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12 Motor developer Plettenberg has designed a drive that is optimised with a propeller design to boost the performance of UAVs (writes Nick Flaherty). The design of the new motor, used in the Nova 15 and Nova 30 product lines, relies on vertical integration from the propeller to the controller to provide optimum efficiency. Working with MagCAD on the propeller, the designers at Plettenberg optimised the motor for specific propeller speeds. “The high level of vertical integration enables the possibility of optimal adaptation to customer requirements,” said Christoph Danders, an engineer at Plettenberg who worked on the project. “Thanks to the manual winding and the SwissDrones has teamed up with 3W International to offer a new rotary engine- based powerplant for the SDO-50-V2 intermeshing-rotor helicopter UAV as an alternative to the current gas turbine, which will remain an option (writes Peter Donaldson). The chosen powerplant is 3W International’s SP-180SRE. Behind the decision is a need to offer a version with greater endurance. Thanks to the rotary’s lower specific fuel consumption, the new version will be able to more than double the current endurance. SwissDrones’ CTO Lukas Obrist emphasised that the turbine- materials we chose, efficiency levels of up to 94% can be achieved with the system.” The first application for the Nova 15 series was a propeller pusher drive for a wing aircraft (UAV) with a large hollow shaft and a standardised propeller attachment to simplify the assembly of standard propellers. The standard motor supports propeller speeds of 2000 to 8000 rpm, while an enhanced S-version supports up to 11,000 rpm. The custom propeller is hand-built from a sheet of carbon composite, and provides a maximum standing thrust at 5000 rpm. This provides a flight speed of 34 m/s with a propeller efficiency of 74% with the Nova 15 motor. At 4000 rpm the powered variant remains a good option for short flights carrying larger payloads. He noted that the main development challenge centred on the design and integration of the cooling package for the engine in its new installation. The SP-180SRE has a water-cooled housing and an oil-cooled rotor. Turbine engines are cooled by the air that passes through them, so do not need separate cooling circuits and the extra heat exchangers and pipework associated with them. The transmission and the rest of the powertrain remain largely unchanged, although significant software adaptations flight speed is 27.5 m/s with the same efficiency. The first version of the 2.5 kg Nova 15 motor drive was air-cooled, and the airspeed of the UAV and design of the cooling system have a major influence on the continuous power output. Depending on the required speed and available power supply, a maximum output of up to 15.6 kW is possible, said Danders. A liquid-cooled version provides a more consistent power output that does not rely on airflow for cooling. The Nova 30 series, based on the same design, provides up to 30 kW with a weight up to 6.5 kg and lower propeller speeds ranging from 2500 to 5000 rpm for larger UAV designs carrying heavier payloads. have been made to take advantage of new safety options, Obrist added. Structural reinforcements have been incorporated to allow for the rotary’s greater weight, although its inherent smoothness is sufficiently turbine-like that no adaptation for extra vibration has been necessary, he explained. Despite the greater empty weight and smaller payload, the lower fuel consumption more than compensates, he said. The rotary currently runs on gasoline, but a jet-fuel-burning version will be offered at the next stage of development, Obrist said. The complete system will be supplied by 3W International. Motor marries to propeller Rotary option for ’copter Airborne vehicles Airborne vehicles October/November 2020 | Unmanned Systems Technology The Nova 15 works with an optimised propeller design to provide efficiencies of up to 94%