Month: August 2015

Flying Again!

The grass has been cut and the skylarks are gone again for another year, but by some miracle we’re sandwiched between two really nasty weather systems. The rain held off all morning and the wind was almost non-existent, although it looked really threatening and not at all like August. I was the first there, but was gradually joined by the Multiplex Xeno flying wing, the guy who’s Sniper I flew the other week, now with a Super Cub, and someone who I haven’t seen for a very long time flying his own design. We talked autogyros for a bit as his one is apparently ready to fly, apart from some method for spinning up the rotor. My ATOM is coming along, but I’m still working on the canopy and cockpit at the moment. I’m about to build a pilot so it doesn’t look so bare underneath the clear canopy.

Anyway, late on in the morning a whole lot of people turned up, but they only had a really tiny quadcopter and a Whipit hand launch. He was flying the quadcopter around when I left, but I never saw the Whipit fly. I managed three flights with the RS352, but that was about it really, apart from talking about Extras with the guy who had the Xeno. Apparently he has a Multiplex Extra 300 which he flew a couple of weeks ago and was absolutely perfect from its first flight. Not like my Extra at all, but I really must get mine flight ready again as it’s just sitting in the cupboard. I need to get the ATOM flown first, though, so back to building the canopy. It’s a Bank Holiday tomorrow, so I should have lots of time on my hands.

Very Strange Weather

Yesterday was 31 degrees and too hot to do anything. Today has started out cooler and sunny, but with the threat of a front arriving later with heavy rain. On the basis of the forecast I decided not to go flying this week and sure enough, round about 11:30am it tipped it down with rain. I would have got very wet, so that looks like a good decision.

On the building front, I’ve been too busy with other things this week to do anything on the ATOM, apart from cut the canopy I made last week free and trial fit it on the fuselage. I have to say, though, it looks fantastic. I just need to make a cockpit and pilot now. I’m useless at making pilots, so I’m going to look through my back issues of RCM&E for a recent article I remember reading about making pilot figures.

 

 

Perfect Weather and I’m Not Flying

The weather looks like a copy of last Sunday, but, for various reasons, I can’t get out to fly this week. I’m just going to have to make do flying the Q4 quadcopter inside. I have been making some progress on making a canopy for the ATOM autogyro though. I’ve bought myself a heat gun from Maplin and I’ve been drinking 17 pence worth of sugar free lemonade all week. OK, I could have just tipped it straight down the sink, but it’s actually quite nice and it took all week to make the canopy pattern.

The Maplin 2000W Heat Gun

The Maplin 2000W Heat Gun with the heat deflector tool.

I’ve been reading the September issue of RCM&E (the one with the Supermarine S6B seaplane on the front) and, by some amazing coincidence, there is an article on making canopies out of plastic drinks bottles with the ATOM canopy as an example. Having read it though, it would be good to have included a few more details as the author has obviously got a lot more experience at this than I have. The last canopy I made was for my Vampire, which I built from the Flying Scale Models plan featured in the March/April 1998 issue. That just shows how old it is. Actually, now I think about it, I also made a canopy for my Extra 300 some time after this, but it was never that good.

My Coke bottle Vampire canopy with a bit of ply framing for scale effect. This model really must fly again.

My Coke bottle Vampire canopy with a bit of ply framing for scale effect. This model really must fly again.

A bit more of the Vampire - there's a lot of it to show. You might just be able to make out Pete, the pilot wrapped up in plastic for storage. He came from Pete's Pilots on a visit to Sandown Park.

A bit more of the Vampire – there’s a lot of it to show. You might just be able to make out Pete, the pilot wrapped up in plastic for storage. He came from Pete’s Pilots on a visit to Sandown Park.

Both the Vampire and Extra canopies were made using a domestic iron and covering the plastic with cloth to avoid burning and it sticking to the iron. I should point out that I had a special iron for model making where the steam mechanism was broken so it had been long since retired for use on any clothes. Having said this, while the technique obviously does work, I wouldn’t recommend it unless it’s your only option. This time I wanted to do it properly and so went out and spend £20 on a Maplin heat gun.

