Hitec Commercial Solutions LLC Join the CAN Movement 10 - 50mm Case Options 4 – 32V Voltage Ranges DroneCAN CAN 2.0A/B MULTIPLE COMMAND PROTOCOLS AVALIABLE Designed specifically for industrial applications, Hitec’s cuttingedge CAN protocol servos deliver unrivalled precision, reliability, efficiency and feedback. Available in a variety of case options with wide voltage ranges, our products allow for optimized performance for your UAV projects. COTS COMMERCIAL OFF-THE-SHELF CUSTOMIZABLE OPTIONS AVALIABLE NON-CHINESE MANUFACTURING Hitec North American Sales & Support San Diego, CA / www.HitecCS.com The S1 Wankel engine For those asking themselves over the past few pages, ‘but why a Wankel engine?’, the answer is primarily that Schiebel’s engineers wanted to maximise power to weight and minimise vibration early on. Vibration especially would directly reduce the resolution and hence value of the UAV’s camera data, and given the highly vibratory nature of rotorcraft, any means of eliminating vibration sources was a must-have. “We actually used two-strokes all the way up to the Camcopter 5.1, both single- and dual-cylinder designs, and with the first Wankel engine integration on the 5.1, that was how we learned that a Wankel was better for our purposes,” Hecht recounts. The first S-100s were powered using a COTS Wankel engine core, modified with Schiebel’s own EFI, ECU and related components, as that COTS engine (manufactured nearby) was used in glider aircraft, meaning it was optimised to run for five to 10 minutes at a time, and not for the continuous six hours of operation that Schiebel aimed for. “Its size and power worked initially, however, so we made all the ancillary systems around its mechanical core, and took out weight where we could. Being a crewed aircraft engine, it still wasn’t as light as we needed it,” Hecht says. “But that supplier couldn’t support us as we took the engine in a different development path than what works for gliders, so we split off into mechanical development and started more or less making our own engine. Luckily, a Wankel doesn’t have so many parts. It’s a simple design compared with normal combustion engines.” That first design was an AvGas-burning Wankel called the S1, although in 2009, Schiebel began designing a heavy fuel engine, as navies (especially in NATO) increasingly turned against taking gasoline to sea for safety reasons. That resulted in the S2: the 23.7 kg, single-rotor Wankel in the S-100 today, which entered service as its standard-issue engine after nine years of r&d in 2018. It occupies 400 x 353 x 312 mm inside the UAV, displaces an effective 440 cc, and produces a maximum continuous 60 hp (44 kW) at a nominal operating speed of 7100 rpm. The system has been designed to run primarily on JP-5, JP-8 and Jet A-1, integrates redundant EFI and electronic ignition systems, and is oiled via a two-port, pump-fed, loss lubrication system. Most importantly, as the thermal management approach has differed in every Wankel we have investigated, particularly with respect to cooling the highly sensitive needle roller bearing at the rotor, the S2 mixes its intake air with oil from one of two lubrication ports, and pushes this through a sealed aperture inside the rotor-bearing section (some readers may note ~
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