tricopter conception


After I started the adventure of quadrirotor, I discovered it was possible to build a Tricopter with standard components, quite simply and cheaply. Watching some videos convinced me  this model was worth to be discovered.




Already accustomed to the structure aluminum tube / carbon of Mikrokopter, here I wanted to create a frame with a fiberglass structure.
I see at least 2 interest:

  • weight: it can be quite significantly reduced compared to an aluminum structure. The strength can remain interesting if the structure is strengthened by a few carbon fiber. By cons, in case of breakage, maintenance is more difficult since it would imply a little resin job. Finally, nothing insurmountable either
  • the look: the benefit of the mold, it can be done with more or less any form as long as the edges are not too pronounced. It can thus be arranged to accommodate the entire electronics with no visible wire

I also wanted to make a model small enough to easily take it everywhere. Its radius (from center to the end of an arm) is 23cm.

Components:

Part Reference Cost
Motor 3x Hobbycity Turnigy 3020 Brushless Outrunner Motor 1200kv 3x $13.51
ESC 3x Hobbycity Hobbyking SS Series 8-10A ESC 3x $7.69
Prop 3x Hobbycity SF E-Prop 7×4 / 178x102mm 3x $1
motor gyro 3x Hobbycity Telebee Head Lock & Standard Gyro (Digital/Analog) 3x $24.79
yaw gyro 1x EK2-0704A Lock Head Gyro Esky environ 10 euros
Servo 1x Hobbycity Turnigy MG90S Metal Gear Servo 1.8kg 1x $5.72
Bat 1x Hobbycity Turnigy 1300mAh 3S 25C Lipo Pack 1x $11.99
RX 1x Hobbycity X8 R6 6Ch 2.4GHz 1x $19.99

For around 150 euros total cost, frame excluded.

The propellers I chose initially  are slightly larger: Hobbycity TP Slow Fly propeller 8 × 3.8.
But experience has shown that engines are running too fast for this size of propeller.
Hobbycity SF propellers 7 × 4 are a little heavier, but are nevertheless very strong.
Coupled with a prop saver, they should withstand many crashes.

I firstly took 4 Ebay esky gyros EK2-0704B Head Lock Gyro Esky for their low price.
Unfortunately, these gyroscopes are not suitable at all for the Tricopter.
I could have kept one for management of the yaw, but its footprint was too large for my frame.
So I took her little brother that I had in stock, and who does the job very welll.
Believe me, the elements of the above table are tested and approved, and it is risky to try others, especially the gyros ;)

Construction

I started by assembling a few pieces of styro with a glue that does not eat moss.
After careful sanding, here’s what you can get:

Reinforcements are prepared by tape and fuse carbon.

After fibering by 3 layers of fiberglass 160g.

I cut one end that is then articulated by a servo motor for yaw control.
I put from that end some acetone in order to dissolve the styro.
A hood will then be cut to accommodate power electronics.



The small 4-channel receiver will only be used for initial tests, we will need at least 6 channels for control and the gain gyros management.




With propellers (not the final ones):


detail of yaw mecanism:

gyro implementation



View of Tricopter completely finished.
Weight without battery is 260g
The 1200mAh battery used weigh 120g.

Settings (for a Graupner MX16S)

We must select the radio model helicopter with 120deg CCPM management (most common now for heli).
The pitch curve will define the average speed of 3 engines and therefore the model’s ability to climb or dive.
Given kv motors and propellers chosen, I limited the max value of the curve to 19 for a minimum value of -100.

The mixing swashplate is left default: pitch 100%, Nick + 61% Roll + 61%

I greatly reduced the rate of dual swashplate because the model is very sensitive:
Nick: +41%, expo +30%
Roll: +41%, expo +30%

For the management of yaw, the control will depend on the assembly and the resultant amplitude.
I had to reduce the amplitude of the channel to -70%, +70%
The gyroscope is positioned head lock to a value of -80%

The 3-channel gain gyros Telebee are connected together and the value is set to -30%
(a stronger gain makes the Tricopter oscillating and a lower gain doesn’t correct enough)
The switch DS is set to ON, the Super Simple ESCs seem to support this mode.

The 3 ESC must be calibrated and programmed without gyro connexion.

Video

http://vimeo.com/8652675

  1. #1 by BC on 20 mars 2012 - 23:54

    Hi! I was wondering if you could help me out a bit with setting up the Graupner for this? You already have some good info here, but something a bit more in depth, as I am pretty new with this. How do I, from scratch, set up the Graupner MX-16 for a tricopter setup?

(ne sera pas publié)