Problems with Brushed Motors
Electro-Fusion
motors are modified versions of standard 540-size brushed motors.
The original 540-size motors made in the 1980’s produced about 50 watts of power,
but
Electro-Fusion
motors can produce as much as 150 watts with the same size
brushes. Since the brushes and commutator on modern motors handle more power,
they wear down more quickly. Brush and commutator wear is the primary source of
power loss in brushed motors.
Motor brushes are typically made of carbon, copper and silver, and vary in hardness.
When a brushed motor turns at high speed, the ends of the brushes and commutator
slide against each other and wear down. If the brushes have hard spots, or wear
unevenly, the commutator can also wear unevenly. As the gap between the
commutator and brushes becomes more uneven, small sparks jump between the
brushes and commutator and accelerate the wear of both. This uneven gap also
increases electric resistance.
As resistance goes up, so does the heat generated by the current flowing through the
brushes and commutator. This heat eventually burns the brushes and turns them a
deep blue color. When this happens, brush manufacturers say, certain lubricating
components are burned out further accelerating brush wear.
Once a brush has worn down to the point where it no longer touches the commutator
it must be replaced. If the commutator wears unevenly, it must be resurfaced on a
commutator lathe or the entire armature must be replaced.
Commutator surface finish is possibly the most overlooked problem with brushed
motors because relatively few modelers take apart and inspect their motors. As high
electric currents pass between the motor brushes and commutator, the surface of the
commutator heats up and oxidizes turning a deep black color. This black finish
increases the electric resistance of the commutator/brush connection and consumes
battery power. Removing the black surface finish can restore electric conductivity
and proper commutator function.
Three-Minute Motor Overhaul
For the best long-term performance of your
Electro-Fusion
motor, service your motor
every six to ten flights using this simple three-minute procedure.
1.
Disconnect the flight battery from the speed controller, and the power cables
from the motor, but leave the motor in your
Corona
helicopter.
2.
Remove the motor pinion gear.
3.
Pull the brushes out past the end of the brush springs so the brushes do not catch
on the commutator washer.
Op er a tor's Guide
Electric Motors
3-6
LITE MA CHINES
