Month: July 2017

Autogyro Musings

There’s a cycling event on this weekend and all the roads are closed, so I can’t go flying today. The weather is also extremely windy, so I don’t know if I would have actually tried flying in these conditions? It’s a day for big gliders which like the wind, as I can see lots of development happening in the clouds as they’re being blown overhead. I probably would have gone flying if I could, but I wouldn’t have risked the autogyro.

On the subject of autogyros, I’ve been reading the modelflying thread on the Atom build to try and get to the root cause of my problems. When I finally got to page 20 (there’s a lot of information there), I read about somebody else having problems with it rolling left on take-off. The reason is given as “insufficient rotor speed”, which is what I had suspected. Now, interestingly, there’s also a bit on hand-launching autogyros and they include a link to the very same YouTube video I mentioned last week. My problem stems from the bumpy nature of the grass I’m trying to fly from, so I either need bigger wheels, or I might have to bite the bullet and throw it. I still need to do some more experiments outside in the wind to see how fast the rotors can be made to spin. In the hand-launch clip, it’s stated that, “you should be able to feel the lift pulling it out of your hand”. I never felt that it was producing as much lift as I would have expected, so that needs some more testing. Hopefully we’ll achieve some air under the wheels in the not too distant future?

I’ve also been looking at the videos I took the week before last, both of the autogyro test and of me flying the RS352. The autogyro test doesn’t show very much, as all I can see is it whizzing off into the distance and it disappears into the grass because of the low camera angle. Watching three flights with the RS352 was interesting with the camera pointing up into the sky and the wide angle fish-eye lens of the GoPro Hero 4 Session camera. The first thing that struck me was, “I don’t remember the sky looking quite so dark and threatening”. It looks like there’s about to be a thunderstorm and you can hear the wind whistling around the microphone. These are the conditions we seem to have to fly in these days. The second thing is that the fish-eye effect is great for showing the area I’m flying in, but I have real difficulty working out what the aircraft is doing. I can’t tell the orientation and height, even though I can see myself standing there flying it. The Cuban Eights are fun to watch though. I might have a go at editing this and posting a flying video if I get the time, as this is the best I’ve managed to produce so far.

Let’s hope the August weather is a bit more co-operative than July and that we get some calm conditions for an autogyro test next week.

Post Autogyro

The weather wasn’t very good this week, so I didn’t get to do any flying. The forecast was for heavy localised showers and, right on half past twelve, it rained. A lot. I might have got wet, or I might have got lucky, but, either way, it was just as windy as last week. If the weather had been calm, then I would definitely have had another go with the autogyro, but there didn’t seem much point with the weather like this.

I’ve been looking into the problems with the autogyro and come to a number of conclusions. Firstly, the video I captured was rubbish and didn’t tell me anything. If I try that again, then I’ll have to get the camera higher up. The next thing is that I don’t think I got the rotors up to flying speed as everything I’ve read says that there is a characteristic “whirring” when this happens. It’s supposed to take off at walking pace, which I achieved, but I think there might be something wrong with the rotor head. I went round all the factory fitted bolts and discovered that some of them were quite loose, which was causing a lot of play in the head. In addition to this, I’ve been reading the “Cruiser” autogyro build article from the November 2015 RCM&E, which is basically the same design as the earlier Atom. There is also the larger “Panther” autogyro article from the Model Flying Workshop Special, published in 2015, which contains all the original articles which were serialised in RCM&E from March 2013. These all contain basic instructions on the design of the head and how to test fly an autogyro. However, while they advocate short hops to ascertain the trim, I’ve seen a video on YouTube where an Atom was hand launched in almost gale force wind. This is something I’d never seen before, but you can apparently hand launch an autogyro very easily: https://www.youtube.com/watch?v=OdrfQxKu1Ik

This video is also interesting, as it suggests that the left wheel sticking to the ground is normal and that you can power on past it: https://www.youtube.com/watch?v=9OVpcZOvsOs

If the camera I was using had worked, then this is a carbon copy of my experience last week, except that I wasn’t brave enough to get it into the air. After some playing around on the ground, my feeling is that the left wheel coming up last is due to the anti-clockwise direction of the main rotor.

