proof or not, ACE has the right products and solutions for vibration damping and vibration isolation of machines. With the new, intuitive calculation tool, ACE offers optimum visualization of a wide range of possible applications.