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.
An unbalanced propeller produces excessive vibration. This vibration travels through the entire airframe affecting the handling of the aircraft, produces inaccurate readings by the sensors, and creates premature failure of motor bearings and parts. A balanced propeller is paramount to a stable aircraft. A balanced propeller produces less vibration and draws less current, which results in greater stability and extended flight times. You should balance any propeller before installing it on your aircraft. Balancing a propeller requires the use of a special tool, you guessed it a propeller balancer. The propeller balancer that I use is the Top Flite Propeller balance. It is essentially a shaft held by two magnets. The magnets create a frictionless surface for the shaft to spin freely. Read More…
