Month: July 2015

Raining Again

I can’t believe it’s raining again. We had a torrential downpour on Friday, then Saturday was OK, but probably too windy to fly. It’s now Sunday morning and we’re back to heavy rain which the forecast says is set for the rest of the day. No flying this week then. I’ve got a lot of work to do anyway, so maybe it’s a good thing?

In terms of aircraft, though, I’m still installing the servos for the ATOM autogyro. I had to add some thin ply shims as the servo retaining screws are so close to the edge it would split the wood otherwise. Hopefully I can now drill some pilot holes and fix the servos in place without causing any problems. It’s been a lot more difficult than I thought it would be with the new Tower Pro servos being deeper than the Futaba ones which I made the original holes for. So I’ve gradually made the holes deeper, adjusted the width and length, added additional ply shims and now everything should fit perfectly. Just waiting for the glue to dry now, then I can finally make the head work.

Also, I’ve been looking at quadcopter flight controllers, and I’m really interested in trying to get the Arducopter software working on some of my own hardware. I don’t actually know at the moment whether it can be made to work on an Arduino Nano, but I would really like to build my own replacement for the HubSan X4 which I seem to have worn out.

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Did Anybody Check the Wind Forecast?

This morning it was just me and the other guy who turned up with his friend and a little green Extra 260. I was too busy looking at the rain forecast to realise that the wind was going to be rather extreme though. Friday’s forecast had heavy rain for just the wrong time on Sunday morning, but, by Saturday, this had altered by a few hours, so the heavy rain was in the early morning. It was excessively windy all morning though, probably in excess of 30mph as the aircraft wouldn’t stay on the ground and kept getting blown over. I still managed 4 flights with the RS352, although it was a little hairy and the landing technique was basically to come in fast and hover it down, then grab it before the wind could flip it over. I hadn’t flown for quite a few weeks, so there was no way I was going to miss this weekend.

Anyway, I got the new servos for the ATOM autogyro during the week and cut the holes for them yesterday. I’ve got 3 new Tower Pro MG90D digital metal gear servos from Robot Birds. They arrived in a couple of days which was fantastic. I thought about getting the newer MG92B, but I was a bit worried about the size as I had already cut the holes for the Futaba servos which the Tower Pro ones replace. The MG92B is a bit bigger than the MG90D, which in turn is a bit longer and deeper than the Futaba ones, so I was worried about being able to modify the already almost complete ATOM fuselage. They went in relatively easy though, so I’m hoping for a fully working head mechanism later on today.

It’s a Funny Sort of Day

I can only think that I must have angered the weather Gods in some way. Maybe I flew too high and this is their way of punishing me? It’s been extremely hot and sunny all week, then Sunday comes and brings lots of wind and occasional humid showers. Just when I’m actually feeling better and have the energy to hop on the bike and take the flying wing out. Here’s an idea though – maybe this is their way of telling me to finish the autogyro?

I spent most of yesterday building and have now got the holes drilled in the blades and I also modified the HK C30 head to take the replacement fibreglass centre part. For anybody else doing this, all I can say is remove the three smaller bolts from the blue plastic centre, then carefully remove the bigger central bolt which is between the two bearings. I also suggest you read the thread on modelflying.co.uk as it’s very easy to wreck the main bearings while performing this process. I almost did this myself, but managed to figure out not to over-tighten the central bolt as the bearings aren’t very good. The forum also suggests reversing the direction of the lock bolt which I’ve also followed.

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The HK C30 head after modification with the new fibreglass centre centre piece. The original plastic parts at the top of the picture are no longer needed.

The underside of the new head centre. DO NOT OVER TIGHTEN THE BOLT!

The underside of the new head centre. DO NOT OVER TIGHTEN THE BOLT!

 

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The top side of the new fibreglass centre piece.

With the head modified, I then set about attaching it to the top of the post in order to start installing the servos and make the head work. Drilling the holes in the post was easy using my Minicraft pillar drill, but when I removed the intended servos from my old Simprop Cap231 airframe I noticed a problem. The Cap231 isn’t likely to fly again as the soft foam fuselage has acquired too many stress fractures over the years and the latest broke its back from the wing trailing edge right up through to the top of the fuselage. This actually happened in the air, not on the ground, but I’ve fixed so many cracks over the years that it’s starting to get too heavy. I was intending to take the three Futaba S3106 servos out of this and put them in the ATOM, but with the aileron and elevator servos in position ready for the links I took one look at the geometry, realised the forces involved and thought, “they should be metal gear servos, not plastic ones!”. To be fair, the ATOM instructions do tell you this, but I hadn’t fully appreciated that the Cap231 servos were plastic geared ones. I’ll have to order three new servos, probably the same EMax ones which I was using in my RS352.

After coming to a halt on the head and control installation, I then moved on to the undercarriage. I bought the 3mm wires a while ago, but I think my wire bending skills are getting a bit rusty as I had quite a job getting the tight 90 degree corner on the bit that slots into the fuselage. You need the tight angle for the wires to sit down on the underside of the fuselage with the saddle clamps holding them in place. Even putting the wire into a big vice and hitting it with a 4lb sledge hammer didn’t really do the trick, so I think I might have to invest in some professional wire bending kit for the future. Once the undercarriage was in place I then fitted the motor onto it’s mount which was a lot easier to do.

Congratulations, it's a grasshopper! I think it's the wide track undercarriage that does it.

Congratulations, it’s a grasshopper! I think it’s the wide track undercarriage that does it.

And the top view.

And the top view.

So there we go, all that’s needed now is to sort out the closed loop control for the tail end and make a canopy. I think we’re almost there apart from some simple installation and covering.

That’s it for now, but I’m also very excited about another project I’ve been working on. I’m currently building a quadcopter simulator in Unity which will be the subject of a later post. At the moment I’ve got a very simple quadcopter model moving forwards and backwards using the mouse as the elevator stick. It works by simulating the PID algorithm which is in the flight controller software of a quadcopter, so that, when you request an angle of bank with the aileron stick, the software measures the current angle of the aircraft and moves it to the pilot’s requested angle of bank. So far, I’ve only spent a few hours on it, but with a little more work it should be flyable.