Selecting the Right
Motor for Your Drone (Part 2)

Author - Chaitanya Khanna


In Part 1 of our blog, we embarked on a journey to understand the landscape of motors used in drone applications, focusing on the transition from Direct Current (DC) Motors to Brushless DC (BLDC) motors. We explored the reasons behind this shift and delved into the intricacies of the two primary BLDC motor configurations: Outrunner and Inrunner motors.
Now, in Part 2, we take our exploration a step further. We'll provide you with an in-depth guide on how to select the best BLDC motor for your drone project. This section will equip you with the knowledge & tools and we'll explore not only key features for selection but also we will discuss this technically with the help of an analysis table needed to make an informed choice among similar types of BLDC motors with different specifications, ensuring that your drone is optimised for performance and efficiency. So, if you're ready to explore the world of BLDC motor selection for drones, let's dive in!

Demands and Requirements Table

Before we delve into motor selection, it's essential to identify the specific demands and requirements of your drone project. These requirements can vary depending on the drone's purpose, size, and payload capacity. Here's a table to help you jot down these essential parameters:

Drone Purpose(e.g., aerial photography, cargo delivery, surveillance)
Maximum Takeoff Weight(including payload)
Flight Time(desired duration per flight)
Power Source(battery, hybrid, or gasoline engine)
Payload Capacity(weight and dimensions of the payload)
VTOL Configuration(e.g., quadcopter, tilt-rotor, fixed-wing transition)
Altitude and Speed Range(maximum operational altitude and desired speed range)
Budget Constraints(maximum budget for motor purchase)
Table 1 : Motor Selection Factors

Now that we've outlined our demands and requirements, let's create decision tables to help us compare and contrast motors based on various factors. These use cases will help us in the field of manoeuvrability and unexpected demand of thrust.

Decision Table: Brushless DC Motor Comparison and Analysis

In this decision table, we will compare and analyse key parameters of different BLDC motors, focusing on thrust, power, voltage, and efficiency. These parameters are critical in determining the motor's suitability for a VTOL drone project.

Motor ModelThrust (kg)Power Output (Watts)Voltage Range (Volts)Efficiency (%)
Motor AT1P1V1-V2E1
Motor BT2P2V3-V4E2
Motor CT3P3V5-V6E3
Motor DT4P4V7-V8E4

Thrust: Thrust is a crucial factor in VTOL applications. Depending on your project's requirements, you may have a minimum thrust requirement that the motor must meet. For example, T1 represents the thrust provided by Motor A. Now according to your configuration of the Project multirotor or not and then Quadcopter (4 motors) , Hexacopter (6 motors) , Octacopter(8 motors) etc. You need to add up the Thrust of all the motors and then see whether the all up thrust is greater than MTOW with a specified percentage of desired Factor Of Safety(FOS) at 100% throttle(generally we use FOS of 2 or any other parameter with general data and historical trendline).

Power Output: Right after you have the desired thrust now we'll jump onto the consumption costs in terms of endurance and range and efficiency which is directly correlated to it's motor energy consumption. The power output of the motor determines its ability to lift the drone and carry the payload. It is essential to consider the power requirements of your VTOL drone, and P1 represents the power output of Motor A. With that we can consider the efficiency by dividing the thrust produced at a specific throttle and power consumption at that we get the efficiency of the motor at that much throttle. Now the more power consumption you save the more battery life you gain that is why you get longer endurance which in turn increases your range.

Voltage Range: BLDC motors operate within specific voltage ranges. Ensure that the chosen motor's voltage range is compatible with your power source or battery setup. V1 - V2 represents the voltage range of Motor A.

Efficiency: Efficiency is a key factor in maximising flight time and battery life. Higher efficiency means more power is converted into thrust, reducing energy waste. E1 represents the efficiency of Motor A.

Example Datasheet
agricultural drone by TSAW

Weightage Table

Once we've identified motors that meet our minimum thrust requirements, we can create a weightage table to compare and evaluate these motors based on additional factors such as weight, efficiency, and power consumption. Assign weightage percentages to each parameter based on their relative importance to your project, and calculate a weighted score for each motor. An exemplary table is made below for you to understand how do you distribute the weightage and choose the motor that is best suited for your specific project :

MotorThrustPower OutputVoltageEfficiencyWeightCostTotal(%)


Selecting the right motors for your drone (capable of VTOL as well) involves carefully evaluating your project's demands and requirements, and then comparing and contrasting motor options based on various factors such as type, power requirements, weight, thrust, efficiency, price, and availability. These decision tables provide a structured approach to motor selection, helping you make an informed decision that aligns with your project's goals and constraints. Remember that the choice of motors is a critical step in ensuring the success and performance of your drone.