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

57 Background The very first UAV offering from Primoco was the One 100, which uses a naturally aspirated, air-cooled, horizontally opposed four-cylinder two-stroke with a displacement of 191 cc and maximum power output of 20 bhp. That engine was an adaptation of an existing unit manufactured in the Czech Republic. Unlike the 500 though, it hadn’t been designed specifically for UAV use, and its performance limits the One 100 to a maximum take-off weight of 100 kg including a payload of up to 20 kg, a maximum cruising speed of 150 kph and a maximum altitude of 2000 m. The original engine had the appropriate configuration for a state-of- the-art UAV but lacked performance for the targets Primoco had for its vehicle as a mid-sized player. Consequently the Primoco 500 retains the concept of a naturally aspirated, air-cooled, horizontally opposed four-cylinder two- stroke, although the similarities end there. The 500 has purposely been designed for UAV use, while its displacement of 500 cc and maximum power of 50 bhp give the new Primoco One 150 a maximum take-off weight of 150 kg including a payload of up to 50 kg, a maximum cruising speed of 200 kph and a maximum altitude of 5000 m. Using essentially the same airframe, the Primoco One 100 and the Primoco One 150 are otherwise similar in specification, with a representative maximum mission distance of 1500 km. Both have the same 4.85 m wingspan and both can take off and land automatically with only a 300 m runway requirement. The One 100 is limited by its engine to operating in ambient temperatures no higher than 35 C, whereas with a pressurised fuel system the 500 has been designed to cope with hotter and more humid environments (the actual figures are yet to be determined). The one significant compromise with the One 150 in its initial guise is a reduction in representative mission endurance, from ten to eight hours, owing to its 150% higher horsepower implying higher fuel consumption. Current development is focused on minimising that drawback. The 500 project The Primoco 500 engine project began with a clean sheet of paper on January 15, 2017, and the first engine ran on the dyno ten months later (around the time of UST ’s visit). Since Primoco did not have engine design, build or development resources in-house it has subcontracted those functions to two local Czech companies of proven performance engine competence: VM Motor and Motordesign. VM Motor is headed by Vladimir Vacha, and is renowned for its 125 cc single and 250 cc twin two-stroke race engines that have had much success in karting at European Championship level. Founded in 1992, VM Motor now employs 40 at its factory in Pisek, a town in the southern Bohemia region of the Czech Republic. Here facilities include an in-house foundry so that components can be cast as well as machined from billet. One is often told that a cast component is made ‘in-house’ by an engine manufacturer, but mostly the actual forging work is outsourced, then the castings are machined in-house. UST was taken on a tour of the VM Motor facility in Pisek, which allowed us to see the foundry for ourselves. A number of high-profile companies contract cast components from VM Motor that start life in the foundry, in addition to it serving the needs for VM Motor and the Primoco 500 project. Our tour included a look at a busy, well-equipped machine shop housing CNC four- (and soon five-) axis machines. They are complemented Primoco 500 four-cylinder, 500 cc two-stroke | Dossier The 500’s light alloy structure means its ready- to-operate weight is only 25.5 kg, including an integrated 24 V 1400 W generator Unmanned Systems Technology | December/January 2018 Illustration of the general layout of the Primoco 500 (with starter motor and generator on top)