Airsoft Teching 101: The DC Moto

Posted | By:  
 3 Comments
  Email
  Print

Airsoft Teching 101: The DC Moto - Austin - as1-599.jpg

When opening up your airsoft replica, whether it is your first endeavor in teching or simply the last in a long line of upgrades, one of the first parts encountered (and often the first to be upgraded) when getting to your gearbox is the heart of your replica: the motor. Though the importance of the right motor is obvious, understanding what makes a good motor is altogether a different story. All too often, members resort to a simple list of "good" motors without ever actually understanding why that motor is used, or understanding the various ways in which it could be made better. This article seeks to remedy this. I present you, a rudimentary (crash course) guide to the DC motor with a focus in airsoft applications. This is going to be a little dirty.How does an electric motor work?First of all, it is important to understand how your motor works as a general concept. The motor in your replica is a DC motor. This means the motor relies on DC current to operate. This just means that if you were to plug one of these motors into, say, a common wall outlet, you would be disappointed to find that your motor does not work! This is because this is AC current, or Alternating Current. In AC, the current "alternates" direction, whereas in DC the current follows a single direction no matter what. So why does this matter?This matters because most portable power sources, such as batteries, are DC power supplies. In example, batteries convert chemical energy into electrical energy and as such can only create a static potential difference. This static difference is what makes a DC circuit. Now I can hear you saying, "Well, Narrator, why don't we use AC motors in airsoft? Aren't there also portable AC power supplies?"Well, yes and no. There are man portable AC power supplies, but they come in the form of man portable generators that are powered by some sort of fuel such as diesel or gasoline. The issue is, that although these are man portable, they are still very large to be used in airsoft. Can you imagine running through the woods pulling a sixty-pound roaring generator behind you? It would take away from the immersion at the very least, let alone leave you entirely too tired to stay in the fight.This is why AC is out, and why the battery takes the cake. "But, Narrator, get to the point! How do they work?"Alright! So, now that you know that your motor is a DC motor that runs off of a battery, we can now begin to understand how the motor works. First of all, current flows from your battery, through your wires, and to your motor. Once it reaches the motor, it goes into the commutator, out into the rotor (because it rotates), around it, back into the other side of the commutator, and back into your battery. So why does the motor spin? When current is run through a wire, an electric field is produced. When paired with external magnets built into your motor (called the stator since they are stationary) and their own magnetic field, you now have a torque acting on your rotor. So what happens? It spins! That's what happens. The diagram below may help.So here, we see current enter the loop:


Airsoft Teching 101: The DC Moto - Austin - as2-600.png

Notice the direction of the current arrows and the magnetic field arrows. The force applied to the loop is the cross product of these two, which gives us:
Airsoft Teching 101: The DC Moto - Austin - as3-601.png

Notice the direction of the current arrows and the magnetic field arrows. The force applied to the loop is the cross product of these two, which gives us:
Airsoft Teching 101: The DC Moto - Austin - as4-602.png

Now, we are halfway through one rotation, noting that the orange and yellow bits have shifted 180* since the initial position. The process continues until..
Airsoft Teching 101: The DC Moto - Austin - as5-603.png

Almost!


Airsoft Teching 101: The DC Moto - Austin - as6-604.png

Boom! We're back at the beginning. Ok, now that the first crash in understanding rudimentary motors is more or less understood, let's move on to how this affects your airsoft experience.The Airsoft Application
Airsoft Teching 101: The DC Moto - Austin - as7-605.jpg
Above, we see a cross section of a typical airsoft DC motor. Note that there are three armatures, each with wire wrapped around it. These wires make up the loops depicted in the previous section. Also notice that the rotor side of the commutator is three part to coincide with this. As the motor rotates, the armature that is next to rotate past one of the stator magnets is electrified, pulling it towards the magnet. As it gets closer, the commutator disengages, it coasts on momentum, and the cycle repeats. Though it is a little more complicated than the two phase motor, hopefully you have a basic grasp of the idea. The graphic below may help.
Airsoft Teching 101: The DC Moto - Austin - as8-606.jpg
So do you understand how it works? Good! Even if you answered no..We press onward.So we need our motor to run our replica, right? Or we're going to have a pretty bum time trying to use it. In our replicas, as many of you may or may not know (and we may go over in another article!), there is a gear train that drives a piston, which oscillates with help from our main spring. In order to do so, we need enough torque to pull the spring back, with enough speed so that each round doesn't take 15 minutes to spool up, right? So we need a motor that balances these two features for our given application, and fortunately, the relation between the two is more or less linear, as the graph below illustrates.


