52 canteen carrying a raw egg, which survived the experience intact. “Once you’ve proved that your idea works then the work begins,” he says. “The leap from an idea to a product is huge.” As they went through development, building subsequent prototypes, things changed drastically. “The first thing we flew looked like a cut-out model, and in fact it was cut out from carbon-fibre foam sandwiched sheets. It had off-theshelf, super-cheap servos we bought on Amazon. We had a little companion computer running some parts at first, and we changed from that,” Klusak says. “We iterated the motors we were using, and the way we were driving our pivoting axes. We changed the type of bearings, their interfaces on the axes and how we used them several times. We moved from concepts that move the arms independently of each other to a fixed system and back a couple of times. We’re probably going to release versions with each because both have pros and cons.” The Pivot MK-V, a mock-up of which was presented at the Commercial UAV Expo in early September, is optimised for hovering. It has two arms that move in a permanently fixed relationship, each supporting two pairs of motors and propellers. However, the technology can also be used in VTOL vehicles with fixedwing and lift-body configurations. “One of the big issues you have is that to get such a VTOL to yaw in strong winds is very hard, because the yaw force induced by motor-speed variation only is not enough to counteract the push of the wind on the wing,” says Klusak. “But if you can move the arms perpendicularly to one another you can induce yaw by pitching one forward and one backward. Then you have a very strong yaw moment. There are use cases where that makes sense and also cases where it is just not necessary.” Powertrain development Orthodrone decided early on to use a hybrid powertrain with a piston engine driving a generator to meet its range and endurance requirements. They chose a 4 kW Pegasus GE70 unit with electronic fuel injection, which provides power for the propulsion and control systems, ‘hotel’ loads and payloads. “It’s the lightest generator system available and gives a power-to-weight ratio unlike any other,” Klusak says. “There are generator systems out there that look like chainsaws and even have pull knobs, and I don’t want that.” Since meeting Pegasus shortly after Orthodrone’s inception, the two firms have developed a strong partnership. “Over the years, we have learned what that generator system can do, and also how to get the most out of it through implementation into our hardware. For instance, we focused on custom solutions for the exhaust and cooling systems, and managed to gain 15% of power and a significant increase in fuel efficiency, enabling us to exceed our hover time and range goals,” says Klusak. Orthodrone chose Alva Altus X60 Duo propulsion units, each consisting of two slotless motors that feature fibre-printed Halbach rotors. Each motor is fitted with a two-bladed Mezjlik propeller, developed especially for the X60 Duo units. By design, the propulsion system has enough redundancy to save heavy, expensive sensors in the event of failure. Keeping it smooth “Vibration is probably one of the biggest issues in gas-hybrid UAS development and it is something we are continuously working on,” Klusak says. “We are very happy with where we are vibration-wise right now, but I think that’s work that will never stop, because the lower the vibration, the better the data you get.” Vibration is affected by many factors, including the payload and anything else attached to the vehicle plus the method of attachment. Relatively small masses such as landing gear can have a significant effect. The forward portion of the Pivot MK-V’s gear is attached to the payload bay, and the rear portion to the engine bay, and there are significant differences in vibration of either based on the gear type and length. “I’ve seen systems that have a common rail for a vibrating range extender and a sensitive payload. And that, to me, does not make sense, particularly when using the kinds of high-quality sensors and IMUs we’ve been talking about,” he says. “On the Pivot, the generator and the payloads are decoupled, each on its own specially tuned vibration-damping mounting structure. In the engine itself, the main masses are naturally balanced as it is a horizontally opposed, twincylinder boxer unit. This is mounted on dampers that isolate its vibrations October/November 2024 | Uncrewed Systems Technology UVD | Orthodrone Pivot The MK-V Pivot has been displayed at recent major trade shows, including Xponential, representing the first production configuration (Image courtesy of the author)
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