Sixth Time in the Air

Fully assembled once more, it's testing time!

With only the control circuit between the autopilot program on the phone and the plane for autonomous flights missing, the weight of the plane is now just below 1.9 Kg. Not bad for all the equipment.

But is it better? Yes!

First, the vibrations are almost gone:

Left picture, previous flight, fully loaded with the stock motor at full throttle.
Right picture, this flight, fully loaded with the new motor at full throttle.

The difference is enormous:

And that's not al. With the new engine, the plane now climbs effortlessly:

In this test, with no one around on the ground or in the air, altitude difference of around 300 m was achieved.

And with no problems with telemetry this time, we learned that the cruising speed at which the altitude can be maintained is around 45 Km/h, which takes about half throttle.

Unfortunately, but not unexpectedly due to all the extra equipment, the gliding profile is somewhat disappointing. With the engine off, the plane glides, but the vertical speed necessary to maintain the cruising speed is around -35 Km/h, peeking at -50 Km/h. In short, it flies but it eats up altitude like crazy as can be seen on the video above at 3:00 mark (yes, the propeller keeps spinning due to resistance).

But, smoother and more powerful motor means better images and video from the cameras, and that's what we want!

Warning, awesome stereo video of the flight:

AVI@TOR MK4 SP4

For better results, use better stuff!

The plane flies, fully loaded even. But! It couldn't climb very high and all the camera recordings were suffering from vibrations coming from the motor.

So, the solution is simple, replace the motor. Implementation, not so much but not on the account of having to turn screws.

Unfortunately the desired one, O.S. 3820-1200 didn't come trough in time, so we got the second best thing, KONTRONIK KORA 15-10.

Cue the montage sequence:

Just add a few more holes since the spacing on this motor a slightly bigger and drill the hole in the center of the prop from 5mm to 10mm because someone goofed up and got the wrong prop mount. But it all balanced out perfectly in the end.

New motor and better regulator. Some day maybe a bigger battery and then a larger plane with newer motor, and so on, but for now this is it.

Few quick tests with a piece of string and a scale, determined the motor with 11x5.5 prop gives out 1.6 Kg of thrust at full throttle. With more aggressive timing setting on the regulator it gave out 1.7 Kg of thrust, but the output was not linear with the throttle.

For comparison, the old motor gave 0.98 Kg of thrust at full throttle.

And another test on the battery capacity gave us: 3 minutes at full throttle and 9 minutes at at half throttle on the new motor. Compared to the 6 minutes at full throttle and 11 minutes at half throttle on the old one. 

Time to test in in the air to see if the trouble was worth it.

Keep Alive Ping

Not dead, just waiting for some parts!

Fifth Time in the Air

Fully loaded and air worthy:

Any yes, it flew! Here's the video to prove it:

And that's not all it did. The camera system works! It successfully takes pictures and video:

Stereo pictures! Might be uncomfortable to look at since the lens distance is not optimized for human viewing, but the depth data is there.

Still taken, synchronized and aligned by hand. There is one more part missing from the plane, and that is the circuit that will relay the data from the autopilot running on the phone to the servos. And part of that will also be automatic synchronised picture taking. As for the alignment, that will be the fun part once we have some real data.

And yes, there is also stereo video. Slightly easier for humans to watch, since distance between lenses is offset by the distance to the object in focus.

But unfortunately the video taken is slightly blurry.  Fault of the stock engine, which is not of the best quality and is causing much vibrations, which are also noticeable on the panoramic video. Not much can be done here but to replace the engine with something better.

And while we're at it, replace it with something more powerful, since while the plane flew, and it flew quite stable, it had horrible climb rate and required full throttle to maintain altitude.

Now with three cameras on board, there is one more flight video:

The landing could be better :P Not used to the extra weight, the runway was missed by 30cm, touching down on high grass and flipping over. So nothing but pride was broken.

And what would a report be without the visualization of the whole flight:

Unfortunately there was problem with the SD card in the phone, so not all the data was captured hence the lack of attitude visualization and force graphs.

