Roger Carignan
Clamp the wheel-cutting fixture to a scroll-saw table. The cutaway section with center
pin will hold the foam blank and allow movement into the saw blade.
Cut square foam blanks to the required thickness. Apply two layers of masking tape to
reinforce centers. Mark and drill these to fit over the fixture pin.
WhEn I WaS building a kit of the Little
Tiny—a 24-inch-wingspan electric
indoor/outdoor Radio Control model—one
objective was to achieve as low an airframe
weight as I could to compensate for use of
heavier servos and receiver than those
specified in the plans. One of the several
weight-saving methods I used was to
replace the kit-supplied wheels with my
homemade foam wheels.
The 11⁄2-inch-diameter wheels supplied
with the kit were nicely made from
laminated 1⁄32 balsa with a plastic hub and
an O-ring tire approximately 0.080 inch
wide; these weighed 840 milligrams (mg)
each.
My first set of wheels was purely
functional, with a flat tread and no paint or
other embellishments. These were 13⁄8 inch
in diameter, 3⁄8 inch wide, and weighed 280
mg each. By rounding the tread to look
more like an aircraft tire, the weight of each
wheel dropped to 260 mg; this is less than
one-third of the kit-wheel weight.
The homemade wheels work well on
most indoor and lightweight outdoor
models and look better than those thin balsa
disk or plastic “spider” type wheels.
Because of the foam material they will not
take a lot of abuse, such as flying off gravel
or similar surfaces, although a coat of
diluted aliphatic resin glue on the tread
provides better endurance on such surfaces.
These wheels will give satisfactory service
on a smooth floor or paved surface.
The larger wheels shown in the article
were made for my park-flyer-size model
that weighs 18 ounces, and they work well
from mowed grass. I used “pink” insulation
foam for all the work in this article; most
other foams with similar compressive
strength should work.
Using common tools and simple
homemade fixtures, wheels can be made to
any required size. The following is a stepby-
step procedure for making the required
tools and fabricating the wheels.
Make Lightweight
Foam Wheels
Photos/drawings courtesy the author Graphic Design by Lydia Whitehead
52 M ODEL AVIATION
1) Make the wheel-cutting fixture as
shown in the drawing from 1⁄4 plywood. It is
important to ensure that the 1⁄16-music-wire
pin in the movable corner piece is
perpendicular to the surface. This pin is the
same diameter as the outer diameter of the
hub bearing that will be used in the wheels.
To make wheels with larger-diameter hub
bearings, make a bushing from brass tubing
to the larger size required and place it over
the fixture pin.
2) Attach the fixture to a scroll-saw table
with C-clamps as shown in the photo. Adjust
to provide the required wheel diameter by
positioning the pin location from the saw
blade. A similar setup could be made using a
homemade hot-wire foam cutter.
3) Determine the size of wheels you
need, and cut square blanks from foam to
the required thickness. Dimensions of the
smaller wheels featured in the article are
shown in the drawing; these may be scaled
larger or smaller as required, but do not
make the thickness at the hub too thin; this
will compromise strength in this area.
4) On one side of each blank, place two
thicknesses of 3⁄4-inch-square masking tape.
This provides temporary bearing strength
during the following cutting and recessing
operations.
5) Mark the center of each blank, and
drill a hole through with the same diameter
as the fixture pin. Try to make this hole
perpendicular to the blank surface; a drill
press helps with this step.
6) Place the blank with masking tape on
top of the fixture pin. With the scroll saw
running, slide the assembly into its location
on the fixture as the blade starts cutting the
blank. While holding the fixture parts
together, turn the blank through 360° to
complete the wheel cutout.
7) Make recesses in the wheel with a
plywood disk covered with a piece of 100-
grit sandpaper. For the smaller wheels
shown, I used a 1⁄16 plywood sandpapercovered
disk. The procedure is to cut a
recess in one side of the wheel then add
spokes to provide a bearing on that side of
the wheel. This allows you to remove tape
from the other side which can then be
recessed.
Two ways of forming the recesses are
shown in the photos. In one method you
attach the sandpaper-covered disk to a
plywood base with a 1⁄16-inch-diameter pin.
Place the foam wheel disk over the pin with
the taped side up and turn by hand to allow
the sandpaper to cut the required recess.
A second way is to make a two-inchdiameter,
1⁄4 plywood disk with a 1⁄16-inchdiameter-
music-wire arbor epoxied through
the center. Place the sandpaper disk over the
arbor and glue it to the 1⁄4 plywood disk.
Place this assembly in an electric drill as
shown, and rotate it at slow speed. Hold the
wheel by hand and guide it over the arbor to
allow the sandpaper to form the recess.
