LibrePilot Forum
Users => Vehicles - Helicopters => Topic started by: jcg1541 on October 27, 2017, 07:29:11 am
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I have a pure direct drive build. The motor spins at 400 kv . There is no mechanical noise, only the sound of wind blowing.
Revo is on the far side of the fuselage, and the picture only shows the side servo pins of cc3d board. It lifts off at
half throttle. Bill of material and discussion are at
https://blog.mpls-phone.com/2017/09/converged-quadcopter-helicopter-device.html
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Thats really cool!
Have a video of the heli in action?
K
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I have only throttled it to lift off from my hand when I was at the Output page of librepilot setting. No lift off from ground yet.
I don't know when I will do it.
I am thinking about refocusing my design direction because my goal right now with heli is to do illegal FPV building
urban proximity diving, like so many youtube videos have done with quads. So, I need a collective pitch 3-servo system
to keep a constant RPM to store large angular momentum while the heli is free falling at zero collective pitch. The
picture's main frame is a fixed-pitch, 2-servo system. But I will continue pure direct drive gearless with the 3-servo system.
Thats really cool!
Have a video of the heli in action?
K
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It might be handy to enable RTB on failsafe with TakeOffLocation set to a distant fixed place so you can switch off the transmitter and retrieve the copter later from a known location. ;) ::)
Of course that means that it must be completely set up for autonomous GPS flight.
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So, I need a collective pitch 3-servo system to keep a constant RPM to store large angular momentum while the heli is free falling at zero collective pitch.
The picture's main frame is a fixed-pitch, 2-servo system. But I will continue pure direct drive gearless with the 3-servo system.
Lets see if I follow,
I understand the motor part and no main shaft, great, and you took the main rotor head unit and gearing from a small size heli with 2 servo system control from something like here
https://www.horizonhobby.com/200-sr-x-bnf-with-safe-reg%3B-technology-blh2080
and now you look for a 3 servo configuration to achieve the goal of gaining greatest momentum while free falling?
I think the 'gaining momentum as falling' has nothing to do if you have a 2 or 3 servo system installed?
But if you can live with cost of the components of a full 3 servo configuration you should do it since so much proven configurations and settings can be used.
Also, for your build with small power you may get away with a tiny gps and the internal mag of a revo nano unit to make a RTB function. That would help a lot right?
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You got most of it. The main shaft's diameter is exactly the same as the main motor's shaft's.
For the stored angular momentum part, it is "angular momentum" of the inherent collective pitch system that allows 300 foot free-fall and yet pull out at the last second with full thrust using the full spool-up rpm speed. It is rotor's "angular momentum", not the craft's "momentum". The variable pitch is critical for illegal urban diving because fixed pitch craft spools down to idle rpm during free-fall of 300 foot drop, and the craft can't spool up fast enough to pull out alive in under 1 second. It is stunt video, not suicide video. Prime example is illegal trump tower diving https://www.youtube.com/watch?v=JHApZ0xL2zg . It can't be done with fixed pitch helicopter because the idle rotor won't spool up in 1 floor drop after a 50 floor free fall.
But quads with small angular rotor momentum will never get long duration military missions that is exclusively helicopter because when we half the rotor diameter, the newton laws half the fuel economy. If we stretch a stunt multi rotor's propeller blades to twice length, it will look like a cargo helicopter, like the Chinook, and won't be able to do the stunt dive.
Collective pitch 3 servo systems are at the sweet spot of both long duration missions and stunts. The dawn of this new trend is this other video https://www.youtube.com/watch?v=3hK8mtg7RQI .
I think the 'gaining momentum as falling' has nothing to do if you have a 2 or 3 servo system installed?
But if you can live with cost of the components of a full 3 servo configuration you should do it since so much proven configurations and settings can be used.
Also, for your build with small power you may get away with a tiny gps and the internal mag of a revo nano unit to make a RTB function. That would help a lot right?
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Ah, now I see what you mean.
Yes a fixed pitch system will have to spool down otherwise it cant fall straight down but would drift away from building.
I remember several years ago I saw a video of a 450 size heli doing a free fall along a high building... left me dizzy :)
edit, found the clip
https://www.youtube.com/watch?v=N-AqVbbfIoI
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I also love this clip dearly. The same pilot now has a new youtube channel called picoflyer . He doesn't
do illegal dive bombing over crowded places now, only smooth dives. When I was younger, I used to do
parking lot flying with stick fixed wings and attracted local police. They were not seriously concerned
because the craft was under 200 grams, and any one could see that it was harmless when they approached.
I am very cautious about keeping craft weight under 250 grams.
Ah, now I see what you mean.
