Prop size matching motor size / power?

I'm using Tiger motors 2212-13 980 KV motors - reportedly these are suitable for blades up to 10" and they are working well for me.

I've seen Tiger motors 2216-?? 980KV which apparently are suitable for larger blades (I forget the size). I'm currently building another QC with a larger frame which could take larger blades, but do I need a larger motors at the same time if I choose larger blades?

If so, why? I presume the 2212 vs 2216 is the size of the coils, so a 16 will have longer coils and therefore larger magnetic field for a given current throughput. That makes sense but what about the 980KV rating? I'd assumed this was related to the power of the motor, but then that would mean both motors only differ in size and so could handle the same size blades.

Can anyone clarify for me please.

Thanks

You probably already know the KV rating is a measure of the motor's no-load speed. Hook a 980KV motor up to 10 volts and it will turn around 9,800 RPM with a load. Start adding a load, say by putting on larger props, the motor will struggle to maintain its design speed and its power consumption (Watts) goes up. Put too large a prop on a motor and not only will the speed fall off, the motor will exceed its rated power and nastiness ensues.

The T-Motors 2213 series motors have power ratings of 230 watts. A motor's power rating is set by its design and is how much heat a motor can dissipate while running. The 2216 series is 280 watts. While there is a 2213-13 980KV model, I don't see the T-Motors has a 2216 980KV model. The closest KV I see they list for 2216 is 900KV, which is sort of close. So the 2216 series can handle more power than the 2213 series.

Since more powerful motors are heavier, you would normally want to put the largest propeller you can on the smallest motor you can. This means you are probably operating near the motor's maximum power rating. So the only way you can add a larger prop and maintain roughly the same RPM without toasting your motor is to select a more powerful motor (i.e., its power dissipation in Watts is greater) with a similar KV.

So in summary, higher powered motors can always be used to turn smaller diameter props at the expense of carrying around motor weight you don't need/use. But smaller motors can't turn larger props beyond their power rating.

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Tom Mahood November 26, 2013 at 7:37am

You probably already know the KV rating is a measure of the motor's no-load speed. Hook a 980KV motor up to 10 volts and it will turn around 9,800 RPM with a load. Start adding a load, say by putting on larger props, the motor will struggle to maintain its design speed and its power consumption (Watts) goes up. Put too large a prop on a motor and not only will the speed fall off, the motor will exceed its rated power and nastiness ensues.

The T-Motors 2213 series motors have power ratings of 230 watts. A motor's power rating is set by its design and is how much heat a motor can dissipate while running. The 2216 series is 280 watts. While there is a 2213-13 980KV model, I don't see the T-Motors has a 2216 980KV model. The closest KV I see they list for 2216 is 900KV, which is sort of close. So the 2216 series can handle more power than the 2213 series.

Since more powerful motors are heavier, you would normally want to put the largest propeller you can on the smallest motor you can. This means you are probably operating near the motor's maximum power rating. So the only way you can add a larger prop and maintain roughly the same RPM without toasting your motor is to select a more powerful motor (i.e., its power dissipation in Watts is greater) with a similar KV.

So in summary, higher powered motors can always be used to turn smaller diameter props at the expense of carrying around motor weight you don't need/use. But smaller motors can't turn larger props beyond their power rating.

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Prop size matching motor size / power?

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