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Old Dec 16, 2012, 02:03 PM
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Help!
Dualcopter

Hello everyone,
I've been making a dual copter since last 2 months and now as we have halted the project I got time to post about it.
I am just a beginner in RC so I don't have much knowledge about it so I want some pros to comment on the build and give their useful tips.
Also tell me how to find it's C.G., i am having a hard time to fly it, it's very unstable.
Is there some calculations for control surface size.?
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Old Dec 16, 2012, 02:11 PM
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This is the test video, i have suspended it with threads.

Dualcopter Test (0 min 38 sec)
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Old Dec 16, 2012, 06:49 PM
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Looking on with Expectation!!!
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Old Dec 27, 2012, 08:47 PM
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We made a frame to test our dualcopter and so that we could easily set the gain of each axis individually, but still we are nowhere regarding gain settings, because no matter what the gain settings are, the response is same.
these are pics of frame, i'll upload 2nd test video also.
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Old Dec 27, 2012, 08:48 PM
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This is the test video,
and each time we go for test we feel like it will never fly, we lose all our hope..
Would appreciate some tips regarding the project.

Dualcopter test 2 (0 min 55 sec)
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Old Dec 27, 2012, 10:05 PM
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That vane looks like it is moving awfully slowly. Looks like the gain should be increased. Perhaps the flight controller is to far from the CG to properly sense the rotation. Ideally it would be centered on the CG. The other thing to check is that if increasing the gain makes it worse make sure it is responding in the correct direction.

The other thing is that you have the batteries mounted on the outside of the machine. It would probably work better if they were on the center line of the craft.

You should run some calculations to determine where the center of gravity and center of pressure are. It is probably impossible to get the CG higher than the CP to achieve stablility but getting them closer together would reduce the load on the flight controller.
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Old Dec 27, 2012, 10:20 PM
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Thank you very much.
I will lower the height of control board, but how to find the cg and cp.?
I was following this video:
Dualcopter (4 min 55 sec)
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Old Dec 28, 2012, 08:29 AM
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Joined Feb 2002
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Like the other poster said...It looks like the Vectoring surfaces are not responding fast enough. You will need very high rate servo's and you will have to adjust the rates in your radio.

If you look at the video that you are using as a reference, the surfaces are moving very fast in response to the controller. Finding the proper CG and getting the controller adjusted to it are paramount for ths type of Vectored Thrust application. Look at any 3D plane that is in a Hover....the elevator and rudder are moving very fast to apply the proper thrust vectoring, the same will apply to what you are doing.
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Old Dec 28, 2012, 08:47 AM
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I wanted to use digital servo but then I found a high speed analog servo.
the specs of servo I used are:

Specification:
● Wire length: 18cms
● Weight: 44 gms

At 4.5V
● Speed (sec/60): 0.08
● Torque (Kg-cm): 2.0
At 6V
● Speed (sec/60): 0.07
● Torque (Kg-cm): 2.2

and these are similar to the one used by the reference dualcopter,
I am thinking of lowering the servo just like reference design, will that do any good.
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Old Dec 28, 2012, 04:17 PM
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I think you need to check that your control surfaces are moving in the correct direction before you try to change anything else.

After looking closer at your video it seems like as soon as it starts to move in one direction the vane moves immediately in the opposite direction required.
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Old Dec 29, 2012, 12:29 AM
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Hmm.
I will recheck the directions.
But the vanes should move in opposite direction to that of tilt as in video to bring back the copter to original position.
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Old Dec 29, 2012, 09:17 AM
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It is hard to tell from your video but it almost looks like it is doing the opposite.

The best way to check is to simply disconnect the motors and hold it up and try moving it in various directions. You will know right away if they are working correctly or not.
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Old Dec 29, 2012, 09:24 AM
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hmm.
Thanks for suggestion, I'll surely check the directions now..
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Old Dec 30, 2012, 06:14 AM
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Quote:
Originally Posted by Helno View Post
It is hard to tell from your video but it almost looks like it is doing the opposite.
Helno dude you have Eagle eyes I must say.
You were right about the gyro direction, I now carefully examined the other test videos I had and VIOLA! they were responding opposite and that's the reason I didn't see any difference even after increasing the gain.
Thank you dude, now I'll give another shot to my project when I return.
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Old Dec 30, 2012, 06:15 AM
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Can you give me some hint on how to find the CG.
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