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« on: April 10, 2018, 03:30:03 PM »
knvshrm
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Hi guys hope you are doing well. How to balance CG in quadcopter ? What effects does it have on the quad ? The electrnics used in the quad are :
F450 frame , Kk2.1.5 FC , 2200 mAh lipo , 1400 kv a2212 motor , 10 by 4.5 prop , 30 amp esc.
Plz help.
Regards
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« Reply #1 on: April 10, 2018, 04:36:28 PM »
K K Iyer
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@knvshrm,
Hi,
Saw your msg in Goli’s thread.
Here’s an easy method that can be understood from the attached pics.
Pic 1 shows unbalanced, ie, CG not at the centre of the quad
Pic 2 shows balanced by moving the lipo a bit towards the lighter side.
Repeat with the other pair of arms.
When properly balanced, all four legs will lift at the same time when you pick the quad up holding the centre of the string!

B194F13C-1B3F-4619-9AAB-62C4578738C5.jpg
Re: CG balancing in quadcopter need help
* B194F13C-1B3F-4619-9AAB-62C4578738C5.jpg (75.42 KB, 800x600 - viewed 382 times.)
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« Reply #2 on: April 10, 2018, 06:08:32 PM »
knvshrm
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Thank you sir need help regarding this too http://www.rcindia.org/beginners-zone/best-diy-plane-for-beginners-which-is-very-easy-to-make/msg286891/#msg286891
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« Reply #3 on: April 10, 2018, 07:27:01 PM »
K K Iyer
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@knvshrm,
1. Is the CG problem solved?
2. What is the status of your quad? Ready? Pl post a photo.
3. Have you tested it yet?

You can take a look at my 3 year old post:
http://www.rcindia.org/multirotors/st360-quad-initial-testing/msg216983/#msg216983

If you are a beginner, tackling your first quad AND your first airplane at the same time maybe too much!

If your quad is ready, maybe you should concentrate on it first. Postpone the airplane for a few days.

I see that on your airplane thread, you’ve already been getting a lot of advice, some of it contradictory!
I’m also posting a response there...
Regards
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« Reply #4 on: April 10, 2018, 07:39:20 PM »
knvshrm
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Thanks sir , the quad is ready I am using
F 450 frame
1400 kv a2212 motors
10 by 4.5 props
30 amp esc
Kk2.1.5
2200 amp 3s 25c lipo

But I have a problem the battery is discharging very quickly I think I need to reduce the prop size . Can you suggest the ideal prop size plz . My friend was using the same electronics but a esc burnt.
Regards
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« Reply #5 on: April 10, 2018, 07:39:59 PM »
knvshrm
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I just hovered the quad. It seemed to be stable
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« Reply #6 on: April 10, 2018, 07:43:05 PM »
knvshrm
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Here are the pics

IMG-20180410-WA0003.jpg
Re: CG balancing in quadcopter need help
* IMG-20180410-WA0003.jpg (43.92 KB, 800x450 - viewed 284 times.)
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« Reply #7 on: April 10, 2018, 08:12:51 PM »
K K Iyer
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Thanks sir , the quad is ready I am using
F 450 frame
1400 kv a2212 motors
10 by 4.5 props
30 amp esc
Kk2.1.5
2200 amp 3s 25c lipo

But I have a problem the battery is discharging very quickly I think I need to reduce the prop size . Can you suggest the ideal prop size plz . My friend was using the same electronics but a esc burnt.
Regards

If you reduce the prop size, the motors will just have to run faster! That’s not the problem. 10x4.5 is OK.

Do you have a wattmeter?
At hover the motors may be drawing, say, 10-11amps each. Or say 44 amps total.
On a 2200mah lipo, that’s 20C.
So 3 minutes to kill the lipo.
Or 1.5 min to use 50% capacity

So during testing, if you get about 1 min of hover, that’s fine.
Tomorrow when I get the mood, I’ll check the current draw on mine at hover.
But from experience my estimate should be fairly ok.

