Friday, October 20, 2017
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The guide to choose motors for your quadcopter and multirotor

motopr

I think most drone lovers have meet the same problem: how to choose right motors for your quadcopters or multirotors? As we know, the motors is the most important part of a drone, it is the drone’s heart. So choose the right motors is very important. But how to choose motors for your drone? If you are a newbie or unfamiliar with motors, this guide will help you know more about motors.

There is a data table for a MT1806 :

how-to-choose-motors

Weight of your drone

Knowing the weight of your drone is the first thing we need to know. When you are building, or planning your next drone build knowing the exact weight can be difficult. However you will need to start somewhere and as choose and change components you can slowly refine the weight estimation.

Thrust to weight ratio

With multi rotors its important to make sure that your motors can produce around 50% more thrust than the total weight of your drone. Or in other words your drone should be able to hover at just over half throttle. This is an important rule to follow is it means that you motors will have enough extra thrust to control your multi-rotor in wind and during aggressive flight maneuvers. If you are always going to by flying gently and smoothly increase the weight so that you hover at around 70% throttle for a less responsive drone. So if your total weight of your quadcopter is 800g, your motors on a quadcopter will need to produce 1.6Kg of thrust in total, or 400g max thrust per motor.

Knowing this data

Based on our weight estimation we know we need to find a motor capable of producing a maximum thrust of 300g each, By inspecting the thrust tables of each motor you will gradual find a few motors that have the required thrust performance. In this case we have come across the data for the MT2204 motor which looks promising.

If you find it hard to know where to start, the best thing is to find a build guide, or quadcopter similar to the one you are building so see what motors and other equipment was used that you can use as a starting point.

motors-data

Checking the thrust

Now we can get on with investigating and extracting useful information from a table such as the one above to find our quadcopter motor. We can see that this manufacturer has tested this motor with two different voltages (2S (approx 8V) and 3S (approx 12V) battery), and a number of different propellers (called paddles in the above table  ). We are then given the amperage that the motor pulls, the thrust that it produces and the efficiency (thrust in grams/power in watts), as well as some other information. We can see from the table that with a 3S battery, these motors will produce enough thrust with 5×3, or 6×3 propellers which produce more than the required 300g each.Comparing the efficiency.You can read this guide:“How to check the motors thrust ?” to know more.

Matching an ESC to your motor

Now that we have confirmed that this motor is suitable for our application, we look at the Amp draw for our chosen motor/battery/propeller. In our case, this is maximum of 7.5A for a 5×3 prop, and 11.5A for a 6×3 prop. Since in our build we chose the 5×3 propellers, so we will need to use an ESC that is rated over 7.5A, so an 12A ESC would be a good choice for this motor/propeller running on a 3S battery.

Choosing a right battery for your drone

Now you should choose a right battery for your drone, according your motors, your battery should light weight, high capacity and high discharge. Based on these motors producing a max thrust of 310g with 5×3 props, our quadcopter should weigh less than 620g. The actual weight of all the electronics and the quadcopter frame come to 368g so that means we can get a battery up to 250g in weight. If you find that you dont have enough weight left over for a decent size battery you might want to go back and choose larger motors, or use larger propellers.

Instead of using all the remaining weight for a battery, a slightly lighter battery at 160g (tattu 3S 2200mah) was used so that our quadcopter will have more agility for racing. About choose the lipo battery, you can read “The analysis of lipo battery parameters and What is the best FPV lipo battery brand?these two articles.

Knowing motors is just a little of build a drone, you should know more quadcopter knowledge,every part is very important. I hope these guide can help you know motors and how to choose motors for your drone. If you have any other tips, I hope you can share for me.


Related articles:

  1. How To Choose A Motor
  2. Motor Basic Knowledge Introduction  
  3. Tattu 2305 2450KV Brushless Quadcopter Motors
  4. How to check the motors’ thrust ?

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