Unmanned Systems Technology 026 I Tecdron TC800-FF I Propellers I USVs I AUVSI 2019 part 1 I Robby Moto UAVE I Singular Aircraft FlyOx I Teledyne SeaRaptor I Simulation & Testing I Ocean Business 2019 report

70 the rod design, so the rods have been manufactured as monolithic parts, machined from 39NiCrMo3 steel. This was another decision made to save on manufacturing costs and assembly time. “We have a range of different machines in-house, but we cut mainly from metal blocks for prototyping the crank parts and con rods,” notes Marino. “When we move towards scale production, we will probably switch to other fabrication methods more suited to bulk manufacturing, such as forging for example, as well as other materials that we will select later. All the engine components have been designed to be ready for mass production.” No bearing is used between the piston pin and the interior of the con rod small end. Instead, smooth movement is facilitated as oil runs through a lubricating hole drilled into the top of the small end, which runs through to the piston pin. That oil comes from the big- end bearing, as a 1 mm groove in the top of it allows it to flow up to the small end, exiting from the bearing at 5 bar of pressure and a flow rate of about 180 g/s, and running up to the pin. This then lubricates the 20-or-so μm space between the two parts. FEM of the con rod’s design has been conducted in Abaqus to assess for static strength and fretting, as well as a fatigue analysis run in MatLab, to minimise the risk of the rod failing or slipping. Operation The UAVE and RES share almost all the same components but have different cam profiles and ECU parameters so that they can be adapted to different operating conditions. As mentioned, the UAVE’s operating speed is 5000 rpm, with a maximum of 8000 rpm given, although that may be subject to change following new rounds of dyno tests starting this June. The system’s highest torque level of 61 Nm is achieved at 2700-2800 rpm. In RES configuration, the engine’s peak power output is 20 kW, which is reached at roughly 4000 rpm. If the operator runs the engine at this speed they will have 47 Nm of torque to drive the generator. The brake-specific fuel consumption of the engine is 168.19 g/kWh at 4000 rpm in RES configuration, and 226.82 g/kWh at 5000 rpm in UAVE configuration. In a drive for efficiency, the compression ratio for both versions has been set at 14:1. Each cylinder has an intake valve measuring 28 mm in diameter, and an exhaust valve 23 mm across. The valves are positioned atop each cylinder head, with a valve angle of 0° for design and June/July 2019 | Unmanned Systems Technology The con rods are made as single components, as the three-section crankshaft makes it unnecessary to design them with a split (Author’s image) The cam lobes in the UAVE were reconfigured to actuate the rocker arms and time the valves for a 5000 rpm operating speed, compared with the range extender’s 4000 rpm speed (Author’s image)