View Full Version : First flight - meet "The Headcrab"
09-05-2010, 09:36 PM
Finally made my first flight today, and prett happy with the result. Meet "The Headcrab"
- Turnigy 2217 860kv´s
- 25A Turnigy Plush ESCs
- One Arduino Duemillanova with a broken FDTI for the moment ( replacement + Mega in mail)
- Turnigy 4000mah for main power, 800mah zippy flightmax for arduino + fonera (nonfunctional atm)
- Arms: Square aluminium tubing from bauhaus. About 75cm motor to motor distance
- Center frame: PVC cutting board "cut to fit" + pvc screws
- "Head" - Upside down food container.
- 10x 4.7 APC propellers
- "Homemade" shield
- Wii MP (original) & Nunchuck (copy)
- Software "1.7.1 Wii Good" version in X mode / acrobatic
Since the USB chip on the arduino went the other night the flight setup is as after my first test: Default PIDs. I also lost the throttle calibration of the ESCs as I had to reset them to reprogram to have brakes on and low cutoff threshold. The throttle stick would not trigger the programming untill I redid the throttle calibration with the ESC connected directly to the receiver. Due to this the "range" of the throttle was to big on this flight - at low speed props hardly turn and it felt like the middle throttle range had too little accuracy. Replacement Arduino and a new mega + protshield in the mail :-)
At first the quad was unstable beyond lifting off the ground - my vibration dampening sheme was way to wobbly. Fixed with 4 pieces of gaffa tape giving it some more stiffness. And the silicon tubes actually broke off during one of the upside down landings. Need to work on a different approach.
After the gaffa tape treatment it flies pretty ok from what I can judge. I can hear the engines "wobbling", but the flight itself is rather stable. Had about 4 flips/sideways crashes, no damage other than slightly greenish propellers ;-) I account that to the bars extending beyond the propeller to save it from "side impact".
Another skill I need to acquire is video photography - sorry for the boring video with the camera too far away. I also had to edit out long minutes with the quad outside the camera. GoPro HD to put onboard is in the mail, which will hopefully prove more entertaining :-)
Seems robust enough! Maybe I too need to pay Bauhaus a visit, been searching for those square aluminium tubes for a while. Seem to be the absolute best choice for quads except for titanium of course :) Not in economy but... My fifth frame which flies pretty well now consists of only a chiseled broom stick, only weighting 150 grams more than my super light weight carbon fiber frame which was too weak.
Your quad seems stable even though default PID. You should experiment more with that later, but for now you can experiment with different vibration dampeners to the sensors. It will affect the flight characteristics MUCH.
Also, don't let your quad suffer more than once :) If you fly a little higher you don't bump into the ground so much even though grass is a very forgiving surface. And also you will see more clearly how it behaves.
Keep on working!
09-06-2010, 08:03 PM
After the first flight comes first ... crash :-)
The replacement Arduino came in the mail today, so I quickly rigged up that without the lipo alarm that I suspect broke the last boards USB chip. As daylight was going away quickly I just ditched all vibration dampening and bolted the electronics box to the center frame.
I couldn´t tell much difference from yesteday - maybe a bit more stable actually. Likely due to the throttle calibration. I flew higher this time - approx 3-5 meters above ground, and had some good fun letting it pick up good speed going forward and back towards me - not straight at me though ;-) Good fun for about 10 minutes or so and I really felt in control of it. Tried acro/stable - not much difference (maybe it was locked to stable mode all along)
Now, the one thing I decided to never do - from reading code and looking at the configurator - was to give full throttle. I´ve seen on the configuration that it has less difference between motors to go on at max. Of course, I had the idea to see how fast it ascends at full throttle - pretty fast. But it also tilted quite bad (almost 45 deg) after getting up to about 6m.
Now If I´d lowered throttle just a bit and tried to level it, maybe I would be ok - but with my inexperience I lowered it almost all the way down, and of course it fell to the ground.
The good news is that the damage is limited to one alu arm only, easily replaced :-) Also as you can see on the picture the rip in the metal is through a hole in the arm - they are there as I simply turned the tube 90 deg after messing up the first drilled holes. Don´t know if I had been better of not having it not rip there though. Maybe it is a good idea to deliberately drill extra holes at strategic places to soften up the arm to absorb impact and possibly vibrations?
So - all in all I call it a success. I think I´ve been lucky to have it perform so stable seeing the vibration problems others have had. I´ll do more experimentation over the weekend, especially analyzing the vibration patterns. I dont really have any reference so maybe it can get even better than it is.
