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AOS UL5

 

The AOS UL5 is an ultralight 5 inch frame optimized for 2-blade props. Experience the feel of a toothpick combined with the dynamic power of a full-sized 5".

The toothpick class has always been about incredible flight performance in a tiny form factor. The 5" Class has always provided the most dynamic and energetic flying experience. It seems only natural to try to combine the benefits of both in an ultralight 5" frame.

A key limitation with ultralight 5" frame design is resonance performance. Placing the motors on the end of very long spindly arms creates a spring-mass system that is prone to resonance in a number of different modes. The AOS UL5 uses finite element simulation to model these modes and topology optimization to identify the most efficient places to add material to counteract them, maximize stiffness and increase durability.

 

The result is a frame that weighs only 67g with resonance perfromance that exceeds frames weighing twice as much. This allows you to run less filtering and higher D gains to unlock spectacular flight performance and unmatched propwash handling.

  •  Standoffs, carbon and steel frame screws included

  •  ~67g with steel hardware

  • Designed for 5" biblade props

  • 5 mm Arms

  • 1.5 mm Top Plate, Bottom Plate and Sandwich Plates

  • One 25.5 or 20 mm mounting up front and one 25.5 or 20 mm mounting in the rear OR One central 30.5, 25.5, 20 mm stack.

  • Fits the DJI Caddx Vista perfectly

  • Fits HDZero 1W VTX in central stack position

  • Fits 19 mm and 20 mm cameras

  • Recommended components:

  • 2004 motors

  • 30A or higher toothpick AIO

  • Caddx Vista + Nebula Pro

  • 4S ~800mAh or 6S ~500mAh w/ XT30

 
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ULTRALIGHT
DESIGN

Ultralight drones feel different

Ultralight drones offer incredibly low propeller disc loading making them extremely agile, direct and resposive in the air. This is point and shoot piloting.

The flight performance and flight feel of toothpick drones stems from their propeller disc loading. Disc loading is the weight of the drone divided by the area swept by its propellers.

When you reduce the weight of a drone as far as possible and use relatively large 2-bladed propellers you can achieve an extremely low disc loading. With a low disc loading the inertia of the drone becomes very small in relation to the thrust of the propellers and the aerodynamic drag created by the propeller disc. The result is a drone that grips the air rather than sliding through it and is incredibly agile and direct in the way it flies.

 

I think the best analogy is comparing a road car to a Formula 1 or NASCAR racing car. The light weight and high downforce of the racing cars allow them to stick to the road while taking corners at speed rather than sliding. A toothpick drone grips the air in the same way and it's able to change direction instantly like a housefly.

 

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THE CHALLENGE 

The Achilles' heel of the  5" Ultralight? Not any more.

 

Vibrations limit flight performance 

One of the key limitations with 5" toothpick frames is their tendancy to resonate. Toothpick frames use very thin carbon fibre arms combined with relatively large motors for their weight to swing larger 5" props.

Even the cleanest motors and props produce large amounts of vibration in flight. These vibrations excite the resonant modes of the frame amplifying vibrations at certain frequencies, increasing their amplitude and energy. These vibrations pass into the gyro and create noise on the signal. This noise requires additional filtering and limits maximum PID gains through motor heating.

 

The result is a flight controller that is slower to respond to propwash and your stick inputs. The AOS UL5 is engineered to solve this key problem to improve flight performance. And flight performance has always been one of the goals and benefits of the toothpick class.

 
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THE DESIGN

Understand the design methodology behind the AOS UL5

Harmonic analysis is the key 

I used Blackbox logging and harmonic analysis to visualize the vibrations of the AOS UL5 during the design process. This allowed me to tune the geometry of every part of the frame, moving the frame resonances up and separating them as far as possible. The UL5 uses topology optimization to identify the most effective places to add material to improve the stiffness of the frame.

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 and flight performance. With the AOS UL5 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.

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KEY FEATURES 

See the key features of the frame

 

Top and bottom plates

Both of these plates are 1.5mm thick to provide an optimal balance between strength, stiffness and weight. 

There are mountings for up to two 25.5 or 20mm stacks with one in the front of the frame and one in the back. If you prefer a single stack you can fit a 20, 25.5 or 30mm stack in the centre. There is even enough space for the HDZero 1W VTX. 

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Arms

The AOS UL5 uses a truss design with a stabilising strut supporting the middle of the arm. This truss design provides enormous torsional stiffness, resolving a key source of vibration in traditional ultralight 5" frames.


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. 

 

The frame features motor protector features on the end of each arm to minimize the risk of damage to those expensive components. Should you ever need to replace an arm, there are only two screws to undo making arm replacement easy.
 

Camera Protection

The AOS UL5 fits any 19mm (Micro sized) or 20mm (DJI FPV) camera.

Slots allow a variety of mounting positions to ensure you can position the camera to be well protected and also keep the camer plates out of view.

Carbon camera plates are stiff, strong and light while being cheap to replace if they are damaged.

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