patternman

My Feedback: (-1)

question on motor rating. The Kv is meant to tell RPM per volt. In the e-flight outrunner, the 400 comes in two Kv ratings. I understand that the slower and larger the prop, the greater efficiency. I am wanting to fly the mini funtana with one of these two. Which Kv should I choose, the larger or the smaller? What do they mean? Do I need a Kt value as well?

BadSplice

My Feedback: (1)

I dont hear people talking much about the kt values, so Im gonna guess it isnt all that important. THe general rule of thumb I learned for kv is that the higher kv means more speed, less power, and lower kv is more power, less speed. Considering what kind of plane the mini funtana is, I'm thinking you'll be way better off with the lower kv.

Greg Covey

The motor Kv doesn't stand for kilovolts but is rather a motor velocity constant given in units of rotational speed like RPMs per volt. If you take the reciprocal of the back EMF constant of a motor, the result is a proportionality constant which relates the voltage applied to the motor terminals to the rotational speed of the coil. Manufacturers often provide a choice of motors with various Kv to allow different gear reduction ratios and cell count to be used. On outrunners, I typically use the higher Kv motors because they require less cells and use thicker wires so I can create higher burst current performance.

E-flite recommends using the 3700Kv Park 400 brushless motor (EFLM1105) with a 20-35amp ESC and a 3-cell ThunderPower 2100mAh Lithium pack to power either the mini Funtana or mini Edge 540. Both models come with a 6.6:1 gearbox that will perfectly fit the Park 400 brushless motor.

I can't wait to get my hands on one of these mini Edge 540s!

Matt Kirsch

My Feedback: (21)

Yep, the K stands for "Konstant" not Kilo.

Unfortunately, you can't make generalizations like, "more power less speed... less speed more power" about two motors with different Kv ratings, like the Park 400 3700Kv and 4200Kv. Both motors are capable of handling the same amount of power; they just put it to the air differently.

Simply put, the 4200Kv motor will spin a smaller prop at a higher RPM on the same Volts and Amps as the 3700Kv, either direct drive, or with the same gear ratio. You can fiddle with the gear ratio and get both motors to spin the same prop at the same RPM on the same Volts and Amps.

What simplifies this is the fact that you can't get just any gear ratio, and in the case of the MiniFuntana/MiniEdge, you get a workable 6.6:1 gearbox with the plane. Sure, you could use the 4200Kv motor with the included gearbox and prop, and sure, you'll have gobs more power, BUT you are also pushing the motor well beyond its limits, drawing too many Amps, and something's gonna burn out sooner rather than later.

tf2psycho

try the gws 11x8 prop with your setup