46 MODEL AVIATION
Mounting Large
Outrunner Motors
by Curtis Mattikow
WITH THE INEXPENSIVE and powerful outrunner motors and Li-
Poly batteries that are available nowadays, a new wave of larger
models is being converted from glow to electric operation. All of these
bigger aircraft come with beam mounts that are unsuitable for motors,
and motors are usually considerably shorter than their glow-engine
equivalents, so the motors can seldom be bolted directly to the firewall.
A few large motor mounts are available commercially, but they are
sometimes expensive and hard to get. This photo-illustrated article will
show you the simple steps required to mount motors. The only things
necessary are a few dollars’ worth of plywood, which you might
already have in your scrap box, and maybe an hour’s worth of time.
What You Need: A table saw with a fence is handy for accurately
cutting the plywood. That’s a long, blister-producing job with a hand
saw.
Make sure you have a ruler, a pencil, five-minute epoxy, screws for
mounting the motor, and the appropriate plywood. I used 1/4-inch
aircraft grade, which you can obtain from Midwest Products. The
motor is a Tower Pro from Nitro Model Planes that is equivalent to a
.50-size glow engine.
You could go down a size in plywood to 3/16 for smaller motors, but
chances are that 1/4 will be more than adequate for even the largest
motors—up to the 90 class. Lightening holes saved close to 1/2 ounce
on this mount without sacrificing rigidity. Plus, they look cool.
Mounting Tips: Check out the step-by-step photos for the lesson.
Notice especially how your propeller driver/spinner/propeller
This easy method allows you to propel almost any model
Measure the amount that the cowl will overhang the fuselage. In
this case, it’s 1cm. Make a note of that figure.
combination go together; some electric propellers extend rearward
behind the propeller driver, as do some spinners, so account for those
items when taking measurements.
I highly recommend that you firmly clamp the assembly while
it cures; clamping pressure makes a huge difference in an epoxy
joint’s strength. A roughing option is to drill a few 1/16-inch holes
1
05sig2.QXD 3/25/09 11:00 AM Page 46
May 2009 47
Epoxy and clamp the four sides, overlapping them as shown. Place
the assembly on plywood and trace around it. Cut out the marked
piece; that will be the firewall.
7
Cut across the lines you made, to make four identical pieces. If
you like, you can stack the pieces and drill lightening holes. Keep
the holes at least 1/4 inch away from any edges.
6
Measure the width of the cross mount; the one shown is 5.5cm.
Draw four vertical lines across the plywood, 5.5cm apart. Be sure
to account for the material that may be removed by your saw
blade, too.
5
Subtract 7.5cm from the cowl length, which is 12.5 - 7.5 = 5cm.
That’s the depth of the mount you will make. Draw a line across
your plywood at that dimension.
4
Measure the cowl from front to back, which is 12.5cm here.
Add the overhang, the motor length, and the thickness of the
plywood (.5cm is roughly equal to 1/4 plywood). That is 1 + 6 +
.5 = 7.5cm.
3
Measure the length of the motor, from the metal cross mount to
the portion you want sticking out of the cowl. Write that down.
As shown, it’s 6cm. Check to see how your propeller driver,
spinner, and propeller combination go together.
Photos by the author
in the gluing areas, to give the epoxy more bite.
This is a quick technique that costs you almost nothing, and the
results are extremely strong and rigid. It took me less than an hour to
make both mounts for the Nitro Model Planes B-25 Mitchell. I spent
more time shopping unsuccessfully for appropriate mounts at the
hobby store and on the Internet than it took me to make this
modification.
Give it a whirl! MA
Curtis Mattikow
[email protected] 2
Sources:
Nitro Model Planes
(626) 968-9860
www.nitroplanes.com
Midwest Products
(800) 348-3497
www.midwestproducts.com
05sig2.QXD 3/25/09 11:33 AM Page 47
48 MODEL AVIATION
Right: The great thing about motors is
that there is no needle valve or exhaust
muffler to carve out of the cowling. Ensure
that there are openings through which
cooling air can pass.
