Sutton Coldfield, UK. Schaeffler has launched a new, compact bearing unit for locating bearing concepts for wind turbine main rotors. The double-row tapered roller bearing unit in an O-arrangement is greased, sealed and supplied pre-assembled. It is flanged onto the rotor via the inner ring and to the nacelle via the outer ring. The internal clearance is already preset, which significantly reduces logistics and installation costs. All the forces generated by the wind have a direct impact on the rotor bearings, and the rolling bearings are subjected to high dynamic loads and operating conditions. For the compact drive train design with a locating bearing concept, this means that all forces and torques have to be supported by a bearing. The tapered roller bearing unit is pre-drilled for flange mounting and enables loads to be supported safely and reliably thanks to the large contact angle and narrow axial guidance of the rotor. ASTRAIOS: simulation models and test runs Schaeffler's in-house ASTRAIOS large-size bearing test rig has played an important part in the development of the tapered roller bearing unit pre-drilled for flange mounting. Whereas calculations of the life of smaller rolling bearings are easy to apply to large bearings, this is not the case for other parameters such as kinematics and friction torques. That is why these simulations must be validated using test results. Measurements are fed back into the simulation models by means of a multi-stage process, and the models then calculate the loads and the kinematic behaviour of a large bearing. If any deformations are calculated, their impact on the functioning of the rolling bearing can now be simulated and validated on the test rig. Since commissioning in 2011, ASTRAIOS has provided key insights into characteristics that previously could not be tested, such as seals and lubrication systems, operation (influence of temperature and connecting screws) and roller speed. The resulting system expertise is used continuously to optimise components and technology to provide customers with an optimum solution. Here, Schaeffler increasingly relies on state-of-the-art heat treatment processes. This allows engineers at Schaeffler to develop new bearing systems for wind turbines in a very short period of time and to customise these to the customer's specific requirements. For more information, please contact Schaeffler UK's Communications & Marketing Department on info.uk@schaeffler.com.