Now, one thing missing from the RCM&E article is how much heat you actually need. The type of plastic will determine this, but I had already realised that, if they were talking about an iron used for Solarfilm in the magazine, then a 2KW paint stripper is probably a bit over the top. It is a really good heat gun though, and it made a really good job of melting my 17p lemonade bottle. The trigger has two settings, so I selected setting one (1300W) and had the heat deflector attachment fitted (see picture), which is what the instructions recommend for shaping plastic. This worked really well, with the large heat gun blowing lots of hot air onto the plastic and the deflector preventing it from getting too hot. It’s also a lot of fun shaping plastic in this way.

ATOM Canopy shaped plastic.

ATOM Canopy shaped plastic. The black tape is holding some spacers to the bottom to jam the pattern tightly into the bottle.

I made my pattern out of balsa and  plywood by sticking together all the scraps from by bits box. While this was quite time consuming, it is hugely satisfying to have used up so much of my scrap wood. The way I made the pattern was to take a piece of lite-ply and cut it so that it fitted flush on top of the ATOM’s fuselage sides up against the front and back of the hole for the canopy. I then built up layers like bricks using 10mm wide and 5mm high strips cut from old balsa sheet. When I ran out of 5mm, I used 3mm and so on with larger blocks and bits of triangle being used on the top. The first few layers up from the plywood base are hollow, with 10mm balsa “bricks” along the outer edge, so the pattern is partly hollow. Once I got to a certain height, I just stuck a piece of sheet flat across the top and started glueing bigger bits together in a 3D jigsaw. One problem I had was that the rails for the elevator and aileron servos were installed in the fuselage, so I had to leave a gap at the back of the pattern in order to allow me to fit it into place on the fuselage for shaping. Once the shape was right, I then had to fill in this hole with balsa block. Then I increased the size of the pattern so that it’s bigger than the hole in the fuselage. This was done by adding sheet to the bottom, front and back to increase the size by about 15mm all around. The extra space will be needed for the plastic to overlap the fuselage sides to make a good fit.

As this was my first attempt, things didn’t go completely to plan, and I did manage to damage the plastic in two places. I washed out the bottle and dried it thoroughly before cutting the bottom off and wedging the the pattern inside using the pine block and some balsa wedges that you can see in the picture. This is very important, as the pattern must not move while the plastic is being formed. The first thing to do is to heat the bottom of the pattern (pine block) and the back where the bottom was cut off the bottle and where the pattern can escape if you were to shrink the neck of the bottle. After wedging the pattern securely in place, just heat gently to shrink the bottle around the pattern. This is where I went a bit wrong as I assumed that the white colour I could see at the back of the canopy was condensation from where I had previously washed the lemonade out.

Not bad, but the plastic is slightly damaged at the top right of the picture (white).

Not bad, but the plastic is slightly damaged at the top right of the picture (white).

Some white discolouration can be seen at the top right of the picture, where I’ve heated the plastic too much. Of course, you can’t tell this very easily when everything is still hot, but closer inspection of the pieces once they’ve cooled down shows the mistake.

More damage to the front right of the canopy visible as the white circle.

More damage to the front right of the canopy visible as the white circle.

The right hand side of the canopy is a bit more of an issue as a white circle is visible where the plastic has become very thin and weak. I’m hoping that this is low enough not to be an issue with the finished product.

OK, now to remove the plastic from the pattern. This is actually a lot harder than I was expecting as the plastic is thin and easily torn, while there isn’t much to get the knife into without it slipping or damaging the pattern. I think the best policy is to cut the bottom of in stages.

And here’s the finished result:

The pattern and the new plastic canopy separated.

The pattern and the new plastic canopy separated.

It doesn’t look that good in the picture because it needs trimming, but that’s not bad for a first attempt in quite a few years. The beauty of it is that I can have another go once I’ve drunk all the lemonade again.