Above: Mark and drill pilot holes, and
install your motor on the mount using
screws. Back the screws out, remove the
motor, and harden the screw holes with
thin cyanoacrylate. Let that dry, and then
reinstall the motor and screws for
maximum security.
Use plenty of epoxy to install the motor mount to the firewall.
Stand the fuselage on its tail and weight it down, to provide
pressure as the epoxy cures. I painted the mount and firewall so
that it would look better through the open radial cowl when
finished.
1 2
1 1
Trace around the mount onto the firewall, and remove the mount.
Rough up the areas marked on the firewall; epoxy adheres better to
an uneven surface. Drill a hole above or to the side of your mounting
area, for your wiring to go through back into the fuselage.
1 0
finished
Measure and mark the horizontal and vertical centerlines of your
firewall, as well as the halfway points of each side of the mount.
Tape the mount to the firewall, aligning the marks on the mount
with the lines on the firewall.
9
Draw diagonal lines across the firewall to establish the center.
Drill a hole, as required, to clear the rear of the motor shaft and
the shaft retainer. Epoxy the firewall to the motor mount.
8
05sig2.QXD 3/25/09 11:01 AM Page 48
Edition: Model Aviation - 2009/05
Page Numbers: 46,47,48
Edition: Model Aviation - 2009/05
Page Numbers: 46,47,48
46 MODEL AVIATION
Mounting Large
Outrunner Motors
by Curtis Mattikow
WITH THE INEXPENSIVE and powerful outrunner motors and Li-
Poly batteries that are available nowadays, a new wave of larger
models is being converted from glow to electric operation. All of these
bigger aircraft come with beam mounts that are unsuitable for motors,
and motors are usually considerably shorter than their glow-engine
equivalents, so the motors can seldom be bolted directly to the firewall.
A few large motor mounts are available commercially, but they are
sometimes expensive and hard to get. This photo-illustrated article will
show you the simple steps required to mount motors. The only things
necessary are a few dollars’ worth of plywood, which you might
already have in your scrap box, and maybe an hour’s worth of time.
What You Need: A table saw with a fence is handy for accurately
cutting the plywood. That’s a long, blister-producing job with a hand
saw.
Make sure you have a ruler, a pencil, five-minute epoxy, screws for
mounting the motor, and the appropriate plywood. I used 1/4-inch
aircraft grade, which you can obtain from Midwest Products. The
motor is a Tower Pro from Nitro Model Planes that is equivalent to a
.50-size glow engine.
You could go down a size in plywood to 3/16 for smaller motors, but
chances are that 1/4 will be more than adequate for even the largest
motors—up to the 90 class. Lightening holes saved close to 1/2 ounce
on this mount without sacrificing rigidity. Plus, they look cool.
Mounting Tips: Check out the step-by-step photos for the lesson.
Notice especially how your propeller driver/spinner/propeller
This easy method allows you to propel almost any model
Measure the amount that the cowl will overhang the fuselage. In
this case, it’s 1cm. Make a note of that figure.
combination go together; some electric propellers extend rearward
behind the propeller driver, as do some spinners, so account for those
items when taking measurements.
I highly recommend that you firmly clamp the assembly while
it cures; clamping pressure makes a huge difference in an epoxy
joint’s strength. A roughing option is to drill a few 1/16-inch holes
1
05sig2.QXD 3/25/09 11:00 AM Page 46
May 2009 47
Epoxy and clamp the four sides, overlapping them as shown. Place
the assembly on plywood and trace around it. Cut out the marked
piece; that will be the firewall.
7
Cut across the lines you made, to make four identical pieces. If
you like, you can stack the pieces and drill lightening holes. Keep
the holes at least 1/4 inch away from any edges.
6
Measure the width of the cross mount; the one shown is 5.5cm.
Draw four vertical lines across the plywood, 5.5cm apart. Be sure
to account for the material that may be removed by your saw
blade, too.
