RC India

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

@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!

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

@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

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

I just hovered the quad. It seemed to be stable

Here are the pics

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

Sir my motor draws 16 amps.

Can I balance props at home I do not have a prop balancer or anything like that .

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.

@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).

Less than 2 minutes. Plz tell me what can I do to elongate the flight time ?? Plz help

Lipo is 3s 25 c

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.

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.

9 inch or 8 inch plz be specific sir.The battery is a new one .

Dude , since it's 3S , get an 8 inch one

8 by 4.5?

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.

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

I don't even know any aeromodeller  who lives near by.

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.

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.

Sir can you plz give specs of the motors you have used ?

 need help in this post too : http://www.rcindia.org/multirotors/problem-with-kk-2-1-5-board-plz-help-!!/msg286992/#msg286992

And should I replace the proprs with 8045 props or are 1045 props fine ?

Sorry that's not the link refer to this http://www.rcindia.org/multirotors/problem-with-kk-2-1-5-board-plz-help-!!/

I thought they were 2212 1400kv with 10x4.5.
Sorry for giving wrong info earlier. Had not even looked at the quad in over a year.

Actually they are ST2210, 1050kv from Quadkopters, with 8x4.5 props.

The 10x4.5 props you have may overload 2212 1400kv motors at high throttle (have to check this).
At the rpm required for hover, I don’t think they will overload.
If you have a wattmeter you could check the amps draw when just lifting off (on 10x4.5 props)

However, as suggested earlier by others, you should try 8x4.5, or 8x4 that may be easier to get.

1. Can you post a close up photo of your motor showing the label?
2. A photo of your lipo. Is it puffed?
3. A photo of your props. Which make are they?

Tomorrow I’ll try to see if I can get 5 minutes of hover time with a somewhat puffed old 2200 lipo.
Regards

No sir the lipo is not puffed.

The props are unbranded sir only the dimensions are written on the props.

No photos I suppose...

Sir when I try to upload photo an error occurs.

Your attachment couldn't be saved. This might happen because it took too long to upload or the file is bigger than the server will allow.

Please consult your server administrator for more information
This is the error

Though on the motor only A2212/10T and 1400 kv is written.

Should I order 8 *4.5 props or stick to these 10 * 4.5 one's ?

It's still showing error will try to upload pictures tomorrow.

See there are two different issues.
1. Will it hover? To check this the 10x4.5s are enough
2. Less duration. Either due to overload or weak battery
To be checked by
a. Reducing load by changing props (actuallythe load at liftoff is the same irrespective of prop, as it is the weight of the quad. Reducing the prop size allows the motors to run at a higher rpm, which may or may not be a good thing.)
b. Changing battery

To hover a 1kg quad, each motor has to produce 250gms thrust.
2212 motors are capable of 700-800gms thrust at full throttle.
So 250gms should be easily possible with a wide range of prop sizes.

My suggestion is
1. Retain existing props
2. Charge lipo to 4.20 per cell, or as close as possible
3. Lift off a little, and hover with as little change in throttle as possible
4. Check duration

Also check what voltage your low voltage alarm is set for...

Sir can lipos clear through customs ? So I can order a new one .

hey,have you bought these motors off amazon or chandni chowk??anyways 10×4.5 is too much for that motor , am also using same specs motor diffrent brand on my copter with a 8×4.5 prop ,copter weighs around 1000grams with a 2200 mah lipo 3s and gives around 7-8 min of hover

I have same specs of the electronics . Got the motors from Rees 52 .

Where can I get 8 * 4.5 props from ??

Hello sir , here are the specifications of the motor :
KV (rpm/volt): 1400
Thrust (g/s) : 1265/4
Efficiency: 80%
Efficiency current: 4-10A (>75%)
Current Capacity: 12A/60s
No Load current @ 10V: 0.5A
Working voltage range: 7- 12v
Shaft Diameter: 3.17mm
Lipo is 2200 mAh 25 c
8 *4.5 props
What flight time will I get plz help.

Will be checking the duration soon .

And sir how will I know when the battery voltage  drops to about 3 volts ? I do not have a low voltage alarm.

On the top left do you have a red connector with one red and one black wire leading to a small black plastic cylinder?
That’s the buzzer for the low voltage alarm.

By the way, going down to 3 volts will surely kill your lipo!
Go to Misc settings in the menu and set the battery alarm to 10.5v or higher. (3.5 per cell or more)

Shocking results sir

I got 6 and a half minutes of flight with 10 * 4.5 props. Was moving the quad back and forth and in circles.

@kk iyer
Thanks a lot sir for your help and support.
Regards

Well done  {:)}

Sir it's all because of your help. It would be great if you can PM me your WhatsApp number as I am now thinking of making a rc plane after a few days so definitely would need help.
Regards

I presume that you're not comfortable sharing your number, no issues sir.
Regards

@knvshrm,
Sent by PM.

Hi sir i didnt understand how u checked CG with threads

Dude , here is an easier way to get the main Idea. The correct centre of gravity of a quad should be at the geometrical centre of the quad body. That is, the quad should balance at the absolute centre of the quad, just like balancing a scale.

Hi Pro,
Dont need no thrds man. Ven u no the CG, As you sd hr:
http://www.rcindia.org/rc-people/how-to-tune-p-i-settings-in-kk-2-1-5-fc-for-quad/msg286768/#msg286768

Nothing great in it. Exactly like a vegetable seller’s scale for equalising the weight on each side...
Have to do it twice though, once for each pair of arms. The lighter side will rise first when you pick it up from the centre of the thread tied to equidistant points on opposite arms...

Regards

@Iyer sir, I didn't mean to disregard you.
I think the OP doesn't know the need to balance a quad.

This is what he said:
“Hi bro i found the CG point on my quad....what to do next?”

That’s why I said no more need for threads (even though I was told it means clothes  :headscratch:)

Guess I’m just getting puzzled by Modern English, like I was with Modern Maths once...

He found the point where it balanced. It is technically the CG, but not the cg we want. Just like, if we put too much lead on the nose of the plane, The plane can technically balance on the nose of the plane

Technically the CG? What’s that?
The CG is the CG, that’s all. It’s where it balances.
Even if it’s not where you want it...
He said ‘What next?’
Perhaps you didn’t see the reply...

Can we let it go, please?