Great Planes RimFire 250 User Manual

250 POWER
SYSTEM

Congratulations, you have just purchased the RimFire 250 power
system components. All the components are sold separately to allow
you to customize your power system to your airplane. The components
needed to assemble your RimFire 250 power system are: RimFire 250
motor, propeller, propeller adapters and brushless speed controls.
This instruction sheet explains how to determine what you will need
and how to assemble each component.

MOTOR

1

Model Stock #

RimFire 250 (28-13 - 1750) GPMG4502

The RimFire motors are labeled to provide the most information at
a glance. For example: the RimFire 250 (28-13-1750) is 28mm in
diameter, 13mm long and has a kV (rpm-per-volt) of 1750 rpm.

28 mm

Weight includes: Motor w/prop adapter.

ELECTRONIC SPEED CONTROL (ESC)

2

An ESC is basically the device that controls your motor through your
radio system. Never run any RimFire motors with a brushed ESC.
It will not work and you may damage both the motor and the ESC.
Always use a brushless ESC. ElectriFly offers Brushless ESCs that will
work with the RimFire 250 motor.

ElectriFly Silver Series 8
(SS-8) ESC (GPMM1800)
for 8A maximum constant
current draw.

ElectriFly Silver Series 12
(SS-12) ESC (GPMM1810)
for 12A maximum constant
current draw.

The SS-8 and SS-12 come with 2mm female bullet connectors that
plug directly into the 2mm male connectors installed on the RimFire
250 motor, so no soldering is required. The SS-8 and SS-12 also come
with a Deans® Micro battery connector that matches the connectors
that are found on most batteries that it will use.

BATTERIES: NUMBER OF CELLS

3

Cells can be connected in series or in parallel. Usually batteries are
labeled by their number of cells, such as a 3-cell LiPo. This means the
cells are connected in SERIES (S). Arranging batteries in series gives
you more power (higher voltage).

Each LiPo battery has 3.7V, so a 3-cell

•

LiPo battery has 3.7 x 3 = 11.1V

If a battery is arranged in PARALLEL it might be labeled as (P). Arranging
the batteries in parallel will give you more duration (more capacity).

ElectriFly offers a full line of LiPo batteries. Airplanes that use the
RimFire 250 motor will typically use batteries with a capacity of 300 to
640mAh, with the higher capacity batteries delivering more fl ying time
but also being heavier. The suggested batteries have connectors that
fi t the recommended ESC.

Due to the constantly changing battery technology, check out the
ElectriFly web site at www.electrifl y.com for the most up-to-date
listing of the ElectriFly battery line.

Weight

20.5g

13 mm

PROPELLER ADAPTERS

4

The RimFire 250 motor comes with a prop saver with sleeves to fi t
a variety of prop hub sizes. If your application will use a spinner, the
motor will require a 3mm prop adapter collet type (GPMQ4959), or set
screw type (GPMQ4930).

GPMQ4930 3mm
Set Screw Type

PROPELLERS

5

There is a wide selection of propellers available for electric use. The RimFire
250 motor uses high performance slow fl y electric props. The larger the
propeller used, the more current your motor will draw. The smaller the
propeller, the less current the motor will draw.

Shown are a few of the recommended electric props. Due to the large
range of propellers and the constant addition of new sizes, visit our web
sites at www.electrifl y.com and www.greatplanes.com for the most up-
to-date listing of electric type props.

APCQ4960 7x4SF Slo-Flyer GWSQ2008 7x3.5 Propeller
APCQ4961 7x5SF Slo-Flyer GWSQ2009 8x4 Propeller
APCQ5000 8x3.8SF Slo-Flyer GWSQ2010 9x5 Propeller

Stock #

GPMP0594
GPMP0595
GPMP0700
GPMP0701
GPMP0704
GPMP0705

DETERMINE WHAT YOU NEED to BUILD YOUR POWER SYSTEM

6

Now that you have one component for your power system, there are
several different ways to select the rest. 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:

1. Find the combination that delivers the closest performance to what

❏

you want, (refer to the ElectriFly web site for typical combinations) or
refer to the airplane manufacturer’s recommendations.

2. Note the recommended battery voltage.

❏

3. Determine the battery capacity needed based on the current draw of

❏

your system and your desired fl ight time.

4. Determine the ESC you need based on the system current draw. 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. Watts = current (A) × voltage (V). Using
suggested power system combinations for reference, determine what
combination gives you the performance you want based on wattage
and maximum propeller size that will fi t on the plane.

3. Note the recommended battery voltage.

❏

4. Determine the battery capacity needed based on the current draw of

❏

your system and your desired fl ight time.

5. 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.

Voltage

7.4V

11.1V

7.4V

11.1V

7.4V

11.1V

Capacity

300mAh
300mAh
300mAh
300mAh
640mAh
640mAh

GPMQ4959 3mm
Collet Type

Weight

oz

0.8

1.1 oz

0.7 oz

1.0 oz

1.4 oz

2.0 oz

(24g)
(32g)
(20g)
(28g)
(39g)
(56g)

No. of Cells

2
3
2
3
2
3

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 fi ne-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 fi ne 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.

