Propellers for multirotors

Multirotors need propellers to convert rotary energy from the motor into lineal thrust. This article covers the most basic aspects and tries to give some guidelines to choose an appropriate propeller for a multirotor.

Choosing a propeller usually comes paired with choosing a motor. Its is a reiterative process where one has to check if the combination works considering mainly the weight and intended application of the multirotor.

Lithium Polymer (LiPo) Batteries

LiPos, also known as LiPoly, are light weight and have a high capacity, this makes them perfect for multicopter applications.

To select the most suitable LiPo, the most important characteristics have to be considered.

• Pack voltage
• Capacity
• C rating
• Weight

This article also cover some aspects related to battery charging, as well as dangers and safety instructions when handling LiPo bateries.

Electric RC motor characteristics

This articles intends to give a simplified view of and electric brushless motor. Because not all possible parameters are considered, the presented model will not be very accurate, but will suffice to compare motors with different characteristics.

The main application focus will be on quadcopters, or any other type of multicopter. The mechanical lift power that keeps a multicopter hovering heavily depends on the motor and on the propellers, which are covered in an different article. Depending on the motor-propellers combination the flying behavior of a multicopter drastically changes. Using a fast motor with little propellers allow for a fast and acrobatic flight, while a strong motor and big propellers change result in a stable flight with strong lift for extra payload.

Also, the input current of a motor depends on the propeller, which translates into mechanical load that needs to be driven. It is to be noted that more current at the same voltage corresponds to a bigger propeller.