Friday, November 29, 2013

Wax Those Wheel Bores for Top Performance
By Randy Davis


If you peruse the various pinewood derby forums, you will know that
the adult racing leagues are highly competitive. These pinewood derby
car builders are always on the lookout for techniques to gain a few
milliseconds. The first article of this season discussed one of these
techniques, the use of fenders to improve the aerodynamics of the car.
Today we will look at another technique, waxing the wheel bores.

Polishing wheel bores is fairly common, and is accomplished using a
product such as Micro-Gloss(1), a very fine crystalline abrasive that
is designed to polish plastic and acrylic products. Waxing the bore
goes a step further by applying a plastic-safe wax (Pro-Bore Wax(2))
and then buffing it with a pipe cleaner. This wax fills in tiny
imperfections in the bore and results in a hard slick surface that is
better than the polished bore. To check this out, let's run an
experiment and see what happens.

EXPERIMENT SETUP
In order to isolate the benefit of waxing the bore, all other
variables need to be eliminated. Therefore, track testing would not be
a viable way to test as too many factors are at play. So instead, we
will use a weighted-wheel spin jig. The equipment used was previously
described in Volume 8, Issue 6 - Grooved Axles.

As a refresher, the apparatus consists of a machined steel ring which
is sized to fit snuggly over a machined BSA wheel. The ring weighs two
ounces, which is essentially the load on a rear wheel of a pinewood
derby car.


Figure 1 - Weighted Wheel Spin Jig

After sliding the ring over the lubricated wheel-axle assembly, the
axle is mounted onto the apparatus. A length of nylon line with a
weight on one end is wound around the ring (there is a small pin on
the ring not seen in Figure 1, to which the non-weighted, looped end
of the string is attached). On each test, the string is wound until
the weight touches the eye hook. The weight is then released and a
stopwatch is used to measure the spin time. The string is sized such
that it is released from the ring before the weight reaches the
ground.

Two wheels and two axles were used for each test. The reason for the
duplication is to ensure that performance is not exaggerated or
degraded due to a "fluke" wheel or axle. The wheels were machined
wheels and were from the same mold number.

The combinations tested were:

Max-V-Lube Graphite - No Wax
Max-V-Lube Graphite - Pro-Bore Wax
Krytox 100 - No Wax
Krytox 100 - Pro-Bore Wax

Each wheel/axle was lubricated in the same manner, and then given two
break-in spins. Next, five spin tests were performed for each wheel
(eight wheels total).

EXPERIMENT RESULTS
As you can see in Figure 2, the use of Pro-Bore Wax improved the
performance for both Krytox 100 and Max-V-Lube Graphite (a longer spin
time is better).


Figure 2 - Experiment Results

How does this data transfer to track time improvement? Certainly the
improvement in track time would be much smaller than shown above, as
many other factors come into play. However, with both lubes, using
Pro-Bore Wax should provide measurable differences on the track.

(1) Bore Polish (Micro Gloss) can be found Here.

(2) Pro-Bore Wax can be found Here.

From Pinewood Derby Times Volume 13, Issue 5

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