Hey, I have a hacker style brushless outrunner which has a rating of 924Kv and i have a 10x4.7 propeller. I need to calculate an estimate of the thrust. I came across this equation for the static thrust,

T = [ (eta*P)^2 * 2 * pi *R^2 * rho ]^0.3333

T = thrust (in Newtons)

eta = prop hover efficiency = 0.7-0.8 is typical for unstalled low-pitch props

P = shaft power = voltage * current * motor efficiency (in Watts)

pi = 3.14159

R = prop radius (in meters)

rho = air density = 1.22 kg/m^3

In this equation i'm not sure what to use for eta (i was thinking 0.75). I also don't know what I should use for current, voltage, motor efficiency and propeller radius. Should i just use the max current and voltage that the motor can take which is 17A and 11V respectively. Should I just assume the motor is around 75% efficient? Will the prop radius just be half the length of the propeller, in my case that will be 5 in (0.127 m).

If i use the values i assumed above i get,

T = [(0.75*11*17*0.75)^2 * 2 * pi * 0.127 *0.127 * 1.22] ^ 0.3333 (0.127 is the radius in m)

T ~= 11.1 N

Does this seem correct?

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