Have you ever encountered a drone that looked… different? Perhaps one with fewer propellers than expected, or with parts that moved in surprising ways? For many enthusiasts immersed in the world of FPV flying, the standard quadcopter has become the benchmark of performance and reliability. However, as the accompanying video with RC Explorer David Windestål vividly demonstrates, the journey of drone innovation has been far from linear, and the allure of unconventional designs, such as the **tricopter** and **bicopter**, continues to captivate adventurous pilots and engineers alike.
In the early days of multirotor development, the landscape was ripe for experimentation. It was a time when limitations in hardware and software often dictated design choices, leading to ingenious solutions that sometimes diverged significantly from today’s ubiquitous quadcopter. It is a testament to this spirit that designs with just three or even two motors, often utilizing tilting mechanisms, were not only explored but sometimes even considered superior.
The Evolution of Drone Design: Revisiting the Tricopter
A **tricopter** is, at its core, a three-motored multirotor where one motor, typically the rear one, is mounted on a servo-controlled tilt mechanism. This unique setup is primarily responsible for managing yaw, allowing the drone to rotate horizontally. In contrast, standard quadcopters achieve yaw by differentially spinning two motors faster and the other two slower, which can impact overall thrust and stability.
Historical Advantages of Tricopter Innovation
Historically, the **tricopter** offered distinct advantages, particularly when quadcopter technology was still in its infancy. As discussed in the video, significant challenges were faced by early quadcopter designs:
- Slow ESCs: Initially, Electronic Speed Controllers (ESCs) were quite primitive, often operating at refresh rates as low as 50 Hz. This meant that the flight controller’s commands to the motors could not be updated quickly enough for precise control, especially for rapid yaw movements.
- Yaw Authority: For large quadcopters, particularly those designed to carry heavy payloads or equipped with 10-inch or even 14-inch propellers, achieving quick and responsive yaw was a considerable hurdle. The “spinning up two motors” method was inherently slow and often led to a noticeable lag, described as being unable to “whip it at all.”
- Software Limitations: Beyond hardware, the flight control software itself was not as sophisticated. Algorithms for managing stability and control were less advanced, making it difficult to compensate for the inherent limitations of slower ESCs and larger props.
It was within this technological environment that the **tricopter** truly shined. By incorporating a tilting rear motor, impressive yaw authority could be achieved without significantly altering prop speeds, thus maintaining more constant thrust and greater overall efficiency. Pilots found these early tricopters to be more controllable and inherently stabler, especially for smooth aerial footage captured eight years ago, long before the acrobatic FPV flying seen today was commonplace.
Modern Tricopters: Blending Old Concepts with New Tech
Despite the dominance of quadcopters today, the **tricopter** has not faded entirely into obscurity. Modern iterations, like the one showcased in the video, are being developed, now equipped with contemporary mini quad gear. This includes advanced 32-bit BL Heli ESCs and flight controllers running Betaflight firmware. However, integrating these older concepts with newer technology presents its own set of challenges.
A critical point of discussion revolves around the servo that controls the tilting motor. While modern flight controller gyros update at a lightning-fast 8 kHz, the servo’s update frequency is much slower, around 250 Hz, and its physical speed is comparatively sluggish. This speed disparity means that while the flight controller can detect changes almost instantly, the servo’s physical response lags behind, impacting overall agility and precision.
To overcome this, innovative solutions are being explored. A notable advancement involves introducing a fourth servo lead dedicated to providing feedback to the flight controller. This allows the controller to know the exact position of the servo at all times, leading to more efficient and precise adjustments. It essentially helps the system anticipate and react more intelligently, reducing unnecessary movements and improving overall responsiveness, even if the servo itself remains a physical bottleneck.
