User Manual

Now that you have a component for your power system,
there are several different ways to select the rest of the
components of your power system. In time, experience will
help you to determine what works best for you, but an easy
way to determine what you need now is the following.
PROCEDURE #1: If you know the size of the propeller you
want to turn and the r pm, then look at the chart included in
the packaging and:
❏ 1. Find the combination in the motor/prop chart that
delivers the closest perfor mance to what you want.
❏ 2. Note the gear ratio you need.
❏ 3. Note the recommended battery voltage.
❏ 4. Determine if you want to use LiPo or NiMH batteries
based on the desired ready-to-fly airplane weight.
Select the number of cells based on the recommended
voltage shown on the char t.
❏ 5. Determine the battery capacity needed based on the
current draw of y our system and your desired flight time .
❏ 6. Determine the ESC you need based on the system
current draw shown on the motor/prop char t. See the
ESC section.
PROCEDURE #2: If you know the approximate weight of
your airplane, including the motor and battery, and the
performance you want from it, answer the questions below
to determine the correct power system for your plane. You
may need to make more than one calculation using
different motors and battery combinations. See the batter y
section for some of the battery weights for the suggested
batteries.
❏ 1. Perform the following calculation to determine the
wattage required:
• If you expect trainer-like perfor mance then multiply
75 x Airplane Weight (lbs)
• If you expect aerobatic or high speed-lik e performance
then multiply 100 x Airplane Weight (lbs)
• If you expect 3D or extreme performance multiply
150 x Airplane Weight (lbs)
❏ 2. The number you get is the minimum wattage you will
need for y our plane to perf orm as you wish. Look at the
chart and determine what combination gives you the
performance you want based on wattage and
maximum propeller size that will fit on the plane.
❏ 3. Note the gear ratio you need.
❏ 4. Note the recommended battery voltage.
DETERMINE WHAT Y OU NEED T O
BUILD YOUR POWER SYSTEM
❏ 5. Determine if you want to use LiPo or NiMH batteries
based on the desired ready to fly airplane weight.
Select the number of cells based on the recommended
voltage shown in the char t.
❏ 6. Determine the battery capacity needed based on the
current draw of y our system and your desired flight time .
❏ 7. Determine the ESC you need based on the system
current draw.
In addition to these two procedures, you can also visit the
Great Planes ElectriFly web site for descriptions of the power
systems recommended for our line of electric and glow
airplanes as well as more detailed explanation on the subject.
UNDERSTANDING MOTORS
kV (rpm/volt): This is a number that gets thrown around
quite a bit when talking electrics and it is important to know
what it is. kV is the number of rpm a motor will spin per
each volt applied (rpm/volt) under no load.
This means that basically a motor that has a kV of 1000
when connected to a 12V battery will try to spin at
12,000rpm (1000x12) under no load. Likewise a 3500kV
motor will try to spin at 42,000rpm (3500x12) under no load.
When a propeller is attached to the motor , the motor will try
to spin the prop at the rated kV. Depending on the diameter
and pitch of the propeller (the larger the diameter or higher
the pitch, the harder it is to spin), the motor’s current draw
can be increased or decreased. There are meters a v ailab le
from your hobby dealer that measure current and voltage.
Because every motor has a maximum current it can take
based on its design and cooling ability, the maximum size of
propeller that can be used with each motor can be
determined. Too large of a propeller and the motor will spin at
a much lower rpm than its rated kV, causing it to draw a lot of
current and overheat. If the propeller/fan is too small, it will
require little effort (current) to turn the prop at the rated kV.
Ideally the motor should be matched with a propeller that
causes the motor to draw 80-100% of its rated maximum
constant current. Once a power system is set up, it can be
fine-tuned by adjusting the propeller size and measuring
the amount of current the motor is drawing.
Please note that the kV of a motor does not change with
voltage, but if a higher voltage is applied to the motor, it will
try to spin the same propeller at a higher rpm. This will
cause the motor to draw more current and possibly exceed
the maximum rated current of the motor . So , if a battery with
lower voltage is replaced with one with a higher voltage, it
is recommended that a smaller propeller be used to keep
the current in check. If a higher voltage battery is replaced
by a lower voltage battery, the size of the propeller can be
increased to keep the motor at its rated current.
Another possibility to fine tune the power system’s
performance is to use another motor with higher kV to
increase the current or a lower kV to lower the current.
