# Drone Motors

In fact, the drone motor is not much different from other aircraft motors such as Brushless DC Motor (It is necessary to read this lesson) But it differs slightly in some manufacturing specifications. Companies produce special motors for each RC aircraft To suit the motors with all aircraft types. We studied aerodynamics that drones have different dynamic properties because the drag and weight forces down so there are some additions that we will consider in choosing a drone motor so you can build fast drones and put your Special equipment to high flying. There are two important considerations in choosing a drone motor:

- Total weight of the drone.
- Dimensions of the drone to match the Propeller to avoid noise.

If you are building a Drone, you may not know the total weight. However, you can determine the total weight by looking at the weight of all the individual components, the frame size will let you determine the size of the propeller appropriate to use, and once you know the size of the propeller and the total weight of the Drone, you can determine how much thrust the drone motor needs to be in the air. Let’s start choosing Drone Motors.

### Thrust to Weight Ratio

Thrust to Weight Ratio is the main dynamic rule that will determine whether the quad or drone can fly in the air or not to maintain a steady flight the higher the ratio, the more load weights and faster calculated from Thrust to Weight Ratio = Thrust force/Weight force.

The ratio must be equal to or greater than one higher the mean higher acceleration of the drone We always recommend that the Ratio between (1.5-2) In order to increase the ratio we need a higher RPM motor so if you want to keep your money use 1.5 if you want high-performance use 2. But don’t worry you can choose any ratio higher than 1.

### Motor & Prop Size

The shaft diameter for the motor determines the size of the Propeller that can be used. 5 mm shaft motors are designed to be used with 3 “, 4” and 5 “fans 6 “blades. From the following table we will explain some additional criteria and how to select the motor and prop:

Recommended ESC | Motor KV | Prop dimensions | Frame dimensions |

12-20 Amp | more 3000 | 3 or less | 150 mm and less |

20 Amp | 2600-3000 | 4″ | 180 mm |

20-35 Amp | 2600-3000 | 5″ | 210 mm |

30-40 Amp | 2000-2300 | 6″ | 250 mm |

check with company | 1600 | 7″ | 300 mm |

check with company | 1000 or less | 8 ″ – 9 ″ or 10 ″ | 450 mm |

### Calculate thrust force

Calculating the thrust of drones is very important to know how much weight a drone can lift. The method of calculating the thrust of motors is simple. These motors are characterized by high rotational speed (RPM). For example, if our propulsion motors are 1500 grams and we want to build a four-wheeled drone first to calculate the total weight that can be raised by the four motors:

Lifting force = number of motors * thrust force (grams)

In our case, the total lifting force = 1500g * 4 = 6000g which represents the maximum load that can be lifted which includes the total weight (frame, motor, lipo battery and electronic equipment). But to make the drone fast enough and keep the flight time longer, we take the safety factor by dividing the overall direction by 1.5 or 2 to be 6000/2 = 3000 grams the best choice for design. So simply fly a drone and we use ESC to control the motors to take the desired direction.