eric's model flying blog

Meanwhile (while I was working on my S500 homebuilt quadcopter), I joined a Dutch drone forum that had just started: www.dronepilots.nl. After a while, they organised a price draw of one of the drones they had received for a review. And guess what? I won! 😃 It's a GDU Byrd, formerly known as ProDrone Byrd. I won one with the old ProDrone logo still on it. It's a full size foldable drone, with a modular gimbal system. Mine came with the standard 1080p camera. It has a holder for a phone or tablet on the controller, and after the accompanying app connects to the controller's WiFi, you get pretty much all the functionality you'd expect from a drone capable of autonomius flight: auto take-off, auto land, GPS and baro assisted position hold, (auto) return to home, waipoint missions, video and photography remote control, etc. Full resolution video is stored on an SD card inside the camera, and (if you indicate that in options) a lower resolution version on the mobile d...

I I wanted to prove to myself that I could program an Arduino Development board to function as a flight controller. Pretty much the same algorithm can be used to control a camera gimbal to keep an action cam steady on a wobbling quadcopter. But since I got the quadcopter to fly already, I did not feel the need to prove myself all over again. So I just bought myself a  HAKRC 3-axis Gimbal  to put my cheap action cam upon. I have a more expensive Drift HD Ghost, but that one weighs about 200 grams, while my cheap no-name GoPro clone only weighs 56 grams... S the choice is simple. It will not render super quality images, with 1080p at a very high compression rate, but it will give a nice idea of the possibilities. But, just simply spending money on a gimbal doesn't get you there. There's a whole brunch of parameters you can play with to get the response you want from each of the three axes. It is hugely important to make sure your action cam sits on the gimbal in perfect b...

Bigger frame, bigger arms means longer wires. It' soldering time again! I gave the motors bullet connectors, and I want to re-use the motors as-is. So with the ESCs further out towards the ends of the arms, I needed longer wires from the main board to the ESCs. Put some bullet connectors on them as well. Gotta love Modular designs 😃 The signal wires leading from the Arduino board to the ESCs needed to get longer too, of course. I used a bit of RGB LED wire (Red, Green, Blue, and black), mounted a pi header to one end, and connected the white ESC signal wires in order to the RGB cable. Note the black rings around the white wires? That are small pieces of black shrink tube to number the wires according to the motor number they are connected to. Simple, but effective! The top plate looks like this, now. Note that the Arduino board now is mounted upside down, to protect it's electronics a little better when I crash again. And crashing I did... Mid-hover, the quad just flipped upsi...

As I wrote before, so far i've ordered everything I used from Chinese web vendors. The argument initially being the price, of course. I did not want to invest too much in a project with an unsure outcome, if that's not necessary. And in my case, there were many possible negative scenarios, making this a sort of high risk project. I did not know if I could pull it off, software-wise. I had some confidence in me getting the mechanical part sorted out. But then, if those two would come together, I did not even know if i could fly at all, or if I would like to fly such an apparatus. Or if I would continue to like it, once the challenge of getting things to work would wear off. But since my experiences with those Chinese vendors was positive all around, I continued to order from there to this very date. I have only once not received an order (out of some 200 orders), and that was settled with a refund after only two messages. Also, I received something different than I thought I...

After connecting up the motors, and the battery (props still removed!), the moment of truth was there... No smoke! So no electrical shorts yet. Then for the first time ever spanning up the motors! I had attached a piece of sticky-tape to the motor shafts, so that I could see the turning direction (the tape bends due to the forces of the air, and stays deformed after stopping the motors). Of course, two out of 4 turned in the wrong direction, so I had to swap two wires per motor to get that corrected. I had deliberately connected the motors with bullet connectors, both for modularity, and for being able to quickly correct this. After swapping the wires, and one last check of the spinning directions, it was time to mount the props. Again, observing the turning directions. Then, outside, with the quad in my hand - looking out for the diameter of the props to be well clear of anything, especially my arms - a first spin-up. With about 1/3 throttle, I tested out if the corrections...

OK. What!?! Vortex Ring State! It's the helicopter variant of a stalled wing. I had not heard of it yet, when I fist encountered the effect. It comes down to this: if you descend vertically, and you do that relatively fast, you get into the downwash of you own propellers. That will cause your props to loose lift, and you descend even faster. Your natural reaction would be to throttle up, because you are now descending more rapidly than you planned, but that makes the downwash - and therewith your predicament - only worse! The only thing you can do is pitch or roll to move out of that vertical column of air, not necessarily with more throttle. Only: you have to think of that, and act on that, before you hit the ground... I didn't. It caused my quad to "land" on one arm, and that was a touch too much... So now I had to go shopping for a new frame arm. I decided that buying a new frame would be a better option, because it is not that much more expensive, and I could imme...

After first flight, comes first mods 😉 One of those things you know in advance about this hobby: once you have a flying system, you recognize opportunities for improvement, which leads to modifications. That's just as sure a bet as saying you will crash at some time.  In this design, I initially had the battery placed between the top and the bottom plate. But there was no good way to secure it such, that it would not slide forward or backward between the plates. And a slidings battery is disastrous for the Centre of Gravity being as good as possible in the middle, as the battery is by far the heaviest component. There was not enough room for friction material. Hook-and-loop would be even thicker, and require the battery to be peeled off, for which there was no room either of course. So the battery had to go under the bottom plate, with hook-and-loop, and a battery strap for added security. But landing on the battery is not the brightest idea, so I ordered some of those l...