5
Subtract 7.5cm from the cowl length, which is 12.5 - 7.5 = 5cm.
That’s the depth of the mount you will make. Draw a line across
your plywood at that dimension.
4
Measure the cowl from front to back, which is 12.5cm here.
Add the overhang, the motor length, and the thickness of the
plywood (.5cm is roughly equal to 1/4 plywood). That is 1 + 6 +
.5 = 7.5cm.
3
Measure the length of the motor, from the metal cross mount to
the portion you want sticking out of the cowl. Write that down.
As shown, it’s 6cm. Check to see how your propeller driver,
spinner, and propeller combination go together.
Photos by the author
in the gluing areas, to give the epoxy more bite.
This is a quick technique that costs you almost nothing, and the
results are extremely strong and rigid. It took me less than an hour to
make both mounts for the Nitro Model Planes B-25 Mitchell. I spent
more time shopping unsuccessfully for appropriate mounts at the
hobby store and on the Internet than it took me to make this
modification.
Give it a whirl! MA
Curtis Mattikow
[email protected] 2
Sources:
Nitro Model Planes
(626) 968-9860
www.nitroplanes.com
Midwest Products
(800) 348-3497
www.midwestproducts.com
05sig2.QXD 3/25/09 11:33 AM Page 47
48 MODEL AVIATION
Right: The great thing about motors is
that there is no needle valve or exhaust
muffler to carve out of the cowling. Ensure
that there are openings through which
cooling air can pass.
Above: Mark and drill pilot holes, and
install your motor on the mount using
screws. Back the screws out, remove the
motor, and harden the screw holes with
thin cyanoacrylate. Let that dry, and then
reinstall the motor and screws for
maximum security.
Use plenty of epoxy to install the motor mount to the firewall.
Stand the fuselage on its tail and weight it down, to provide
pressure as the epoxy cures. I painted the mount and firewall so
that it would look better through the open radial cowl when
finished.
1 2
1 1
Trace around the mount onto the firewall, and remove the mount.
Rough up the areas marked on the firewall; epoxy adheres better to
an uneven surface. Drill a hole above or to the side of your mounting
area, for your wiring to go through back into the fuselage.
1 0
finished
Measure and mark the horizontal and vertical centerlines of your
firewall, as well as the halfway points of each side of the mount.
Tape the mount to the firewall, aligning the marks on the mount
with the lines on the firewall.
9
Draw diagonal lines across the firewall to establish the center.
Drill a hole, as required, to clear the rear of the motor shaft and
the shaft retainer. Epoxy the firewall to the motor mount.
8
05sig2.QXD 3/25/09 11:01 AM Page 48
Edition: Model Aviation - 2009/05
Page Numbers: 46,47,48
46 MODEL AVIATION
Mounting Large
Outrunner Motors
by Curtis Mattikow
WITH THE INEXPENSIVE and powerful outrunner motors and Li-
Poly batteries that are available nowadays, a new wave of larger
models is being converted from glow to electric operation. All of these
bigger aircraft come with beam mounts that are unsuitable for motors,
and motors are usually considerably shorter than their glow-engine
equivalents, so the motors can seldom be bolted directly to the firewall.
A few large motor mounts are available commercially, but they are
sometimes expensive and hard to get. This photo-illustrated article will
show you the simple steps required to mount motors. The only things
necessary are a few dollars’ worth of plywood, which you might
already have in your scrap box, and maybe an hour’s worth of time.
What You Need: A table saw with a fence is handy for accurately
cutting the plywood. That’s a long, blister-producing job with a hand
saw.
Make sure you have a ruler, a pencil, five-minute epoxy, screws for
mounting the motor, and the appropriate plywood. I used 1/4-inch
aircraft grade, which you can obtain from Midwest Products. The
motor is a Tower Pro from Nitro Model Planes that is equivalent to a
.50-size glow engine.
