how to choose motors for Quad ?

Hi,

 

I'm building a Quad from sketch.

My goals are-

it needs to be stable,

it needs to carry a heavy DSLR

therefore i will go BIG. say around 80-100CM.

 

I'd like to get guidelines for choosing the motors.

rather higher or lower KV/(rpm/v) ?

small propellers with big pitch ? or large propellers with small pitch ?

 

any other tips for choosing motors and propellers ?

 

how about ducted fans ?

if i were to use 4 ducted fans instead propellers - is there a reason that all QUADs use propellers and not ducted fans ?

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  • guys, i still dont understand what is the relation between motor KV , propeller size and thrust,

    could you give some simple mathematic to convert motor KV and propeller size into thrust (its better if thrust in Newton)

    thanks in advance

  • Developer

    It is possible to use EDF's but as stated here any many other posts. EDF's are not fast enough to reach speed changes and that way you cannot get good and accurate control of your quad. EDF quad's are always a bit wobbly to fly.

     

    Whole EDF is based on idea to maximize airflow in a "turbine" tunnel. Quad control then again needs really accurate airflow control

     

    Here is a really good video of EDF quad... Like they say, picture is worth of 1000 words and video is worth for million words.

     

    Low KV motors with big propellers are always good combination for quads.

  • The reason EDFs are not used is because you cannot obtain CW and CCW variants. Without this the quad rotates around the yaw axis at the combined velocity of all the EDFs at once. Hover = slowly, WOT = fast. No counter rotation no point in trying to be accurate.

    As for sizing especially that big I have no idea.

  • I don't know much about this yet, but I think that the reason that they don't use ducted fans is that the fan uses a lot of battery and can't adjust to throttle changes quickly enough.
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