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Introducing the Newest and
Most Advanced Weighting Technique available
The New Tungsten Slotted Disc
Taking the GuessWork out of
Placing Your Weights
To give you an idea of why the slotted
disc was designed, take a look at the bottom of our
Pinewood Derby National Championship Car "Zero Gravity"
below. As you can see, the tungsten disc is placed
very near the rear of the car, forcing us to cut down
the axle length on each side to avoid the solid disc.
With the slotted disc, you have an open
space in the back to allow for axle holes to be cut into
the space. Each slotted disc comes with one 1/4"
tungsten spacer (0.4 ounces) and a 1/4"
piece of wood that you can glue into the slot prior to
drilling your axle holes as shown below. (We
glued the spacer into the slot and sanded the ends flush
with the disc in less than two minutes total time.)
That way, you can use the axles at their
normal length and still place the tungsten disc towards
the rear of the car for optimum COM which is needed for
dominating speed. A picture of a block with a
slotted disc and wood spacer is shown below. In
this case, you would simply cut the disc hole first,
glue the wood spacer into the slotted disc, sand the
ends to be flush with the disc and then glue the disc
into the block. Align the wood spacer in line with
the axle line and you are ready to drill your axle
holes. In this case, we drilled two 13/32" weight
holes in the corners of the rear of the car to optimize
our final weight and COM. As you can see, the axle
holes are right in line with the slot.
If you want to go a bit further with your
weighting, the disc package also has a tungsten spacer
that fits into the slot for added weight and lower
moment of inertia (better stability).
To help with implementing the slotted
disc, here is a series of pictures and discussion of
measurements for an extended wheel base pinewood derby
car with a 3.5 oz. slotted disc with the tungsten spacer
included instead of the wood spacer. (One can
easily translate these measurements to a standard wheel
base car) For the initial lines, draw one line
down the center of the block 7/8" from each side and
draw lines on each side of the center line 3/8" from the
sides to mark the outer edges of the disc. Draw
your axle line, in this case, the rear axles are 5/8"
from the rear of the block. Draw another line just
over 3/8" from the rear of the car to denote the rear
edge of the slotted disc. This line should be just
under 1/4" from the axle line.
Then place your disc on the car body and
line the rear and the side edges of the disc with the
three lines that you have drawn. The middle of the
slot should be in line with the axle line. If not,
then move the disc such that the center of the slot is
in line with the axle line and remark the line for the
rear edge of the disc. Then draw another line
intersecting your center line 1/2" from the line for the
rear of the disc. This intersection is the center
of the spot where you will drill your 1" hole for the
slotted disc.
The additional weight holes for the
tungsten cylinders in this case are each 5/16" from the
rear of the car body and 5/16" from the side of the car
body. We use a 13/32" perfect point drill bit for
precise drilling of these additional weight holes and
use the 1/8 and 1/4 oz. tungsten cylinders for optimum
COM placement.
The body with the slotted disc and
tungsten spacer will look similar to this when finished.
Alas, if you are going to use the tungsten spacer, then
you may have to clip off the very tips of your axles.
If necessary, use a pair of heavy duty wire cutters and
just clip the tips. In this case, we would clip
about 1/16" or so off the tip of the axles. (One
could easily file off such a small amount as well.)
One can also use some lead tape or just drill additional
holes in front of the slotted disc to go with a less
aggressive COM if so desired. The real benefit of
the slotted disc is its flexibility.
Note: We have shown the slotted disc pictured with
vertical cylinder holes for the 1/4 and 1/8 oz. cylinder
weights to customize your options. The slotted
disc provides other options as well. You can take out
the tungsten spacer and place 3/16" cubes or other
smaller weights in the slot such as tungsten putty,
lead, etc. You can use the slotted disc as a normal disc
also without aligning it with the axle lines if you want
to cut a weight hole across the car body and behind the
axle line similar to how we cut some of our pre-cut
cars. That way, you have even greater options to
get the desired COM. You can even turn the disc
around such that the slot is in the front for more
aggressive COM or even angle the slot for off-center
weighting in a three wheel setup.
Two Different Sized Slotted Discs Give
You
Ultimate Flexibility in Weight and COM Placement
With the 3.4 oz. disc, you can use the disc with the
tungsten spacer for a 3.4 oz. disc or without for a 3.0
oz. disc. With the 3.1 oz. disc, you can use the
disc with the tungsten spacer for a 3.1 oz. disc or
without for a 2.7 oz. disc. One can even go a
little crazy and use the discs without the spacer and
place 3/16" cubes in the slot for even smaller
incremental weighting. So, with two discs, you can
add anywhere from 2.7 ounces to 3.4 ounces of weight not
counting your supplemental weights with the smaller 1/8
and 1/4 oz. cylinders or cubes. Incredible
flexibility and you still retain the optimum COM
placement and low moment of inertia for maximum
stability. The absolute best of both worlds. |