Yes a fixed pitch system will have to spool down otherwise it cant fall straight down but would drift away from building.
I remember several years ago I saw a video of a 450 size heli doing a free fall along a high building... left me dizzy :)
edit, found the clip
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Thats really cool!
Have a video of the heli in action?
K
I have the same heli in flight video, but it is with gears in the video. I am hoping to make the gearless video next week. I am kind of distracted to the downward facing camera for eliminating drift.
https://www.youtube.com/watch?v=j5X_UOc73KI
I have 3 builds, 2 on the car dash board, as seen in the video. I aim to keep 2 fly-able at all time. The video is shot by the car dash cam.
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Thats really cool!
Have a video of the heli in action?
K
It is a snow storm outside. I fly the gearless configuration in the low ceiling hotel room. The ground effect (bed sheet effect) is crippling the flight. The closeup of the gearless is at the end of the video.
https://www.youtube.com/watch?v=hYm5WIyCE2c
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OK, I got the outdoor footage after the snow. The liftoff happens at 1 minute mark.
https://www.youtube.com/watch?v=fzghJSv4ivk
The tail wagging in previous hotel room was fixed after using the denser mounting tape that came with CC3D atom.
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John, this gear-less idea is really cool!
Yes, much better tail holding now.
You still looking for a suitable Collective Pitch Rotor Head pack for your build?
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Karla, I am already using CCPM head with 3 servos. It is a blade 180 rotor hub mixed with Oxy2 main grips. It is a full fledged acrobatic heli. There is a servo saver tutorial out there that makes the craft crash proof. It is as hearty and robust as racing quads, if not more robust. Upon crash, the servo arms are dislocated, and I just dial back the arms to its original position, and continue flying. Most quads need replacing props when crash because the props are not foldable. The heli's foldable blades solves this problem.
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Ah, great.
So next thing you going to sort that ground fixing tech to keep no drift and then do proximity stunt?
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Yes. It needs the pitch curve and throttle curve mixing on the radio transmitter setup. CC3D setup is all finished. Actually either the gearless or geared craft uses the same cc3d UAV config. The gearless just flies with perceived higher precision because there is only one rotating gyro. I am a bit distracted by the downward facing usb camera with the on-board raspberry pi right now. I don't have software to run the usb camera. I have 3 builds, 2 flyable. I have 2 cameras on the craft now. One for fpv, the other for higher level computing.
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I need to confess that I just did a very controlled hovering endurance test, and the geared version lasted exactly as long as the gearless version. 16 minutes on the 800mah pack. One went from 12.6v to 11.2v , another went from 12.6v to 11.15v , well within margin of error. They are basically the same. But, the gearless version weighs 249.9 grams while the geared version weighs 240.1 grams, both with the on-board raspberry pi weight of 10 extra grams.
That means that, to add 2nd camera or gps, the gearless version will have to go over 250 grams. But, my flying field is just on the border of 5 mile radius from a airforce base.
So, it is going to be a tough decision to go with the gearless and register with FAA and all that opposite of fun.
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OK, I got the dive bombing practice footage. The first diving happens at the 0:38 mark,
https://www.youtube.com/watch?v=xCKVXw8cKkc
. I used attitude mode to fly this. And when the elevator stick is all the way forward,
the diving is only 70-80 degrees, not vertical 90 degress.
But, this thread can be concluded that the only difference between regular gear heli
and gearless setup on the CC3D configuration is that the failsafe for tail is -100%
for the direct drive, so that when you want to power on the servos to work on tuning
the servos, the tail is powered off. So, CC3D config is here,
https://drive.google.com/file/d/1S_8A7ODSe-Kncj7hl1GtejdZaLcz_qwL
, and the build material and discussions are at
https://nocomputerbutphone.blogspot.com/2017/12/converged-drone-developers-platform.html
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I will talk about tuning the stick mixer of CC3D in the other thread "Cliff Diving PID" .
Right now I am still trying to figure out if my P gain is too big and that the airfoil goes over the
critical attack angle at the bottom of the dive when I let go the cyclic stick to neutral. CC3D
should be generating the maximum compensation at that point. And what is the swash angle
at that point ? I don't know.
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I used attitude mode to fly this. And when the elevator stick is all the way forward,
the diving is only 70-80 degrees, not vertical 90 degrees.
Coming along nicely I see.
I think when you do set up the pitch- and throttle curves on the transmitter, you can just set a common 3D flight combination that will include a negative pitch angle and then you can do 90 or why not 110 degrees dives. I think attitude mode will be fine. Just let go of pitch stick and it should level out, fc will do it. Or use Rate and then you will do it yourself.