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What
are the parts of a motor and what do they do?
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. A lot of the newer cans, like the Trinity
D4 will allow you to remove the magnets. The can
holds the bearing that supports the long end of
the shaft.
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.
What does the turns mean on a electric motor?
A Turn is number of times the wire inside the motor
is wrapped around the armature poles. Stock motors
have 27 wraps (or turns) of 22 gauge wire, that
is, 22 gauge wire wrapped around the armature poles
27 times. Modified motors can have as low as 5 or
6 turns or as many as 20 to 25.o have more comm
wear.
What does single, double, triple, or quadruple
mean on a modified motor?
A Single has one thick wire, a Double is a two thinner
wires, a Triple has three thinner wires than the
Double, a Quad has four thinner wires, and so on.
So, an 8 Double will have TWO (Double) thin wires
wrapped around the pole 8 times. A 12 Triple will
have THREE (Triple) wires wrapped around the pole
12 times, and the 10 Single will have ONE (Single)
thick wire wrapped around the pole 10 times.
What are the advantages of a single, double,
triple, or quadruple modified motor?
A Single provides harder acceleration (torque),
while a Quad will provide a much smoother power
band. The 8, 12, 10, 14, or 16 turn motors will
provide a lot more rpm than a stock 27 turn (less
wire means less weight), but, obviously, the 8 will
have the best rpm (typically).
Are there any other differences between
a stock and modified motor?
A Stock motor has a set timing and has bushing in
the can and the end bell. A modified motor has adjustable
timing and has bearings in the can and the end bell.
What is a motor lathe?
A lathe is a machine that cuts away small amounts
of the comm to restore it to a trued state. Lathing
or cutting the comm can be done many times to return
it to an almost new state. Having a comm that is
smooth and no grooves from the brushes, helps the
brushes make better contact.
Are the different kinds of lathes?
Yes, there are lathes that are for non-rebuildable
(closed end bell) motors and lathes for rebuildable
stock and modified motors. There are also two different
kinds of bits for a lathe. A Carbide bit usually
comes stock with a lathe. A carbide bit doesn't
last as long a diamond bit. A Diamond bit is usually
a upgrade and with proper care they should last
for the duration of your racing career. Diamond
bits cut the comm more accurately than a carbide
bit.
What tools do I need to clean a motor?
A comm stick, motor spray, soldering iron, solder,
small point Philips screwdriver, cotton swabs, bushing
or bearing oil, comm drops, hobby knife, rag and
possibly new brushes. If you are really lucky a
motor lathe or a friend that can true the comm for
you.
What is the best way to clean you motor?
Cleaning your motor can be easy by following these
few simple steps.
Step #1 - Remove the motor from you vehicle.
Step #2 - Remove the springs. Note which color of
spring is located on the positive (+) side of the
motor. The positive side marked with a small + sign
on the top of the end bell.
Step #3 - Slide the brushes out of the brush hood.
If you are going to have your armature lathed then
skip to step #5
Step #4 - Insert the comm stick into the slot where
a brushes go in the brush hood. Give the motor a
few spins in one direction and then repeat going
the opposite. You can attach a pinion gear to the
end to help you.
Step #5 - Unscrew the end bell from the can. Note
is this is a modified motor make sure you mark the
timing and position of the end bell with the can.
Step #6 - Clean the inside of the end bell with
motor. Make sure there are no motor shims inside
before you clean the end bell. Note: If you are
planning on using the same brushes again do not
get motor spray on them. Motor spray robs brushes
of there lubrication.
Step #7 - Remove the armature from the can and place
it aside. Note the location of a shims and washers.
Step #8 - Clean the motor can. You can use motor
spray, but it is not recommended that it be sprayed
on the magnets. The motor spray can eat away at
the glue that holds the magnets in the can. Use
a mild soap with water to clean the inside.
Step #9 - Use a cotton swab to make sure no dirt
is in the bushing or bearing especially where the
arm goes through. A little motor spray applied to
the tip of the swab helps get rid of any debris.
Step #10 - Have someone lathe you armature. If you
don't have a lathe skip to step #11. Make sure the
gaps in the comm are free of any extra copper. You
can do this by running a hobby knife or razor blade
through the gaps. Be careful not to scratch or touch
the comm.
Step #11 - Spray the armature off with motor spray
and place it back in the can and screw the end bell
back in place. Remember to shim it the same as before
and stock rebuildable motors have a small tab on
the end bell that lines up with a notch on the motor
can. Screw in the two set screws.
