Lubrication-free and maintenance-free bearing technology in wing model for flow measurements

The wing model of RWTH-Aachen uses corrosion-free iglidur plastic plain bearings.

This wing model is used for research work in the field of "Flow Influence and Flow-Structure Interaction" at the Institute of Aeronautics and Astronautics at RWTH Aachen University in order to carry out measurements of the wake vortices of airfoils. A list of requirements has been defined for the bearing arrangements used here: they should be small, low-vibration and low-clearance, permanently maintenance-free and cost-effective, among other things. Today, iglidur plain bearings are sometimes used here.

What was needed: iglidur plain bearing technology
Requirements: As the flow tests are carried out with water as the medium, the bearing technology should not be susceptible to corrosion. It also had to be small, operate maintenance-free over a long period of time, be insensitive to contamination, be clearance-free and low-vibration, generate hardly any heat and be cost-effective at the same time.
Industry: Aerospace, aviation
Success for the customer: By using plastic plain bearings, it was possible to keep the manufacturing costs of the individual production low. The plain bearing met the requirements for low clearance, low vibration and moderate heat generation. Organic materials are also non-corrosive.

Problem

Within the framework of the DFG Collaborative Research Centre 401 "Flow Influence and Flow-Structure Interaction on Airfoils", measurements of the wake vortex of airfoils, among other things, are carried out at the Institute of Aeronautics and Astronautics at RWTH Aachen University. A so-called reference wing (half span 675 mm, solid construction, material: X42Cr13) serves as the measurement object. It was intended to convert this half-wing model as part of research work. The aim was to investigate the wake vortex of an airfoil with the help of this new application in the in-house water circulation channel and in the towing channel of the DST in Duisburg. If successful, it would offer economic and safety benefits for civil aviation in practice. One focus of the design was the development of a transmission gearbox. It was necessary to be able to use the bearing of this assembly especially for use in the water circulation channel without showing signs of corrosion. But there were a number of other requirements for the bearings. It should be as small as possible in order to influence the flows as little as possible, work without maintenance over a long period of time (no corrosion, insensitive to dust and dirt), be as clearance-free and vibration-free as possible, have only moderate heat generation and be cost-effective.

Solution

According to theoretical methods, tests with various transmission gears and iglidur polymer bearings were carried out during the one-year project to determine the most suitable solution for the task. A toothed belt drive in combination with plain bearings was selected. The system is driven by a shaft-hollow shaft combination, which is connected to the model in the wing root by a large sized plain bearing (floating bearing) and in the wing tip by shell-shaped plain bearings (fixed bearing). In addition to the toothed belt pulleys, there are two pulleys on the shaft that are supported axially against the plain bearings, which in turn are secured against axial slippage by the clamping plate located between the belts. The clamping plate is also intended to maintain the wing stability and apply the pretension of the toothed belt. By using plastic plain bearings, it was possible to keep the manufacturing costs of the individual production low. The plain bearing met the requirements for low clearance, low vibration and moderate heat generation. Organic materials are also non-corrosive.