Month: March 2016

Easter Rain Day

It’s Easter Sunday today and the clocks went forward onto British Summer Time this morning, so I had already lost an hour of flying anyway. After the current run of good flying weather, it’s all been brought to a halt over the Easter weekend. So far this morning we’ve had gale force winds, torrential rain, thunder and lightening, hail and bright sunshine. I remember when I used to test fly my new models over Easter and could get several consecutive good days of flying in. One year I remember bringing a succession of Kyosho F16 EDF, Vampire EDF, Extra 300 and Flying Wing on different days to comments of, “I’ve seen you here four days running with four different models” from a guy I bumped into.

Needless to say, pressures of work mean I haven’t got the ATOM Autogryo finished yet, but I have made some progress with “Bob” who’s going to be flying it for me. You can see him here in the cockpit and I’m really rather impressed with how he’s looking. Bearing in mind I was intending to do a pilot with a helmet and then changed my mind after reading the RCM&E article on pilot models. This was about how you don’t ever see someone flying a plane in a motorcycle helmet like the ATOM prototype has, so I think it’s come out really well considering. I had already made the head helmet shaped, so added a cardboard peak for the baseball cap and painted the top of his head red. That worked, so I mixed some red and white and gave him pink skin. Later today I’m going to give him some blond hair, eyes, nose and a mouth. The eyes I can cover up with dark glasses, but I think the nose and mouth might be my undoing (scarf?). Anyway, I’ve got two weeks off work so I’m hoping I can finish this now and fly it when the wind finally drops. I have discovered a bit of a problem, though, in the way the motor wires don’t reach through to the speed controller. I’m going to need to make the hole in the firewall a lot bigger and just hope for the best. Other than a few awkward bits and pieces (and painting and covering), there isn’t much left to do but make it work.

As for doing any flying this Easter, I do have 18 batteries (yes 18) left over from the Royal Institution session we did a couple of weeks ago. That would give me quite a lot of flying time with the HubSan X4C, but I am starting to get really fed up with quadcopters. I want to do something unusual, so have a look at the 3D printed frame on the left in the picture below:

IMG_20160327_140802.jpg

Does it remind you of anything? Have a look at some of these images of an Eagle from Space 1999: https://www.google.co.uk/search?q=space+1999+eagle+images

That might surprise a few people if they saw it flying around. It’s an Eagle, NOT a Drone.

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Viggen, Su27,Quad

Another flying week and I was beaten to the field by a guy with a couple of white aeroplanes. Walking across the field I was thinking, “Eurofighter? – no, Mirage? – no, Viggen – yes!”. You don’t see many Saab Viggens being modelled and I’ve always fancied building myself one. He actually had a Viggen and an SU27 made from depron sheet, both using pusher props. The Viggen had a single two blade prop on the back, while the SU27 had thrust vectoring and two rear mounted three blade props. He had actually 3D printed the thrust vectoring units himself and proceeded to show what crazy manoeuvres it could do, looping almost within its own length. Just to add to the collection he also had a quadcopter based on the F450 with the longer racing body. The first flight with this, though, ended in a crash. He flew out, something happened and it twisted left in an odd way, recovered, then flipped out again and crashed into the ground. The cause turned out to be a broken dual diversity antenna on the radio causing him to lose radio contact. This was an interesting one, because, without the second antenna working in an alternate orientation plane, it was fine flying away from us, but the turn caused the radio to drop out due to orientation and carbon fibre blocking the signal. So the initial glitch caused it to move into a bad orientation, which quickly turned into an even worse situation with total loss of radio. It didn’t suffer much damage other than a broken prop, so it should be flying again soon with its second antenna soldered back on.

In addition to depron warplanes, the E-Flite Advance also had a few flights, I managed three with my RS352 and then another guy with a racing quad in a box came along. Near the end of the morning we were also joined by another guy with a DJI Phantom in its big carrying case, plus a dad and his two small kids with a Multiplex Easy Star. This was interesting, because he had it set up with two transmitters using the trainer function so he could teach the little ones to fly. That was interesting in itself because, although he said that they could manage on the simulator, once they were out in the real world it all went a bit crazy. I had to leave them to it unfortunately.

As for my flights with the RS352, it is definitely making more noise than it was before I replaced the motor shaft. I put it down to the washer and circlip at the front of the motor as there is a definite “metal on metal” sound that wasn’t there before. It might be the prop adapter slipping as I thought after the first flight that there was more space between the back of the adapter and front of the fuselage. I tightened it all up and kept an eye on it for the next flights, but nothing seemed to be wrong. After dismantling it this afternoon, it looks like it might have been slipping, so I’m going to make myself a spacer to use when fitting the prop adapter so I can check whether the distance has changed after every flight. The trim doesn’t seem too far off, but the weather the last two weeks has been far from ideal with the gusty conditions. I do seem to be getting problems on the up and down lines which might be due to a changed thrust line though.

Finally, I’ve managed to fix my bench power supply, which needed a new fan. I’ve been using this Ripmax Pro-Peak supply for years and it’s been really useful, so I didn’t want to just throw it away.

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My RipMax Pro-Peak power supply with a new Maplin 40mm fan fitted. The fan in the picture is the old one with broken bearings.

The bearings on the fan had gone, so I managed to get another 40mm fan from Maplin and replace the old one. I’m not going to give too many details, because it’s one of those things where if you need to ask, then you shouldn’t be doing it. I had to remove the four tamper-proof screws from the case to get into it before I could then replace the fan, changing the connectors over from old to new.

The picture shows the old fan, with the new one installed and working. It’s currently putting my batteries back to a storage level, so it looks like it’s working again.

The rest of today I’m going to make an effort to get the autogyro closer to flight ready as it’s Easter next week and I always seem to end up test flying all my new models at Easter. There’s no point in flying it until the wind drops though.

