Please explain prop pitch...

[Gunter]

I have got to a stage where I have to select props for the heli. I am just trying to understand the theory of the prop pitch, so that I can select a good blade for the heli. I am building an octo with jdrones 880kv motors:

Does a higher pitch mean that the blade is angled more, meaning faster acceleration? I have an image in my mind that if there is less pitch, the prop will have to spin faster to keep it up, but may be smoother when pushing the gas stick up?

What I am looking for is 1. obviously best battery life and less work for the motors and 2. as smooth flying as possible, ie when I push it up, it accelerates slightly more gently to keep everything nice and smooth. (I want to do aerial videos)

So I'm looking at xoar props, 12" but either 4" or 5" props..not sure which is going to be best.

Thanks, Gunter.

 

[Bartman]

gunter
the prop pitch is the distance, in an ideal world, that a prop will move forward through the air in one revolution.
lower pitch means it will pull harder at slow speeds but have a slower top speed. higher pitch means it won't accelerate as well but it will be capable of a higher top speed. somewhere in the middle to low end of the range is where we should be operating. 3.5 to 6" pitch seems to be a good range depending on what you want to do. with those motors a 4 or 5" pitch should be fine, i'm running 12x5 props on my okto with 770 kv motors.

 

[Bartman]

gunter
it's interesting also that even though a prop may have a pitch of say 5", if you look at the blades they are very high pitch at the hub and low pitch at the tip. the 5" ends up being an average of sorts of the different points along the blade.
the pitch varies along the blade because the root of the blade turns much slower than the tips. The steeper pitch at a slow speed makes an amount of lift that is similar to what the shallow pitch is making with the higher speed at the tip. by varying the pitch along the blade they try to distribute the lifting force equally along the blade so that the tips aren't making very much more than the root is. then they give it a number you can use to understand the overall nature of the prop and that is the pitch.
bart

 

[CMonteiro]

Hi Gunter,
This site contains interesting information and a sugestive picture to explain pitch.
Have a look
C.Monteiro
http://www.rc-airplane-world.com/propeller-size.html

 

[Gunter]

Thanks guys, my thoughts were confirmed...the higher pitch means a faster heli, so I really want to go for a slightly lower pitch which in theory should make it smoother to fly?