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I understand the concept of lower KV bigger prop to increase the lifting capacity.

But sometime that is not possible if your drone frame is just so big. For example I have a S550 I like to increase its lifting power to include bigger battery and other equipment.

it uses a 2212 980kv brushless with a 1045prop 30A esc.

I measured the space and that is the biggest prop that can be used.

I wonder installing a 2212 2450kv brushless 40A esc does it increase its lifting power or it is just doesn't have enough torque?

Kindly advice a noob like me

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Faster motors will definitely give you more thrust. However the relationship isn't linear but increases with the square of the speed. So doubling the kV will give you 4 times the power, and going from 980 to 2450 will give you a bit more than 6 times as much. That's almost certainly too much power for motors (and ESCs) of that size.

For double the power, you only need to increase the kV by 1.4 times (so about 1400kV). Then you'd need to double the ESC size to 60A, or do some bench testing to see how much current they actually draw. You'll also need to watch how hot the motors get when they're running at higher power. They might be OK, or might just need to cool down between flights, or they might need to exchanged for larger motors. If you're changing the motors anyway, you might as well get bigger ones that can handle the higher power.

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  • $\begingroup$ "However the relationship isn't linear but increases with the square of the speed". Please, would you have a reference that talks about this relationship? $\endgroup$
    – Arcaniaco
    Commented Jun 24, 2021 at 12:29
  • $\begingroup$ @HigorMaiaConcessa propeller theory is complicated, but most aerodynamic forces are proportional to speed squared. You can see the V squared term in these equations for lift and drag: en.wikipedia.org/wiki/Propeller_theory#Forces_acting_on_a_foil $\endgroup$
    – Robin Bennett
    Commented Jun 25, 2021 at 7:58
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From a practical standpoint, 2450kv 2212 on 1045 is too much prop. If you want more power, either current or voltage must increase, since you're not changing voltage, current will increase significantly.

Increasing the cell count gives you the same change in RPM, but with more granularity. I assume you're using 3S right now, 4S might do it, but keep an eye on temperatures. 1045 is commonly a "slowflyer" style propeller, with a thin neck where the blade joins the hub. Be very careful pushing these up above their (very low) rated RPMs as they can explode (I have a scar to prove it)

Other options for increasing the lifting capacity:

  • Multi-blade propellers

While less efficient (one blade is the most efficient, but not practical), increasing blade surface area increases the air moved, and can increase lifting power

  • Coaxial motors

Again, inefficient, but redundant and a size-constrained way to increase power.

I'd also like to note that the lifitng capacity of 550 size multirotors is already quite high, and if you're toying with increasing that significantly, you're getting into dangerous territory. Care must be taken to ensure all of the systems can handle it. A blender strapped to a brick is no longer a toy

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