Step #12 - Replace the brushes if they are short,
show discoloration, have chips or signs of excessive
wear. If not skip to step #12B. Brushes come with
two different kinds of shunts, eyelets or just straight.
If is recommend that you solder you brushes to top
of the end bell rather than using the eyelets for
better electrical contact. If you do decide to solder
the brush on, then lightly tin the end of it with
solder and attach it to the end bell. If the solder
doesn't stick to the end bell, then use light sandpaper
to rough up the surface. Make sure that you don't
get to much solder on the shunt, because this will
make the brush have difficultly moving in the brush
hood once the springs are reattached.
Step #12B - To reuse an existing brush clean the
brushes with the comm stick to get rid of any glaze
or deposits. I recommend protecting you fingers
with a rag so the small pieces of fiber glass from
the comm stick don't get in your fingers. Don't
ever touch the end of the comm stick. Fiberglass
hurts and stays in your fingers for along time.
Step #13 - If you have comm drops put a drop on
the end of each brush. This help lubricate the brushes
and will help the brushes properly seat against
the comm. Put the brushes back inside the brush
hood.
Step #14 - Reattach the springs. Remember which
one goes on the positive (+) side of the end bell.
Step #15 - Apply a few drop of oil to the bushing
or bearings.
You are now ready to break in your clean motor!
How do I break in a rebuilt motor?
You will need a 4 cell battery pack and a way to
attach it to your motor. Attach the 4 cell pack
to you motor. Make sure you note the polarity (+)
and (-) on the motor is the same as the battery.
The top part of the battery with the nipple is positive
(+). Let the motor run for almost a minute or so.
I don't recommend spraying motor spray on the comm
while it is running, because motor spray is flammable
and duh there are sparks being made between the
brushes and the comm. Oh and make sure you lubed
your bushing or bearing with oil. This will help
the arm spin freer in the can.
What are capacitors?
Capacitors? help stop radio noise caused by electric
motors that may interfere with your receiver and
cause radio glitches. For more information on soldering
capacitors see my soldering tips page.
How should I gear my motor?
This depends largely on the type of motor, track
layout, track conditions, and the type of driver
you are. First need to understand what a gear ratio
is. Check out my RC TUNING page for a gear ratio
explanation and starting point gearing chart. Before
you put down your car on the track. Study the design
of the track. To often people gear their cars to
the straightway and not the whole track. If the
track is full of turns, use a small pinion gear
that will give you more acceleration or bottom end
speed. The reason behind this is because before
your car reached top speed, the next turn would
come up and your car would have to slow down again.
If the track has many straight and long paths use
a larger pinion gear that will give you more top
speed acceleration. The reason behind this is because
a straight track will give you a longer period for
your car to travel at top speed. Just remember the
larger the pinion the less bottom end / take off
speed you have. Always make sure you are checking
to see if the motor is running hot when you take
it off the track after three or four minutes. If
the motor is hot go to a smaller size pinion. Every
motor is different so experiment.
What do the numbers mean on a stock pro motor.
How do I know which motor is the best?
The labels on many stock pro or dyno'ed motors have
the following abbreviations: RPM or revolutions
per minute, Power or Wattage, Eff or Efficiency
and Torq or Torque. The main number to look at would
be the Power or Wattage of the motor. This represents
the overall power of the motor. A motor that has
a better power rating than other motors is most
likely to produce faster top speeds and better acceleration.
For a Trinity motor a power rating of 130.0W is
really good. The Eff on the label is the motors
overall efficiency. The higher this number is will
result in better run times and cooler, more consistent
performance. Torq and RPM are interrelated because
usually the lower the RPM the more Torq a motor
will have. Even if you have two of the same kind
of motor you may have to gear them different depending
on there Torq and RPM. For the most part picking
a motor with the best power rating and then looking
at the other numbers is your best bet.
How do you care for the magnets in the motor
can?
The best way to care for you magnets is to avoid
overheating your motor. A magnets loose magnetism,
but you can slow this process down by finding a
gear ratio that doesn't overheat them. Using a small
pinion and a larger spur gear will help in keeping
your motor cool. So let the motor cool off before
you go run the next pack. Avoid trying to cool a
motor down to rapidly because there is a possibility
of cracking the magnets. Be especially careful when
using compressed air cans, because when turned upside
down they can actually freeze objects. Also avoid
putting to many harsh chemicals on them while cleaning.
Many chemicals can eat the glue that adheres the
magnets to the can. If you have lots of money to
blow then you could also get a magnetizer which
gives magnets their life back.