Why don’t you search for and contact by PM the real multirotor experts on this forum?
Regards

Edit
These guessed at current draw estimates are completely off.
See subsequent post of data from wattmeter
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« Reply #8 on: April 10, 2018, 08:16:22 PM »
knvshrm
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Sir my motor draws 16 amps.
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« Reply #9 on: April 10, 2018, 08:18:06 PM »
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Can I balance props at home I do not have a prop balancer or anything like that .
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« Reply #10 on: April 10, 2018, 10:58:56 PM »
K K Iyer
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Sir my motor draws 16 amps.

Or say 64-66amps for all four.
Or 30C on your 2200mah lipo
Or your lipo will die in 2 minutes
So getting 1 minute is quite ok...

Balancing the props is a different issue. Reqd if you have vibration. Nothing to do with duration.
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« Reply #11 on: April 10, 2018, 11:49:52 PM »
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@knvshrm
What's the current flight time you're getting?

Those motors give good results with 8x4 props (on 3s) and 9x4.7 props (on 2s).
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« Reply #12 on: April 11, 2018, 06:20:17 AM »
knvshrm
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Less than 2 minutes. Plz tell me what can I do to elongate the flight time ?? Plz help
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« Reply #13 on: April 11, 2018, 06:21:20 AM »
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Lipo is 3s 25 c
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« Reply #14 on: April 11, 2018, 07:21:43 AM »
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1] Try 9 in. props.
2] Reduce weight. (remove sponge-balls if possible)

I suspect you are unknowingly using an old battery with substantially reduced capacity. Ask a local senior aeromodeller to do a capacity test.

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« Reply #15 on: April 11, 2018, 12:15:31 PM »
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Tomorrow when I get the mood, I’ll check the current draw on mine at hover.

[/quote]

Hello Sir,  did you happen to check the current draw during hover?  I will be happy to see the result.
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« Reply #16 on: April 11, 2018, 01:53:58 PM »
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9 inch or 8 inch plz be specific sir.The battery is a new one .
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« Reply #17 on: April 11, 2018, 02:28:30 PM »
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Dude , since it's 3S , get an 8 inch one
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« Reply #18 on: April 11, 2018, 02:29:58 PM »
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8 by 4.5?
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« Reply #19 on: April 11, 2018, 02:46:10 PM »
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9 inch or 8 inch plz be specific sir.The battery is a new one .

Try an 8x4 or 8x4.5.

Even if the battery is new, it won't hurt to do a capacity test using a good charger.
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« Reply #20 on: April 11, 2018, 02:59:02 PM »
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Are 1400 kv motors fine for this quad with 8 by 4.5 props . The motor use 16 amp.what will be the flight time I get with 2200 mAh 25 c lipo ? The weight is 1 kg .
Regards
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« Reply #21 on: April 11, 2018, 03:00:53 PM »
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I don't even know any aeromodeller  who lives near by.
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« Reply #22 on: April 11, 2018, 03:14:02 PM »
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The kV doesn't determine the thrust of a motor. kV determines the RPMs , the wattage of the motor determines the power. Power is the amount of work that is done by a motor in a specific time interval. So, more work = more power= more thrust ,or since work = FS, you could also say, work directly proportional to the force it can excert. So, larger motor=more thrust.
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« Reply #23 on: April 11, 2018, 06:14:06 PM »
K K Iyer
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Hello Sir,  did you happen to check the current draw during hover?  I will be happy to see the result.

Yes I did, and got a surprise.
My quad weighs 820gms including 200gms for 3s 2200mah lipo.
The props are 8x4.5
It lifts off drawing only 8-9 amps (~100watts)

Assuming you draw say ~11amps average during hover testing, and use only 50% capacity of the 2200mah lipo, you should get 6 minutes.
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« Reply #24 on: April 11, 2018, 06:47:14 PM »
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Sir can you plz give specs of the motors you have used ?
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