Prop size vs KV value

[kammelryder]

Another noob question. Is there a link to a chart that gives a guide to prop size to KV value of the motor?
I've picked up 4 x 600kv motors for my scratch build and I get that low kv = large prop/ more torque but I can't see what size props to use.
Thanks.

 

[oOFutteOo]

I requeted somthing of the same about a month ago but no luck. I dont get it it would not be hard to do if one had acces to a lot of diferent motors.

 

[oOFutteOo]

Youe need to write what the max AMP rating is on the motor is and how manny cells you plan to run it with to get a ancer from sombody with expiriance

 

[quorneng]

kammelryder
The kV of a motor sets the rpm a certain voltage will produce but has no bearing on the power a motor produces. That is set by a whole series of design parameters that will determine the maximum current that the motor can handle.

The diameter and pitch of a prop determines how much power is required to drive it at a given rpm.

From these definitions you can see there is no direct link between motor kV and prop size as it requires the Voltage (number of cells), maximum amps rating of the motor and ultimately the motor weight to be taken into account as well.

With so many variables it is much better to start with a motor/prop/battery combination that is proven to work for the plane in question.

 

[nerdnic]

On 3s you'd need like a 16" prop. Even on 4s you're still at 14".

How big is this build?

 

[kammelryder]

On 3s you'd need like a 16" prop. Even on 4s you're still at 14".

How big is this build?

Errrrrrrr quite big. :0 semi scale Gotha from ww1.

 

[trevoof]

Try ecalc: http://www.ecalc.ch/motorcalc.php?ecalc&lang=en

 

[kammelryder]

kammelryder
The kV of a motor sets the rpm a certain voltage will produce but has no bearing on the power a motor produces. That is set by a whole series of design parameters that will determine the maximum current that the motor can handle.
Cool, I can't find the listing for the spec on the motors. They were bought originally for a heavy lift quadcopter and I picked them up cheap from an rc group.


The diameter and pitch of a prop determines how much power is required to drive it at a given rpm.

From these definitions you can see there is no direct link between motor kV and prop size as it requires the Voltage (number of cells), maximum amps rating of the motor and ultimately the motor weight to be taken into account as well.

With so many variables it is much better to start with a motor/prop/battery combination that is proven to work for the plane in question.

It's a scratch build I wanted a slower / torque motor set up for noise and I wanted to swing a big 4 bladed prop set up on 4 engines.
Thanks for the reply I'll get back her when I've got the motors in front of me.

 

[kammelryder]

this is the info from the manufacturer Detrum.

86MB96-3020-600KV
Weight (g) 145
Watts 300
Diameter (mm) 37
Length (mm) 40
stator 30*20
No of cells (lipo) 3
max efficiency (%) 80%
max efficiency current (A)? 12-23A
no load current (A) 0.6A
current capacity (A/s) 35A/60S
Internal Resistance (mohm) 62
Shaft Diameter (mm) 5
Shaft Length (mm) 60
Class (SIZE) rocket series
KV (RPM/VOLT) 600
Turns (for cars)Poles 10
Max Voltage 14.8
Wire Size 0.28*7
Bullet Connectors Male
Bullet Connector Size 4*19.5

 

[trevoof]

Used your motor specs and made up some numbers about your airframe to put into ecalc, you should try it yourself to get a better idea.