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Remote control (RC) vehicles are loads of fun, and getting one often means you want to get even more. When you start shopping for a new RC vehicle, you will see some with brushless motors and others with brushed motors. What is the difference between brushless and brushed motors? Does it matter which you choose? If it matters, which is better?
What is the difference between brushless and brushed motors? Brushless motors are lighter, more powerful, and longer-lasting. Brushed motors are less expensive, handle harsh conditions better, and may be easier to control. If you are after absolute performance, brushless motors are the way to go. If cost, control, or torque are important, brushed motors are worth a look.
To understand the differences in the two types of motor, we’ll have to look at what makes electric motors tick.
How Electric Motors Work
We’ll have to go back to elementary school science class to understand how electric motors work. Think back to playing with bar magnets. Each magnet has a positive end and a negative end. The positive end of one magnet is attracted to the negative end of another, while two positive ends (or two negatives) will push each other apart – strongly.
This is such a strong reaction that you can move one magnet without touching it. You can push it around using the same-polarity ends, or pull it with the different ends. If you line up the angles right, you can make a magnet spin around. That’s the basic action inside an electric motor.
Also, remember that if you wrap lots of coils of wire around a metal bar and introduce an electric current, you will get an electromagnet. This electromagnet also has a positive and a negative end. If you reverse the polarity of the wires (like changing which wire is on each end of the battery), you reverse the positive and negative ends of the magnet.
Why is this science important? It’s because electric motors use permanent magnets, electromagnets, and reversing polarity to spin a shaft. The fixed magnets always have the same polarity, while the electromagnets change polarity to keep the motor spinning.
By changing the polarity of electromagnets as the motor spins, the spinning rotor is always pushed away from where it is and pushed toward where it should be. If the polarity didn’t change, the rotor would align itself to the polarity of the magnets and sit there. It’s like dangling a carrot on a pole in front of a donkey. Just as the donkey always steps forward after the carrot, the rotor keeps spinning to chase the right polarity.
The technology used to change polarity in brushed and brushless motors is the key difference in design and performance of different motor types. Both kinds of motor keep flipping the polarity to keep the rotor chasing the right polarity, but the tech used to do it makes a big difference.
Brushed Motors
Brushed electric motors are a very old technology – the first DC electric motor dates back to 1837! These motors have fixed magnets and a rotating electromagnet. The electromagnets, called armatures, change polarity as the shaft rotates. When they change polarity, the rotor is pulled around half a turn. When the half-turn completes, the polarity is switched again, and the rotor keeps spinning.
The key piece that switches the polarity is the brush (hence the name of the motor). There are a pair of carbon brushes that contact the wire wrapped around the armature. The brushes carry power from the battery to the electromagnets. One brush carries positive polarity, the other negative. When the armature completes half a turn, the contact with positive and negative brushes is switched.
Switching the polarity means that the end of the armature that was negative is now positive, and the positive end has become negative. Just as the two arms get into an alignment with the magnet that they like, the polarity switches. The switched polarity makes the motor spin.
Drawbacks of Brushed Motors
Brushed motors have two major disadvantages compared to brushless motors: brush friction and armature weight. These two factors combine to make brushed motors heavier and less efficient than brushless motors. Let’s look at why.
The contact of the two brushes to the spinning armature creates friction. A brushed motor is kind of like a bicycle with the brakes out of adjustment – there is always a little friction on the wheel. If you are riding a bike with the brake rubbing, you’ll have to work harder to get the same speed. The wheel rim will also heat up as the brake rubs.
Brushed motors always struggle with this friction. They run hotter than brushless motors, and brushed motors peak at about 75% efficiency. On the other hand, brushless motors peak at 90% efficiency. The extra 15% efficiency in brushless motors is waste heat in brushed motors. Incidentally, this is also why brushed motors don’t last as long – the brushes eventually wear out from rubbing.