Airsoft Teching 101: The DC Moto - Austin - as9-607.jpg

So do you understand how it works? Good! Even if you answered no..We press onward.So we need our motor to run our replica, right? Or we're going to have a pretty bum time trying to use it. In our replicas, as many of you may or may not know (and we may go over in another article!), there is a gear train that drives a piston, which oscillates with help from our main spring. In order to do so, we need enough torque to pull the spring back, with enough speed so that each round doesn't take 15 minutes to spool up, right? So we need a motor that balances these two features for our given application, and fortunately, the relation between the two is more or less linear, as the graph below illustrates.


Airsoft Teching 101: The DC Moto - Austin - as-enter-610.jpg

Well, for higher strength, stronger stator magnets are a must. This increased the magnetic field, and thus the torque exerted by the arm. Neodymium is a common choice for stronger motors because neodymium provides a stronger magnetic field than ferrous magnets. This is because the metal is more "lined up" than that found in ferrous magnets. This is simply because of the way the two are formed. Well, that was easy.Next, your windings on your armature.


Airsoft Teching 101: The DC Moto - Austin - as11-609.jpg

These windings make up the loops we discussed earlier. As you can probably guess, more windings equals more electric field, which equals higher torque, and you would be correct! Not only this, but lower gauge (thicker) wire also creates a larger electric field. So why not use a million windings of 0 gauge wire? Well, we do have to fit this all in a canister about the size of a pill bottle, so choose wisely! Finding the sweet spot between winding count and winding gauge is tough, but with enough trial and error (or some quick math if you want me to walk you through it) will yield you the highest optimization a motor can achieve, netting you the most bang for your buck!But what about the armature itself?Modifying the armature itself is a double edged sword. While lightening it can increase operational speed, one factor that actually increases power is armature mass. This means that lightening it may result in lower power, if not more speed. The other issue lightening your armature can cause is disrupting the balance of the motor, which causes the armature to wobble causing undue friction in the motor, seeping power and reducing the lifespan of your motor. Modify at your own risk!Lastly, we can talk about the commutator. The easiest way to get more power out of your motor is to put more in! Cranking up the current will get your motor spinning faster and more powerfully. Why? Well, remember that electric field we keep mentioning? That's why. It boosts that field and causes more torque! Upgrading your commutators to survive more current or apply more area to the commutator shaft is an easy way to squeeze a little extra power out, though using a higher rated battery is another way to do this! Be careful, though, as forcing too much current through could burn up your motor!Hopefully, you have learned something on this crash course on DC motors in the airsoft application. A lot was simply glossed over here for sake of basic understanding so if you have further questions, feel free to contact me here on the forums (TheLost)! *I claim no ownership to the photos used. All were stock photos pulled from various search engines or made/taken myself.Triston Anders is an Engineer from Columbus, Ohio, an avid car enthusiast, and a proprietor of all things airsoft! For more, check him out @TheLost here on the forums, or find him on social media!

Airsoft Teching 101: The DC Moto - Austin - as10-608.jpg
Posted in
  Email   Print
3 COMMENTS
Posted: 
June 4, 2017  •  07:26 PM
much informative, very learning, such tutelage
 
Posted: 
June 4, 2017  •  11:14 PM
I needed a lovely compilation like this regarding motors, very timely! :) Thank you.
 
Posted: 
June 25, 2017  •  11:42 PM
Awesome article, thank you! Always good to learn more :)
 
POST A COMMENT