The Quirks and Challenges of Flying a Modern Tricopter
Piloting a modern **tricopter** is described as a unique and sometimes “squirrely” experience, especially for pilots accustomed to the predictable stability of quadcopters. Several distinct characteristics are observed:
- Throttle Management: Unlike quads that can maintain yaw authority even at very low throttle thanks to features like “air mode,” a **tricopter** requires continuous thrust to control its yaw effectively. If the throttle is cut too quickly, the yaw authority can be lost entirely, leading to unpredictable spinning. Smooth throttle control is therefore paramount.
- Unique Flight Dynamics: The way a tricopter responds to control inputs, particularly during rolls and pitches, can be quite different. It might “blow out” in unexpected directions or exhibit unusual camera angles, requiring pilots to adapt their muscle memory and control strategies significantly.
- The “Challenge” Factor: It is suggested that flying a **tricopter** today is less about capturing perfectly smooth footage and more about the sheer enjoyment of mastering a novel and demanding flying experience. It represents a different kind of fun, pushing pilots out of their comfort zones and encouraging a deeper understanding of flight mechanics. It is often emphasized that the experience is highly enjoyable precisely because it presents a challenge.
Unveiling the Bicopter: The Ultimate Multirotor Challenge?
Beyond the **tricopter**, the video introduces an even more radical design: the **bicopter**. This minimalist multirotor features only two motors, each mounted on its own tilting mechanism. The aesthetic appeal of such a design is undeniable, and it certainly stands out from the crowd.
However, flying a **bicopter** presents an entirely new set of complexities. Control inputs become highly integrated: pitch might be controlled by tilting both motors, while roll could be achieved through differential thrust and tilt. Yaw is likely managed by tilting the motors in opposite directions. The prototype shown in the video, still in early development and with minimal tuning, exhibited extremely challenging flight characteristics, particularly in stabilized mode. Issues such as difficulty flying backward and unpredictable behavior during maneuvers were observed, indicating that considerable refinement is required.
The **bicopter** is explicitly “designed to be a challenge,” and its current state highlights the significant engineering and software hurdles that must be overcome to make it a more manageable flying platform. It underscores the idea that innovation is often a collaborative effort, with calls for community involvement to help fine-tune its firmware and control algorithms.
Innovation and the Future of Multirotor Design
A significant takeaway from the discussion is the critical importance of continuous innovation in hobbies like FPV drones. Often, when a “superior” format like the quadcopter emerges, development in alternative designs can stagnate. However, it is argued that this mindset can stifle creativity and limit unforeseen breakthroughs. The success of mini quads, for instance, was not initially driven by their utility for carrying large cameras, but by the sheer fun and challenge they offered to early adopters.
The pursuit of unconventional designs like the **tricopter** and **bicopter** serves as a powerful reminder that the drone hobby is not merely about incremental improvements to existing platforms. Instead, it is also about daring to experiment, to build for fun, and to collaborate on making the impossible possible. David Windestål’s projects, poised to be available as kits, actively invite this collaboration, encouraging enthusiasts to buy, fly, and contribute to the ongoing development of these unique machines. The potential for new discoveries and further refinement, perhaps by adapting specialized firmware like Triflight, remains vast, promising an exciting future for those who embrace the challenge of flying something truly different.
David Windestål on Bi- and Tricopters: Your Rotor-Driven Questions Answered
What is a tricopter?
A tricopter is a type of drone (multi-rotor) that uses three motors. One motor, typically the rear one, is mounted on a tilting mechanism to help the drone steer horizontally.
What is a bicopter?
A bicopter is a unique drone design that features only two motors. Both motors are mounted on tilting mechanisms, which are used to control its flight and movement.
Why would someone choose to fly a tricopter or bicopter?
Pilots might fly these drones for the challenge and unique experience they offer, as they are less common than standard quadcopters. Historically, tricopters also provided advantages in control before modern quadcopter technology advanced.
Are tricopters and bicopters more difficult to fly than regular drones?
Yes, these drones are generally considered more challenging to fly. They have different flight dynamics and require pilots to adapt their control strategies compared to the predictable stability of standard quadcopters.