INST ALL THE PINION GEAR
Once you have determined the
gear ratio you need, the brass
pinion gear will need to be
installed on the motor shaft.
The brass pinion gear is a
press fit on the motor shaft and
it will need to be heated and
pressed on. Never force the
pinion gear on the shaft without
suppor ting the other end of the
motor shaft. A small wheel
collar works well for supporting
the motor shaft. If you have a
drill press the motor can be placed in a vise with the motor
shaft supported on a small wheel collar. Use a small micro
torch to heat the pinion gear and use the drill chuck of the drill
press to press the pinion onto the shaft. Note: The pinion
gear uses a small set screw to secure the pinion gear to the
motor shaft. When installing the pinion gear make sure that
the flat on the motor shaft is aligned with the set screw.
If you do not have a drill press a small vise can also be
used. Place the motor between the jaws of the vise with the
end of the motor shaft supported and the pinion gear
centered on the motor shaft. Heat the pinion gear and
slowly close the jaws of the vise. You may need to use a
second wheel collar so that the pinion gear can be pressed
on past the end of the motor shaft.
ASSEMBLE YOUR POWER SYSTEM
Once the pinion gear is in position on the motor shaft,
apply a drop of Threadlocker to the threads of the set
screw and tighten it down on the flat of the motor shaft.
REMOVAL OF THE PINION GEAR
The best method of removing the pinion gear is by heating
it with a micro torch and using a pinion puller to carefully
pull the gear off.
REPLACING THE SPUR GEAR
To remove the spur gear, loosen and remove the two
2.5x17mm flat head machine screws and 5.5mm
aluminum spacers.Remove the backplate being careful to
not lose the 5mm bearing spacer.
Press the output shaft out of the
spur gear and remove the spur
gear pin. The spur gear can now
be replaced. Reverse the order to
reassemble the gear drive. Be
sure to use a drop of threadlocker
on the two 2.5x17mm flat head
machine screws to prevent them
from loosening during operation.
Loosely mount the motor to the back of the back plate with
two 3x20mm SHC screws and tw o 3mm flat washers . Place
MOUNT THE MO TOR T O
THE GEAR DRIVE
a piece of notebook paper between the pinion gear and the
spur gear. Squeeze the two gears together while tightening
the two 3x20mm SHC screws. Remove the piece of paper
and the gear mesh should be set. Rotate the gears to make
sure they rotate smoothly. If they do not, slightly loosen the
gear mesh until the gears do rotate smoothly.
In the center of the header card you will find the mounting
hole pattern template for the Brushless Medium Motor
Mount. The Motor Mount has the same bolt mounting
pattern as the Great Planes .20-.48 and .40-.70 Nylon
Engine Mounts. If you are replacing a glow engine with an
electric motor system, remove the n ylon engine mount and
replace it with the 28mm Motor Mount using the same
bolts to attach it to the firewall. If the firewall has not been
drilled for an engine mount and blind nuts, use the
mounting template on page 8 to locate the mounting holes.
Attach the Backplate to the
firewall using four 6-32
machine screws and four
#6 flat washers. Note that
if you are using a gear
drive you may have to cut
a hole in the firewall for the
motor. Most motors and
gear drives can be
mounted to the Front Plate
using 3mm machine screws. If you are using a different
gear drive other than the Great Planes gear drive the hole
locations may need to be modified.
In-runner motors that will be run direct dr ive or gear drive
and are mounted inside the front plate.
MOUNT THE BRUSHLESS
MEDIUM MOTOR MOUNT
Out-runner motors can be mounted inside the front plate in
some situations using four 3x8mm SHC screws, but most of
the time they will be mounted on the front of the front plate.
Install the prop adapter on the motor shaft or gear drive
output shaft. The Brushless 28mm Gear Drive uses a 5mm
prop adapter (GPMQ4966 Collet Type or GPMQ4939 Set
Screw Type). The Ammo 28mm motors direct drive uses a
3.175mm prop adapter (GPMQ4962 Collet Type or
GPMQ4933 Set Screw Type).
COLLET TYPE PROP ADAPTER INSTALLATION
Slide the prop shaft ov er the output shaft of the gear drive or
motor. Next slide the prop shaft retainer over the prop shaft.
Note that the hole through the retainer is tapered. Make sure
that the side with the larger diameter hole is installed first.