So now all that’s left is to build it into a removable hatch for the ATOM. I’m thinking of making a base with pilot, dashboard and attach it all with magnets. I’ve also got the ATOM head mechanism attached with the servo pushrods in place, so the only major bits left to do are the tail section. Maybe it will actually fly this Summer after all?

26 Degrees and Sunny

The bike and the mini-wing with the electric fuselage.

The bike and the mini-wing with the electric fuselage.

Perfect weather for flying? Well, no, actually. Although we are in the middle of a two day heatwave and today was comfortably cooler than yesterday, the flying conditions were very unusual this morning. Firstly, I was on the bike as my lift is on holiday this week, but I bumped into my friend with the HobbyZone Champ as he was walking across the field with his bike. Now, I’ve flown his Champ in all sorts of windy conditions well outside what it was designed for, but today it just didn’t seem settled at all. Even so, I managed 17 minutes from the first flight with a 150mAH battery which is really good going as I managed to find quite a few thermals and was able to turn the power off completely for extended periods of time.

After flying the Champ (apparently it’s really an Aeronca) I assembled the mini flying wing and had my first flight with that for quite some time. The assembled crowd were really interested to see it fly, so I warned them that my launches usually end up throwing it into the ground as the wing needs to be moving in order for the tips to generate the stabilising force to counteract the aerofoil’s natural negative pitching moment. The only way to launch it is to be positive, which I proved when the first attempt headed skywards at a rate of knots. It flew really well for about five minutes, then I brought it down, mainly as a precaution as I still don’t know how long it flies for. Post flight analysis showed that the pack was still at 76%, so the answer is at least 10 minutes.

The next flight was the Champ again, but on giving it back to its owner to fly, he immediately ended up so far downwind that I had a real job to bring it back. Then, in demonstrating how fierce the wind was on the downwind leg, I ended up doing exactly the same thing and had the power cut when it was still half way across the field. To be fair though, the wind was really throwing it around and it was going backwards for a lot of the flight.

Next up was another flight with the flying wing, which seemed to be flying much better in these conditions. I even managed a roll, but it did scare the life out of me. Wings are strange aerodynamic beasts and the roll was in stages, more barrel than you would imagine possible and losing a huge amount of height. I didn’t want to push my luck too much, as I also seemed to be having a problem with the motor and speed controller exceeding its RPM limits on maximum throttle and skipping. This didn’t happen on the first flight, so I need to check the motor. I probably need to rethink the whole power train anyway, as it would go a lot better if it was a bit lighter.

We were both beaten to the flying field this morning by the guy who used to have the two delta rays. He was there with his wife and two kids, while one of them was flying a combination of an EPP SuperCub and a foam board F22. Both aircraft flew really well, but the F22 did look unusual because of its strange shape in the air (and I’m flying a wing).

Part way through the morning another guy turned up with a Sniper II, which is 3D profile plane very similar to my RS352.  After a number of attempts at taking off from the ground the prop came off and nobody had any allen keys. We watched his plane as he went off to a nearby hardware store to get some, and the prop was firmly attached after what seemed like an enormously long wait (he got lost apparently). His next attempt at taking off nosed over on the long grass and sheared the spinner off. Having lost his nerve a bit, he asked me to get it in the air, so I checked out the damaged to the spinner and prop, which just looked like the spinner had sheared off at the screw holes. Anyway, I put the aircraft on the ground, applied throttle progressively and up it went. I offered him the transmitter almost straight away as it was flying perfectly, but he wouldn’t take it, so I checked out the balance with some dive tests, then loops to check lateral balance. Everything was spot on, apart from a tendency to screw out of an outside loop to the right. Also, he has nowhere near the amount of rudder movement that I have, but that might be a good thing. Checks complete and I landed it and handed it back. Only when he was fitting the battery to fly himself did he discover that the prop was damaged by the earlier aborted take-off, so that was it for the day.

