It’s a bit overcast, a bit windy and there was a little bit of rain, but it was good enough to get the RS352 back in the air again this weekend. It’s been far too long since I’ve been able to fly a proper plane rather than these quadcopter things. Speaking of quadcopters, we ran the Royal Institution Coding for Year 9 session on Saturday where we gave 5 quadcopter kits to 30 year nine students (13 years old). The remains of what was left after the mass flying session is in the picture below:
The kit is a modified HubSan X4 H107C with connectors soldered onto the motors and flight controller so the kids could follow the instructions and push the right motors in to the right holes with the right propellers. The frames are all 3D printed and there was a Dragonfly as well, but there was a bit of an incident. We thought this might be a problem, but the body is too thin so it broke in half, at which point one of the kids said, “shall we throw it in the bin now as it’s broken?”, to which we replied “no, we can fix it”. I’m hoping it’s still back in the office somewhere, but I can’t actually remember seeing it.
I’ve also had a play with the 0.3 mega pixel camera that’s on the unmodified HubSan. We now have 6 of these cameras, so we might do something interesting with them in the future. In addition to this, I also flew the 3D printed H Frame, which does fly more or less like the HubSan that the electronics were originally stolen from. The interesting thing is that we had 6 brand new HubSans, which I tested before modification, and they all fly slightly differently. One felt a lot more powerful than the others and was a lot twitchier, so, whether this is quality control or different settings, I don’t know. One other thing I did notice though was that a lot of the motor housings were cracked and broken. At first I thought that I was doing this taking the motors out, but they are definitely cracked as delivered, so quality is a bit of an issue here.
Anyway, despite the fact that I now need to sleep for about a week, Sunday looked like the first flyable day in about a month, so I headed off with the RS352. When I got to the field there was an Inspire flying and another guy was already there with his Phantom and a much more impressive FlyBaby that flew great. Apart from the EFlite Advance and some people with what looked like a HobbyZone box who decided to fly on their own at one corner of the field, there was also another guy with his two kids, a Sukhoi, various small foam planes and a DJI Phantom 3. It was this Phantom 3 which caused the argument about what constitutes safe flying as he was being an idiot. Apart from putting it right in the middle of all our planes and insisting that it was a good idea to take off and land inches away from the planes and us, he was flying FPV without a spotter and going to extreme distances. First he went over into the other field and tried to hit the trees over the roundabout by hovering just feet away from the branches (it was quite gusty), he then went a long way out over some more trees, along the other side of the road, then back and over the tree line where the microwave link is at the edge of the field where we keep losing models. Unfortunately, not his this time, as it’s not often I say that I would have been very happy for him to lose his model and not find it again. He actually went behind the trees and down so there was no line of sight. After he landed we tried to point out to him that this is illegal in this country (I think he’s Italian from the accent), but all he did was proceed to tell me how reliable the iPhone attached to his DJI transmitter and FPV kit was. Despite pointing out that we gave him 50/50 at the point when he went behind the trees and if they were wet and had leaves on then both his 5.8GHZ video link and 2.4GHZ radio link would have failed, but he just said that he had a magic button that brought it back. When I pointed out that his magic button sent a 2.4GHZ signal that might not get through, he just said that it would return to home on its own. We’re not sure if it would actually have cleared the trees, but pointing out that this still relies on the GPS, which can fail, he tries to tell me that they never fail and that he knows a lot more about them than me. Never a good idea to do that, especially when he then tries to say that he has a signal strength meter on his phone, I mention RSSI and he doesn’t know what it is. He also doesn’t seem to appreciate that it can also fail instantaneously if you go behind an object like a tree. An interesting point here was that he wasn’t even using a circular polarisation antenna, just the standard DJI one. I saw some kit on the BBC the other night where they had the exact same DJI Phantom, but had replaced the standard antenna with a circular one and a patch. I’m so annoyed by his attitude that I might even take my FPV kit with me next time and jam his if he turns up again. Anyway, on his next flight he was still insisting on taking off from the middle of us when it tipped over and landed on two of the props. Unfortunately the aircraft was still unharmed.
OK, that’s enough getting annoyed about quadcopter FPV idiots, I had two flights with the RS352, had a really nice chat with some American tourists and their two children who were very interested in the aircraft and loved the story about the Coding for Year 9s session with the quadcopters yesterday, then my motor shaft broke on my second landing. This was really weird because I was going to hand launch and it felt like all the thrust was pulling downwards, so I aborted to check the aircraft over. Everything was fine, went to launch again and everything was normal, so off I went thinking it was probably just the wind. At the end of the flight I felt that the power was dropping off very early (4 mins instead of 8), then it started to get very unstable one turn from finals. Now, with no power and a very twitchy aircraft, I put it down on its wheels, wing tip and spinner a fair way away as it tip stalled to the right close to the ground with no power to get out. It was also quite windy, so I was thinking that it was the wind at this point, plus a battery not used for a while, even if I did peak it before flying. On getting to the aircraft, I could see immediately that the motor shaft had sheared clean off at the bearings in the front of the motor. The prop was still in one piece and attached to the adapter, which still had a cleanly sheared bit of the motor shaft inside it. My thinking is that this must have happened in the air and my aborted first launch was a symptom of the shaft not running straight. Then the loss of power and handling problems were the shaft in the process of shearing, finished off by dumping it into the earth. I just can’t see a 3mm shaft breaking like that and leaving the prop intact. It’s probably all these high torque and gyroscopic reactions which caused the fatigue in the first place, but this is the first time I’ve ever seen this happen. Oh, well, I’ll just have to get a new shaft and try and extract the motor.
After breaking the RS352, I then went and had a go with the HubSan X4 H107C with its 0.3 megapixel camera. Watching the video of this back is really interesting, but I should really have been concentrating on what I was filming and not talking to the guy next to me. You get a lot of shots of grass, but it’s the take off and landing that really gets me.
It’s interesting to see the video, but you really need the new high resolution camera to get the best out of it. It’s probably better indoors, although the stop start button for the recording is a bit fiddly and you never really know if you’ll get a recording.
One final thing, but on our way home we saw another person flying a small white trainer type aircraft (badly) in the wrong field. I hope somebody points him in our direction for next week.
Right, I’m off to fix a motor shaft and build and autogyro.