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The Night Before the Autogyro Test Flight

I’ve spent most of today getting the autogyro ready for its third test flight tomorrow. Firstly, I now understand what the shim under the blades does. As the blades are fixed to a flat disk that spins, if the blades were at zero degrees incidence, then all the lift produced would be upwards. The shim gives the blades negative incidence, so there is a small component of the lift in the forward blade direction. Now, with the blade fixed to a spinning disk, this forward component of the lift makes the blade spin. The more negative incidence you add, the more force there is to spin the blades.  There must be an optimum amount of incidence which causes the blades to spin at the correct speed to produce enough lift for flight, but I haven’t worked it out yet. I’ve just added a bit more to my blades for tomorrow’s test flight. It’s easily removed if it doesn’t work, though.

The next thing I did was to correct the tracking by bending the left u/c leg back into position. I can’t think how it got bent… Now it looks nice and straight, so I’ve moved on to looking at the control movements. There isn’t much I can do here, except make it all nice and square and get the head back to 90 degrees to the mast, which is the suggested neutral trim position.

Then I had a look at the videos of last week again. It’s all very consistent when you watch. As soon as it gets to a certain speed something kicks in and it yaws abruptly to the right. After wracking my brains about P effect and gyroscopics, I realised that I was missing the obvious. It’s almost certainly the reaction force as the the rotor head spins anti-clockwise. The yaw force is clockwise, so that great big triple rotor on the top is the most likely culprit. I took the head apart, I oiled the bearings and I put it back together again, which is about all I can do with it.

That’s all there is to it really, so I’m hoping for some wind tomorrow so I can do a hand launch. We’ll just have to see how it goes.

A New Thing Spreads Its Wings

It’s blowing an absolute gale this week, so I’m still grounded. That’s probably a good thing, though, as it’s the drone masterclass next week and I’m snowed under with work.

Earlier in the week I got a new 3D printed quadcopter frame to fly. It’s a very strange and mysterious creature from the early Jurassic. Can you guess what it is?

OK, it’s the Dimorphodon model. When I was filming the first flight, it was a bit dark and I looked back at the flight video and saw that the shadow it cast on the wall looked just like the fossil picture I was copying it from. So, afterwards, I got a desk lamp and hung the model on a piece of wire so it cast a shadow. Following a tricky bit of juggling with the Dimorphodon on a wire, swinging around in front of the lamp while I tried to work the camera one handed, I got the photos above. If you look at the pictures, the wire it’s hanging from is obvious, but it does look like a fossil.

We decided to go back to the model with the wings spread out full span, rather than the folded wing model that I showed a couple of weeks ago. I’m really pleased with that decision as the results are fantastic. I’ve always wanted my own flying pterosaur ever since I saw the one in the movie “War Games”. Of course, a bigger, gliding, version would be better, but a micro quadcopter will have to do. These images show what it really looks like:

And, yes, the head is held on by foam tape, but it’s all I had and I was in a hurry to film it flying. I think the flying videos are going to have to wait until next week.

That’s it for now, I’ve got an aero turtle to make…

Still Grounded

It’s been drizzling with rain all morning, so, in retrospect, staying indoors was definitely the right choice. I’ve built an FPV micro quadcopter for the workshop we’re running in a couple of weeks.

OK, so the camera’s a bit wonky, but I’m waiting for the glue to set before I fix it properly. I’m quite pleased with this as the flying weight is 54.9g, whereas a regular HubSan X4C (HD) is 51.0g. This is the quadcopter frame from the “Acrylic Blue” video in January, which is the lightest I have. The FPV camera is a cheap one which only cost £30, but weighs over 9g, compared to the 4g weight on my £50 Hyperion camera. This way, I’m hoping to get flights of over 4 minutes out of it, but I haven’t done a proper duration test yet. All the electronics check out, using both the FatShark Goggles and my Black Pearl screen. To make the screen work, I’ve made myself a custom power lead which has the Black Pearl 12v jack plug on one end and a Deans connector on the other. That way I can use my regular flight LiPos to power it as the screen’s internal 3S battery is completely wrecked. The funny thing is that the goggles worked straight away, but I had to switch the screen from NTSC to PAL. I’ve had both of these working with my Hyperion camera on NTSC previously, so I can only think that I must have already switched the goggles and just forgotten about it? For anyone who doesn’t know, once you get the right band and channel, you should see some sort of image that you recognise. If it’s black and white with the image rolling slowly down the display, then the NTSC/PAL setting is wrong and the transmitter and receiver are using different modulation schemes. I haven’t found any compelling reason for choosing one over the other yet, so stuck with the PAL that the camera was set to. It’s usually configurable at both the transmitter and receiver end, but the cameras are tiny and usually harder to figure out. The video looks really good, so I’m looking forward to flying it around the house (with blade guards added).

