Unmanned Systems Technology 017 | AAC HAMR UAV | Autopilots | Airborne surveillance | Primoco 500 two-stroke | Faro ScanBot UGV | Transponders | Intergeo, CUAV Expo and CUAV Show reports

58 Dossier | Primoco 500 four-cylinder, 500 cc two-stroke by gear-cutting equipment and a CMM-equipped quality control laboratory. There is also an in-house dyno facility, developed for VM Motor kart two-strokes and now adapted to meet the needs of the Primoco 500’s development. The design of the 500 was headed by Ing Jiri Smat of Motordesign, in Prague, who has recently led engine development for Skoda factory motorsport projects. He has also been responsible for adapting the VW 1.2 litre TDI automotive engine for microlight applications. Development of the Primoco 500 is a joint effort by Motordesign and VM Motor in conjunction with Primoco’s vehicle engineering team. The engine is built from scratch at VM Motor, then integrated with the Primoco UAV at the Primoco factory. There, much of the airframe is made in-house using the company’s own composite manufacturing facilities. Design philosophy Before giving the green light to the 500 project, Primoco’s engineers scoured the market in search of available engines of comparable power output; these included two-stroke reciprocating and four-stroke rotary engines. In every case though the cost of a suitable unit proved a particular drawback – fully equipped with starter, generator and so on, there was nothing available for less than e 5,000, and the price was often far higher, up to e 45,000. Through thoughtful design and by manufacturing in-house, however, Primoco has been able to keep its price for a complete power unit package (as supplied to a third-party UAV or perhaps microlight user) to no more than e 14,000. Given that the Primoco One 150 is designed for endurance missions (eight hours or more) and that the engine life target is 500 hours between overhauls, durability was a paramount factor in the design, Smat emphasises. So far, Primoco has made 20 examples of the One 100, and the Primoco 500 draws on the lessons of that commercially successful project. Compared with the same configuration engine used in the One 100, the bespoke 500 uses state- of-the-art ignition control, and its design specifically for UAV applications includes consideration for ease of maintenance. That designed-in serviceability recognises the fact that in practice many UAV engines are worked on in the field by mechanics who lack the facilities of a proper workshop. For example, compared with the smaller, four-cylinder in the One 100, the 500’s design makes it more straightforward to remove the generator or the starter motor. Everything has been thought through, with both ease of use and durability as key design considerations, Smat emphasises. General layout In the One 150 application, the Primoco 500 is in a pusher configuration (in other words, it is mounted on the rear of the fuselage). It is cantilevered from a fuselage bulkhead immediately ahead of it, with its vertical mounting flange connecting via four pick-up points arranged in a square pattern. Rubber isolation mounts are used to keep the airframe free of engine vibration. Hereafter, when saying ‘front of the crankshaft’, that refers to the propeller hub end, which is actually located at the rear when in a Primoco UAV-style pusher configuration. Equally though, the engine can be used as a puller if a customer wishes. In essence, the 500 consists of a pair of horizontal twins arranged in tandem within a common crankcase December/January 2018 | Unmanned Systems Technology The Primoco 500’s crankshaft is split in the centre For every engine of comparable power output on the market, the cost of a suitable unit was a particular drawback