Uncrewed Systems Technology 048 | Kodiak Driver | 5G focus | Tiburon USV | Skypersonic Skycopter and Skyrover | CES 2023 | Limbach L 2400 DX and L 550 EFG | NXInnovation NX 100 Enviro | Solar power focus | Protegimus Protection

92 Dossier | Limbach L 2400 DX and L 550 EFG Forward of the coupling, between two ball bearings, sits a small steel gear with 18 angle-cut teeth; these are quieter than straight-cut gears, with negligible increases in axial loads and mechanical stresses. That gear engages with a 40-toothed larger gear, giving a reduction ratio of 2.22:1. “We use 6305 and 6205 standard bearings, and before the first bearing we have a sealing ring,” Simmerkuss says. “That creates a closed chamber for the transmission output, which has enough oil spilling around to keep the gears and bearings lubricated for the lifetime of the gearbox.” Ahead of the large driven gear is a dog clutch. The output shaft extends forward from there, and on it is fitted a series of springs to mitigate the impact and torsional stress on the gearbox caused by a prop strike for example. Further development of the gearbox is planned, particularly tests of different housing materials to identify where weight can be removed without losing too much ruggedness. Future plans Limbach plans to continue adopting new technologies for better torque density and hybridisation. In addition to the improvements set out here, it also plans to adapt ePropelled’s generators to the L 2400 series, to allow heavy UAV makers to get the high horsepower and electrical power they need. “We also want to offer a wider range of starter/generator options, such as 6 and 10 kW systems alongside the 7 kW unit, for each aircraft’s weight and power requirements,” Simmerkuss adds. Limbach is also developing a new ECU for its two-strokes to enable throttle servo control and data monitoring over CAN, which it says is a 12 V system but will also be available for 24 V using an integrated DC-DC converter to ensure the injectors still get 12 V. It will also have several self- programmable analogue and digital inputs and outputs for additional sensors and other electronic devices, as well as a smaller and lighter housing. The ECU, along with new engine mounts and vibration dampers for the L 275s and L 550s, is due to be available this summer. In a final disclosure, Limbach says improvements in its four-stroke and two-stroke exhaust systems are in the works. February/March 2023 | Uncrewed Systems Technology L 2400 DX Four-stroke Four-cylinder boxer 98 or 95 octane gasoline Turbocharged Air, water and oil-cooled Bore: 97 mm Stroke: 82 mm Displacement: 2424 cc Maximumpower (for take-off): 118 kW at 3000 rpm Maximum continuous power: 103 kW at 3000 rpm Maximum speed: 3100 rpm (maximum usable is 3000 rpm) Fuel consumption: 255 g/kWh at WOT L 550 EFG Two-stroke Four-cylinder boxer 90 octane gasoline Naturally aspirated Air-cooled Bore: 66 mm Stroke: 40 mm Displacement: 548 cc Maximumpower: 36.77 kW at 7000 rpm Some key suppliers L 2400 DX Spark plugs: NGK Fuel injectors: IWP Electric fuel pumps: Pierburg Crankshaft: in-house Crank pins: in-house Con rods: in-house Enginemanagement system: Trijekt (modified in-house) Starter: Magneton Generator: Brise Turbocharger: in-house L 550 EFG Spark plugs: Bosch Fuel injectors: Magneti Marelli Crankshaft: in-house Crank pins: in-house Con rods: in-house Main bearings: SKF Oil seals: various Enginemanagement system: Trijekt Generator: ePropelled Specifications A bearing sealing ring creates a closed chamber that has enough oil spilling around to keep the gears and bearings lubricated for their lifetimes