Great Planes Ammo 12mm Power System - GPMG5105-5110 - 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.
Select 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 ESC you need based on the system
current draw shown on the motor/prop chart. 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 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.
Select 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 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 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. 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.
INSTALL 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. If the
brass pinion gear fits loose on the motor shaft, the pinion gear
will need to be secured to the motor shaft using a retaining
compound such as Great Planes’ (GPMA6062). For the most
secure fit, roughen the motor shaft with 320-grit to 400-grit
sandpaper. Clean the motor shaft and the inside of the pinion
gear with denatured alcohol. Apply a thin film of retaining
compound on the motor shaft and inside the pinion gear. Slide
the pinion gear on the motor shaft and allow the retaining
compound to set. Usually 1-2 hours.
If the brass pinion gear fits tight on the motor shaft it will need
to be pressed on. Never force the pinion gear on the shaft
without supporting the other end of the motor shaft. A small
cap head screw works well for supporting the motor shaft. If
you have a drill press the motor can be placed in a vice with
the motor shaft supported on a small cap head screwe. 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.
ASSEMBLE YOUR POWER SYSTEM
INSTALL THE PINION GEAR
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 with a 4-40 cap head screw, tack
glued to one jaw of the vise, and the pinion gear centered on
the motor shaft. Use a small micro torch to heat the pinion gear
and use the vise to carefully press the pinion onto the shaft.
REMOVAL OF THE PINION GEAR
Whether the pinion gear is glued on or pressed on, 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
The spur gear is simply pressed over a spline on the output
shaft. Due to crashes and other unfortunate mishaps, the
teeth on the spur gear may be damaged or the spur gear
may twist off of the spline. If this happens, remove the
damaged spur gear and press a new gear over the spline.
To accomplish this, use a tube or socket placed over the
output shaft and against the new spur gear. Place this
assembly in a vise and press the gear over the spline.
Mount the motor to the gear drive body with two 1.6x6mm
machine screws.
The Great Planes Stick Mount Gear Drive is designed to be
mounted on a 5x8mm stick. Slide the Gear Drive over the
stick. If the gear drive fits loosely on the stick, a drop of CA or
a small self-tapping screw can be used to hold it in position.
The ElectriFly SS-8 (GPMM1800) works great with the
Ammo 12mm motor and gear drive. Use the instructions
included with the ESC to correctly connect the ESC.
INSTALL THE BRUSHLESS ESC
MOUNT THE GEAR DRIVE
TO THE PLANE
MOUNT THE MOTOR TO
THE GEAR DRIVE
The prop saver prop adapter is included with the IPS Gear
Drive. If you prefer to use the collet type prop adapter or
set screw type prop adapter, you will need the:
GPMQ4959 3mm Collet-Type Prop Adapter
GPMQ4930 3mm Set Screw-Type Prop Adapter
PROP SAVER PROP ADAPTER INSTALLATION
Install the cowl if the plane comes with one. Note that on the
prop saver hub the center protrusions have different
diameters on each side of the hub. Determine which diameter
fits the prop you are using. Then, install the prop saver hub on
the output shaft of the gear drive with the correct diameter
facing outward. Tighten the two 2.5x7mm machine screws
against the output shaft, in the prop saver hub.
Install the prop on the prop hub and secure it with a rubber
o-ring looped over both of the machine screws.
INSTALL THE PROP ADAPTER
AND PROP
COLLET-TYPE PROP ADAPTER INSTALLATION
Slide the 3mm prop shaft over the output shaft of the gear
drive. 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 3mm prop adapter over the output shaft of the
gear drive. 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.
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 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
short out the attached ESC.
• DO NOT cut the wires from the motor. The wires are part
of the windings and are coated with an insulating material
and cannot be soldered without removing the coating,
which is very difficult. 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/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).
ElectriFly 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 carries the full line of
Great Planes and ElectriFly products.
IMPORTANT PRECAUTIONS
AMMO MOTOR MAINTENANCE
GPMZ0022 for Ammo 12mm Systems
Entire Contents Copyright © 2006
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