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Comp ARF Lightning + 7xDS8911 servos = VERY HIGH BATTERY CONSUMPTION

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Comp ARF Lightning + 7xDS8911 servos = VERY HIGH BATTERY CONSUMPTION

Old 11-16-2009, 03:42 PM
  #51  
tassos p
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Default RE: Comp ARF Lightning + 7xDS8911 servos = VERY HIGH BATTERY CONSUMPTION

ORIGINAL: olnico

Hi Tassos. You will certainly get something out the article. Especially since I explain how to compute the equivalent weight ballast for the intended aerodynamic load.
This wil enable you to do a proper electrical system test under realistic flight load and check the validity of your system and battery sizing as well as thermal endurance of the Powerbox regulators ( something to consider as well when having such a big electrical load )

What we could do here is go on the practical side of the article and make a proper simulation together.
Have a look at the article and at the RC calc software:
http://www.geohei.lu/olin/data/model...calculator.xls

Then give me all the flight control dimensions: average cord and span.
Then I'll need the control horn arm and maximum speed as well as average aerobatic speed ( I assume that you don't go full blast all the time )
Thanks alot for your help Oliver,

That's really nice of you to help and its highly appreciated. However I haven't got my plane with me, cause I leave it in a warehouse at my flying field and I will get this data on Saturday when I go there.

But please verify for me a few things to help me and correct me if I'm wrong. When you say the average cord of the flying surface you mean the that if the flight surface looks like a trapezium (like for example the aileron in the attached pic) then it is the (inner cord + outer cord) / 2 ? And the span you mean the length of the surface?

And which control arm are you talking about? The servo's or the surface's or both? And what about the length of the linkage between the servo horn and the flight surface horn.

Average aerobatic speed I estimate around 220km/hr and max speed around 330km/hr. Most of the times I fly with 50% throttle (with my P180 it is more than enough).

Thanks alot once more,

Tassos

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Old 11-16-2009, 10:28 PM
  #52  
olnico
 
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Default RE: Comp ARF Lightning + 7xDS8911 servos = VERY HIGH BATTERY CONSUMPTION

The average cord is at the center of gravity of the flying surface ( assuming that the build density is even ). On a rectangular shape it is at the middle. Not on a trapezoidal shape.
Of course you cannot remove every FC to check its CG. Just evaluate it roughly and that should do the trick.
On your picture, the flaps average cord is more or less at the middle and the aileron at the first 40% of the span.

You are correct for the FC span: it is the length of the control.

I need the control horn arm length. The servo arm is given as an output data...
Old 12-04-2009, 03:34 AM
  #53  
tassos p
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Default RE: Comp ARF Lightning + 7xDS8911 servos = VERY HIGH BATTERY CONSUMPTION


ORIGINAL: Dave Wilshere

Tassos

No I use a std Powerbox. I have a H 9 meter and also the Graupner Amp Clamp. But I do it by ear and total battery consumption. I charge new models batteries before setting up the model, set it up which usually takes me not much more than 10min inc mixes etc...so about a flight time, plus any other testing on gear etc.
Before I test fly I charge the batteries again and always note mAh used..as during the life of the model this tells you so much. I have an expected consumption. So if I was doing your Lightning and I guessed 20min total on time I would expect on 5-600mAh use from each battery.

I then fly it and monitor battery use.

Dave
ORIGINAL: i3dm

Is the Gangar 9 any different than a regular watt meter, such as this one ?

http://www.hobbycity.com/hobbycity/s...dProduct=10080

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my Jet gallery: http://www.runryder.com/helicopter/g...1/?script=jets
Ok here's what I've done.....

It looked really strange to me how the Powerbox Royal has been measuring so large batteries consumptions.

I bought the item Lior is mentioning in his post (thank you Lior for the idea)

I connected it in series with one of the batteries to the PB as shown in the first picture.

Then I put my 14MZ to cycle all the servos on the ground without any load for 10mins or so. The results:

- PB displayed consumption of Battery 1 (2nd pic) : 1097mAh
- External power meter reading (3rd pic): 151mAh

This is 7 times less than the PB!!!

In addition last weekend I made 5 flights. After the flights I measured exactly the mAh charged in each battery. And guess what, each took around 1700mAh, which means an average of 340mAh per flight (under flight load).

