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Aug 20, 2020, 10:03 AM
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Amp question


I'm trying to figure out the amps for a 2216 1120 kv turning a 6-3 3 blade prop. Is there a chart I can use?
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Aug 20, 2020, 10:10 AM
Registered User
Not properly without an amp meter

https://www.amazon.com/RGBZONE-Analy...7936214&sr=8-6
Aug 20, 2020, 12:52 PM
An itch?. Scratch build.
eflightray's Avatar
There are some power calculators here --

e-flight calculators, motor- and prop-databases (compilation)

You could get a 'ball-park' figure, but there are still some variables. Why would you want to know ?, to select an ESC amps range?

.
Aug 20, 2020, 04:56 PM
aka: A.Roger Wilfong
gnofliwr's Avatar
Well, no. You need to know the battery voltage, too. The calculators above will give you an estimate.

As a rough estimate, an 1120Kv motor turning a 6x3x3 prop is going to draw ~5A on 2S, ~7.5A on 3S and ~11A on 4S. But that motor is intended to turn a 9-11" prop on 2-4S @ ~25A - it's loafing on a 6x3, even if it's a 3 blade.

- Roger
Aug 20, 2020, 06:06 PM
Registered User
Thread OP
I will be using a 3s 2300 lipo. So basically I should go up on the kv to use a 6" prop. Like up to 2000 kv or better?
Aug 20, 2020, 09:37 PM
B for Bruce
BMatthews's Avatar
If you're limited to a 6 inch prop then yeah, you will need a 2000 to 2500Kv motor for 3S packs from what I've seen for that sort of size of motor.

Again if you are stuck with a 6 inch diameter look up a variety of 2216 motors with higher Kv values and see what any charts for the motors suggests. And read the user comments which often include prop sizes and motor draws with those props.

And yes, invest in a wattmeter. They cost no more than an inexpensive brushless motor and are invaluable tools for testing such things and avoiding bad choices.
Aug 21, 2020, 09:09 AM
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Thread OP
Awesome thank you very much!
Aug 21, 2020, 01:45 PM
Registered User
Thread OP
FMS Motor: 2212 KV2250 Edge 540 750mm (LXLWMP)

I found this motor that fits my needs. Does anyone have any suggestions?
Aug 22, 2020, 08:34 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Quote:
Originally Posted by jeepma
I'm trying to figure out the amps for a 2216 1120 kv turning a 6-3 3 blade prop. Is there a chart I can use?
What do you want to power? Make, type, size, mass?

Quote:
Originally Posted by jeepma
I will be using a 3s 2300 lipo. So basically I should go up on the Kv to use a 6" prop. Like up to Kv=2000rpm/volt or better?
Would result in very high rpm.


Note that Kv says nothing about power and torque.
It's all about what the motor wants to do versus what the motor can do.
Kv matches rpm and voltage, nothing more.
  1. Kv and voltage determine how fast motor wants to run (rpm_noload = voltage Kv).
  2. Rpm and prop determine current (current = torque Kv, in SI units!).
  3. Max.current and power determine whether that battery/motor/rpm/prop combo can run without going up in smoke.

  1. Kv and voltage determine how fast motor wants to run.
    rpm_noload = voltage Kv
  2. Rpm and prop determine torque, torque in turn determines current.
    current = torque Kv (in SI units!)
  3. Max.current and max.power determine whether that voltage/motor/rpm/prop combo can run without going up in smoke.


Prettig weekend, en wees voorzichtig Ron
• Without a watt-meter you are in the dark ... until something starts to glow •
e-flight calculatorswatt-metersdiy motor tips&tricksCumulus MFC
Aug 22, 2020, 10:22 AM
B for Bruce
BMatthews's Avatar
Quote:
Originally Posted by jeepma
FMS Motor: 2212 KV2250 Edge 540 750mm (LXLWMP)

I found this motor that fits my needs. Does anyone have any suggestions?
You need to flesh out what you're trying to do. The questions you're asking are not much more clear than "how long is a piece of string?". Plus that particular motor when I search for it has no data at all at any of the three links I found.

So we don't know what you want to fly, the aggressiveness you will use when flying for aerobatics or why it MUST be a 6" prop. So the only answer we can offer is "maybe". Typing is cheap, give us more to work with so we can be more helpful.


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