ASSEMBLE YOUR POWER SYSTEM

7

The RimFire 250 can be mounted directly to the front of the fi rewall or
behind the fi rewall using the optional reverse shaft (not included).

At the back of this manual, you will fi nd the mounting hole template
for mounting the RimFire 250 motor to the front or the back of the
fi rewall.

Installing The Propeller

A propeller can be installed onto the RimFire using the included prop
saver adapter or a collet-type prop adapter (not included).

If you are installing the
motor onto the front of
the fi rewall (common
installation), the propeller
can be installed onto
the prop saver adapter,
requiring only a rubber
O-ring to secure the prop
in place.

The included prop saver
adapter can be installed
with either end facing
forward. One end has a
diameter of 5mm and the
other end has a diameter
of 6mm. For other prop
hub sizes, 7mm and

7.85mm adapter sleeves
are also included to fi t
over the 5mm diameter prop saver end. Orient the prop saver adapter
in the direction that best suits your propeller and install it onto the
front of the motor shaft and tighten the screws against the fl at spots
on the shaft.

Install the cowl if the
plane comes with one.
Install the prop on the
prop saver and secure
it with a rubber O-ring
looped over both of the
machine screws. Check
the O-ring for wear
before each fl ight. If the
O-ring shows any cracks,
replace immediately.

Front Of Firewall Mounting Method

Use the template from
this manual to locate
and drill the mount­ing holes and the relief
hole for the end of the
motor shaft. Attach the
RimFire mounting plate
to the fi rewall using
three #2x3/8” [2x10mm]
sheet metal screws (not
included), or a type/size
specifi ed by the airplane manual.

Optional Reverse Shaft Installation

An optional reversing shaft is available for purchase separately
(GPMG1403) and will allow you to mount the RimFire 250 motor
behind the fi rewall.

Remove the set screw
that secures the motor
shaft to the motor front
case (this requires a

0.9mm allen key which
is not included). With
the set screw removed,
push the motor shaft out
through the bottom of
the motor being careful
not to lose the washer on the shaft. Tip: The shaft is a very tight fi t in
the motor case. An arbor press machine or a drill press (with a small
drill bit inserted upside down in the press) can be used to easily press
the shaft out of the motor.

Carefully remove the
c-clip from the aft end of
the motor shaft. A fi ne,
fl athead screwdriver or
small needle nose pliers
are useful in doing this.
Tip: Crawling around on
your hands and knees
looking for a lost c-clip is
no fun. Wrap a sandwich
bag around the shaft
before attempting to remove the c-clip. If the c-clip fl ies off the shaft,
it will be contained by the bag. Also, be sure to wear safety glasses
when removing the clip!

Reinstall the c-clip into
the groove on the reverse
shaft along with the
washer. Insert the reverse
shaft into the motor case.
The fl at spot on the shaft
near the c-clip groove
must be aligned with the
set screw in the motor
front case. Tighten the
set screw against the fl at
spot on the shaft.

The motor can now be mounted from the back side of a fi rewall with only
the shaft protruding forward of the fi rewall. The prop saver adapter or an
optional collet or set screw type adapter can be used to attach the propeller
to the motor.

Collet Type Prop Adapter Installation

Slide the 3mm prop shaft
over the motor shaft. 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 fi rst. Install
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 motor shaft.

Set Screw Type Prop Adapter Installation

Slide the 3mm prop adapter
over the motor shaft. Tighten
both of the set screws against
the shaft. Install 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
motor shaft.

INSTALL THE BRUSHLESS ESC

8

Mount your ESC in the desired location. Always make sure that the ESC is
positioned so that it gets some cooling air fl owing over it.

Use the instructions included with the ESC to correctly connect the ESC.

RIMFIRE MOTOR MAINTENANCE

9

RimFire 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. The only thing that needs to be checked is
to make sure all the screws and set screws remain tight.

IMPORTANT PRECAUTIONS

10

• 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
specifi cation of each motor.

• DO NOT apply currents to the motor that exceed the maximum
specifi cations 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 coated wires from the motor. If you must remove the
bullet connectors, unsolder them.

• Allow the motor to cool after each fl ight.

• 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.electrifl y.com

or visit your nearest hobby shop that carries the full line of Great
Planes and ElectriFly products.

Copyright © 2009 GPMG4502

Template

RimFire 250 Accessory and Spare Parts

GPMQ4625 Rimfi re Prop Saver (complete set)
GPMM3111 2mm gold plated bullet connectors - female (3)
GPMM3110 2mm gold plated bullet connectors - male (3
GPMG1401 Rimfi re 250 Replacement Shaft Kit
GPMG1403 Rimfi re 250 Reverse Run Shaft
GPMG1451 Rimfi re 250 Bearings (2)
GPMG1430 C-clip (10) for 3mm Rimfi re Motor Shafts
GPMG1405 Prop Saver O-rings (5)