Unmanned Systems Technology 027 l Hummingbird XRP l Gimbals l UAVs insight l AUVSI report part 2 l O’Neill Power Systems NorEaster l Kratos Defense ATMA l Performance Monitoring l Kongsberg Maritime Sounder

70 August/September 2019 | Unmanned Systems Technology NorEaster helicopter engine Radial eight-cylinder, four-stroke Naturally aspirated Carburetted Weight: 91 kg Size: 92 x 92 x 30.5 cm Maximum power output: 100 hp Operating power output: 80 hp Maximum torque: 950 Nm (700 lb-ft) Operating torque: 760 Nm (560 lb-ft) Bore: 6.826 cm Stroke: 5.588 cm Displacement (per cylinder): 205 cc Total displacement: 1640 cc Compression ratio, 8.5 to 1 Compatible fuel types: petrol Operating speed: 750 rpm The NorEaster’s cam case comprises seven main components. An eight- sided cam housing forms the main structural block, with the inner side being cylindrical and featuring a rim running around the middle. The cam housing is CNC-machined from an aluminium billet. While no coatings are currently used, future versions might be anodised for corrosion resistance. Piston rod apertures are then drilled radially inward at the centre of each of its eight faces. Next, two circular guide plates are installed inside the cam housing. These are also CNC-machined aluminium with potential for anodising, and each plate is fastened to one side of the cam housing’s inner rim, with 32 M25 fasteners. Eight slots are cut axially into the guide plate to the same length as the piston stroke, with a central aperture for the output shafts and main bearings. Sixteen additional holes are cut into the guide plate for cooling and reduced weight. The engine has a pair of four- lobe (38 cm at maximum diameter) drive cams machined from plates of hardened steel and coated using a proprietary method and material, with one over each guide plate. The concentrically arranged output shafts are machined separately from hardened steel and welded on afterwards. It also has four main ball bearings, two on each shaft – two in the space between the output shafts, and two between the shafts and housing covers to hold the drive cams in place. A tool steel valve cam for driving the intake and exhaust valves is bolted using six fasteners atop the upper drive cam, around the wider output shaft. After the cam case’s sides are ground to accept the pistons and cylinders, eight COTS aluminium cylinders with Nikasil inner coatings (cylinder heads machined in-house, also from aluminium) are fastened to each of the eight sides, using four M10 fasteners each. The pistons are also machined from aluminium, with three rings about the piston head. The top two are compression rings, with an oiling ring underneath. A piston rod 5 cm long extends from under the head, with a cross-member extending from either side and mounting two pairs of ball bearings for contacting with the drive cams. The cam case is closed on either side by a pair of housing covers. These octagonal aluminium plates might also be anodised for added corrosion resistance in future versions of the engine. Each housing cover is bolted to an opposite opening of eight-sided cam housing using 32 M8 fasteners and 18 M32s. Anatomy Many of the NorEaster’s key components, including the guide plates, were CNC-machined from aluminium