Which means I can trust the $25 power meter I bought but I cannot trust the $650 PB Royal I bought to read for me the power consumption amongst other things it does.

I sent an email to PB and they said it may need calibration. This is one H$$L of calibration they need to do.....

I wonder if anyone else out there is having the same setup as I have and is seeing the same measurements as me. Is it just my PB?

Thanks alot everyone for your help.

Regards, Tassos
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Old 12-04-2009, 03:37 AM
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Carsten Groen
 
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Default RE: Comp ARF Lightning + 7xDS8911 servos = VERY HIGH BATTERY CONSUMPTION

Hi Tassos,
that explains quite a bit, and yes, "calibration", hmm, in my book it is something like a few percent or so, but a factor of 7 [X(]
Good you found the explanation though !
Old 12-04-2009, 07:50 AM
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Default RE: Comp ARF Lightning + 7xDS8911 servos = VERY HIGH BATTERY CONSUMPTION


ORIGINAL: tassos p



Which means I can trust the $25 power meter I bought but I cannot trust the $650 PB Royal I bought to read for me the power consumption amongst other things it does.

I sent an email to PB and they said it may need calibration. This is one H$$L of calibration they need to do.....

I wonder if anyone else out there is having the same setup as I have and is seeing the same measurements as me. Is it just my PB?

Thanks alot everyone for your help.

Regards, Tassos
Hey Tassos.

This is exacly what I tried you to explain the whole time to use a simple battery checker.
The discussion about high amps of the 8911 is simply just NOT the case!!!!!
Happy for you it turned out right.
Old 12-04-2009, 11:00 AM
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Default RE: Comp ARF Lightning + 7xDS8911 servos = VERY HIGH BATTERY CONSUMPTION

ORIGINAL: Didier

Hey Tassos.

This is exacly what I tried you to explain the whole time to use a simple battery checker.
The discussion about high amps of the 8911 is simply just NOT the case!!!!!
Happy for you it turned out right.
Thanks alot Didier,

I was struggling to understand what was wrong. However I never expected the truth to be so far out. 10 or 20% difference I'd understand but 700% difference I don't understand.And you know when you see this on your plane its frightening and makes you think what is wrong with your setup!!!!

I will investigate in depth with Powerbox to see what is wrong. Maybe it is a software bug that they have not discovered yet.

Thanks,

Tassos

Old 12-04-2009, 11:55 AM
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schroedm
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Default RE: Comp ARF Lightning + 7xDS8911 servos = VERY HIGH BATTERY CONSUMPTION

At least it's an error in the right direction [&:]
Old 12-05-2009, 03:43 PM
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Default RE: Comp ARF Lightning + 7xDS8911 servos = VERY HIGH BATTERY CONSUMPTION

Tassos

I am finally getting ready to start my Lighting build with UL wings. i noticed your pilot and cockpit. looks good! can you tell me where you got both?

thanks.



i have a NIB BlueBox F-15 cockpit but not sure i feel like disectting it to make it fit. i was thinking about a Skymaster Cockpit but after reading about fragile nature of the ViperJet Cockpit i may have to re-think that idea.

best regard


Joe
Old 12-05-2009, 04:06 PM
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Default RE: Comp ARF Lightning + 7xDS8911 servos = VERY HIGH BATTERY CONSUMPTION


ORIGINAL: JoeEagle

Tassos

I am finally getting ready to start my Lighting build with UL wings. i noticed your pilot and cockpit. looks good! can you tell me where you got both?

thanks.

i have a NIB BlueBox F-15 cockpit but not sure i feel like disectting it to make it fit. i was thinking about a Skymaster Cockpit but after reading about fragile nature of the ViperJet Cockpit i may have to re-think that idea.

best regard

Joe
Hello Joe,

Yes the cockpit is a Bluebox F-15. This for sure does not disintegrate, but its heavy, together with the pilot the weight comes to 750g about double the cockpits of Skymaster, Feibao etc etc. If you want close up pics I can send to you. The fact is that because the BBI F-15 cockpit is not in production any more it may worth while selling it since it now sells for more than $500 since it's very hard to find.

The pilot I got from Frank Tiano ( www.franktiano.com ).

Good luck with the built.

Tassos


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