VXS: The 135.6 MPH Ugly Duckling

By Phanny P on May 14, 2017

0 414  6 

VXS - The S doesn't stand for sexy

Hit 135.6MPH today with a 5s... and a little help from the wind. Speed was disappointing since there was a lot of help from the wind. Blackbox revealed that only 78% power was being utilized due to a misaligned motor (see project page: https://downanddirtydrones.com/portfolio/vxs/ ) Not only that, PIDs are a bit off.

More info on the frame/series of frames: https://downanddirtydrones.com/portfolio/
Drone Physics: https://downanddirtydrones.com/drone-physics/

This is the Stretch version of the VX1. The head on this one is definitely not pretty, but I did what I could to protect the FC. As long as it does the job, I'm happy. Looks like a giant mosquito from The Lost World. This will probably end up being my favorite quad in the fleet since it is optimized for general flying/racing.

One nice thing about this frame is that a Mobius mini can be strapped to the back without having a detrimental effect on the cross section.

ONCE AGAIN - I managed to get HORRIBLE video. At least it's on Mobius Mini which was set at a bad angle. At least it can be easily fixed for next time around.

Same notes about speed GPS as before:

  • Note 1: OSD speed is in FEET PER SECOND, 174ft/s = 118.6mph (not sure why altitude is not showing up)
  • Note 2: GPS for velocity readings: After much research, I have found out that GPS is the most accurate way to determine speed. GPS velocity is based off of Doppler calculations - not change in position. This is why the positional accuracy for the ublox M8N is 2.5m, but the velocity accuracy is 0.05m/s. Not many people realize this and it is the reason many think radar guns are more accurate when all evidence actually points to the contrary. However, in order to get better readings, the GPS (ublox M8N) had to be reconfigured to use the "airborne <2g" dynamic platform model. This is much better suited for quads and is MUCH more responsive and accurate than the default setting - I have no idea why the Betaflight gps_auto_config sets the dynamic model to "pedestrian" since these things hardly move like a pedestrian. Ublox resources:


Part List


Down and Dirty Drones (2 builds)
See Site

Flight Controller

BetaflightF3 Flight Controller (3 builds)


4 x Super RacerBee 30A BLHELI_S (Now Dshot Ready!) (2 builds)


4 x Cobra Motor Black CP2207 2450kv (2 builds)


RK5051 Triprop Smoke (Set of 4) (3 builds)

FPV Camera

Crazepony 700TVL Wide Angle FPV Camera 700TVL 3.6mm Lens NTSC for QAV250 (3 builds)

FPV Transmitter

AKK X1 40CH 25mW/200mW/600mW Switchable FPV Transmitter with Push Button and Digital Display (7 builds)


Anbee FPV 5.8Ghz Circular Polarized Clover Leaf Antenna High Gain Aerial Set w/RP-SMA Plug (4 builds)


Lemon Rx DSMX Compatible Diversity Satellite (DSM2 backward compatible but must use DSMX compatible primary receiver) LM0037 (10 builds)


SMC Extreme 1400mah 4S Racing Battery - True Spec Extreme (11 builds)

Misc Parts

Tarot Dia 10MM 3K Carbon Fiber Tube Boom 280MM TL68B22 For FY680 Quadcopter Hexacopter Multi Rotor (3 builds)

Misc Parts

MIDWEST PRODUCTS 5742... CARBON FIBER STRIP,.057x.177 ( (2 builds)

Misc Parts

Micro uBlox M8N GPS GLONASS W/ (18x18mm) (3 builds)

Misc Parts

MagiDeal Pack of 4 Carbon Fiber Tube 8*6mm 330mm DIY Vanished Surface Tail Tube (3 builds)

Misc Parts

Braided Carbon Fiber Round Tubing ~ 1.75" ID x 24" (2 builds)
See Site
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