This is the other hand launch video of an Atom that I found: https://www.youtube.com/watch?v=5bVkgLwmBAc  I’m just not sure I’m that brave.

Anyway, I’ve checked the balance by measuring the hang angle using some rulers and a bit of trigonometry. By my calculations it’s 18.5 degrees, which is spot on. I’ve also modified the 0.8mm shims on the underside of the rotor mounts as they were getting caught every time the blades got tangled up last week. I’ve now lengthened them and covered over them, but I suspect that this might be where my problems lie. When I spin up the rotors on the ground, I just don’t feel like I’m getting much movement of the air. Now, the HK head has a known problem in that it’s constructed upside down and shipped in a state where the rotors would give no lift (souce: modelflying.co.uk Atom build thread). I took it apart as directed, fitted the fibreglass triangle to replace the plastic one which breaks and rebuilt it the other way up. I’ve added the shims as instructed, which put the blades at a more negative alpha and aid in spinning up the rotors. I’m not convinced that this is right, though, so I’m going to do some more investigating before I try and fly again.

That’s it for this week, but work is taking over again, so I’m not sure how much I’m going to be able to do on the autogyro. I’ve got this close to getting it in the air though, so I’m not going to give up now.

First Autogyro

IMG_20170716_104333.jpg

 

I was determined to test fly the Atom autogyro this weekend and I finally managed to get everything together. I don’t know whether this is the first autogyro that’s been flown at this site, but in all the years I’ve been flying here, I’ve never seen another one. I also don’t know whether this counts as a flight, because the left wheel never actually left the ground, but this was my first attempt.

My first flight of the morning was with somebody else’s UMX Champ. Weighing only about 35 grams, this was probably a stupid idea in the steadily increasing wind, but I’ve flown it perfectly well in windy conditions before. This time, though, a gust flipped it upside down and I crashed into the ground. I was able to partially rescue it, so there wasn’t much impact and it was undamaged.

Then I put the rotors onto the autogyro and had run out of excuses for not flying it. Although, it was a close call as the wind was way above the recommended “light winds” stated in the magazine article for the first test flight (RCM&E Autumn 2015 Special). I was determined to give it a go and try running it along the ground and “hopping” when the rotors began to lift. The rational behind this is to trim the head angle, but I didn’t have much luck. I had the foresight to take a GoPro Hero 4 Session camera with me and record the flights so I could watch them back later, but I had it in the wrong mode for the first set of flights and only ended up taking stills. I really don’t like that camera, but I had lent my preferred RunCam to somebody on Thursday.

As far as the test “hops” went, the rotor would spin up fairly easily in the wind, but I’m not convinced I was getting up to full flying speed before running out of runway (for “runway”, read “patchy bit of bumpy grass”). I wasn’t able to steer effectively with the rudder and it seemed to be yawing to the right. When it did start to lift off, the left wheel seemed stuck to the ground and it wanted to roll over onto its left side. I thought this might be a head trim angle problem, so I progressively added right aileron trim, up to the point where I had 15 clicks right trim and there seemed to be no difference, even when holding right aileron while it ran along the grass. The airframe is impressively resilient though. I had it tip over on its left side numerous times and tangled up the rotor blades, but it still went home in one piece. I think that, in all the years I’ve been flying, maybe I’ve learned how to crash well?

After resting the autogyro for a bit, we then had another go with the Champ. This time it went really well, much more like I would expect, so either the wind had eased off a bit, or it was just less turbulent than before? However, while I was flying the Champ, the Atom got blown over onto its side twice, tangling up the three rotor blades again. Luckily, there was no damage, but, with its three rotors now attached, the wind was causing them to spin very fast, resulting in it tipping over. I would have said that it was at flight speed at one point, they were spinning that quickly in the wind. Seeing this happening, I brought the Champ down for an almost perfect landing and rushed over to the Atom with the transmitter still in my hand to assist the owner of the Champ who was trying to figure out how to stop the blades. This confused him completely as he missed my landing and thought his aircraft was still in the sky. Anyway, still no damage to the Atom or Champ. The RS352 tried to take off on its own as well, but it’s fairly indestructible. I’m starting to think that maybe this wasn’t the best day to test fly an autogyro?

