It’s been over a year and a half since our last story, and so much has happened since then. In the fall of 2019, our high school and engineering teacher donated a multirotor to our club that was previously used in video production. It came with a complete carbon fiber frame and legs, eight motors and many sets of propellers, ESCs, and other components.
We did the maiden flight in a quadcopter configuration, and did further testing with an octocopter configuration that we decided to take to competition. A lot of the original components were far to old to be used such as the ESCs, so we upgraded to T-Motor F35 ESCs. The drone ran with two 6s batteries in parallel totaling to 20Ah at 22.2V. At the same time, we attained a V5+ flight controller through sponsorship from CUAV, and a NEO V2 GPS. Over the following year, various other components such as an antenna for Wi-Fi connection, multiple design iterations of the winch used for airdrop, and several electronics plate layouts were added.
As more components were added, the weight of the drone increased. We didn’t realize how little battery capacity summer 2020 when we had until an extended Wi-Fi uplink test was conducted.
The batteries were partially drained but we only got around 15 minutes of flight time before Macron literally fell out of the sky. To add to our problems, the SUAS competition organizers were changing the task requirements for the 2021 competition, requiring us to fly around 20km. At the speed our drone flies this would take a minimum of 30 minutes non-stop, excluding time taken by the airdrop and imaging tasks. We all knew that Macron needed serious propulsion upgrades but in a last ditch effort, we removed all non essential components and flew with a four battery configuration, doubling our capacity. This failed almost immediately as the PX4 was unable to fly the drone due to the motors being maxed out while trying to lift a much heavier multirotor.
We immediately got to work searching for a new propulsion system. We knew that a switch to 12s or 44.4V would decrease the current drawn by the motors, increasing efficiency and safety. After looking at motor and propeller configurations from various manufacturers, we selected the XOAR TA6012 130KV motor running enormous 24x9in propellers. This provided us with all the thrust we could ask for with amazing efficiency at the lower loads we would be running at, all at a somewhat reasonable price. This would be accompanied by sponsored Zubax Myxa FOC UAVCAN ESCs, and four of our 6s batteries in series and parallel, offering 20Ah at 44.4V. After testing the motors ourselves, we calculated a 47min hover time with a 9 kg drone at a 1.5:1 thrust to weight ratio; more than enough for competition.
This is a render of Macron with a the new setup. To accommodate the truly massive propellers without making the footprint larger, we needed to alternate the motor orientation for every arm, creating a sort of overlap. Further testing is required to determine whether too much efficiency will be lost in such a configuration.
Stay tuned for further updates once we start testing over the coming months!
P.S. the render of the new Macron configuration is not for competition but rather a separate side project. Expect a few stories about that soon!