All in all a very successful test flight. What works and what doesn't is known, so the next logical step is to work out the kinks and try again!

AVI@TOR MK4 SP3

We know the plane flies and can even do some simple acrobatics. But the real question is, can it fly with all the equipment?

Only one way to find out, which means it's time for some more modifications!

First we determine the location of the camera mount on/in the fuselage:

 

Keep in mind where the center of gravity will be once the cameras are on the plane, then cut the carbon tubing holder size box on one side and appropriate placed holes on the other side of the plane.

Center it just right and it looks like this:

Now that we have the camera holder in place it's time to use the camera holder mounts we prepared and printed.

The mounts will hold the holder to the wing so it wont move about and also to redistribute the weight a bit more evenly:

First locate and mark a good spot, close enough that will hold the stand and leave enough room so the cameras could be put on, but still far enough so the stand can be slide in and out.

Then mark the spot, carve it out (watch out for the servo wires) and protect the servo wires with wax (so once everything is coved with glue and the plane is beyond repair we can remove the servos without it's wires being glued).

Once that is done, drill appropriate holes in to the mounts so the fit around the carbon tube holding the wing, fit them inside the holes and drown them in glue.

After some time when the glue is set, we have out wings with mounts that look like this:

To fully assemble and disassemble the plane now is a whole process, but it's worth it when the end result looks like this:

Will it fly? Only one way to find out :P

From Imaginary to Real World for Real

Knowing the full process, it's time do make the part that will hold the camera stand for real.

First we need some quick measurements,so we can call it engineering instead of art:

Then some modelling:

 

Then proofing and fixing the model:

And finally, setting up and printing:

Two parts, two slicing methods, to see which one works better. First one without support beams and the second one with. The hollowed out back part held better shape with support beams (not being squished by gravity), but other then that, was about the same.

And of course, the final product:

Support beams removed and rough edges sanded. Now we're ready for the next plane upgrade!

From Imaginary to Real World

So, the plane flies. Now we need to put the 3D camera stand on it!

But the stand has quite a bit of weight to it, not to mention it's not exactly a "plug and play" part for the plane.  Solution?

Make a holder for the stand for the camera :P And the easiest was to do it? Print it :D

So it's another skill we're learning here. And to learn it, let's make a simple spacer for the rods, to test the process and the scale of the printed product.

The process is "simple" ...

Step 1: design the part. In our case, we're going to use Blender.

It's free, it's powerful and (after checking some tutorials) the newer version has a 3D printing toolbox which saves some trouble. But in out case, we just used a measurement plugin to to check the distances. Once you're done, change Blender Units to Metric Units and export as .STL file.

Step 2: check the part for errors. In our case, we're going to use netfabb.

Very powerful and expensive software for 3D printer modelling and prepping, but the free version let's you do some simple editing and error checking. We fix any holes in the part, set the correct scale (turns out Blender to Metric conversion is 1 Blender Unit to 1 m not 1 mm) and export the now checked and ready .STL file.

Step 3: slice the file so the printer can print it. In our case we're going to use Slic3r.

No screenshot here, but you're not missing much, just the settings for your printer. Hope everything is calibrated and now you can get your .gcode file for the printer.

Step 4: print it. In our case we're going to use RepRapPro Mandel 3D printer and Pronterface program.

Nothing to do here, but wait and see what comes out.

And once it's done printing and you let your parts cool down, you get something like this:

Not bad for the first try. Some quick measurements and we have almost exactly what we wanted. Turns out that he melted plastic and the resolution of the printer "blurred" the part ever so slightly.

The hole was supposed to be exactly 10mm, but it came out 9.5mm. Which means the plastic in our case expands 0.25mm outside the designed boundary, which is not bad at all.

Step 5: optionally (but in our case mandatory) process the part with some sand paper or a drill.

Slightly smoothing and enlarging the hole and we have a perfect fit:

And now that we know how, let's start on the real thing! What is "the real thing"? join us next time and see for your self.