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

68 The shaft sections are held in the central crank section using an interference fit of about 0.1 mm. As the design team modelled the dimensions of this fit, they were concerned that the torsional forces being transmitted through the crankshaft, combined with the bending forces generated from the con rods, could cause wear and even misalignment of the crank journals and the central part over time. Finite element modelling (FEM) was used to simulate the worst-case scenario here. By importing the .step files of the UAVE’s crank section models from SolidWorks into Abaqus, the team conducted assessments for stress, fatigue and slippage at a range of crank angles at maximum torque. This made up most of the FEM work carried out for the engine, and enabled the team to predict the torsional loads and bending moments imparted throughout the crankshaft during engine operation. From these it was determined that, even when the interference is at its minimum level possible, the crankshaft geometry should still not change. Owing to the extended length of the RES’ rear crank (199 mm), it is used as a mount and direct drive for the ‘operative’ part of the engine’s configuration. That is, when configured as the Robby Moto RES, a conical coupling is used to mount the rotor of the electric generator on the end of the rear crank. In the UAVE, the front crank measures 247.5 mm long in order to enable propeller mounting on the front of the engine. The rear crank is 198.2 mm long to mount the distribution gear for driving the camshafts, as well as the starter/ generator. Each of the two con rods is about 140 mm long, or 103 mm between the centres of the small and big ends. As the crankshaft is made in three sections, this negates the need for a split in June/July 2019 | Unmanned Systems Technology Dossier | Robby Moto UAVE The RME Avio division of Robby Moto Engineering was set up in 2006, as a result of the company’s increasing competence in aircraft propulsion systems and Papetti’s interest in transferring and applying his team’s experience in thermodynamics and fluid dynamics to light aircraft (such as those Papetti flew in his spare time). The first project to come out of this division was the RAP 98-90i, a four-stroke boxer engine, configurable for fixed- wing and rotary aircraft. This 72.5 kg, 2715 cc four-cylinder design measures about 660 x 653 x 453 mm, with a bore and stroke of 98 and 90 mm respectively. It features a patented oil-to-air cooling system as well as an all-aluminium structure and an 11:1 compression ratio. When the RAP’s ECU is programmed for a fixed-wing aircraft, the engine has a maximum speed of 3000 rpm, a peak power output of 77 kW at 2750 rpm and a maximum torque of 275 Nm at 2420 rpm. Set for a helicopter, the top speed is 3500 rpm, maximum power is 88 kW (at 3400 rpm), and torque peaks at 270 Nm, at 2300 rpm. After talks in 2013 with the Lombardy Aerospace Cluster of aviation engineering companies in northern Italy, the company began developing its TEPS (Twin Engine Pack System) twin independent four-cylinder engine integrated into a single unit for helicopters. The total displacement of this 130 kg patented engine is 5400 cc, with a 3600 rpm top speed, 88 kW rated maximum power output (at 3400 rpm) and 270 Nm peak torque (at 2300 rpm). The similarities in performance between the four-cylinder RAP and the eight-cylinder TEPS come largely from the latter being principally conceived and designed as two independent RAP units built together for redundancy, sharing a common crankcase. The Avio division used many of the same design points in the TEPS as the RAP, including the same Heron cylinder design with the same bore, stroke and compression ratio. The aforementioned oil-to-air cooling system was also implemented. Although TEPS was envisioned for use in helicopters with MTOWs of 600 kg for two-seaters or 1000 kg for four- seaters, the Avio division has recently conducted a study into a use case for the engine in stratospheric flight. This configuration sees the engine being used for take-off and landing for a HALE-type unmanned aircraft, which would operate for several days at a time at altitudes of between 16.76 and 18.28 km. When operating at low altitude, the HALE UAV would fly with only one TEPS block active (as intended with the system’s design), and at high altitude the craft would have the other TEPS block activated. One block is calibrated for use with high efficiency at altitudes from sea level up to 30,000 ft. The other is calibrated for use between 30,000 and 60,000 ft. In its final configuration, the HALE craft is envisioned as having integrated PV cells for power at high altitude. The end goal will be to offer the craft for applications such as telecoms, environmental surveys and maritime traffic radar, at far lower cost than satellites. Further development of both engines’ use cases are planned following further dyno tests this summer. Robby Moto’s RME Avio division