That’s ticked off my main task for today, but now I’m off to fix the geometry on my Dimorphodon quadcopter frame so I can do a 3D printing test tomorrow.

Downtime

The weather has been appalling recently, with gale force wind and rain, so I’m stuck inside this weekend. I’ve been keeping busy by converting another of the HubSan X4Cs for a workshop we’re running in March. It took all day as I’ve been filming the process as I go along, so it should be interesting to see how the final video turns out. This time around we’ve also got a £20 FPV camera so we can give them a go with the FPV goggles.

DanaTheDimorphodon.png

Also for the workshop, I’ve been playing around with a new design of 3D printed frame. This time, it’s a Dimorphodon dinosaur skeleton. It’s a bit ambitious, and I’m not sure if it’s going to work, but it’s been fun sketching it out. I think I’m going to stick with the flat style of 5mm high extruded frame rather than go the whole hog and make it properly 3D. I’m not entirely sure where I’m going to put the four motors yet, though.

In addition to this, I’ve finally got two new LiPos for my RS352.

I opted for some Hyperion 1300mAh LiPos, similar to the original ones which worked really well. I ordered them from Robot Birds on Sunday and they had arrived by Tuesday. Fantastic, but those XT60 connectors will have to go as I use the Deans ones. I would have swapped them over today, but I’ve been filming the HubSan conversion process for most of the day. That can wait until next Saturday when, hopefully, we’ll have better weather. It sounds like the wind is trying to tear the roof off at the moment.

 

Waiting for Rain

It’s dull and grey this morning, with a weather forecast that’s predicting rain at 11am, getting heavier as the day goes on. No flying this week then, so I’ve posted the video I took last week of my new 50g quadcopter’s first outdoor flight. The effect of the Sun and the mist is just fantastic.

In case you’re wondering, this is what I’m flying:

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We’ll ignore the bit at the end where I crashed it into the ground, but the throttle wasn’t picking up the thrust fast enough and the LiPo had gone by this point. The PIDs need a bit of work too, but this is still a work in progress. This one is using the HubSan 55mm blades, and I’m also going to test with some 75mm blades once I make a bigger frame. The general idea was to see how easy it is to manufacture a custom frame with everyday components and without using an expensive 3D printer. I’ve just cut out the blue acrylic using scissors and used it to sandwich some Depron. My only sticking point at the moment is how to hold the motors on. The one above is a friction fit in a bit of old plastic tube, but this requires a lot of skill and effort to make. My next evolution is going to use a slit cut into the tube so the radius can open and grip the motors without having to get the diameter exactly right. This also means using half round cups at the ends of the frame where the motor holders will be glued in. This might be too fragile, so I’ll have to see how it comes out.

I’m a bit tied up with work this week, so the only other thing I’ve done is to fix the prop adapter on my RS352. Here’s hoping for sunny and frosty next weekend instead of dull and rainy.

Halloween Drones and Lost Models

It was a bit busy this week, despite the very windy conditions. When I arrived there was someone just leaving who I hadn’t seen for over a year. Apparently he’s been coming up and flying his foam beginners F3A style model and leaving before 09:30, so we’ve been missing each other. Then I got to do the maiden flight of an Ares UMX Taylorcraft. This is a lovely little aircraft, which flew straight out of my hand and handled the now quite breezy conditions very well. It’s just like the Champ I’ve flown, but feels a lot more solid in the air. We think it’s a bit bigger than the Champ and the motor is a longer can version, which should give more torque. Anyway, the flight was over much too quickly, despite finding time for a loop and a very bad roll with just the rudder. The landing was much better than my usual lightweight aircraft landings, actually rolling along the wheels before coming to a stop right in front of me. You usually don’t get that with this type of aircraft as there isn’t any momentum and once the wheels touch they just tip over.

Anyway, after that I had a flight with the RS352, which was followed later on by another two flights. I was mainly trying out knife edge flight and I’m starting to get the hang of the elevator/rudder coupling. I think the trick is not to try and go too straight as the rudder easily holds the nose up, but causes a curved flight path due to the pitch coupling.

After my first flight with the Taylorcraft we had a couple of drone pilots turn up. They had the idea of trying to drag a Halloween skeleton figure underneath the drone, which you can see in the video above. I’m not sure how successful this was as the wind was causing havoc with the control because of the huge sail that the drone was dragging underneath it. Landing was a bit of an issue as well. It looked rather fun though and reminded me of the DaVinci Aerial Screw, which was difficult to fly because of being top heavy. I really must make a bigger version of my prototype and try it outdoors.

