ACE's low-frequency pneumatic leveling mounts isolate disturbing vibrations

Professor Wilhelm Hannibal and his students at South Westphalia's University of Applied Sciences have an ambitious goal: They want to optimize oil pumps to reduce fuel consumption of combustion engines. The way there is paved with numerous tests. One of the test facilities caused unwanted vibrations. PLM, low-frequency pneumatic leveling mounts, provided by ACE Stoßdämpfer GmbH, isolated the equipment successfully from the disturbance.

At the location in Iserlohn, Germany, the study program 'Automotive' offered by South Westphalia's University of Applied Sciences provides a broad-based, application-oriented, technical training for the automotive industry on a scientific basis. The curriculum for young academics is specifically geared to the automotive supply industry with courses and applications close to practice such as the development of energy-saving drive systems. According to Sebastian Schuette, research assistant of Professor Hannibal, an important key lies in the oil pump of the engine: "In the engine design of earlier times, oil pumps always worked under full load, today they are controlled aggregates. And if they can be used at a reduced flow rate, it is also possible to reduce their power consumption." In this special case, it was necessary to record oil pump characteristics and to compare different control strategies to get to the optimum control state. For this purpose the team of the Automotive study program built a test bench with a length of 2,500 mm, a width of 900 mm and a weight of 1,500 kg.

Vibrations transferred to another test stand in the same room
On the test set-up an electric motor drives the pumps at 300 to 7000 revolutions per minute. "We knew from the outset that this speed spectrum is sufficient to cause vibrations and that we had to counteract to get reasonable results," says Sebastian Schuette. As he explains, on the one hand the students carry out tests on this particular construction to analyze hydraulic, volumetric and mechanical efficiencies and to check and optimize the flow behavior as well as to avoid leakage and to reduce friction. On the other hand, the control technology is also tested to get answers to the question which is most effective? For this reason, the test stand had to be prepared against the vibrations and was placed on six rubber-metal isolators. Even though they caused a reduction, "our test stand had to perform even better," Schuette sums up the students' first experience and adds that the vibrations were sufficiently strong to influence another test station in the same room.

ACE supports students in many ways
ACE Stoßdämpfer GmbH is not only leading in the field of industrial and small shock absorbers, but has also gained an excellent reputation in vibration control within a few years. In addition, the company provides free training courses for companies and is also present at universities, supporting academics with hands-on demonstrations and guest lectures. For this reason, Sebastian Schuette turned to ACE's head of training, Joerg Brinkmann. "He told us about ACE's solutions to control vibrations." In addition to rubber-metal isolators, vibration-isolating pads and low-frequency pneumatic leveling mounts (PLM) belong to the portfolio. The latter should ultimately replace the solutions previously used by South Westphalia's University of Applied Sciences. However, before this happened, Joerg Brinkmann, together with his colleagues, Dieter Wohlschlegel, Engineering Manager at ACE, and technical consultant Gregor Jandt paid a visit to the academic team in Iserlohn to check the present situation. For this, they used a special company-owned measuring case and an external measuring sensor that was connected to a tablet PC. Based on the as-is state and the values determined, Dieter Wohlschlegel in a next step presented the dimensioning and lay out design for the pneumatic leveling mounts.

"Both test stands now work flawlessly"
PLM, the six low-frequency machine elements that were then installed under the test stand, enable all types of equipment to be isolated from undesirable vibrations and at the same time can be used for perfect leveling via the integrated valve. When used as a vibration absorber, the internal air chamber provides a significant isolating effect, starting at 5 Hz. The ratio of horizontal to vertical natural frequency is 1:1 and only 3.0 Hz in optimally loaded conditions. In addition to the use under test facilities, PLM are particularly suitable for providing excellent decoupling of disturbing vibrations even under superstructures with measuring systems. In addition, they also isolate, for example, high-speed presses or all kinds of production systems of vibrations. They are provided with a vulcanized threaded insert, whereby compressed air can be supplied to the air springs either via a standard tire valve or a pneumatic screw connection. Special connections are not necessary with these easily leveled, innovative elements. In the event that no level control valves are used, a regulating control unit can also be provided to regulate the pressure and the height of the connected parts. However, this was not necessary in Iserlohn to achieve the desired result. "Both test stands now work flawlessly. This will enable us to continue our work even better than before," says a satisfied Sebastian Schuette. Thus, an important step on the way to more energy-efficient motors has been taken for the team of Professor Wilhelm Hannibal at South Westphalia's University of Applied Sciences.