When testing wheelchairs, manufacturers play it safe for understandable reasons. That's why three mechanical engineers took no risks when they developed a drop test bench for wheelchairs on behalf of the renowned company Meyra - they rely on miniature shock absorbers from ACE to protect their design.

Arne Hankemeier, Julian Raimann and Tobias Ridder completed their training as state-certified technicians in the field of mechanical engineering as part of an in-service training course at the Felix-Fechenbach-Berufskolleg in Detmold. Volker Geise is responsible for pedagogical management there. As he assures us, the mechanical engineering technology course at the technical college places great emphasis on practical work. He therefore welcomed his three graduates' plan to work closely with MEYRA GmbH, part of the internationally active MEYRA Group from Kalldorf, as part of their final thesis. The company is one of the world's leading manufacturers of high-quality wheelchairs and has also made a name for itself as a supplier of rehabilitation aids. In line with its own claim "We move people", MEYRA employees support and motivate many people with disabilities around the world to achieve greater mobility and independence. MEYRA brings together the know-how and experience of individual core competencies in order to gain new perspectives and develop innovative solutions. The constant exchange with those affected and with experts from the fields of medicine, therapy and care, as well as the close cooperation with the specialist medical supply trade, enable the development of practice-oriented products.

This holistic and practice-oriented approach of MEYRA was very much in line with the learning group of the Felix-Fechenbachs-Berufskolleg, whereby the path to the next generation of technicians is not far anyway. This is because Tobias Ridder, one of the three junior employees, works as a design engineer in the wheelchair manufacturer's special production department. Together with Arne Hankemeier and Julian Raimann, he has developed a drop test stand for wheelchairs as his final project, which is intended to test the load-bearing capacity of new models in particular.


High load capacity required

This test device is designed in such a way that each test specimen is loaded with the maximum permissible weight and driven into the test stand. The respective wheelchair is then latched onto a gripper and lifted by means of pneumatics and dropped from a previously defined height after being unlatched. In order to dampen the force of the lifting device's impact plate and protect the structure, the three technicians had the idea of installing shock absorbers. After all, not only should the stability of the wheelchairs be proven, but the test device itself should also be stable and not have to be repaired after just a few cycles. Another argument in favor of the hydraulic damping elements was that they do not have any rebound effects thanks to their linear characteristics. This ensures that the already time-consuming drop test is not prolonged too much. "Thanks to a presentation by ACE Stoßdämpfer GmbH, which we were able to attend as part of our lessons, we knew that shock absorbers are not only better at solving the tasks intended for them in terms of their damping properties.they also help to make testing quieter than, for example, damping with steel springs or rubber buffers," recalls Arne Hankemeier. As potential cases can be displayed on the homepage www.ace-ace.de at any time and the corresponding products can also be ordered directly, the student team turned to ACE in Langenfeld. To their delight, the sales engineers not only confirmed the students' design data, but also provided them with free samples of four small shock absorbers. This has been ACE's practice for years, as the company has found that such support measures and cooperation with young academics and technical college students often result in innovative solutions and even new product series. Last but not least, both the wheelchair manufacturer MEYRA and ACE, as a supplier of all kinds of damping solutions, have the same goal: to provide customers with advice and support so that they can do as much as possible independently.


Hydraulic damping elements are problem solvers

After the team received the four MC25EUM mini shock absorbers from ACE, everything happened very quickly: the hydraulic components are predestined to be quickly integrated into existing constructions thanks to their compact design. Available in versions with and without a rolling diaphragm, the dampers optimize a wide range of machines by braking masses quickly and non-destructively. Customers can choose between adjustable and self-adjusting versions. In the Detmold case, self-adjusting types were used. The outer bodies of the dampers, which are manufactured from solid material, are filled with temperature-stable oil and also have an integrated fixed stop. The machine elements are also maintenance-free. The models used are suitable for energy absorption of 2.8 Nm/stroke with a stroke of 6 mm. The teamwork of the three vocational college graduates worked perfectly throughout the entire project. Tobias Ridder was responsible for the design, while Arne Hankemeier and Julian Raimann were responsible for the layout and documentation. The integration of the four ACE components was a minor exercise in the end, says Arne Hankemeier and draws this positive conclusion: "We were able to make the adjustment precisely using the fine thread and reliably hold it in the preset position using the lock nut. The dampers cushion the permissible load reliably, quietly and quickly and fulfill their purpose to the full extent. We have also had the positive experience that a large load can be slowed down almost silently and without any rebound in the smallest of spaces."