Oh, and I need to get some proper leds for night flying too :-)
Hmm, yeah I am too a little unsure of how it would react with absolute 100% throttle, but as I have flown for some months now with only slight SW modifications, I am starting to feel more confident manually flying it. What I can tell is that the quad somehow either by aerodynamics or by code levels itself out VERY nicely if you let it descent quickly by almost lowering throttle to 0 (ALMOST! :) ) and then put it up to about 80% when too close to ground. I did have to do this to prevent a similar crash to yours while trying out altitude hold. So don't be afraid of apply throttle if quads' going down too fast. Actually it's quite fun playing with the throttle stick...
I think that if you didn't have that extra hole in that arm maybe something else would have broke (center plate, motor mount etc.), so that probably was a really good thing.
By the way, I can't find those square tubes on Bauhaus site, I can just find an electric towel bar (expensive!) that seems to have those mounted. Did you buy them separately? And what dimensions/lengths do they have? Guess I'll have to go see for myself though :)
09-07-2010, 07:57 PM
Thanks for the tip on the leveling. I remember doing a maneuver like that today, but more out of accident :-)
So as you understand I went flying today again after fixing the arm - didn't take long to remount a new arm. This one without the side holes as I got it right the first time ;-) Todays surprise what that it was totally not wanting to stay level - I then realized I had fastened the battery off center. After making sure it was all aligned on the center it was back flying as before. Seems it is vital for the the balance point to be center, at least on mine.
Into my second battery pack it started wobbling quite a bit. Turned out one of the engine mounts had started unscrewing.. :-o tightened it and went up again. Then again shaking - this time one of the "pedestals" on the turnigy 2217s was loose. If the prop had not been fastened on top of the screws it would have fallen off. So - next up is a bit of glue on the screws of the mount.
Bauhaus (at least at the Oslo south branch) has a selection of aluminium tubes and pipes available, aswell as solid rods, sheets etc. As far as I can understand its part of their normal inventory. The one I have are in lengths of 1m and 1.2cm square - 2mm walls I presume - so I simply cut them in half and put them onto the quad as that. They have longer too - about 2m. I also got the nylon bolts from bauhaus. If you stop by, have a look at the elbow fittings they stock for joining the aluminium tubes - I was wondering if it could be used as a center... Set aside some time to look around :-) Price I cant really remember I think it was something like 50 kr for the one meter or so, maybe less.
I was on Bauhaus today and they got really many dimensions of these aluminium square tubes!
They didn't got the 12mm but just 10 or 15, so I took 2m of 15mm square tube. Gonna make 5 X 40cm arms so I have one in to spare and that would make for about 80-90cm from motor to motor at longest which is what I have planned. I already got a center plate in aluminium that I have used for 2 previous frames.
They even had black plastic couplings (4-way) that were meant for sticking a 10 square mm tube in, but they seemed to weak... Otherwise I would not have to do anything at home! It's like they have quad kits on Bauhaus :)
I like your frame so I'll try my 6th frame to be similar to yours. Do you thing drilling through the tubes make them weaker in flight, i.e. produce more vibration than without holes through it? Holes through would be the simplest, but you can put 2 screws on the sides of it too...
09-18-2010, 08:56 PM
Nice :-) Mine might be 10mm to be honest, didnt measure, just took it from memory. The plastic couplings might be something for a smaller size quad?
I dont think the holes contribute much to making the arms flex more. If your center plate is pretty stiff then the stress point wont be around the holes.
A hot tip: Seal of the ends with something so you dont get dirt into them. Its impossible to clean out when you can run them under water due to the motors - and it spreads all over you workdesk.
HMm. I believe Mikrokopter uses 10mm arms and screws not through but at the sides of the arms. Those plastic couplings would work for any size I think, pressfit but you could just use one screw per arm to 100% secure the arms.
Anyway, I aim for a super foto/video quad, so I went for the 15mm because the 10mm seemed to flex some at 50cm lengths. And we can't have that when I want 40cm arms with terrible motor vibration and aim to lift both a FPV cam and a compact cam :)
I have noticed the stiffer the frame, the lower the vibrations. My 180g carbon fiber frame was as big as the one I got now, but with terrible flopping around! Now I have put together my newest frame with those 15mm tubes and an aluminium center plate. Weights 360g with screws. Very stable. Will post pictures later.
hehe actually I had the same problem with round carbon fiber tubes I had before... :) But now my motor mounts will be outside of the ends of the arms and I have learnt not to fly when it wobbles around, so hopefully I won't crash.,.. Ok we all do! :) But still, the blades gets outside of the arms.
