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Old Jun 10, 2011, 01:46 AM
UAV Pilot
UndCon's Avatar
sweden
Joined May 2007
1,005 Posts
Quote:
Originally Posted by sfakias View Post
This is with the servo positioned at bottom of wing. For top mounted servo, the horn should be tilted rearwards when the servo is at the neutral position, correct?
My horns are almost 45degrees forward direction when rudders are neutral.(servos mounted on bottom side of wing)

About Tilt rear - correct - your goal is still the same.

As is right now I have 4 channels for my wing
2 ailerons and 2 flaps

I did not use the advantages of trimming any surface separately and If I do I can do so with the linkage instead.

I'm going to solder a bunch of Y-cables to solve this and it most likely requires reversing of 2 servos mounted in the wing (internal servo mod)
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Old Jun 10, 2011, 04:35 AM
Seafax ROV
WalneyCol's Avatar
United Kingdom, Barrow-in-Furness
Joined Feb 2011
371 Posts
Quote:
Originally Posted by venquessa View Post
If at 100% throttle it needs 60amps to achieve close to it's Kv, then at 50% throttle it will draw 60amps (or more!) for 50% of the time.
Cheers Venquessa, I know it should have been obvious but it was quite a lightbulb moment for me. :-)
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Old Jun 10, 2011, 08:06 AM
Registered User
Joined Aug 2010
901 Posts
Venquessa and vegasbs, thanks for the explanation. I've been googling and reading a lot and understand what you are saying, I see how the loads may be focused on one winding only at 1/3 throttle instead of spreading the load to all windings, very interesting.

Where I am going off of the tracks is with this example.

I'm looking at this Turnigy Motor

Dimension: 36mm x 51mm, 70mm(with shaft)
Weight: 181g (kv1450) (not including connectors)
Diameter of shaft:?strong>F5mm
Length of front shaft:?strong>F19.1mm
Lamination thickness: .2mm
Magnet type: 45SH

Specification:
No. of cells: 3-6S
RPM: 1450kv
Max efficiency current: 45A-50A
No load current: 11.1/4.6A
Current capacity: 70A/20sec
Internal resistance: 0.010ohm

Max performance;
Voltage: 3-6S
Prop: 7x5, EDF90
ESC: 60A
Thrust: 1450-2300g
Power: 1600W
For EDF 1500~1800g model airplane.

Kv (rpm/v) 1450
Weight (g) 181
Max Current (A) 50
Resistance (mh) 0
Max Voltage (V) 22
Power(W) 1600
Shaft A (mm) 5
Length B (mm) 51
Diameter C (mm) 37
Can Length D (mm) 30
Total Length E (mm) 70

The motor states it can take 1600 watts. If I deliver 22V (6S) and 50Amps (max rated), I am only delivering 1100watts. How would I ever get to 1600 watts without exceeding a limit??

People using this motor are reporting pushing this motor to 1597 watts but it takes 92amps. Are they vastly overamping the motor?? THANKS AGAIN!!
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Old Jun 10, 2011, 08:24 AM
Gravity is patient............
Joined Mar 2006
1,910 Posts
Quote:
Originally Posted by thekubiaks View Post
Venquessa and vegasbs, thanks for the explanation. I've been googling and reading a lot and understand what you are saying, I see how the loads may be focused on one winding only at 1/3 throttle instead of spreading the load to all windings, very interesting.

Where I am going off of the tracks is with this example.

I'm looking at this Turnigy Motor

Dimension: 36mm x 51mm, 70mm(with shaft)
Weight: 181g (kv1450) (not including connectors)
Diameter of shaft:?strong>F5mm
Length of front shaft:?strong>F19.1mm
Lamination thickness: .2mm
Magnet type: 45SH

Specification:
No. of cells: 3-6S
RPM: 1450kv
Max efficiency current: 45A-50A
No load current: 11.1/4.6A
Current capacity: 70A/20sec
Internal resistance: 0.010ohm

Max performance;
Voltage: 3-6S
Prop: 7x5, EDF90
ESC: 60A
Thrust: 1450-2300g
Power: 1600W
For EDF 1500~1800g model airplane.