You could go down a size in plywood to 3/16 for smaller motors, but
chances are that 1/4 will be more than adequate for even the largest
motors—up to the 90 class. Lightening holes saved close to 1/2 ounce
on this mount without sacrificing rigidity. Plus, they look cool.
Mounting Tips: Check out the step-by-step photos for the lesson.
Notice especially how your propeller driver/spinner/propeller
This easy method allows you to propel almost any model
Measure the amount that the cowl will overhang the fuselage. In
this case, it’s 1cm. Make a note of that figure.
combination go together; some electric propellers extend rearward
behind the propeller driver, as do some spinners, so account for those
items when taking measurements.
I highly recommend that you firmly clamp the assembly while
it cures; clamping pressure makes a huge difference in an epoxy
joint’s strength. A roughing option is to drill a few 1/16-inch holes
1
05sig2.QXD 3/25/09 11:00 AM Page 46
May 2009 47
Epoxy and clamp the four sides, overlapping them as shown. Place
the assembly on plywood and trace around it. Cut out the marked
piece; that will be the firewall.
7
Cut across the lines you made, to make four identical pieces. If
you like, you can stack the pieces and drill lightening holes. Keep
the holes at least 1/4 inch away from any edges.
6
Measure the width of the cross mount; the one shown is 5.5cm.
Draw four vertical lines across the plywood, 5.5cm apart. Be sure
to account for the material that may be removed by your saw
blade, too.
5
Subtract 7.5cm from the cowl length, which is 12.5 - 7.5 = 5cm.
That’s the depth of the mount you will make. Draw a line across
your plywood at that dimension.
4
Measure the cowl from front to back, which is 12.5cm here.
Add the overhang, the motor length, and the thickness of the
plywood (.5cm is roughly equal to 1/4 plywood). That is 1 + 6 +
.5 = 7.5cm.
3
Measure the length of the motor, from the metal cross mount to
the portion you want sticking out of the cowl. Write that down.
As shown, it’s 6cm. Check to see how your propeller driver,
spinner, and propeller combination go together.
Photos by the author
in the gluing areas, to give the epoxy more bite.
This is a quick technique that costs you almost nothing, and the
results are extremely strong and rigid. It took me less than an hour to
make both mounts for the Nitro Model Planes B-25 Mitchell. I spent
more time shopping unsuccessfully for appropriate mounts at the
hobby store and on the Internet than it took me to make this
modification.
Give it a whirl! MA
Curtis Mattikow
[email protected] 2
Sources:
Nitro Model Planes
(626) 968-9860
www.nitroplanes.com
Midwest Products
(800) 348-3497
www.midwestproducts.com
05sig2.QXD 3/25/09 11:33 AM Page 47
48 MODEL AVIATION
Right: The great thing about motors is
that there is no needle valve or exhaust
muffler to carve out of the cowling. Ensure
that there are openings through which
cooling air can pass.
Above: Mark and drill pilot holes, and
install your motor on the mount using
screws. Back the screws out, remove the
motor, and harden the screw holes with
thin cyanoacrylate. Let that dry, and then
reinstall the motor and screws for
maximum security.
Use plenty of epoxy to install the motor mount to the firewall.
Stand the fuselage on its tail and weight it down, to provide
pressure as the epoxy cures. I painted the mount and firewall so
that it would look better through the open radial cowl when
finished.
1 2
1 1
Trace around the mount onto the firewall, and remove the mount.
Rough up the areas marked on the firewall; epoxy adheres better to
an uneven surface. Drill a hole above or to the side of your mounting
area, for your wiring to go through back into the fuselage.
1 0
finished
Measure and mark the horizontal and vertical centerlines of your
firewall, as well as the halfway points of each side of the mount.
Tape the mount to the firewall, aligning the marks on the mount
with the lines on the firewall.
9
Draw diagonal lines across the firewall to establish the center.
Drill a hole, as required, to clear the rear of the motor shaft and
the shaft retainer. Epoxy the firewall to the motor mount.
8
05sig2.QXD 3/25/09 11:01 AM Page 48