The need to spin big wire armatures instead of small magnets makes brushed motors heavier than brushless motors. At a given power level, a brushless motor will always be lighter than a brushed motor. Conversely, at the same weight, a brushless motor will be more powerful.
Brushed motors also have a shorter service life than brushless motors. Eventually, the brushes wear out, and contact with the armature is broken. When that happens, you either have to replace the brushes or get a new motor. One sign that a brushed motor is wearing out is seeing sparks inside the motor. This is an indicator that the brushes aren’t making good contact and electricity is arcing instead of just passing through the metal.
Brushless Motors
Brushless motors are a much newer technology, with the earliest designs dating back to the 1970s. In these motors, the magnets rotate, and the coils are fixed. Instead of using a brush to reverse the polarity of the electromagnetic coils, brushless motors use an electronic controller – a small computer chip. The controller changes the polarity of the coils rapidly as the motor spins.
Because the wiring to the coils doesn’t have to touch a moving part, there is much less friction in a brushless motor. The spinning armature is also much smaller, so the motor doesn’t have to work as hard to keep itself spinning. The motors also last longer because there is no rubbing brush to wear out.
This combination of advantages is why brushless motors are so much better. At a given voltage, a brushless motor will always be lighter and more powerful than a brushed motor. RC cars are no different than any other vehicle in this respect – a car with an engine that is both lighter and more powerful will always be faster.
Brushless motors are quieter, as well. Since there is less contact with internal parts, there is less rubbing and so less noise. Sound usually isn’t a big concern with RC vehicles, but applications that require a quiet motor work best with brushless motors.
Drawbacks of Brushed Motors
Are there any disadvantages to brushed motors? Not in terms of performance, but there are disadvantages in design and construction. The electronic controller in a brushless motor requires more design work upfront and is much harder to manufacture. This increases the cost of brushless motors compared to the older brushed design.
Advantages of Brushed Motors
Less powerful, shorter life, and heavier – why would anyone ever opt for a brushed motor over a brushless one? There are a few reasons: cost, torque, water resistance, and limited power. Let’s look at these factors to see when a brushed motor makes sense.
Cost
It’s easy to see why brushed motors cost less than brushless motors. It’s 1830s tech vs. 1970s tech. Brushed motors don’t require any programming or fancy tech; it’s just magnets and wire. Brushless motors take more design and programming work to make them function.
The simplicity and low cost of brushed motors make them great for entry-level RC vehicles. If you are just starting out in the hobby and don’t want to spend a lot of money, brushed motors make a lot of sense. You can get a vehicle, have some fun, and start to figure out whether you’d like to spend more money.
Torque
If you want all-out speed, brushless motors are the way to go. If you need low-range power to move an RC vehicle from a dead stop, brushed motors are fine. Brushed motors are great in rock crawlers that have very low gearing. These little brutes have big tires to crawl up rocks and other obstacles. They are designed to move slowly through obstacles. Since the top-end speed is so low, using a brushless motor isn’t an advantage here.
Water Resistance
No electric motor works well when it’s in water, but water is less damaging to brushless motors. If a brushed motor gets wet, you can open it up and let it dry out. All the parts are sturdy metal or carbon; once the brushed motor has dried out, it will run just fine. That’s not the case with brushless motors.
Brushless motors include a circuit board. Circuit boards and water don’t mix at all. Get it wet, and you’re looking for a new motor. You can waterproof the case around the motor, but if anything goes wrong, the motor is fried. Stick with brushed motors for wet, muddy RC fun.
You may want to stick with brushed motors for RC boats, as well. Brushless motors are available for boats, but why take chances? Even the best seals on water-proof engine compartments can fail sometimes. Leaks won’t ruin a brushed motor, but they will ruin a brushless RC boat motor.
Limited Power?
It seems odd to think that limited power could be an advantage of brushed motors, but that is sometimes the case. Imagine giving a 700+ horsepower Challenger Hellcat to a sixteen-year-old with no time behind the wheel. That is…not a recipe for success.
