Andrey_Rakhmanov's blog View Details
Posted by Andrey_Rakhmanov | Dec 18, 2019 @ 06:05 PM | 5,101 Views
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(this is the translation of my article written in Russian)

Summary: I like manufacture 2-engine aerobatic flying wings. Such models have a non-standard control scheme - due to the presence of 2 engines, they are close to quadcopters and need stabilizing gyroscopes. But the 2-motor models cannot be connected directly to the flight stabilizer, and for such models I created a separate signal mixer based on the Arduino Pro Micro (I have already written several articles about it). The latest version of the mixer uses the FrSky-S8R stabilizing receiver. Mixers of this type flew a few dozen hours on various 2-engine models and performed quite well. But at the same time, some shortcomings were found in the mixer:

- To set up the mixer, a relatively complicated calibration procedure is needed. He inherited this property from an older version of the mixed with semi-analog PWM signals. But FrSky-S8R generates digital SBUS signal which comes directly in digital form from the transmitter - why we need to calibrate it if all the parameters are stable and can be set in advance?

- Low accuracy. The mixer generates PWM signals for motors and servos. The fronts the PWM signals are generated by the ATmega32u4 processor with accuracy about 1-2% of the signals duration, although ATmega32u4 can produce precision digital PWM signals directly from the built-in timers.

- Not optimal signals mix for the elevons. In previous version I did analysis to find the optimal signal...Continue Reading
Posted by Andrey_Rakhmanov | Sep 13, 2019 @ 06:22 PM | 1,958 Views
For my pilotage 2-engine Arlequin I manufacturer square cockpit canopy. The canopy protects model electronics compartment from dust and moisture.
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It is quite easy to do, I briefly describe describe the process by several photographs.

First we need to prepare pressing form. I cut parts of the form from 4 mm polystyrene sheet.
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Description: ...Continue Reading
Posted by Andrey_Rakhmanov | Sep 10, 2019 @ 05:13 PM | 1,202 Views
Milling carbon fiber (3X speed) (2 min 1 sec)

I have a need to cut carbon parts for my airplane models and decided to create CNC capable to do carbon cutting.

Requirements for the machine:
  • Total price of components less than $300.
  • Weight less than 15 kg (30 pounds).
  • Should cut A4 size carbon sheet with precision about 0.1 mm.
  • Should be portable and environment friendly - designed to do cutting and to be stored in the apartment living room,

Finally I found cheap CNC ($125-$225) on banggood and re-designed it:
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Major improvements:
  • 500 Watts spindle ($50-$80).
  • Vacuum cleaner hose attached($10).
  • Bridge Cable Chain($10).
  • LED work zone light.($10)
  • New couplings and bearings($10-$20).
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Posted by Andrey_Rakhmanov | Jul 22, 2018 @ 05:14 PM | 3,221 Views
Previous stabilization scheme for the 2-engine Arlequin used Eagle Tree Guardian flight stabilizer. This stabilizer is quite old (more than 10 years) , so I decided to replace it with a more modern and popular one. It is not easy to do because very few stabilizer can match qualities of Guardian. Finally, the choice fell on a popular receiver with built-in stabilizer - FrSky S8R.

I tested FrSky S8R with classical scheme model, and what I found:
- Relative small price - $ 40 - $ 50 - 8 channels for a telemetry receiver with stabilizer isn't bad!
- It has telemetry channel - it is possible to measure the voltage of the battery.
- Can output data in SBUS format - allows to avoid PWM wires mess. Now receiver can be connected with one cable.
- An ability to do full configuration directly from the transmitter (Taranis + Lua scripts).
- A large number of flight modes (3D, horizontal stabilization, hover, knife).
- Active support from FrSky - new firmware releases, utilities, etc.
- Receiver configuration menu features minimum possible number of settings.
- Complex and unobvious processes of installation, configuration and calibration - for the understanding it's better to watch the video on YouTube.
- Support - only 3 basic types of plane models (classic, delta wing, v-tail) 'hover' and 'knife' flying mode aren't enabled for delta wing and V-tail type models.
- Not very obvious stabilization scheme. Impossibility to set the "general"...Continue Reading
Posted by Andrey_Rakhmanov | Jul 20, 2018 @ 04:47 PM | 2,808 Views
I usually write posts in Russian for Now I decided to start mirror publications in English here . I am placing below links to old rc-aviation articles - if someone needs to translate them in English - does good job here.

Latest version specifics - Arlequin III
Previous version (review)-
Previous version (building) -
Previous version (pre-flight tuning)
2 engine signal mixer building and programming -