Unmanned Systems Technology 007 | UMEX 2016 report | Navya ARMA | Launch & recovery systems | AIE 225CS | AUVs | Electric motors | Lethal autonomous weapons

52 April/May 2016 | Unmanned Systems Technology Wankel-type Single rotor Effective displacement, 225 cc Naturally aspirated Heavy fuel, Avgas or gasoline Aluminium structure Nickel silicon carbide coated trochoid surface Needle roller main and rotor bearings Steel eccentric shaft Steel rotor Twin plugs, single injector Engine management system Peripheral port Maximum rpm, 8000 The 225CS’ rotor housing is flanked by endplates, the one of which on the non-drive side expands outwards over the combined fan, counterweight and timing wheel assembly. In turn it is closed by a bolt-on cover that provides access to that assembly. Industrial- strength sealant or O-rings are used throughout rather than conventional seals or gaskets, with the exception of the front of the eccentric shaft. The endplates each incorporate a bore to house the eccentric shaft bearing, the drive-side one of which is a normal radial bearing, the other a smaller bore thrust bearing, and the endplate incorporating a shoulder to accept the axial load it imparts. The stationary gear is formed with an integral flange that acts as a mounting face to attach it to the respective endplate via four screws. The steel eccentric shaft is hollow to minimise weight. It is formed as one piece with a keyway and a female thread at both ends. The front thread accepts the screw that retains the propeller drive hub. The hub with keyway for angular location carries the front counterweight. The equivalent rear fixing is for the combined fan, counterweight and timing wheel assembly. There is no coating on the eccentric shaft but the lobe and journal surfaces are superfinished. A plate is attached to each side of the eccentric by three rivets, those plates axially retaining the rotor needle roller bearing. The steel rotor is formed as two parts. The inner section incorporates a wide, flat ring, the inside surface of which forms both the surface that runs against the bearing on the eccentric shaft lobe and the adjacent gear. That gear runs around the stationary gear held by the respective side housing (having the 1:3 ratio necessary to ensure the correct operation of the rotor). This inner ring, having a flat outside surface, slots inside the main rotor joined at three local areas on its circumference. Each of those areas is contacted by a pad formed inside the main rotor, with a retention dowel running through it and down into the inner ring. For assembly, the outer section is heated so that it expands to allow the inner ring to be inserted as an interference fit, in addition to the subsequent dowelling. The top of each radial dowel actually forms part of the combustion chamber floor. In addition to the three radial dowels there are three axial ones, forming a cross-pin arrangement for additional security. As well as the pads, the main outer section of the rotor, which is primarily triangular, forms fins that project inwards, into the hollow section between it and the inner ring. Those are to assist thermal transfer away from the combustion chamber formed on the other side of the rotor. Anatomy of the AIE 225CS Key components of the 225CS