Prop size in relation to motor's KV

[nickyb]

Hi All,

Just need a bit of clarification. I now understand KV on motors and am hopeing to get some DYS 640KV motors for my Tarot quad.

I';ve been told these motor';s (pancake style) are torquey'; so it would be best to get around 11-12 inch blades since it will reduce power consumption. I think they come with standard 10 inch versions.

Is this correct, should I got for bigger props?

Thanks for your help,

Nick

[The.Quadfather]

what size battery are you intending to use - 3S/4S (or higher) - as this makes quite a difference ?

[QuadBod]

And a link to the specific motor (size makes a difference).

[nickyb]

what size battery are you intending to use - 3S/4S (or higher) - as this makes quite a difference ?

Hi there,

Thanks for the post. I intend to run 3S size batteries.

Here is a link to the motor I intend to use with my Tarot quad

http://www.rclegends.co.uk/parts/motors/dys-motors/dys-be3608-11-630kv-motor.html

Cheers mate

Nick

[The.Quadfather]

I would say 12" minimum for a quad <=1.5Kg
10" would be Ok for 4S+ LiPo

I typically end up using ecalc to evaluate options, but can be tricky to use if the exact motors you want arn';t listed

example: if quad is 1.5Kg AUW with 12" SF props and guessed numbers for your motor gives 4.1A hover (per motor) @ 69% throttle (<- bit high!)
as above with 13" props gives 3.8A hover (per motor) @ 56% throttle

[nickyb]

I would say 12" minimum for a quad <=1.5Kg
10" would be Ok for 4S+ LiPo

I typically end up using ecalc to evaluate options, but can be tricky to use if the exact motors you want arn';t listed

example: if quad is 1.5Kg AUW with 12" SF props and guessed numbers for your motor gives 4.1A hover (per motor) @ 69% throttle (<- bit high!)
as above with 13" props gives 3.8A hover (per motor) @ 56% throttle

Many thanks for the sound advice. I will probably go for the 12" versions now.

What happens if I use say 10 inch probs, would it induce wobble?

cheers

Nick

[The.Quadfather]

What happens if I use say 10 inch probs, would it induce wobble?

may not take-off !

actually, it depends on the weight, but the motors would be running high rpm which wouldn';t help stability

[nickyb]

now I understand, will take this advice and for for 12 inchers.

One thing. Does it matter if they are Carbon or Plastic?

Cheers

N

[guest325]

Don';t think that pancake motors are the b all and end all for high torque, quite simply they';re not!
I can show you a much smaller diameter motor that will spin an even bigger prop, you need the right relationship between diameter and length to get the most efficient motor, for what you are doing I would be looking for a 40-45mm dia motor 20-30 long depending on cell count I want to use  I think you may need to consider 4S because you possibly are looking to keep the props a reasonable size to avoid getting them in your field of view. 10" would make sense, but have a close look at what pitch you can get away with, I';m looking at an idea that uses 13" x 7" props, promises to be a bit of a beast!!!