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Pinewood Derby Myths

(An imaginary conversation between two Cub Scouts a month before the
pack pinewood derby race).

Johnny: What ya' got in that baggie in your pocket?

David: These are my pinewood derby wheels. I'm "marinating" them in
graphite so they will go faster.

Johnny: That's silly! What you really want are grooved axles. They
reduce friction.

David: No they don't! But you can reduce friction with a raised wheel.

Johnny. I don't think that reduces friction, but I think if you angle the
axles so that the wheels run on one edge, you'll reduce friction and go

David: Hah, where did you hear that one? On Car Talk? Really, I think
the main thing is "aerodynamism". You know, like race cars.

Johnny: You mean "aerodynamics". But that doesn't do anything at
slow speeds. But we do have a super secret lube we are going to use
this year that will let us win the council race.

David: Oh really! There's no such thing -- you know that "Lemon
Pledge" isn't the silver bullet don't ya'?

Johnny: It's not Lemon Pledge, trust me. But we're also going to put
the weight in the front of the car so that it gets moving faster.

David: That won't help. Lightweight wheels are what you need to get the
car going faster. Besides, my dad is a science teacher, and he says
that weight doesn't matter because of some guy named Newton.

Johnny: Well my dad's an engineer, and he says that weight does
matter. We'll just see whose dad knows more after "I" win the race.

David: You mean after "I" win the race!

Well, that conversation was a bit confusing, wasn't it? Although the
boys seemed confident of their "speed tips", in my mind I now have more
questions than I started with. For example:

- Which of the boy's statements are true, or are they simply a myth?
- Is Johnny or David's dad smarter?
- Who will win the race?

I can't answer the last two questions, but I can certainly take a crack at
whether any of Johnny or David's statements are fact or fiction. Over the
past several years, I have run across quite a few pinewood derby myths,
and have experimentally confirmed or busted many of them. So in
today's article, we will review the main pinewood derby myths and label
them as confirmed, plausible, or busted.

Graphite reduces friction when applied to the wheel to axle contact
surfaces (wheel bore, inner hub and outer hub). There is also a slight
benefit to coating the inner edge and tread surface of the wheel with
graphite -- see Volume 8, Issue 2 - October 15, 2008 at
Obviously, there is no benefit to coating the non-contact surfaces such
as the inner and outer walls of the wheel.

So, the question is whether immersing the wheels in a bag of graphite is
more or less effective than purposefully placing the graphite on the
contact surfaces. In my testing I have found that graphite is most
effective when it is worked into the contact surfaces by repeated
spinning (or similar). Just placing graphite on the contact surfaces is not
sufficient; the graphite must be worked into each surface.

So, simply placing the wheels in a bag of graphite (even if the bag is
massaged around the wheel) is a less effective technique than
purposeful application of graphite.

BUSTED - One point to Johnny

In Volume 8, Issue 6 - December 10, 2008 at
we discussed grooved axles at length. From that discussion we learned
that grooves do not reduce friction (the friction is just relocated).
However, we did find that grooves can be of benefit in specific situations.

Figure 1 - Grooved/Non-Grooved Experimental Results

When running on BSA-type nail axles, grooves were of benefit with both
graphite and liquid lubes. But when running with oversized axles, the
advantage/disadvantage of grooves was indeterminate.

PLAUSIBLE - One point to David for knowing that grooved axles
don't reduce friction. One point to Johnny for knowing that grooved axles
can be of benefit

Contrary to David's statement, raising a wheel does not reduce friction
(the frictional forces are just increased on the other three wheels).
However, there are other benefits to a raised wheel including a reduction
in wheel inertia.

In Volume 4, Issue 14 - April 6, 2005(1) a raised wheel experiment was
conducted which showed a significant benefit to racing with a raised front
wheel (see Figure 2).

Figure 2 - Effect of Raised Wheel on Performance

CONFIRMED - One point to David for knowing that it helps, one
point to Johnny for knowing that it does not reduce friction.

The term "canted" means an object set at an angle, thus "canted axles"
are axles which are attached to the car at an angle. Sometimes this is
done accidentally, but usually car builders cant axles in an attempt to
reduce the amount of contact between the wheel tread and the track.