At this point a couple of guys arrived with a chair and a drone and proceeded to sit right where I had been doing the Atom test hops before. I’m not sure where they were from, but their English wasn’t great. There was also another drone flying right up the far end of the field, ignoring us completely. This was an East European couple and their son, as the lady did come over to us later on to borrow a screwdriver to change the battery in her son’s mini drone.

OK, so having had a think about the autogyro, and with the wind lessening a bit, I had another go. This time, though, I managed to get the camera in the right mode, so I’m hoping there should be some video there for me to review later. This went the same as before, trying various directions into wind and trying to get forward speed and rotor speed for flight. Along the ground it was yawing to the right if the rotors were spinning, but tracking more straight if the head didn’t spin. The ground handling wasn’t good enough to to keep it in a straight line along the runway I was now using, which was almost directly into wind, but narrow and with stubby grass either side. I kept ending up in the grass to the right. Moving to another area didn’t really help as the aircraft would never pull its left wheel off the ground. In the end I gave up, which was very disappointing. I would have taken any sort of air under the wheels, even millimetres. So, to review, rotor spinning means yawing right on the ground and left wheel won’t unstick despite extreme right tilt and good rotor speed. I need to go away and do some research for next time.

After that I had 3 flights with the RS352, which loved the conditions on its new batteries. I had one of the older batteries (3S 1100mAh, 18 months old) in the Autogyro, which showed 50% full when analysed after the test flights. The other one I flew in the RS352, but it just didn’t have the punch of the newer cells. As I had the GoPro set up anyway, I decided to point it at a patch of sky and film myself flying the RS352. I don’t know what footage I got yet, but maybe I got something good with the wide angle lens?

While I was flying the RS352, we had another person arrive with a drone who I’ve never see before. She also wasn’t like all the other drone flyers as she knew what an autogyro was, even if she didn’t know the English word for one. My guess is that she was East European from her accent, with bright red hair and a mini drone which she had constructed from bits herself. It was a bit bigger than a 100 size (but not by much) and had tiny brushless motors and FPV. Unfortunately, she had forgotten to charge the goggles, so couldn’t fly with FPV and didn’t feel confident enough to fly with line of sight because of the orientation. She apparently files bigger drones too, but she obviously knows what she was talking about as we were discussing why neither of us would do some of the stupid things the other guys were now doing with their DJI Phantom. After that a husband and wife also turned up with a Mavic, but I had to go at this point.

That was quite an eventful day of flying, so now I’ve got to go away and do my homework on autogyros.

Funny Old Weather

There was a forecast of sunshine and 8mph winds this morning, but it seemed more like a 15mph wind sneaked in when nobody was looking. It was an odd sort of day where, one minute the Sun is burning you through the back of your shirt, then great big black clouds came over looking threatening. It never actually rained, but the occasionally overcast conditions and breeze made for a cool respite from the relentless heat.

The first flight I had this morning was with a Radian electric glider, which the owner also flew himself on a couple of occasions during that one flight. There were already two people there when I arrived, one flying an Inspire while the other was watching the FPV from under a cover. There was also another guy with what looked like a Mavic drone flying from about 20 metres away, not wanting to be friends with us. Later in the day we also had one of those moments when you say, “if we’re all here, who’s that flying a drone above us?”, then realised that there was a guy standing at the very edge of the field with a transmitter. In addition to the two anti-socials, we also had two regulars with a Nieuport biplane, Ripmax Transition VTOL and a small quadcopter.

In addition to the Radian and 5 flights with my RS352, I also tried out some FPV with my 3D printed micro quadcopter. This was a bit of a last minute addition to the kit this morning, as I just threw all the bits into my bag as I was leaving, but it was certainly worth it. I’m not a big fan of FPV, but it was quite fun to fly the 45g quadcopter in circles around where we were standing. Looking back at myself through the eyes of the aircraft nearly made me fall over, but you soon get the hang of it. Judging speed, distance and height is very difficult because of the camera’s field of view. You always look like you’re doing about Mach one over the grass because you’ve suddenly been shrunk down to the size of a bird. I still think doing slow, lazy aerobatics with the RS352 is a lot more fun, but I’ll give the quadcopter another go in its natural habitat – indoors around the furniture.

