AOS 5.5 Freestyle Quadcopter Frame
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WishlistThe AOS 5.5 builds on the scientific approach used to design the AOS 5. It boasts vibration performance just as good as its smaller sibling despite being capable of handling larger props and motors. The frame has been designed from the ground up to carry the heavier GoPro Hero 8 and Hero 9 cameras without compromise. A combination of finite element simulation and real-world flight testing gives this frame exceptional vibration and resonance performance. This means you can run less filtering and higher PID gains for a smoother and more responsive feel with greatly improved mid-throttle oscillations and cool motors.
Specifications
- Approx. 125g with all hardware
- Designed for up to 5.5 inch props
- 6 mm Arms
- 2.5 mm Top Plate, Bottom Plate and Sandwich Plates
- One 30.5×30.5 mm or 20×20 mm stack in the center
- Two more 20x20mm stacks front and rear
- 32x32mm GoPro mounting holes in top plate
- Fits the DJI Air Unit or Caddx Vista (using 14 or 20cm coax) perfectly
- 20mm camera option for DJI Camera, 19mm option for Caddx cameras
- Recommended motor size 2307, 2208
- Standoffs, frame and motor screws included
GoPro’s are getting heavier, frame design needs to evolve
To understand why I have developed this 5.5″ frame we must ask why 5″ quads are so popular? It comes down to a balance between responsiveness and disc loading. As you make a quad larger is becomes less responsive but the larger props are able to carry a heavier load at the same disc loading.
When you balance these two factors for a quad carrying a GoPro Hero 5 session weighing in at 75g you find that a 5″ quad is an ideal size. And so it is no surprise that pilots everywhere grew to love the 5″ class.
However, as we know, GoPro stopped manufacturing the Hero 5 session and released the Hero 6 and then the Hero 7 both weighing in at 116g. Then the Hero 8 at 126g and now the Hero 9 at 147g.
Now the calculation of responsiveness vs disc loading looks very different when you consider the additional weight of these much larger cameras. 5″ is no longer ideal. In fact for the Hero 8 and 9 a 5.5″ prop provides a much better disc loading than 5″.
The AOS 5.5 is optimized to carry these heavier cameras. And to do so with no compromises.
Harmonic analysis is the key
I used Blackbox logging and harmonic analysis to visualize the vibrations of the AOS 5.5 during the design process. This allowed me to tune the geometry of every part of the frame, moving the frame resonances up and away from the motor frequencies and separating them as far as possible. This avoids, as far as possible, the situation where the motor frequencies match a frame resonant frequency and so amplification is minimized.
As a result, you can run less filtering. Every layer of filtering adds delay that’s mathematically related to how effectively it removes vibrations. This delay prevents the flight controller from responding rapidly enough to propwash leading to poor propwash handling. Reducing the amount of filtering is the best way to improve propwash handling. With the AOS 5 you’ll be in the best possible position to reduce your filtering to an absolute minimum.
Another advantage of lower noise is the ability to run higher PID gains. Higher PID gains allow the quad to track your stick movements with less delay and more precision. The result is greater confidence, particularly when flying tight lines where fast reactions are vital.
Top and bottom plates
Both of these plates are 2.5mm thick to provide an optimal balance between strength, stiffness and weight. The cut outs in the top and bottom plate of the AOS 5.5 are tuned using finite element analysis to preserve as much of the bending and torsional stiffness of the plate as possible whilst minimizing weight.
Compared to the AOS 5 the AOS 5.5 has a stiffer front section of the top plate to further improve handling of heavier cameras. A battery strap slot is also included in the center with space for a second strap to the rear.
The flight control stack is now centrally mounted. This was a key change required to maintain the exceptional vibration performance of the frame despite the increase in the length of the arms and the expected weight of the motors.
Arms
The AOS 5.5 uses the same distinctive truss design for the arms as the AOS 5. This truss design provides enormous torsional stiffness, resolving a key source of vibration in traditional frames. It also allows two particularly harmful resonant modes to be individually modified to separate them in frequency.
Truss structures are inherently very strong as they convert bending loads into compression and tension in the individual members. Carbon is much stronger in pure tension and compression than in bending. Elongated slots for the outer motor screws are just one of the many ways weight has been trimmed from every part of the frame.
Y-shaped motor protectors minimize the risk of damage to those expensive components. Should you ever need to replace an arm, there are only two screws to undo and neither are shared with your electronics.
Camera Protection
The AOS 5.5 uses 2.5mm Carbon Plates to hold and protect the camera. These are stiffer, lighter and cheaper to replace than aluminum or titanium.
The camera plates include a larger stiffener for the top plate than the AOS 5 to increase stiffness and better manage the additional weight of a GoPro Hero 8 or 9 mounted on the included 32x32mm mounting holes.
Go Pro Mount
The AOS 5 has 32×32 mm M3 mounting holes for 3D printed mounts for your HD camera.
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