Is This Spring?

It’s bright and sunny with a bit of a breeze today and yesterday it was definitely starting to feel like spring. I’ve managed to fly two weeks running now, which hasn’t happened in a while. The skylarks are back too.

It started out this morning with the heli guy doing his inverted thing and tail sliding with a big aerobatic helicopter. Then I was joined by the e-Flite Advance and then by an extremely polite drone pilot with a camera and a DJI Phantom in his backpack. A little later another two drone pilots arrived, having been told they were in the wrong field by some passers-by. They had what looked like a racing quad, but it took a while for them to set it up. We saw the DJI Phantom make a few flights, with its very distinctive shape in the air. Both sets of quad groups went to the opposite extreme ends of the field and left us to our proper aircraft in the middle.

This was the first flight of the RS352 after fixing the motor shaft which broke last week, so I had also brought my Acrostik along as a backup plane. I needn’t have worried as the RS352 worked fine and the thrust line was at least vaguely correct. It was hard to do a proper trim in the gale that was now blowing, but I got 3 flights with the RS352 and 1 with the Acrostik, taking off from the ground and proving that it still goes like a bat out of hell. For a plane that must be at least 15 years old it’s not doing bad and the speed is just what you want in windy conditions.

The RS352 took me all week to fix, as you have to cut off the fibreglass motor mount which is epoxied to the foam fuselage front and pinned with cocktail sticks. I had to drill out the cocktail sticks and then cut the fibreglass mount free just to get at the motor.

Once the Hyperion ZS22-13 18 motor was removed, then I could have a look at what caused the shaft to break.

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The broken ZS22 shaft. The front is the left end, so you can see how it broke cleanly at the groove to hold the circlip on the front of the motor bearings. The flat on the shaft goes at the back of the motor to hold it in the rear bearings with two grub screws.

Looking at how clean the break is, right through the circlip groove, this must be put down as a component failure as a motor shaft isn’t supposed to break as easily as this one did. Usually they get bent rather than snap in two. It’s also interesting to note that the replacement shaft is of a different type.

When I tried to order a replacement last Sunday, I found that the direct replacement was unavailable, so, looking at the specifications of the other two variants of the ZS22, I figured that the ZS2209 would probably work. You can see that it’s about 4mm shorter, but these motors are designed to have the prop attached to either the front or back and so have an extended shaft protruding from the rear bearings.

In the event, I needed to extend the flat milled into the shaft by 2mm to make sure that the grub screw locked onto it. Also, these motors require a huge amount of force to remove the shaft, which is a very tight interference fit in the rear bearing. I managed this with a bench vice and wooden spacers to exert pressure on the shaft from the back without damaging the motor can. Once it got to flush with the rear can I then had to use a 3mm bolt in a quickly bodged jig to push it all the way out the front. After that the new shaft went in fairly easily, using identification marks which I put on the rear of the motor to enable me to push the shaft in the right amount and also line up the flat on the shaft with the grub screw positions.

After a quick run on the bench to see that it worked, I then rebuilt the front of the RS352. The motor is placed into a plastic bag and the fibreglass motor mount is glued in place using epoxy and wooden pins to hold it in place. Due to the original pins being drilled out of the foam, this had left a bit of a mess, so the mount is now in a slightly skewed position. It’s actually rotated anti-clockwise a few degrees because of the fact that you can’t completely drill out all of the old pins, so the new ones are about 1mm out.

Once the motor was in, the glue had dried and I had cut the motor out of its protective bag, I gave it a first test. I put the prop back on, checked it was all running true and blipped the motor (very little). It was running backwards, so I swapped two of the ESC wires over and gave it another go. Everything seemed fine, so the only thing left was to go and fly it.

Like I said earlier, it all worked fine, although it does sound different in the air. I took it easy on the first flights and checked the grub screws were still in place and nothing else had come loose, but it all appears to be working perfectly. Only further flights will prove this though.

Well, that’s one aircraft fixed, so I’m now going to spend the rest of the day building an autogyro.

How to Make Micro Connectors

If you’re wondering how I made the 1mm ‘bullet’ style connectors for the modified HubSan X4 quadcopters, then it’s really easy to do. They’re made from 25 way D connectors that I bought on the high street from Maplin:

http://www.maplin.co.uk/p/maplin-d-sub-connector-25-way-yq48c

http://www.maplin.co.uk/p/maplin-d-sub-connector-socket-25-way-yq49d

 

First, you need to separate the shells to get at the white bit inside which holds the pins. The only thing that holds the two shells together are the ‘riveted’ holes either side. When they’re made, the holes are punched through, and it’s only this that’s holding the two halves together. To get them apart you just have to hold the metal containing the holes on the left and right with pliers, working them back and forward and also twisting to make a slot separate which you can insert a screwdriver into. Then you can use the screwdriver to lever the two halves apart. Alternatively, just cut off the hole and you can open it up.

Then separate the two white inner parts with you fingers and all the pins (or sockets) fall out.

The gold connectors then form a male and female pair which you can solder wires on to and then add 1.5mm heat shrink over for insulation and mechanical strength. I was using 15mm long heat shrink for the pins (male) and 20mm long heat shrink for the sockets (female).

Let’s be fair though, I did make 80 of these connectors, and they did work very well when tested to extremes by a class of 13 year olds. The first time you push them together they are a bit tight, but once the heat shrink has stretched they’re easy to use. We had a class of 30 connecting quadcopter motors to flight controllers without any problems. I use this technique on any small connectors that I need because it’s cheap, quick and easy to source the parts on the high street.

Flying Both Days!

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:

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One butterfly, 2 H Frames, 2 Ghosts, 1 X Frame and the unmodified HubSan H107C. Dragonfly is still missing in action.

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.