All in all, it was quite a good flying session this morning. I would have been annoyed at not being able to get the autogyro ready to test fly if it hadn’t been for the wind. The forecast was perfect for a test flight, then a rather hectic week at work took its toll and I couldn’t get the aircraft ready in time, then the conditions turned out to be rather less than perfect. Having spent so long building it, there’s no point in rushing into a test flight in the wrong weather conditions. During the week, I discovered that it’s actually a lot harder to get the blades to attach to the head than I realised. I’m also going to have to do some further reading about the various “shims” people have added to get the blades at the right alpha to generate lift. Then I need almost dead calm conditions to do some runs up and down the runway. Anyway, I’m off to do some reading about autogyros and I might even try and write a simulator to practise flying one – that’s something I’ve never seen. Here’s to next week’s weather and an easy week at work.

Only Me

I thought the weather forecast was for heavy rain to clear early on, leaving a dry day with 10mph winds. When I looked out of the window this morning, the anemometer on the house over the back was spinning like a crazy thing. It was just as windy as last week and bright and sunny with it. Obviously the gale force wind had blown all the clouds away, leaving a clear blue sky and 25 degree sunshine. This is precisely my least favourite type of weather, because it looks like a nice day to go flying, but you know you shouldn’t.

I went flying anyway, working on the basis that the wind would decrease throughout the morning. It didn’t, so all of the four flights that I had with the RS352 were a bit hairy. When I tried any sort of aerobatics containing a vertical manoeuvre, the aircraft got blown about 10 metres towards me. In the end I decided to try and solve the problem I’ve always had with this aircraft, where outside loops go completely screwy. I know, trimming an aircraft in 20mph winds isn’t recommended, but I tried a couple of clicks of left rudder to see if it helped straighten the loops. From inverted, it makes no difference, but from the right way up, I think it does help leave the nose pointing in the entry direction on exit. I’ll have to work on this when there’s no wind, but I noticed that my current trim has the ailerons almost exactly level with a small amount of right rudder. It does seem to have a much more central trim than before, which might be due to the motor change a while back. Swapping out all the servos at Christmas must have had an effect too, but you wouldn’t expect the control surfaces to be in a different position, just the servos in a different position to achieve the same control deflection. Whatever the reason, I now seem to have a more balanced trim than before. So, why does it roll horribly on the initial quarter of an outside loop? I need to investigate this a bit more.

Anyway, I had an interesting conversation with the man who collects the dustbins, as it turns out that he used to fly here many years ago too. I thought I was going to be on my own for the whole morning as nobody else was stupid enough to fly in the windy conditions. Then, right at the end, a guy with a camera came over and sat on the bench. It was only after talking to him for a while that I realised the rucksack he was carrying was the DJI Mavic one. Sure enough, he had a Mavic in it, but initially didn’t fancy flying it in the wind. I had to leave before seeing it fly, but I’m fairly sure he got it into the air, so it wasn’t only me flying this week.

On a drone related note, I also got my 3D printed micro FPV drone to fly during the week. I managed to get the FPV power lead soldered on and gave it a go in the house. This is using the F3 EVO Brushed controller and my Futaba transmitter, so it’s much more professional kit than the HubSan’s we’ve been flying. Even so, it was very hard to achieve a stable hover, although I could fly it up and down the hallway and through the doorways quite easily. More practice is needed I think.

Finally, the ATOM Autogyro is almost flight ready. All it needs is a final control check, some bolts for the blades, keepers tightened up on the head and a way of holding the canopy in place. I’m thinking tape for the canopy and everything else is just tightening things up. I had wondered whether this week would be a good week for a test flight, but I’m glad I rejected that idea. What I need now are clam conditions so I can run it up and down the runway to get the head sorted out before committing to the air for the first time.