Are there different types of springs and
if so what do they do?
Springs come in a variety of different degrees.
90, 115, 135, 150, 180. Each type of spring puts
a different tension on the brush. The most common
of the springs are the 135 degree and 150 degree
springs. The 135 degree springs will give you more
RPM, less power, same torque and less comm wear
than a 150 degree spring. The 150 degree spring
will give you less RPM, more power, same torque,
better results overall for stock and modified racing
and more comm wear than a 135 degree spring. The
135 degree spring is the most common type of spring
used.
What is a shunt wire?
A shunt wire is the wire that is part of a brush
that you connect to the motor hood. This wire is
made from very thin twisted strings of copper and
are usually tin coated. The wires are very thin
to make it as flexible as possible. This is done
so that when a softer spring is used so it won't
stick in the brush hood. Some brushes are even available
with two shunt wires for increased power but often
cause a disadvantage due to sticking.
What are brushes?
A brush is what makes contact with commutator and
conducts electricity to the comm.
Should I use a brush with an eyelet or no
eyelet?
If you are just beginning in RC the eyelet is probably
the best way to go. The eyelet provides an easy
way to change brushes. If you do decide to go with
an eyelet type brush make sure is gold plated. This
type of eyelet will have the best contact. If you
can't make a good solder joint a screwed on eyelet
is much better than a screwed on eyelet. When you
become a more experienced racer then I would recommend
soldering your brushes to the top of the motor hood.
Just be careful to not over tin the end of the shunt
wire. Try to use a smaller tip soldering iron when
soldering your brushes to help not over tinning
you shunt wire. Also once you have you brush in
place, whether you solder or use the eyelet, make
sure that the brush can move freely without sticking
in the brush hood holder.
Are brushes made from different compounds?
Brushes are made from three different compounds
(Graphite, Copper and Silver) each one has different
characteristics depending what type of racing you
are going to do.
What types of brushes are recommended for
stock and what type are recommend for modified?
A brush made from a silver compound is recommended
for stock. Silver Brushes also leave sludge behind
that can only be removed by lathing the comm. Silver
should be used for competitive racing where the
last percentage of power is needed to win. A brush
made from a copper compound is recommended for modified.
Copper brushes don't leave behind sludge and works
best with high RPM motors.
What are the main differences between the
three types of brushes?
The graphite brushes are not really recommended
for racing. They have the lowest comm wear, lowest
brush wear, high lubrication and the lowest power.
The copper brushes are recommended for modified
racing. They have the medium comm wear, high brush
wear, lowest lubrication and medium power. The silver
brushes are recommend for stock racing. They have
the least amount of resistance. The have the highest
comm wear, medium brush wear, medium lubrication
and highest power.
Are there different shapes of brushes for
stock and modified?
Yes, stock brushes are a laydown brush they are
wider than a standup brush. The purpose of the laydown
brush is to get maximum wrap around the comm to
increase the RPM and are usually thicker than a
modified brush. Modified or standup brushes are
taller than a laydown brush.
What is timing?
A motor's timing is the position o its brushes relative
to its magnets. When brushes are perfectly centered
over the magnets, the motor has zero timing. When
you rotate the endbell (and the brushes) in the
direction in the direction opposite the motor's
rotation, the timing is "advanced". When the endbell
is rotated beyond the zero-degree mark in the same
direction as the motor's rotation, the timing is
"retarded".
How is timing measured?
It is meaured by the degrees the brushes have been
rotated away from the center position. Most motors
come with a lablel that indicates the degrees and
calibration marks to show where the timing is set.
Eventhough timing refers to the position of the
brushes in relation to the magnets, all motors have
either a moldeded-in pointer or an endbell screw
that measures timing at a "zero point". This is
usually aligned exactly between the two mounting
screws on the bottom of the motor can.
Can timing be advanced or retarded to far
and what are the effects?
Yes, when the timing is advanced to far the amp
draw and motor rpm increase, but overall efficiency
and torque begins to suffer. When timing is retarded
at all, the motor will run slower and hotter (which
is why it's never really used!); zero timing is
the lowest point at which a motor timing should
be set. A good rule of thumb is that motors with
15 of fewer turns are best set with 0 to 15 degrees
of advanced timing, and winds of 15 and above work
with as high as 20 degrees of advance timing. If
you are unsure how much timing to run, set it on
the cautious side and run with less timing; your
motor will run cooler, and your car will also run
longer!
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