09-19-2010, 05:06 PM
Had a majestic crash today, flew higher than before in the same location as the video above, and got a bit scared as it was wobbling in the wind. Hit a branch in one of the treetops and came down hard. Had to pull hard to get one arm up from the ground. Another broken off at the same spot as last time. New this time was that batteries both were flung away from the quad. Both fastened with welcro inside the boxes. I consider that a safety feature in case of a hard crash ;-) No video, the non-gaffers tape mount let it fall off just after start.
I hope noone got hurt though! ... But think of this: next time you will secure your batteries better (or know it is a safety feature :P ) and you probably saved a lot of money because of that arm breaking.
I am finished with my alu tube frame, 85cm motor to motor diagonally (and 60cm the other way you know..) but now I have to solder in longer leads to the ESC's :) Gonna be stable but it is quite heavy, 850g with just motors and frame and screws, that excludes my 125g flight board, camera, battery... Well :) What does your weight? I have had different frames all from 1000g ready to fly to 1700g ready to fly.
09-20-2010, 07:08 AM
Mines a heavy 1800g - thats with the heavy pvc cutting board center plates and the extra battery box underneath it. After the problems with the initial vibration dampening scheme my logic has been to avoid both weight,vibration and PID optimization until I had it flying (keeping it mind though of course). I get about 15 mins flying time on a 4000mah battery.
None hurt in the crash part from two alu tube arms and one prop broken off at the center. And a tree is missing some. I´m rebuilding it now and switching to Arduino Mega and the latest software. - And led lists for night flying! Going to meet up with my RC helicopter friend next weekend so I have to make it look good ;-)
09-25-2010, 08:17 PM
Today I visited my friend who is flying RC helicopters - and had him try out my quad. Seeing how he handled it I now realize how crap I´m at hoovering ;) There was quite some wind today, so we were both impressed it managed to stay that stable. Easily offended scandinavians might want to turn off volume as there is one instance of some very mild swearing on the audio track.
Still on 1.7 Wii good version. I had the trunk code + Mega and new homemade shield up this week, but I had some serious stability issues, so reverted back for this weekend. After going back to 1.7 I realized I had the sensors front-to-back... Hoping to have this fly the 2.0 code this week and join in on experimenting with improvements.
09-28-2010, 03:15 AM
Today I visited my friend who is flying RC helicopters - and had him try out my quad. Seeing how he handled it I now realize how crap I´m at hoovering ;) There was quite some wind today, so we were both impressed it managed to stay that stable...Looking good. What are your Acro, Heading Hold and Stable mode settings?
If you get a chance to try stable mode with the latest shield and code please let us know how it goes.
Nice! Guess that's more motivation for you to start tuning the new code so you can have it even more stable :) It seemed like it was making small controlled movements all the time, don't know how much it was the pilots or quad's effort? But I wanted to see some super flips and whatnot :P
By the way, I only heard "helvete" sometime, and then a really funny laugh at the end :)
09-28-2010, 12:30 PM
@RCVett - This is again with the Wii_good version, all defaults that has worked good for me from the start.
@Honk Sadly you missed a few flips - when I was at the controls it was a bit more wobbly... My friend almost ran for cover as I had it flying towards us in quite a steep angle. Apparently they teach heli pilots to take cover in that case ;-) Most dramatic was a crash landing in a deep pond. Had it not been for the battery box the lipo had been well underwater.
Flips - yes, goint to attempt one when I have 2.X stable ( and I can pencil in some time rebuilding it after the crash ;D)
Hehe, run for cover is probably a pretty healthy instinct with these things!
I feel that the 2.0 code is better at responding to my sticks, but some of it depends on that I have changed RECEIVERLOOPTIME to only 20ms instead of 50ms making it 50Hz as the Receiver actually puts out, try that to get better response. Also I noticed it got much more stiff in the air when stiffing up the sensor board mount and wrapping it in rubber bands.
I have it stable now, but I don't wanna risk my last set of props trying to do flips yet! :P
09-28-2010, 01:03 PM
Well, I´ll send you a set of APC props in the mail if you attempt one, hows that? ;-) You can select from the 10x4.7 or 12 inches. Actually I havent had the 12x3.8 on yet. So much to do , and little daylight!
Hehe, then I gotta start flipping right now! I know, it's so dark here now! I'll try to film it. You said "attempt", right? :P
I just got the barometer and stable mode working with Mega/Wii/BMP085 :)
Said and done norweigan! :)
09-28-2010, 04:58 PM
Hehe - Nice :D, as said PM address and I´ll have it shipped over :-)
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