Kv (rpm/v) 1450
Weight (g) 181
Max Current (A) 50
Resistance (mh) 0
Max Voltage (V) 22
Power(W) 1600
Shaft A (mm) 5
Length B (mm) 51
Diameter C (mm) 37
Can Length D (mm) 30
Total Length E (mm) 70

The motor states it can take 1600 watts. If I deliver 22V (6S) and 50Amps (max rated), I am only delivering 1100watts. How would I ever get to 1600 watts without exceeding a limit??

People using this motor are reporting pushing this motor to 1597 watts but it takes 92amps. Are they vastly overamping the motor?? THANKS AGAIN!!
The 1600 watts is a peak number and the amps is a continuous number. So continuous power out of this motor is 3.7x6x50x.8(efficiency) = 900watts continuous. Working backwards, the 1600/.8 = 2000 peak watts in. 2000/(3.7x6) = 90 amps peak.
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Old Jun 10, 2011, 08:26 AM
But often down to earth
Floater73's Avatar
Oklahoma, USA
Joined Sep 2010
736 Posts
I don't use the motor but your post said the motor can take 70A for a while. A fully charged 6s has 25.2v. At 25v and at 70 amps that's 1750 watts. That wouldn't be maintained for long but 1600 could.
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Old Jun 10, 2011, 02:49 PM
Registered User
Denmark, Capital Region of Denmark, Brøndbyvester
Joined Jun 2009
606 Posts
I would really like to pan my camera, but the rudder use my pan-channel. Should I drop the use of rudder, and only turn left/right with the use of ailerons, so that I can pan ?

I have a 7 channel Futaba, but I guess that the last 3 channels are controlled by the switches.
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Old Jun 10, 2011, 02:52 PM
Registered User
Firatp's Avatar
Turkey, Istanbul
Joined Dec 2010
413 Posts
Quote:
Originally Posted by SpookiePower View Post
I would really like to pan my camera, but the rudder use my pan-channel. Should I drop the use of rudder, and only turn left/right with the use of ailerons, so that I can pan ?

I have a 7 channel Futaba, but I guess that the last 3 channels are controlled by the switches.
I would advice not to cancel rudder. During low speeds ailerons are not enough to steer.
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Old Jun 10, 2011, 03:00 PM
Registered User
Denmark, Capital Region of Denmark, Brøndbyvester
Joined Jun 2009
606 Posts
Quote:
Originally Posted by Firatp View Post
I would advice not to cancel rudder. During low speeds ailerons are not enough to steer.
I guess you are right Thanks.

I have a switch on my Futaba with 3 positions (up/center/down). Would it be possibly to use this as Left/Center/Right-position for my pan-servo ?

---

I just did a test, and it worked just fine using the switch for Left/center/right-pan. I think I'll use that.
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Old Jun 10, 2011, 03:36 PM
Whats the wrst that can happn?
AdamChicago's Avatar
Chicago, IL USA
Joined May 2010
2,657 Posts
And depending on the level of aerial videography you do, it's nice to be able to point the plane/camera in a cross wind while keeping the plane level

Quote:
Originally Posted by Firatp View Post
I would advice not to cancel rudder. During low speeds ailerons are not enough to steer.
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Old Jun 10, 2011, 05:04 PM
UAV Pilot
UndCon's Avatar
sweden
Joined May 2007
1,005 Posts
Quote:
Originally Posted by SpookiePower View Post
I would really like to pan my camera, but the rudder use my pan-channel. Should I drop the use of rudder, and only turn left/right with the use of ailerons, so that I can pan ?

