Unmanned Systems Technology 021 | Robot Aviation FX450 l Imaging Sensors focus l UAVs Insight l Liquid-Piston X-Mini l Riptide l Eurosatory 2018 show report l Zipline l Electric Motors focus l ASTS show report

56 August/September 2018 | Unmanned Systems Technology Liquid-Piston X Mini Rotary engine Single rotor Effective displacement, 69 cc Naturally aspirated Gasoline fuel Aluminium structure DLC-coated rotor working surface Two needle roller rotor bearings, two side housing ball bearings Steel eccentric shaft Steel rotor One plug per chamber, single injector Engine management system Rotor-integrated intake and exhaust ports Compression ratio, 9.5:1 Maximum rpm, 9000 (14,000 potential) The main components of the X-Mini are the aluminium alloy centre and side sections of the rotor housing, the steel rotor and the steel eccentric shaft, which is made in two pieces. Fourteen bolts tie the centre and side housings together. The intake and exhaust flows occur on the same side of the engine. The rotor has an integral gear that runs on a stationary steel gear carried by the side housing on the intake/exhaust side. The centre housing carries three apex seals, while the rotor carries side seals. The side seals run against a chrome-plated surface on the respective side housing. The apex seals run against a DLC-coated rotor working surface. The seals are currently all cast iron. The eccentric shaft runs in steel bearings. There is a pair of ball bearings, one carried by each side housing, while two needle roller bearings run between the rotor and the eccentric shaft. The eccentric shaft carries an integral counterweight on the gear side and one on the other side that is attached. It also carries a fan on the non-gear side. Ducting feeds air from the fan through the rotor and over the housing. Steel exhaust shrouds are fitted to the gear side housing. Spark plugs are mounted horizontally and project on the gear side. There is one spark plug per combustion chamber. The ignition is taken from a three-cylinder, four-stroke engine. The fuel injection system uses a single, solenoid-type injector fed by an electric pump at the tank. Controlling the ignition and the injection is a Microsquirt open source ECU. The intake is via a throttle body feeding into the eccentric shaft with a single injector located downstream of a servo-controlled butterfly. The intake manifold is 3D-printed glass- infused nylon. Some key suppliers to this engine Machining: Century Tool Rotor: Century Tool Gears: Riley Gear Gears: Perry Gear Eccentric shaft: Century Tool Bearings: Koyo Bearings: SKF Spark plugs: NGK ECU: Microsquirt Sensors: Kistler Sensors: HBM Sensors: Omega Data acquisition: National Instruments Alternator: Sullivan Exhaust: in-house Intake manifold: Synergeering Air filter: K&N Wiring loom: Megasquirt DLC: IBC Coatings Bore coating: US Chrome Metals: McMaster Carr Surface treatments: IBC Coatings Heat treatments: IBC Coatings Machine tools: Haas Anatomy The X-Mini seen from the cooling fan side (without fan and ducting) The X-Mini seen from the intake/exhaust side