Great Planes Ammo 24mm Power System - GPMG5150-5185 - Manual (Page 4)

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 rpm, then look at the chart included in
the packaging and:
❏ 1. Find the combination in the motor/prop chart that
delivers the closest performance 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.
S elect the number of cells based on the recommended
voltage shown on the chart.
❏ 5. Determine the battery capacity needed based on the
current draw of your system and your desired flight time.
❏ 6. Determine the E S C you need based on the system
current draw shown on the motor/prop chart. S ee the
E S C 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.
S ee the battery
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 performance then multiply
75 x Airplane Weight (lbs)
• If you expect aerobatic or high speed-like 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 your plane to perform 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 YOU NEED TO
BUILD YOUR POWER SYSTEM
❏ 5. Determine if you want to use LiPo or NiMH batteries
based on the desired ready to fly airplane weight.
S elect the number of cells based on the recommended
voltage shown in the chart.
❏ 6. Determine the battery capacity needed based on the
current draw of your system and your desired flight time.
❏ 7. Determine the E S C 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 available
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.
S o, 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.
INSTALL THE PINION GEAR
Once you have determined the
gear ratio required, the brass
pinion gear must be installed
on the motor shaft. The 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 supporting 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.
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.
ASSEMBLE YOUR POWER SYSTEM
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 4mm 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
S HC screws and two 3mm flat washers. Place
a piece of notebook paper between the pinion gear and the
spur gear.
S queeze the two gears together while tightening
the two 3x20mm S HC 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
S mall Motor
Mount. The Motor Mount can be attached to the firewall
using 4-40 machine screws and blind nuts installed in the
back of the firewall. Use the center lines on the template to
properly align it on the firewall.
Attach the Backplate to the firewall using four 4-40 machine
screws and four #4 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.
MOUNT THE BRUSHLESS
SMALL MOTOR MOUNT
MOUNT THE MOTOR TO
THE GEAR DRIVE
In-runner motors that will be run direct drive or gear drive
and are mounted inside the front plate.
Out-runner motors can be mounted inside the front plate in
some situations using three 3x8mm
S HC 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 24mm Gear Drive uses a 4mm
prop adapter (GPMQ4965 Collet Type or GPMQ4936 Set
Screw Type). The Ammo 24mm motors direct drive uses a
3mm prop adapter (GPMQ4959 Collet Type or GPMQ4930
Set Screw Type).
COLLET TYPE PROP ADAPTER INSTALLATION
S lide the prop shaft over 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
S lide 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
Ammo brushless motors require virtually 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 battery is connected to the E S C, 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
short out the attached E
S C.
• 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 rpm.
DO NOT attempt to touch the shaft while it is rotating. If
setting up the motor/E
S C 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 sight at:
www.greatplanes.com
www.electrifly.com
or visit your nearest hobby shop that carries the full line of
Great Planes and ElectriFly products.
IMPORTANT PRECAUTIONS
AMMO MOTOR MAINTENANCE
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
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"
S HC screws and eight #4 flat washers,
spaced out as far as possible. A drop of threadlocker on
the screws will prevent them from coming loose.
When mounting some of the Rimfire out-runner motors you
may need to remove the brass collar and install the aluminum
spacers on the motor shaft to space the collar behind the
Front Plate to prevent it from rubbing on the Front Plate.
Because most of the power systems using the 24mm
Ammo motor are drawing less than 25 amps constant, the
ElectriFly
SS -25 Brushless E S C (GPMM1820) will work
well. Note that if you will be operating the motors at the
surge currents a higher current E
S C will need to be
installed. Always make sure that the E S C is installed in a
location that allows plenty of cooling air to flow over it.
Follow the instructions included with the Brushless E S C to
properly install and program it.
INSTALL THE BRUSHLESS ESC
GPMZ0024 for Ammo 24mm S ystems Entire Contents Copyright © 2006
Ammo 24mm 4fold.qxd 6/15/2006 11:49 AM Page 2