Apply light pressure and periodically lift the
wheel blank to blow away the foam dust that
accumulates.
8) The wheel’s hub area must be
Place the foam blank over the fixture pin with the taped side up. Slide the movable part
of the fixture into its final position, allowing the blade to start its cut into the blank. Turn
the blank through 360° to complete the cut.
One method to make wheel recesses is with a sandpaper-covered plywood disk secured
over a 1⁄16-diameter pin on a 1⁄4 plywood base. Place the blank over the pin with masking
tape up, and slowly turn by hand until the recess is completed.
An alternate way to make wheel recesses is to make a 2-inch-diameter plywood disk
with a 1⁄16-inch-music-wire arbor epoxied through the center. The smaller disk is 1⁄16 thick
plywood covered with 100-grit sandpaper.
January 2003 53
reinforced to support the model’s weight
and landing stresses. This can be in the form
of spokes or plywood disks glued into the
wheel recesses. My smaller 13⁄8-inchdiameter
wheels used three 1⁄32 balsa spokes;
these were 0.110 inch wide and made to a
length that provided a snug fit between the
wheel-recess diameter and 1⁄16-inch center
pin. Make sure all three spokes are exactly
the same length so the wheel will run true.
Strengthen the end grain of each spoke,
where it will contact the hub, with
cyanoacrylate glue (CyA); you can do this
easily by placing a drop of CyA on plastic
from a poly bag then dipping the spoke end
into the CyA using tweezers or the tip of a
hobby knife.
Larger wheels for heavier models will
require 1⁄64 plywood disks to reinforce the
hub area; make these with concentricity
between the outer diameter and inner hole.
9) Place the wheel over the cuttingfixture-
board pin. Radial lines spaced 120°
apart on the fixture help guide the spokes’
placement. Glue the spokes or plywood disk
into the wheel recess. I used aliphatic resin
glue for the spokes and epoxy for the
plywood. Do not use CyA unless it is foamcompatible.
Allow the glue to set fully
before proceeding.
10) Remove the reinforcing tape from
the wheel and recess the other side.
11) Glue the spokes or plywood into the
second-side recess using the fixture pin to
assure that the hub will be perpendicular to
the wheel.
12) You may round the wheel tread for a
more realistic look. The 2-inch-diameter
plywood disk that was used in an electric
drill can be used to turn the wheel while
shaping. Place the disk in the drill with the
sandpaper recessing disk toward the drill
chuck. Apply a light coat of spray adhesive,
and allow it to dry to a very light tack. Place
the wheel over the mandrel and against the
disk. Use 100-grit sandpaper to rough-shape
the wheel tread; use finer-grit paper for the
final finish. Reverse the wheel on the
mandrel and shape the other side.
13) You can make the hub bearing from
aluminum or plastic tubing; my smaller
wheels used 1⁄16-inch-outside-diameter
tubing, and the larger ones used 3⁄32 inch.
Cut these to length, insert in the wheel, and
epoxy in place, making good contact with
the spokes or plywood disk.
At this stage the wheel is serviceable,
and you may attach it to the model. The
subsequent steps enhance appearance and
durability with the consequence of
additional weight. The accompanying table
indicates the weight penalty of various
enhancements.
14) You can coat the wheel tread with
aliphatic resin (carpenter’s wood glue)
diluted with water to a brushing
consistency; this will provide additional
resistance to wear if the wheel is operated
on rough surfaces.
15) If you want a colored wheel, use
water-based paints. I used paints from
children’s paint sets, but you can use any
Place the wheel with one side recessed over the cutting fixture pin. Spoke locations are
guided by 120° spaced lines on the fixture base. Glue in place with wood glue or epoxy.
Apply spokes similarly to the opposite side after recessing.
You may round wheel tread (before installing hub bearing) by placing over 1⁄16 mandrel
in disk used to recess wheel. Place sandpaper disk toward drill chuck and use light
spray adhesive with slight tack on disk face. Use 100-grit paper to rough-shape and
finer grits to finish. Reverse to round other side.
Epoxy the plastic or aluminum hub bearing to the spokes on both sides.
54 M ODEL AVIATION
paint that will not attack the foam. If you are
concerned about weight, stay away from
heavily pigmented paints.
16) You can dress the wheels neatly by
covering the recessed spokes with colored
paper, as shown.
Try these wheels and benefit from
considerably reduced weight compared with
commonly available wheels made from
other materials. These also have a better
scale look than many of the “lightweight”
wheels available. MA
Roger Carignan
39 Glen Rd.
Wilmington MA 01887
[email protected]