We did get another two additional visitors though, in the form of a guy with a DJI Inspire and his helper on an electric unicycle. They had a few flights with it in order to set it up and take some pictures. He’s apparently doing his accreditation to fly commercially, so he was getting in some practice while the weather was good.

That’s it for another week, but the ATOM is still coming along really well. I’ve got all the head linkages installed and I’m planning to make the canopy tomorrow. You never know, but it might actually be flying soon?

Replacing a HubSan Q4 Motor

The front left motor on my HubSan Q4 stopped working recently, so I bought some new motors and replaced the broken one. This is a step by step guide to how I accomplished the repair.

The tools you will need to make the repair

The tools you will need to make the repair

In order to make the repair, you need a soldering iron and solder, a screwdriver, tweezers, and pack of new motors. A small pin vice might also be useful, but fingers can work just as well.

Remove the propeller by pulling it gently upwards. They usually come off fairly easily. If it doesn’t then use a soft plastic (or balsa?) implement as a lever between the top of the motor and the base of the prop hub.

Pull the propeller off gently with your fingers.

Pull the propeller off gently with your fingers.

Next, carefully release the motor.

Release the motor from its mount.

Release the motor from its mount.

And push the two white mounting clips inwards to release the white plastic motor mount from the PCB. This leaves the motor free, apart from the two soldered power wires. This is done after lifting the motor upwards and out, otherwise there isn’t enough room for the clips to move in and clear the PCB.

Push the two white plastic clips inwards.

Push the two white plastic clips inwards.

Next, desolder the two motor wires, noting that white is (+) and black is (-), although it’s identical to the other motor. Don’t use too much heat, it should only require an instant to release the wire. This is where the reason for removing the white plastic motor mount first becomes apparent. It’s too close to the solder pads to avoid melting it with the soldering iron otherwise. The picture below went a bit wrong as I accidentally clicked the motor back into place when I put it on the desk to take the picture. Just pretend the motor is hanging through the hole as in the previous shot.

Desolder the old motor.

Desolder the old motor.

Remove the old motor completely and mark it as defective so it won’t get confused with any of the new ones. Select the correct type of new motor from the pack. In this case it’s the black and white wire motor, not the red and blue one.

The new motor and the defective one it replaces

The new motor and the defective one it replaces

Insert the new motor into the plastic mount, making sure to get the wires coming out of the correct side and from the right hole. This is what the tweezers are for, as it’s a very fiddly operation.

The new motor goes into the mount.

The new motor goes into the mount.

Note the position and orientation of the motor wires.

Note the position and orientation of the motor wires.

Now solder the new motor in place. The pictures with the soldering iron are actually posed for the camera. There are two reasons for this: firstly, I don’t solder on a piece of white cardboard and, secondly, I only have two hands. The soldering iron is cold in the photos and propped up precariously on its stand with me holding the tweezers. The pictures show the motor, NOT clicked into position, but held by its powerful magnets against the metal pin vice. This will work well, but I found it just as easy to hold the job with my fingers and solder it that way. Obviously, not burning your fingers is the most important point if you choose to hold it, so only do this if you are confident with a soldering iron and do it every day. If you press the wire down against the PCB so that the exposed part sits on the solder connection, then you can just about get away with it without burning yourself. Otherwise, use the tweezers to press the wire against the PCB and use as little heat as possible. A little solder run onto the wires and pads always helps.

cpa1

Carefully solder the motor wires onto the correct pads.

cap2

The motor isn’t clipped in place at this point, I’ve just poked the wires through the hole in the PCB for now. Magnetism is holding it to the pin vice.

When soldering the wires, make sure to get the direction of wire entry to the solder pad correct. This will aid with tidying up the wiring afterwards and make sure it doesn’t catch on anything. They both point inwards like in the picture.

It's important to point the wires inwards.

It’s important to point the wires inwards.

At this point I like to test that the electrical connections are all good and that it all works as expected. In order to see the motor spin, I’ve attached a piece of tape to the spindle.

The tape allows you to see the motor spin. Buzz the throttle lightly and see that it works.

