Ask DH – Brushed vs. Brushless Motors

Brushed Brushless Motor

Sometimes there are questions you have about RC you’ve always wondered, but for one reason or another, never asked.  Whether you’re a seasoned veteran or brand new, we’re going to bring you up to speed. Have a question you’ve been wanting to ask? Let us know in the comments!

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Often mentioned, but rarely easily explained, is the great Brushed vs. Brushless Motor question. In the hopes of keeping you from saying “forget this…just give me a bottle of nitro and an engine”, we want to shed some light on this topic. This can have a big impact on which truck you choose, and while conversion kits are able to take you from one to the other, it’s cheaper and easier to pick the one you want from the beginning.

So let’s start with the basics…

Brushed Brushless Update Motor RC

Brushed Motors

A brushed motor has been around for a few centuries and is one of the simplest types of motors. Performance is often expressed in ‘Turns’ (number of times the wire is wrapped around the armature core – e.g. “19T”) and ‘Winds’ (number of strands in the wire, typically 1-4). The number of turns you want depends on your needs: lower turns means higher top speed but less torque, while higher turns means lower top speed but increased torque.

Two permanent/stationary magnets sit inside the ‘Can’ (outer case) of the motor. The battery is connected to two ‘Brushes’ which make contact with the copper ‘Commutator’. The ‘Armature’ is connected to the commutator and consists of a core that is wrapped multiple times with wires.

Electricity is transferred from the battery, to the commutator, and then to the wrapped wires. As power flows through this electromagnet, the ends of the armature become ‘Poles’.  It is the attraction and repulsion between these poles and the permanent magnets on the edge of the can that turn the axle. This polarization of the wires flips as the armature turns and the two halves of the commutator make contact with either of the brushes, beginning the cycle all over again (and move your truck).

Limitations of Brushed Motors

While cheaper, there are drawbacks with brushed motors (and why many use conversion kits to take their trucks from brushed to brushless) mostly due to friction between the brushes and the commutator. Where you have friction, you have heat and degradation, which means frequent maintenance. As motor-wear increases, imperfections on the commutator develop and periodically break contact with the brushes, which means momentary loss of power. In a backyard bash, this may be unnoticeable, but in a race this can mean the difference between winning or losing. This can be solved by ripping open your motor and retooling/replacing components on a regular basis, but can get expensive and labor-intensive when you’re in between races.

Brushless Motors

Enter the solution: brushless motors. A brushless motor is the inverse of the brushed motor and performance is expressed in ‘Kv’, indicating how many volts are required for a certain RPM (2200Kv motor x 3V = 6600RPM). Instead of stationary magnets and spinning wires, you have stationary wires and a spinning magnet, with the key benefit of no friction. Electricity is fed from the battery and controlled by the Electronic Speed Control (ESC) to create the electromagnetic attraction/repulsion, the wires being polarized at different times (as determined by the ESC) to drive the field magnet and axle. Make sure you choose the right Motor / ESC combination if you’re putting in new brushless parts. Some motors have sensors to communicate the position of rotation for improved precision, though many companies like HPI have chosen to go sensorless in their Flux series since the small increase in performance often won’t be needed compared to the increased cost.

More Info

  • Want to know our favorite brushless truck? Check it out here.
  • More of a visual/video person? Check out this one from Learn Engineering on brushless motors.
  • Only have two minutes and want a quick run down of the pros/cons? Ba-Bam.
  • Tired of electromagnet nonsense and want to stick with engines? Put one of these in your truck and then send us a video. Please!