The Multiplex Xeno arrived shortly after the Halloween drone had been abandoned and proceeded to fly as beautifully as ever in the gusty conditions. Then we had the Multiplex FunJet which proceeded to fly over and around us at breakneck speeds, along with the Hyperion Sniper II which got damaged the other week. A couple of guys with FPV equipped flying wings also turned up around this time, but it was at this point that the Sniper was lost over the trees on its first flight of the day. It had got blown downwind a long way and over the trees you can see in the drone video above. After that it was just an orientation and control problem which ended with it (we think) hitting the back of the tallest tree’s canopy. The three of us spent a good half an hour looking around in the trees, but failed to find any trace of the aircraft. We all thought that blipping the throttle or servos was our best shot at hearing it, but whether it was damaged, or the drone flying overhead was masking the noise, we never discovered. My opinion is that it was too high up at the top of a tree, or we were just looking in the wrong place. After going behind the tree, it could have continued to fly for quite a way if it didn’t hit anything, so it might just be sitting there now on the floor of the forest waiting for someone to discover it.

This is Autumn

It’s blowing a gale this morning. Then it started raining. The type of light misty rain that means if you have to wear glasses to see the aircraft, like I do, then you need windscreen wipers. I’ve missed three weeks running because of the weather now.

Anyway, I’ve finally covered the AutoGyro. At least I think I’ve covered it. I’ve never know an aircraft like this. Normally you cover the bottom of the fuselage, then the sides, top, bottom of wing and top. There are so many awkward bits to cover on this that it’s taken ages, plus the 35 degree ambient temperature hasn’t helped. When I put it all back together I keep finding bits to cover that I hadn’t realised needed it. The front face of the main former holding the mast is a case in point. It’s highly visible because of the cut-out for the head control rods. I didn’t know whether to do it black or the silver blue colour, so I opted for blue in the end. With all the exposed wood, I don’t know what to cover and what to leave, so I’ve just been doing a bit at a time and then seeing how it looks the next morning. This is why it’s been taking so long, but it’s been quite fun to do.

I really like the silver blue, but I think I need some white trim in places. Now I need to put all the radio gear back in and make it work again. That only leaves the balancing and covering of the blades as the last major item.

Summer Weather

This is the scene that presented itself this morning:

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Yesterday’s weather wasn’t bad, but it’s the wind that really did it for flying this morning. You can’t see from the photo, but those clouds are moving right to left at quite a rate. On the basis of what I’ve see so far, I would have got wet at around 10:30 and 11:30, with 11:30 more of a highly localised downpour. Now the Sun’s just come back out and we’re back to hot and humid again. It’s what you expect from a Bank holiday really, so I’ve resigned myself to this being a long building weekend.

I still haven’t finished covering the autogyro because of the extreme heat last week. I have decided on doing the tail in red, so I might get around to that later today. I’ve also been working on the quadcopter simulator. It’s really interesting looking at how Cleanflight works and I’ve tried to replicate it as closely as I can in the simulator. It now works on angular rate targets rather than absolute angles, so it flies a lot more accurately than before with more of that “locked-in” feeling rather than drifting all over the sky. I didn’t know this before, but Cleanflight actually reduces the PID rates in response to throttle changes. That’s not something I’ve implemented yet, but I’m going to experiment with it later. Now I’ve started getting into autopilot software and automatic control, I’ve been thinking about new things that I can do with this skill. I’m still interested in looking at some of the really old designs of aircraft (circa 1900) that failed and add modern computerised control software.

OK, now I’m going to use the time today to do some long awaited maintenance on the RS352. I’ve needed to change the battery in my Futaba FF8 for a while as it’s not holding its charge very well. Once that’s done I’m going to go through the programming with the RS352 and check all the control surfaces.

 

Virtual No Flying

I’ve been a bit busy with work this weekend and the weather is also quite windy, so I ended up cycling over to the flying field with nothing to fly. I was really late and didn’t arrive until about 11:30 and stayed until 12:30 hoping somebody else would turn up. In the end nobody did and I sat there playing PicaSim on my phone to amuse myself. It’s not the same as the real thing, but the weather was against it this week. I did notice, though, that the top of the flying board was missing which I don’t think was the case last week. That’s rather annoying, but we could really do with getting it fixed anyway.

The building of the autogyro is going quite well and I’ve got the radio in and the head working. I’m going to try and use an inclinometer to get all the movement angles right before cutting the pushrods to length as I don’t want to cut too much off. The pilot is glued in, so I need to figure out how to fix the canopy in place. For such a large hollow fuselage, it’s amazing how little space there is for the installation.

That’s it I’m afraid, back to work again now.

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.