After a hiatus of nearly four months, I’m in the air and taking photos again. I’m happy with the performance of the rebuilt plane and took it out for a test run the week-end. I am still waiting for the auto-pilot, so I flew it manually.
It’s flying nice and stable and the camera mount and remote trigger works well. I took a few hundred photos of the area where I re-maidened it and built up a composite photo from the photos. Results are a bit rough as a human cannot hope to fly as consistent as an autopilot, but I’m happy that the individual photos look good enough. Which means that the new nose is at the very least not causing more vibration to reach the camera than the old nose did.
The trigger also retracted the lens back to safety both flights, so I am much happier about the safety of the camera than I was with the old setup.
In the mean time, I have acquired a Bixler 2 plane that I plan to use for casual FPV flying and as a trainer for the kids.
They are really sweet planes and very popular as a cheap and no fuss FPV platform. I will maiden it tomorrow and plan to have it set up and ready for the summit as an extra example of cheaply getting a video platform in the air. It would not be able to carry the still camera, but it will easily carry the keychain video camera and even a GoPro sized video camera.
I will report back here once I have flown it.
I have finished the shelf on which the camera will rest and cut the hole in the bottom through which the lens will look. I have also managed to get a nasty glue-gun blister on my thumb for my troubles.
After having endless problems with wheels ripping off in thick grass, I decided to leave the wheels off and make the plane a belly-lander. I did however add a single centre line wheel if I have to land on hard surfaces. It’s partially embedded in the body so it should not snag on anything.
One concern with the wheel is that it sits right in front of the camera’s lens hole and can potentially throw dirt right on to the camera lens. I have however built a remote control for the camera using an old servo board. With that I can extend and retract the camera’s lens by connecting the camera’s USB port to a channel on the receiver that is assigned to a switch on my remote control. That way, the camera lens will be safely retracted with it’s lens cover over during take off and landing. Later, the channel can also be controlled by the autopilot if need be. I’ll post details on the camera remote-control later.
I still need to tidy up the servo wires in the non-removable part of the aircraft, but I will always have two loose ones as they have to detach when the wings are removed. I will also have to add a shelf for the autopilot once it arrives. The autopilot will probably not be in time for the summit, so “Mark I Eyeball” flying will have to do for now!
I have some plans for reducing the weight of the plane too by cutting holes in the wings and the body and covering those with film or Vinyl, but I’m still undecided on this.
After my crash near Harrismith, I threw a bit of a temper tantrum and took a break from everything drone. The crash really baffled me and killed the autopilot in the process. So I could not ever retrieve telemetry to see what went wrong. I did figure out the reason eventually (see details below).
Life went along and my job at ESRI South-Africa assigned me to do a talk on UAVs and their use in aerial photography in the upcoming summit. The topic is covered over a whole day and includes a demo and processing of the data.
So, I had to procrastinate later and get the drone up and flying again. Since the nose was a bit mashed after the last crash, I decided to implement and idea that I have toyed with for a long time – rebuild the nose completely. So I started removing what was left of the nose:
My experimentation with 75x75mm PVC gutter downpipe on other planes were quite successful and matched the width of the old body quite closely. I decided on a design that allows the nose to be detached. The “avionics package” (RX, autopilot, speed controller, BEC, etc.) will stay in the body of the plane, whilst the “payload” (cameras, batteries, etc.) will go into the detachable nose. This way I can make noses custom crafted to the mission.
The new nose has way, way more space than the old one. Gone are the 2-3cm thick foam walls, replaced by 2-3mm of PVC pipe wall. This is going to make packaging much easier in the future. The autopilot and camera equipment will also now be nestled in the middle of the plane body, far away from crashes. The canopy is made from old 5 litre purified water bottle heat formed over a wooden blank. So the canopy also has very thin wall thickness. I also repainted the plane white as I was tired of the ugly orange that did not really help much with visibility of the plane.
I also decided to enlarge the rudder fin. I always felt it is too small and have read that other people had good results enlarging this on this plane body. In the process of rebuilding it, I finally found out what caused the plane to crash. The rudder servo was dead. It explains the behaviour of the plane right before it crashed. The auto pilot was flying the let-down pattern and was on the downwind leg, and on trying to turn to the base leg, it would not turn. The plane banked, but would not turn and kept heading away. I took over from the Autopilot and tried to turn it manually, giving it more bank and pulling more on the elevator. It suddenly spinned and was on the ground in two rotations. My guess is that the servo died with the rudder stuck hard over (I could not see it after the crash as the rudder was ripped off) and it was banking in the opposite direction. The low speed, high angle of attack with lots of rudder in the steep bank was probably just too much and physics took over.
This is the second servo failure on this plane. I tried to use good quality metal gear digital servos. Bot failures so far was the expensive ones. The cheap replacements have never died in other planes nor this one. The first failure was an aileron failure and did not cause much trouble. I have now rebuilt the tail with a bigger fin, and a split elevator with a servo driving each half, giving me redundancy on the elevator (the possibility of a servo failure on the elevator has kept me awake for long enough now). Once I get my replacement autopilot, I will setup it back to it’s default of not using the rudder at all. It makes for less tidy flying, but since I don’t have redundancy on the rudder, I will leave it for manual flying and compensating for wind on landings only.
Here is a side view showing the new tail a bit better:
I hope to maiden the new setup this week-end and will post updates and more photos of the insides.