Propellers

Propeller choice is one of the most important decisions of your quadcopter.  These are the footwear of your quadcopter.  Propellers affect the agility, stability and efficiency of your quadcopter.

Propellers commonly come in 2, 3 and 4 blades.  The more blades on the propeller, the less efficient they become.  However, more blades produce less noise and are able to handle higher power requirements.

Propellers are specified by their diameter and pitch.  The diameter is measured length of the propeller.  The pitch is how far the propeller will advanced in one revolution.  For example, a 10×4 propeller has 10 inch diameter and will travel 4 inches in one revolution.

Propeller Size

The diameter of a propeller dictates how much thrust can be generated.  The larger the propeller the more thrust can be generated and also the more energy is needed to spin the propeller.

Propellers come in two spinning directions: clockwise and counterclockwise.  The spinning direction is also referred to as “tractor” (counterclockwise) and “pusher” (clockwise) propellers.  Tractor propellers are more common than pusher propellers.  A quadcopter needs a matched set of tractor and pusher propellers.   Because pusher propellers are less common than tractor propellers, propeller choice will be dictated by which propellers are available in pusher configuration.

Importance of Propeller Pitch

I discovered that my initial propeller choice of a 3-blade 8×6 propeller was the root of all my frustration in trying to stabilize Scout’s flight.  After weeks of tuning Scout’s stability, I began to hit a wall.   Even with the best tuning, Scout would still drift and sway during flight.  I could not get Scout to hover in one place.   I began to track down why Scout was so unstable.  I initially thought it was too much vibration that was overloading the sensors.  I added more foam padding to the sensor board and balanced the propellers.  The stability marginally improved, but not as much as I would like.

I then thought it was the ArduPirates code that was the problem so I switched to the ArduCopter code.   Scout was still unstable.  I then remembered I had bought a set of 2-blade 8×4 propellers.  I decided to give them a try.  Eureka!  Scout’s performance was remarkable.  Scout transformed into a different animal.  Without changing the tuning settings from the previous propellers, Scout’s stability is as smooth as glass.  I surmised that the issue was not the 3-blade to 2-blade choice but the pitch of 6 inches was creating choppy turbulent air and the quadcopter could not stabilize.

I recommend using APC propellers.  They are both rugged and perfectly balanced from the factory.

Posted in Guide, Propellers by Russell

4 Responses to “Propellers”

  1. Paul Gilberti says:

    Totally confused. You state: “Propellers are specified by their diameter and pitch. The diameter is measured length of the propeller. The pitch is how far the propeller will advanced in one revolution. For example, a 10×4 propeller has 10 inch diameter and will travel 4 inches in one revolution.”

    Question#1) Is it Diameter/Pitch or Pitch/Diameter? As you state in one section -“I discovered that my initial propeller choice of a 3-blade 8×6 propeller”

    “but the pitch of 6 inches was creating choppy ”

    Question#2: What do you mean by “will travel 4 inches in one revolution.” ?
    A prop just spins. A 6″ prop tip travels 6″*3.14 per revolution.

    • Russell says:

      #1: It is Diameter/Pitch. The 3-blade propeller had a Diameter of 8 inches and a Pitch of 6 inches. I then changed to a 2-blade propeller that had a Diameter of 8 inches and a Pitch of 4 inches.

      #2: The 6″ of travel does not refer to Pi. Think of a propeller as a screw, If the pitch of a propeller is 6″ then in one revolution it will travel in the air a distance of 6″ inches. The greater the pitch the more air the propeller is moving through and therefore the more turbulence it causes.

  2. Myron says:

    So I noticed that on Scout 1.0 you used ducted fans for propulsion, but went with propellers for propulsion for your 2.0 and 3.0 versions. Would it be possible to use ducted fans for your flying versions of Scout?

  3. Vivek says:

    Is there any way that i can calculate the required thrust with some motor+propeller pair?

Leave a Reply