The tape allows you to see the motor spin. Buzz the throttle gently and see that it works.

That’s almost it, but you have to release the motor from the plastic mount as if you were going to take it out, then push the white mount fully into the PCB before replacing the motor. The reason for this is that there isn’t enough clearance for the mount to go into the PCB with the motor taking up all the space inside. Also, note in the picture two small plastic lugs which must be carefully located into a cut-out in the circular PCB hole. If you look at the circular hole carefully, you can just see the cut-out to the left of the “B” where the two wires are disappearing underneath.

Don't push all the way yet!

Don’t push all the way yet!

Release the motor to make space to click the mount in.

Pull the plastic over the top of the motor apart while simultaneously pushing the motor upwards to gently release it.

Pull the plastic over the top of the motor apart while simultaneously pushing the motor upwards to gently release it.

Now push the white motor mount downwards to click it fully into place. The white plastic is quite brittle, so it’s important not to use too much force. Slip the motor to one side before pushing down so that it reduces the stress and the lever effect as the clips go in. Otherwise you can crack the mount. In other words, make sure the motor isn’t pushing the top lugs outwards when you push the mount down into place.

The motor is now released.

The motor mount is now in position and the motor is about to follow.

cap

A different view showing how the mount fits into the PCB.

Finally, push the motor back into place and fit the propeller.

The motor back in position.

The motor back in position.

Push the prop back on.

Push the prop back on.

And we’re ready to go flying again!

TX on, RX on, blinking, bind, ready to go.

TX on, RX on, blinking, bind, ready to go.

Everything works and it lifts up into the air again. I’ve never managed to film myself flying it yet, because every time I try and get the quadcopter into the camera’s view I lose control and crash into something.

Also, don’t forget that the trim is likely be a long way out after changing the motor, so you might want to do a trim reset first on a level surface. Mine was drifting back and right quite a lot, but I was just happy to be flying it around again. I have a knack for finding the neutral operating point after years of test flying other people’s models and have a habit of just flying models the way they are. I’m not sure if that’s a strength or a weakness, but I have had a few occasions where I’ve flown a model seemingly perfectly, then, when somebody else flew it after me, they nearly crashed. There was that electric glider that went vertical immediately after launch which was a bit of a shock for the pilot, but I probably shouldn’t mention that.

It’s Not Raining

It’s not raining, but it is the “Ride London” event this week, so I’m trapped inside the course and unable to go flying. The only good flying day for the last six weeks and all I can do is sit here and stare out the window at the bright sunshine, motionless trees and perfect conditions.

I’m still building the ATOM autogyro, but I had a bit of a problem with the ATOM’s head servo linkages. I should probably have checked first, but I assumed the threaded pushrods I had in my bits box were the 2mm variety. When I came to connect them to the ball links on the autogyro rotor head it was obvious that they were too small. Having looked everywhere for a bit of 2mm wire and even considered stealing coat hangers, there is nothing suitable in the house, so I’ll have to order some piano wire. I might get away with soldering or threading a joiner to make two longer links, but the 20cm needed to connect between the servo heads and the ball links on the rotor is a lot longer than anything I’ve been able to find lying around. After getting stuck on the ailerons and elevator, I started looking into the rudder linkage again, so I’ve just started assembling the tail sections which I now need built in order to get the correct spacing. I’ve made a linkage from a bolt, the sintered brass front of an old speed 400 motor, a piece of fibreglass board and a servo pushrod connector. I don’t really understand how these servo connectors work, as the screw is always going to loosen as the servo moves the wire back and forward. Because they have to rotate, mechanically, the screw will always come off. Anyway, mine were brass, unlike the picture, so I’m going to solder it once I get the mechanics working. The ATOM rudder linkage isn’t exactly what they were designed for anyway.

I’ve also been fixing the broken motor on my HubSan Q4 quadcopter this morning. There will be another post later with the pictures, but the battery is blinking at me to say it’s charged, so I’m off to fly it now, even if it is just indoors.