RC vehicles can be the same way. If you are just starting out, a vehicle with the most powerful brushless motor can be hard to control. Losing control and crashing isn’t a recipe for fun. If you are still learning to control the car, a brushless engine just means you crash that much harder when you lose control of the car.
Likewise, if you are striving for maneuverability and control over speed, a brushed motor can be fine. When you never hit the top-end speed, it doesn’t matter how fast it is. It’s like a Lamborghini in a school zone – when you only run the car at low speeds, the extra horsepower really makes no difference.
When to Go Brushless
The top-end RC motors are brushless. They are the best motors for serious RC hobbyists. If you want lighter weight, more power, and speed, or longer life in your vehicle, brushless motors are the way to go. Brushless motors shine for racing, especially on paved surfaces. Racing is a kind of driving where every last little bit of speed matters.
Motors for Beginners
When you are just starting out with RC vehicles, brushed motors are fine. They brushed motor will cost less and let you get started learning how to operate the vehicle. If you are running a car on a paved surface – especially if you are racing – you will probably want to upgrade to a brushless motor fairly soon. Brushless motors just give you more speed; that’s what it takes to win races.
On the other hand, if you are running the vehicle off road, motor type doesn’t matter as much. You still won’t have the top-end speed with a brushed motor, but that’s less important. You can work on technique and control for a while. Once you are really good at driving, that is the time to switch to a brushless motor.
Switching Out
Many RC vehicles have removable motors. That means that, when you are ready, you can make the jump from a brushed to a brushless motor easily. There is a little more work than just swapping motors, but this lets you keep your initial investment in the car itself, and just spend the cash for an upgraded motor. This is a terrific option to use as your skills grow.
Be aware that you will have to do some soldering to make the changeover. You also have to replace the electronic speed controller when you switch motors. If you have never done this, it can seem a little intimidating. Don’t worry about that, though. Learning how to upgrade your vehicle is half the fun of the RC hobby.
RC Motor Maintenance
Both types of motor will last longer if you maintain them properly, although the benefits are more noticeable for brushed motors. Both types of motor need to be removed to maintain them. Make careful note of the wire hookups when you remove the motor so that you can re-install it the same way.
Brushed Motor Maintenance
It is particularly important to take care of your brushed motor so that you can get the most life from the brushes. Here are some tips to get the most life from your brushed motor. You will need a soft cloth, an old toothbrush, a can of compressed air, and some silicone motor lubricant:
· Use a damp cloth to clean dirt and grime off the outside of the motor
· Gently scrub the bushings to clean the bushings at either end of the shaft
· Blow out the inside of the motor with the compressed air
· Lubricate the bushings with a drop of oil
· Blow out the transmission case with the air
· Re-install the motor
Getting grime and dust off the brushes and bushings will make the motor last a lot longer. The brushes are the first thing that will wear out; keep them clean to keep your motor running strong.
Brushless Motor Maintenance
The lack of brushes to rub and wear out makes brushless motors much longer-lived than brushed motors. Even so, these motors also benefit from occasional cleaning. You need the same supplies to clean a brushless motor as for a brushed one.
· Wipe down the outside of the motor with the cloth
· Remove any screws and washers that hold the cover on the motor. Be careful not to lose them!
· Disassemble the motor and blow dust and grit out of the parts
· Lubricate bearings and other wear points
· Reassemble the motor and re-install it
If you like the brushless motors over the brushed ones, you can always swap it out. This video will show you the best way to convert your brushed motor on your RC car to a brushless one.
Which is Better?
When it comes to absolute performance, there is no doubt that brushless motors are better. They have more power with less weight. That translates into more speed.
However, top-end speed isn’t the only important thing. Brushed motors are a good choice if you are on a budget, are just starting out, or if your RC driving doesn’t need great speed as much as good control.
Which motor is best for you comes down to your goals and the kind of RC driving you do. As long as you are having fun, either motor is a good choice.