Install the spinner backplate (if used, not included), the
prop, prop washer and then the prop nut. Tighten the prop
nut against the prop. This will cause the tapered hole in the
prop shaft retainer to squeeze the prop shaft around the
output shaft. Carefully pull on the prop to make sure it is
securely attached to the output shaft of the gear drive.
SET SCREW TYPE PROP ADAPTER INSTALLATION
Slide the prop adapter over the output shaft of the gear
drive or motor. Align one of the set screws with the flat on
the output shaft of the gear drive. Apply a drop of Great
Planes Threadlocker (GPMR6060) to the set screw and
install it in the prop adapter, tightening it against the flat of
the gear drive output shaft. Remove the second set screw
that does not tighten onto the flat. When installing the prop
adapter onto a shaft that does not have a flat spot, tighten
both of the set screws against the shaft. Install the spinner
backplate (if used, not included), the prop, prop washer
and then the prop nut. Tighten the prop nut against the
prop. Carefully pull on the prop to make sure it is securely
attached to the output shaft of the gear drive.
Determine the distance the prop adapter needs to be from
the firewall by using the recommended distance in the
airplane instructions or by installing the cowl and measuring
the distance from the firewall to the front of the cowl. Add
approximately 3/32” to 1/8” to the distance. Attach the Front
Plate of the motor mount to the Back Plate using the eight
4-40x1/4” SHC screws and eight #4 flat washers , spaced out
as far as possible. A drop of Threadlocker on the threads of
the screws will prevent the screws from coming loose.
Ammo brushless motors require vir tually no maintenance.
There are no brushes to wear out and replace. The
precision bearings have a very long service life and should
last a very long time. The internal parts of the motor should
not require any cleaning.
• Once the batter y is connected to the ESC, stay clear of
the motor and prop.
• DO NOT apply an input voltage that exceeds the
maximum specification of each motor.
• DO NOT apply currents to the motor that exceed the
maximum specifications of each motor.
• DO NOT allow the input connectors to accidentally touch
each other while power is applied to the motor. Make sure
all input connections are insulated electrically.
• DO NOT allow water or moisture to enter the motor, as it
can cause permanent damage to the motor and possibly
shor t out the attached ESC.
• DO NOT cut the coated wires from the motor. If you must
remove the bullet connectors, unsolder them.
• Allow the motor to cool after each flight.
• The motor shaft of the motor will rotate at very high r pm.
DO NOT attempt to touch the shaft while it is rotating. If
setting up the motor/ESC on the workbench, make sure
the motor is securely attached and that nothing is
attached to the motor shaft BEFORE applying power.
• Never attempt to use a damaged motor (having
mechanical or electrical defects).
• Great Planes carries a complete line of Ammo (in-runner
style) and Rimfire (out-runner style) brushless motors,
gear drives, motor mounts, prop adapters and speed
controls. For a complete list of these products, check out
our web site at:
www.greatplanes.com
www.electrifly.com
or visit your nearest hobby shop that carr ies the full line of
Great Planes and ElectriFly products.
IMPORTANT PRECAUTIONS
AMMO MOTOR MAINTENANCE
The 28mm Motor Mount comes with an optional Motor
Bracket. If you have installed a 45mm or longer motor in
the Motor Mount we recommend installing the optional
Motor Bracket. Attach the Motor Bracket to the sides of the
Motor Mount using two 4-40x1/2” SHC screws, #4 flat
washers and 4-40 lock nuts. Position the Motor bracket as
far back on the motor as possible. Once the Motor Bracket
is installed, secure the motor to the Motor Bracket using
the nylon strap.
Because most of the power systems using the 28mm
Ammo motor are drawing less than 35 amps continuous,
the ElectriFly SS-25 Brushless ESC (GPMM1820), for
power systems drawing less than 25 amps, and the SS-35
(GPMM1830), for power systems drawing less than 35
amps, will work well. If you will be using an Ammo motor
and prop combination that draws more than 35 amps
continuous, use the SS-45 Brushless ESC (GPMM1840).
If the SS-45 ESC is used, three 4mm to 3.5mm bullet
connector adapters (GPMP3123) will need to be installed
on the motor. Alwa ys make sure that the ESC is positioned
so that it gets some cooling air flowing over it.
Use the instructions included with the ESC to correctly
connect the ESC.
INST ALL THE BRUSHLESS ESC
MOTOR BRACKET INSTALLATION
(OPTIONAL)
GPMZ0025 for Ammo 28mm SystemsEntire Contents Copyright © 2006
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