Brushed Electric Motors for RC Vehicles Explained
Armature: The armature (or arm) is what spins in the motor and makes your car or truck move. It is made up of the commutator, laminations, shaft and winds. Electricity flows through the wires from the ESC to the end bell. It then travels through the brushes to the commutator, and into the windings on the arm. Since the windings are wrapped into a coil, they create a magnetic field when current is passed through them. This magnetic field is repelled and attracted to the magnets in the can causing the arm to turn.
Armature Stack: The stack is constructed of laminated steel. It holds the windings of the motor and helps increase the magnetic force created when current is passed through them. Most modified motors have a solid stack; most stock motors have a slotted stack. The slotted stack allows for higher rpm, the full stack allows for more torque.
Armature Label: Rebuildable Stock motors are labeled so it is easy to tell if this arm was made for this motor. This is for racing purposes to make it easy to examine the motor to make sure it is legal for stock racing. Modified motors do not require a label.
Brush: Made of a silver, copper, or graphite compound and at the end of the shunt wire. They are what makes contact with the commutator and transfer the electric current to the comm.
Brush Hood: These hold the brushes in place and keep them at a perpendicular angle with the commutator. The hood holds will sometimes contain hood springs that keep the brush from vibrating inside the brush hood.
Bushings or Bearings: These are in the can and the hood of the motor. The shaft rests on these. Their sole purpose is to reduce friction. Bushings are made of copper and are found in ROAR legal stock motors and some budget modified motors. Bearings are always found in quality modified motors.
Can: The outer part of the motor. It is usually made of steel or some other metal that can contribute to enhancing the magnetic field. The can contains the magnets.
Commutator: Typically referred to as the Comm. The comm takes current from your brushes, which ride on this part of the arm, and sends it to the windings. The comm is not one solid piece, but is actually made up of 3 separate pieces. This allows the current to be switched to the different windings of the arm as it spins. Because it rubs against the brushes as the arm spins, the comm needs to be cleaned and shaped every few runs. This requires items such as a comm stick (for cleaning off all the carbon deposits on the comm and brushes), a lathe (for ‘truing’ the comm back to it’s original shape), and motor spray (for spraying out all the excess dirt and debris).
Endbell: The part of the motor that consists of the brush hoods and the tabs. The endbell holds the bearing that supports the short end of the shaft.
Laminations: The part of the armature the winds are wrapped around. These are usually about half a millimeter thick, and are stacked on top of each other. The laminations are sometimes shaped to provide a stronger field. They are usually made of iron ferrite.
Magnets: They are found inside the motor can. They provide the opposing force that the armature’s magnetic force pushes against. If you don’t have magnets (or more specifically, an opposing magnetic field) then you don’t have an electric motor.
Shaft: The part of the armature that rests on the bushings or bearings. I will refer to the shaft in two parts. The long end is the part of the shaft where the pinion gear is bolted on. The short end is the part of the shaft which the commutator is attached to.
Shims: These are placed on both ends of the shaft. They reduce any unwanted space between the can/endbell and the ends of the armature. They are usually made of steel or Teflon.
Shunt: This is the braided wire that comes out the end of the brush. Some shunts have eyelets on them so you can screw them onto the brush hoods. Soldering them gives maximum electron flow, and better efficiency.
Springs: These keep the brush in constant contact with the commutator. They are sold in different weights. You can change the motor’s performance by adjusting spring tension.
Spring Posts: These are what the springs are wrapped around.
Tabs: There are 2 tabs per side (positive and negative) on the motor. You can use both sets for soldering leads, diodes, capacitors, etc…
Timing Ring: This is used to advance the timing of the motor. In a stock motor, the timing ring is fixed, and cannot be moved. It is also what the endbell screws into to keep it attached to the can.
Windings: Each pole of the arm has copper wire wrapped around it. This lacquer coated wire (the lacquer is for insulation) is what the battery current passes through and creates a magnetic field so the motor will run.