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FEATURE


CLUTCHES, BRAKES & COUPLINGS


A SHIPSHAPE SOLUTION FOR YACHT DESIGN


When it began building a range of hybrid pleasure yachts, an Italian shipbuilder turned to Stromag for its 2in1 combinations of a clutch and flexible coupling


W


ith the introduction of low emission zones, developed to improve air quality by limiting the release of Nitrogen Oxide


(NOx) from diesel engines, shipbuilders are adopting hybrid diesel-electric propulsion


systems for new yacht designs. There are many benefits to the use of hybrid


yachts – including decreased levels of NOx emissions and silent running, with hybrid


propulsion systems also providing fuel efficiency and range, as well as generating additional power beyond the requirements of the propellor. To enable this, a clutch allows seamless


switching between diesel and electric power; while a flexible coupling is also needed, as marine powertrains are resiliently mounted to protect the hull from diesel engine vibrations. Consequently, the movement generated must be damped in the propulsion system to protect equipment. So when an Italian shipbuilder began building hybrid pleasure yachts and wanted to source a complete drivetrain, it turned to a global marine propulsion system OEM. A key aspect of the project, however, was selecting a suitable clutch/coupling combination for installation between the motor and diesel engine. The company therefore turned to Stromag.


THE SOLUTION With experience in providing power transmission solutions for ships of all shapes and sizes, Stromag had a solution already available. Its 2in1 combinations of a clutch and flexible coupling are specialised for marine applications, with a wide range of options available to meet varying powertrain specifications.


50 DESIGN SOLUTIONS APRIL 2023 Mustafa Metin, product specialist for flexible


couplings at Stromag, explained: “This project was interesting due to the fact that we were involved very early on in the prototyping phase. In fact, we had to propose several 2in1 combinations, as the motor shaft size hadn’t yet been defined by the OEM. They entrusted us to make a suitable selection and sized the motor shaft based on our 2in1.” The compact 2in1 developed for the yacht is


a combination of a PVN 43631 flexible coupling with a MWU 240-600 electromagnetic clutch. PVN couplings are ideal for dampening the torsional vibrations of diesel engines due to elastomer construction, while the MWU is designed specifically for switching power


sources in hybrid applications. In operation, the yacht initially runs on electric


power. When switchover to combustion power is required, the control system matches the speed of the diesel engine with the motor. Once synchronised, the MWU carries out a smooth engagement and changeover. This ensures no drop in cruising speed when switching between power sources. With the engagement of the 588 kW diesel engine, the motor can now be used as a generator to provide additional onboard power. Stromag carried out a comprehensive


torsional vibration analysis (TVA) to ensure the correct torsional rigidity for the flexible coupling. As a result, in all operating conditions, whether under engine or motor power, and even during misfiring, the PVN has the desired rigidity to protect the powertrain from potentially damaging resonances. Stromag delivered a complete solution for the


new yacht design within the project deadline. Metin explained: “The 2in1 is a perfect fit


for this application, backed by our extensive engineering analysis of all aspects of the propulsion system. Our ability to offer a combined clutch/coupling combination from a single source is unique and a big advantage for shipbuilders implementing hybrid drives in new yacht designs. The customer definitely thinks so – we’re currently undertaking an additional 2in1 powertrain project for another line for luxury yachts.”


Stromag


T: +49 2303 102239 www.stromag.com


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