New Vulkan Integrated Shaft Coupling Design (ISC)

VULKAN Couplings, Herne, Germany, recently introduced a unique breakthrough design combination of the proven RATO- DS highly flexible coupling directly connected to a lightweight VULKAN Composite shaft. The high radial stiffness combined with the comparably low axial and bending stiffnesses of the RATO-DS makes it suitable to work not only as a torsional coupling but also as an integrated misalignment coupling when directly connected to an intermediate shaft. At the aft end of the intermediate shaft a torsionally stiff misalignment coupling creates the second bending flexible pivot point thus providing a true double cardanic design. This new combination consisting of RATO DS and intermediate shaft is called the VULKAN Integrated Shaft Coupling (ISC).

It was found that the angular deflection of the RATO-DS causes – even under high misalignment conditions – a rather low strain level compared to the torque load and thus only a low power loss level in the rubber element. Therefore no misalignment coupling is required between RATO-DS and the VULKAN shaft. The result is that the intermediate shaft can be directly connected to the inner ring of the RATO-DS coupling without an additional radial support bearing.

It was found that the angular deflection of the RATO-DS causes – even under high misalignment conditions – a rather low strain level compared to the torque load and thus only a low power loss level in the rubber element. Therefore no misalignment coupling is required between RATO-DS and the VULKAN shaft. The result is that the intermediate shaft can be directly connected to the inner ring of the RATO-DS coupling without an additional radial support bearing.

The allowable mass of the intermediate shaft is limited by the radial natural frequency of half of the shaft plus the inner part of the RATO DS. The design radial natural frequency is selected to not be less than 120% of the design rpm. In most cases a light weight VULKAN Composite shaft will be the preferred solution for the intermediate shaft. In order to get a double cardanic design the intermediate shaft is connected at the aft end to a VULKAN steel membrane or a METAFLEX coupling.

The advantages of the new ISC design over previous designs are a significant weight savings, a significant reduction in parts due to the elimination of the separate bearing and no periodic maintenance (lubrication) is required. Additionally this design breakthrough leads to reduced installation and alignment efforts. Moreover with the ISC design there is no noise transmission path over metallic or bearing parts between engine and gearbox. The ISC provides excellent sound isolation against structure borne noise due to the RATO- DS rubber element which leads to a better crew and passenger environment

The combination of the torsional resilience RATO-DS coupling combined with the torsional resilience of the VULKAN Composite shaft can be tuned in such a way that results in an optimized torsional system which in turn leads to a reduction of the vibratory torques and stresses in all parts of the drivetrain. Depending on the shaft speed the ISC design based on the RATO-DS coupling can be combined with VULKAN Composite shafts up to 7m (23 ft) in length. All RATO-DS coupling elements whether single row or dual couplings can be used for the ISC design.