In Volume 8, Issue 8 - January 7, 2009 at
a canted axle experiment was documented. The results show that up-
canting the rear axles on an aluminum track may provide a very slight
benefit. In Figure 3 the amount of change between the data points is
within the statistical variation of the heat times, so the data is

Figure 3 - Effect of Canted Axles

PLAUSIBLE - One point to Johnny

As it applies to pinewood derby cars, aerodynamics refers to the affect
of air flow on the movement of the car. Johnny is correct that the effect
of air flow on a vehicle does increase at higher speeds, and decrease at
lower speeds. But does the effect go away at pinewood derby speeds
(10 to 15 MPH average)?

In Volume 3, Issue 9 - January 21, 2004(1), an aerodynamics experiment
was documented. In this experiment, the frontal surface area of a car
was varied with a removable air dam. The results are shown in Figure 4.
As you can see, an increase in frontal surface area does reduce
performance for a pinewood derby car.

Figure 4 - Effect of Aerodynamics

CONFIRMED - One point for David

The use of an effective lubricant is critical to car performance, and there
are certainly a vast number of possible lubricants that can be used.
These include dry powders, liquids, and liquids that become dry to the

Over the years I have tested a large number of these lubes, including but
not limited to:

Graphite (at least fifteen blends)
Molybdenum Disulfide (several particle sizes)
Tungsten Disulfide
Boron Nitride
Powdered Teflon

Krytox 100
NyOil II
Several exotic oils, both synthetic and petroleum-based

Wet to Dry
Silicon Spray
Emery's Slide All
Several graphite suspensions
Several boron nitride suspensions
Spray and non-spray waxes, including Lemon Pledge

After all of these experimentation, I have found that a good quality
graphite (such as Max-V-Lube) or a good quality synthetic oil (such as
Krytox 100) gives the best performance.

So, is there a super secret lube? I can't absolutely confirm or bust this
myth, but I don't believe there is a secret lube. If there was, it would not
remain secret for very long, as it would be publicized on the Internet and
be available from pinewood derby stores such as ours. There are likely
other lubricants that rival the performance of Krytox 100 and Max-V-
Lube, but I don't believe there are lubes that are significantly better.

UNCONFIRMED - No points awarded

The location of the ballast weight on a pinewood derby car affects the
center of gravity (generally referred to as the "balance point"). The
optimal balance point varies from track to track, but that position is
somewhere between the center of the car and the rear axle location (1 to
1-1/4 inches in front of the rear axle location is a good rule of thumb for
most tracks).

In Volume 3, Issue 14 (March 31, 2004)(1) a weight experiment was
documented. In this experiment, the balance point was adjusted from
the front to the back of the car. The results are shown in Figure 5. As
you can see best performance was attained with a rearward balance

Figure 5 - Effect of Balance Point Location

BUSTED - One point for David

In recent years, lightweight speed wheels have become readily available.
These wheels are weight-reduced by removing excess plastic from the
interior of the wheel.

Reducing the weight of the wheel reduces wheel inertia - the tendency of
a wheel to not spin. So, lighter wheels should provide a faster start for a

In fact, this has been proven to be true. In Volume 7, Issue 3 (October
31, 2007) at
a wheel weight experiment was conducted. The results of the
experiment show that reducing the weight of the wheels (and adding that
weight to the car) does improve performance (see Figure 6).

Figure 6 - Effect of Wheel Weight on Performance

CONFIRMED - One point for David

While Sir Isaac Newton is credited with the "discovery" of gravity, it was
Galileo that showed that the mass of the object did not affect the
acceleration of the object due to gravity (true in a vacuum). However, on
a pinewood derby track there are other factors at work. Most pinewood
derby tracks today have a sloped section (where gravity accelerates the
car), and a flat section. On the flat section, the momentum of the car,
aerodynamics, and friction are among the factors that affect how fast the
car slows down. Momentum is based on speed and mass, the heavier
the mass, the greater the momentum. So, heavier cars tend to hold
their speed for a longer period of time, and thus tend to be faster.

In Volume 3, Issue 14 (March 31, 2004)(1) a car weight experiment was
conducted. The results of the experiment show that increased weight
improves the performance of the car (see Figure 7). A similar test with
weight beyond five ounces was documented in Volume 7, Issue 5
(November 28, 2007) at

Figure 7 - Weight versus Performance

CONFIRMED - One point for Johnny

Well the debate between Johnny and David ends in a five to five tie. But
now that you have the facts, you will be better armed for your next race
(or pinewood derby debate). Good luck, and may the best car win!

(1) These articles and others are available for immediate download at:

Read More at: Pinewood Derby Times Volume 8, Issue 12

A feature article is a regular part of the Pinewood Derby Times Newsletter. To subscribe to this free e-newsletter, please visit:

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