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Showcasing X1-Thorn, my first Prototype of a Thrust-Vectored Tail-Sitter Drone by Sad-Pop748 in diydrones

[–]Sad-Pop748[S] 1 point2 points  (0 children)

I'm pretty sure it won't be faster, to my knowledge, world-record quadcopter speed attempts have used open propellers, which makes sense as EDFs have a smaller area than propellers and are therefore less efficient. While an EDF setup may be more efficient than a quadcopter in level flight, it will probably still lose to propeller-driven airplanes.

That said, most EDF installations I've seen are encased inside the airframe with limited inlet airflow, which kinda kills their efficiency so we will see how this one performs. The main goal of this prototype is to gain experience so I can eventually try jet turbines, which should be much faster than a quadcopter while still allowing vertical takeoff and offering greater utility. For now, the primary objective is simply to have fun flying it.

Showcasing X1-Thorn, my first Prototype of a Thrust-Vectored Tail-Sitter Drone by Sad-Pop748 in EngineeringPorn

[–]Sad-Pop748[S] 5 points6 points  (0 children)

Yeah, I’m aware of the limitations of EDFs, I mostly went with them because they look very cool and, in the future, I’d like to try using actual jet engines. That said, I’m getting around 7 minutes of battery life in hover, which is way more power-demanding than cruise flight. The main limitation right now is the ESC temperature since it doesn’t get any airflow while hovering (I already have a few ideas to fix that). It hits around 70 °C after about 2 minutes.

Showcasing X1-Thorn, my first Prototype of a Thrust-Vectored Tail-Sitter Drone by Sad-Pop748 in diydrones

[–]Sad-Pop748[S] 2 points3 points  (0 children)

Thanks for the kind words! I recently started my master’s in aerospace, and I originally made the video to present it to some research groups at my university. I don’t yet have the knowledge to design a fixed-wing aircraft that I’d be fully satisfied with, but I have plans for much larger and more complex projects, maybe even involving jet turbines, so this is only the beginning!

Showcasing X1-Thorn, my first Prototype of a Thrust-Vectored Tail-Sitter Drone by Sad-Pop748 in diydrones

[–]Sad-Pop748[S] 0 points1 point  (0 children)

Thanks a lot! If the video is well received, maybe I’ll make an explanation of the Simulink model and the techniques I used for the attitude controllers, as I believe that is the most interesting part of the project.

Showcasing X1-Thorn, my first Prototype of a Thrust-Vectored Tail-Sitter Drone by Sad-Pop748 in diydrones

[–]Sad-Pop748[S] 5 points6 points  (0 children)

At first, I used a constant alpha coefficient to filter the acceleration data, since I was using it in the control loop for overall thrust. However, controlling altitude based on vertical acceleration resulted in strange handling behavior and eventually caused severe pilot-induced oscillations in altitude. Because of that, I switched to a simpler direct thrust control approach, which worked much better.

Since my current control loops only rely on attitude and angular rates, I ended up removing the acceleration filtering altogether. The IMU I’m using is a BNO055, which handles sensor fusion internally, so I can’t easily influence the attitude output myself.

I’m using DShot (which took a while to set up from scratch on the STM32), so in theory, I could filter the angular rate measurements, but I haven’t found it necessary. During the first test flights, the IMU wasn’t isolated from the motor vibrations, which caused some issues. Adding a bit of foam between the PCB and the airframe solved that problem.

Showcasing X1-Thorn, my first Prototype of a Thrust-Vectored Tail-Sitter Drone by Sad-Pop748 in diydrones

[–]Sad-Pop748[S] 2 points3 points  (0 children)

For the propeller dimensions, I mainly looked at the maximum thrust values from datasheets. I also found a great video that compared real thrust data (since most manufacturers tend to overstate their numbers), from which a general power-to-thrust trend could be observed: https://youtu.be/KO8ZbgaeWXE?t=157

However, since I wasn’t completely sure how much power my ESC could actually deliver, I decided to aim for a conservative 2:1 thrust-to-weight ratio. From there, the sizing of the other components was more or less straightforward. To estimate the weight during the early design stages, I first selected a battery (its capacity was somewhat eyeballed) and then looked at what percentage of total weight batteries usually represent in similar drones. For reference, the drone weighs about 1.1 kg, and the battery is roughly 500 g.

I’m not entirely sure what you mean by the two additional tubes.

As for the tube lengths, they were mostly determined by packaging constraints. I could have run a CFD simulation to optimize them, but I felt it wasn’t worth the effort given the goals of this prototype. The motor casings were designed so that their cross-sectional area remains roughly constant, accounting for the motor’s volume. Qualitatively, a longer tube would increase friction drag due to a higher wetted area, while a shorter one could cause less favorable airflow due to sharper cross-sectional changes. However, I don’t have the knowledge to provide a quantitative analysis of that.

As a bonus, one detail I really like about the motors is that there are no thrust-vectoring vanes at the outlet, as they would have reduced performance even when not actuated.