Simple Wheel Preparation
Most of these techniques will apply to even the most-restrictive "wheel
rules." All of those which I've read allow at least smoothing the outside
diameter of the wheels to remove mold flash and irregularities. The rest
covers similar cleanup to the axle hole and should be allowable, but
please check your wheel rules to be sure.
All of the steps below are things that you can do with your son.
I wouldn't trust 8-to-10-year-olds with power tools unsupervised, but
this is a good opportunity for a little cooperative work and training.
Also note the safety goggles. Please protect your eyes and get
him in the habit of wearing protective eyewear whenever using power
tools!
Tools and materials you'll need:
-
Safety goggles for both you and your son
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A variable-speed electric drill (A drill press is even better)
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A bench vise or stand for the drill
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A wheel-turning mandrel (available from
the Scout Shop or from your local hobby
shop)
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A small block of hardwood, about 1/2" x 1" x 2"
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220-grit aluminum oxide (dry) sandpaper
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400-grit and 1500-grit wet/dry sandpaper
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Powdered Pumice (from the hardware store)
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Polishing compound (I prefer "Maas Polishing Creme" from
Maas International
P.O. Box 128
La Grange, IL 60525-0128)
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A couple of soft cotton rags
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A dish or margarine tub to hold water
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A 3/16" drill bit
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Pipe cleaners (the big fuzzy "craft" kind, not the
skinny ones you'd use on a real pipe)
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A pair of pliers (needle nose are preferred)
Steps in preparing the outside diameter of the wheels:
-
Clamp the drill in the vise, attach the wheel to
the mandrel with the supplied screw and chuck it
in the drill.
-
Tear off a piece of the 220-grit sandpaper to fit
around the wood block. Running the drill at low
speed, carefully sand the tread area of the wheel
just enough to take off the mold "flash" at the
outside edge of the tread and smooth the tread
area down to take out the "dimple" which is
typically where the wheel was cut off the "sprue"
or mold tree. Also sand the inside edge of the
tread just enough to remove the mold flash which
is usually there, as well. Use light pressure and
keep the sandpaper moving to avoid building up
heat and scuffing or melting the surface of the
wheel!
-
Using first the 400-grit and then the 1500-grit
wet/dry sandpaper, wet, further smooth
the tread (both the main flat surface and the
inside edge) to remove the scratches left by the
relatively coarse 220-grit sandpaper. As you
use finer and finer abrasives, you can speed the
drill up, especially with the wet/dry sandpaper
and the pumice, since the water will keep the
wheel cooler. Don't forget the inside edge of
the tread!
-
Tear off a small piece of the rag, wet it, and dip
it in the pumice. Polish the wheel with the
pumice to get it ready for final polishing.
-
Using another piece of the rag and the polishing
compound, bring the tread area to a near mirror
finish. Remember to polish the inside edge of
the tread, as well, since it will rub against
the guide rail on the track. This final polish
can be done at a relatively high speed if you
are careful not to press too hard.
Steps in preparing the axle holes of the wheels:
-
Holding the wheel in one hand, and the 3/16"
drill bit (or countersink bit) in the other,
carefully clean up the mold flash at
both ends of the axle hole. You don't want
more than 1/16" of countersink depth, just
enough so there is no ragged flash to run
against the axle and cause drag.
-
Take a 3" length of the pipe cleaner and
bend it back on itself. Using the pliers,
crimp the wire center of the pipe cleaner
so it is tightly folded. Chuck the cut
ends of the pipe cleaner in the electric
drill so the folded end is sticking straight
out.
-
Put some polishing compound on the pipe
cleaner and press the wheel over the
pipe cleaner with the electric drill
turning slowly.
-
Polish the inside of the axle hole by
running the pipe cleaner with the drill
and moving the wheel back and forth so the
polishing compound is spread over the pipe
cleaner and buffs the inside of the hole.
You are after an absolute mirror finish
here, since the surface finish will determine
how much drag there is between wheel and
axle.
A few more things to do for the finishing touches:
-
Take a small piece of 400 grit wet/dry and
lay it face up on your work surface. Add
a few drops of water and hold a wheel with
the inside hub facing down. Move the wheel
in a circular orbit, rocking it around the
axis of the axle hole until all of the flash
and rough edges are gone from the hub.
-
Repeat this process with the 1500 grit to further
smooth the hub. You should end up with a just
barely noticeable "crown" to the hub (higher in
the center, lower on the edges) which reduces
the surface area in contact with the car body and
further reduces friction.
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