PVC V-Tail Photos for DocWelch


Here's what I can do for photos this late in the game. I really should have taken build photos before everything got covered up with electrical tape and zip ties ;) The craft is crude, but I'm really happy with how it flies with modded 2.9.1b firmware. I'm working on 3.0.1, but tonight's weather got in the way of my test flight.







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  • sorry yaw not pitch

  • Hi Bob...looked at yopur mixing do you think the attached will work as well, trying to get motor nums and + - right....this uses motor naming like quad could you take a look,,,I compare yours as well..


    add_motor_raw(AP_MOTORS_MOT_1, -0.7, 0.7, -0.23, 1);//FRONT_R CW

    add_motor_raw(AP_MOTORS_MOT_3, 0.0, -0.7, -0.7, 3);//REAR_L CW

    add_motor_raw(AP_MOTORS_MOT_4, 0.7, 0.7, 0.23, 4);//FRONT_L CCW

    add_motor_raw(AP_MOTORS_MOT_2, 0.0, -0.7, 0.7, 2);//REAR_R CCW


    add_motor_raw(AP_MOTORS_MOT_1, -1.0, 1.0, -0.32, 1);//FRONT_R CW

    add_motor_raw(AP_MOTORS_MOT_2, 0.0, -1.0, 0.5, 3);//REAR_L CW

    add_motor_raw(AP_MOTORS_MOT_3, 1.0, 1.0, 0.32, 4);//FRONT_L CCW

    add_motor_raw(AP_MOTORS_MOT_4, 0.0, -1.0, -0.5, 2);//REAR_R CCW


    Pitch numbers seem to be reversed?

  • I think the right answer would be to remove the frame type parameter and simply make the mix table configurable from within mission planner (i.e. one mix table, populated from eeprom). I'd like to also see a throttle factor added for each motor, but unfortunately the new stability patch code would have to be rewritten to consider it. 

  • Fantastic work on the code.  Perhaps we could consider adding a V-tail as a selectable frame type?

  • I should point out that the tail boom was originally PVC, but it flexed a bit too much in the roll direction, so I replaced it with a piece of carbon tubing - same exact size (and weight) as the PVC, but much more rigid.

    When I get a chance, I might reduce the front arm/tailboom lengths to make it more 450 frame size instead of 550 -which could probably do without the carbon.  

  • Thanks Bob,

    going to rework my dead-cat quad to VTAIL soon...

  • Here's a video from a front mounted gopro. There's a yaw spin in there, along with some flips n rolls and even a crash at the end when I got too close to the ground... 

    DropBox Video

    You can download the video to get higher def, but it's mostly just grass blurring by ;)

    Shared with Dropbox
  • Details:


    Rear props angled 30 deg

    10 x 4.5 propellers

    D3530/14 1100kv Motors

    30A HK ESCs (SimonK )

    APM 2.5 brain with 915 Radio + GPS

    4000mAh 40-80C nanotech battery

    All up weight 1672g 

    Flight times are only about 7 minutes, but it has a ton of punch and speed. 

  • Here's the basic code changes:

    in AP_MotorsQuad::setup_motors(), add a vtail mixer:

      }else if( _frame_orientation == AP_MOTORS_VTAIL_FRAME ) {

        // hack - VTAIL (1=NE CW, 2=SE CW(INV), 3=SW CCW(INV), 4=NW CCW)
                                                               // R, P, Y, TO
        add_motor_raw(AP_MOTORS_MOT_1, -0.7, 0.7, -0.23, 1);
        add_motor_raw(AP_MOTORS_MOT_2, 0.0, -0.7, 0.7, 2);
        add_motor_raw(AP_MOTORS_MOT_3, 0.0, -0.7, -0.7, 3);
        add_motor_raw(AP_MOTORS_MOT_4, 0.7, 0.7, 0.23, 4);

    And also add this to AP_Motors_Class.h:

      #define AP_MOTORS_VTAIL_FRAME       4

    You just have to get the signs right depending on how your props are configured. Mine are in this config:

      Motor 1=Front Right: CW,

      Motor 2=Back Right: CCW(INV) <- my tail motors are upside down

      Motor 3=Back Left: CW(INV),

      Motor 4=Front Left: CCW

    After downloading, manually set your FRAME parameter to 4 in the advanced parameter list with mission planner. 

    In the mix table above, you'll see that the roll is controlled by the front props only. Typically VTails also get set up with yaw on the rear only, but I added some cross prop balance (0.23 factors) since the V was causing some roll when yawing. I set up the prop rotations so that the yaw torque changes help yaw in the same direction as the V push.  

    Those numbers might need to be adjusted to match your particular frame. My complete changes include a throttle factor to take some power out of the front props, but I actually only ended up cutting 5% out - you could just as easily adjust the front to back weight distribution instead. 

  • Good work Bob.

    Can You please publish code changes regarding V-Tail motors control?

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