I have a 7 channel Futaba, but I guess that the last 3 channels are controlled by the switches.
I have my camera connected to elevator /rudder with Y-cables and I really like it
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Old Jun 10, 2011, 06:17 PM
FPV junkie
m_beeson's Avatar
United States, UT
Joined Jan 2011
3,382 Posts
So,




I got my skywalker together. I took it up the other day, and tried to fly it.

Despite the lack of thrust that it was exhibiting; I continued to try to fly it until

I crashed it.



I got it repaired and waited for a good day which happened to be today...


When I launched it, It still showed a lack of thrust (with a higher pitch prop) , but it was flying. I went to bank it to the right, to bring it on course & nothing...

I let off the throttle, and it started to bank, but then it nosed in.

I thought I tested it on the ground, but now I can't remember. When I showed up to the crash site, everything was working.

I'm starting to get a little frustrated. I just want to fly. I never used to have this many problems with nitro pull prop set-ups.


motor 780 kva

prop circa 9 1/2x10

Battery 3s 5300 mah

CG 30mm behind aileron wires.

I can't figure out why the it woudn't bank.
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Old Jun 10, 2011, 06:40 PM
KJ6BFN
henkvdw's Avatar
United States, CA, Fountain Valley
Joined Aug 2008
732 Posts
Quote:
Originally Posted by m_beeson View Post
So,
I got my skywalker together. I took it up the other day, and tried to fly it.

Despite the lack of thrust that it was exhibiting; I continued to try to fly it until I crashed it.

motor 780 kva
prop circa 9 1/2x10
Battery 3s 5300 mah
CG 30mm behind aileron wires.
With a Voltage constant (kV) of = 780 RPM/V and a 9.5"x10" prop one could probably run on 5S before the motor will generate the thrust needed.
Although 10" pitch prop is in my opinion not well suited to this plane. The SW flies relatively slow. That 10" pitch is for moving fast. So you are probably also stalling it. 6" pitch is more than enough.
On the 3S pack that you are running you should have a motor with kV of 1300 to 1450.
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Old Jun 10, 2011, 07:30 PM
FPV junkie
m_beeson's Avatar
United States, UT
Joined Jan 2011
3,382 Posts
Quote:
Originally Posted by henkvdw View Post
With a Voltage constant (kV) of = 780 RPM/V and a 9.5"x10" prop one could probably run on 5S before the motor will generate the thrust needed.
Although 10" pitch prop is in my opinion not well suited to this plane. The SW flies relatively slow. That 10" pitch is for moving fast. So you are probably also stalling it. 6" pitch is more than enough.
On the 3S pack that you are running you should have a motor with kV of 1300 to 1450.
I'm watching the video right now. That's another story. My computer is having a problem with Emperex files.



Anyway, it reaches a speed of 20mph, and I can see when I give it aileron to bank right, it doesn't react.

Then it banks right, but I give it left aileron and it stays in a right bank.

Full throttle, until it circled 270 degrees, then I let off, and when it nosed in, I punched it, but it wouldn't pull up because it was in a right bank.
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Old Jun 10, 2011, 07:32 PM
FPV junkie
m_beeson's Avatar
United States, UT
Joined Jan 2011
3,382 Posts
9x6 prop with this motor on a 3S didn't have enough thrust to glide
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Old Jun 10, 2011, 09:36 PM
FPV junkie
m_beeson's Avatar
United States, UT
Joined Jan 2011
3,382 Posts
Everybody likes to watch carnage these days. Enjoy

unresponsive SkyWalker (0 min 55 sec)



If you watch the ailerons, you can see that I hold them in the right-bank position for about 5 seconds before I get any response.

Then I hold them in the left-bank position (trying to level it out) and it remains in a right bank.


Mike


p.s.

I'm settled down now a little, and not clouded with anger & frustration any more.

I'd like to figure it out though before I chuck this thing in the air again.

Has anyone else experienced these symptoms?

Does anyone have a stall-speed on this airframe?

I am wondering if I just tip-stalled d/t insufficient thrust & speed. I'm thinking about purchasing a more suitable motor.
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