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Scaling Up Part 2: Design a Pinewood Derby Car from a Toy Car

In the first part of this article ("Scaling Up: Design a Pinewood Derby Car
from a Toy Car", Volume 6, Issue 12 - March 7, 2007), the various
aspects and considerations of a scaling up from a toy car were
considered. These considerations included scale factor, fenders,
wheelbase, etc. If you haven't read this article, you can find it Here

In today's article, we will go through the process of scaling up a toy car,
including photos and comments on each step of the process. In
general, this process can be adapted for any toy car.

CAR SELECTION

The first step is to select a car to build. In picking the car, certainly
consider ease of building, as well as aesthetics. After scrounging
through my son's collection of cars, I chose a recent model VW Beetle
(see Figure 1). Ever since I drove a 'Bug' in high school, I have always
thought it would be fun to own one; at least now I will have a pinewood
derby version!


Figure 1 - VW Beetle Toy Car

Although the final result will not likely be a speed demon, it will be
'cute', and will adequately demonstrate the scaling process. But more
to the point, it is a design that I have confidence that I can build without
pulling (the rest of) my hair out!

SCALE FACTOR, ETC.

To calculate the scale factor, first measure the length of the toy (2.46
inches) and divide this number into 7 inches, resulting in a factor of
2.85. Multiplying this factor by the height (0.85 inch) results in 2.4
inches. This is rather tall for a pinewood derby car, but will still
meet the height limits and can be achieved by gluing two blocks
together.

The width of the toy car measures 1.29 inches. Scaling this up results
in a width of 3.26 inches. Obviously, this is too wide, so we will stick
with the basic body width of 1.75 inches plus 0.375 inches of fender on
each side (overall width of 2.5 inches). The resulting car will appear
slightly narrow, but that's the breaks.

To maintain the look of the car, let's directly scale the wheelbase. This
will result in a wheelbase that is longer than a standard BSA wheelbase,
so the car might not be legal in all races. If desired, the wheelbase
can be adjusted to match the BSA wheelbase (or any wheelbase), but
for this exercise I prefer to keep the look of the car as close as possible
to the model. Axle locations: Toy - 0.39 inch, Model - 1.1 inches from
ends of the block

TEMPLATE

Now that we have crunched the numbers, I'll share a simple method to
create a properly scaled template for the side of the car. First, take a
digital photo of a side of the car. This photo must capture the side of the
car as dead-on as possible; if the photo is skewed left, right, up, or
down, the template will be skewed in a similar fashion. I recommend
using a tripod, and then taking several photos at slightly different
positions until you get a perfect side-on shot.

Next, bring the photo into a photo editing program. Crop the photo tight
against the two ends and the bottom of the car. Then scale the photo to
7 inches long, allowing the height to adjust proportionally. Print out the
photo onto a piece of card stock, cut out the outline, and voila, you have
a perfect template (see Figure 2).


Figure 2 - Template of Side View

BUILDING

As mentioned, the model car will require two standard blocks glued
together to achieve the height, and two 3/8 inch pieces of wood, glued on
either side of the car to accommodate the fenders and achieve the
overall width. With that much wood, the weight of the car will likely
exceed 5 ounces. So, I picked two of the lightest blocks I could find.
Still, much wood weight will need to be removed; I'll show you an easy
way to do this.

First, glue the two blocks together, aligning the sides and ends as
closely as possible. Make sure to clamp the blocks firmly, and allow the
glue to completely dry. Then sand the sides of the blocks flat,
eliminating any 'bump' at the glue joint.

Next use the template to mark the axle drilling locations and trace the
outline. The outline will not be used for cutting out the car, but will
instead be used to help mark an area of the block for removing excess
wood weight. In Figure 3, the area marked with the 'X' will be cut out.
When marking this area, make sure to leave sufficient material to glue
on the sides of the car, and leave the area around the fender wells intact.
I also marked two spots on the bottom of the car for weight holes.


Figure 3 - Marked Block

Now it is time for the first machining steps. Drill the axle holes (#44 bit
for BSA axles, 3/32 inch bit for Awana axles). I drilled the axle holes 1/8
inch off the bottom of the block, all four wheels on the ground. Then drill
the two weight holes with a 25/64 inch bit (or similar - to accommodate
lead wire). Next, cut out the center area. Figure 4 shows the result of
these steps.


Figure 4 - Machined Block

Now we shift to the side pieces. I recommend using Basswood. This
wood is clean-grained, softer then pine (simplifies shaping), and is
readily available in various shapes at most hobby or craft stores.(1) I
used a piece measuring 24 x 3 x 3/8 inches. Trace the template and
mark the axle locations, then flip the template over and repeat (in other
words, create a mirror image for the other side of the car). Make sure to
leave material below the car outline to simplify creating the wheel wells
(see Figure 5).


Figure 5 - Marked Sides (right side of photo is cropped off)

Now we will use an appropriate-sized Forstner bit (the diameter is
calculated from the toy).(2) Make sure to place the side piece on a scrap
board as you drill, or the wood will 'chip out' as the bit exits the wood.
Then cut off the excess wood from the bottom of the side pieces (see
Figure 6).


Figure 6 - Machined Sides

Now it is time to glue the side pieces onto the main body. I used two
scrap BSA wheels and axles to make sure the fender wells lined up with
the axle holes. Again clamp firmly, and allow the wood to dry before
continuing (see Figure 7).


Figure 7 - Sides Glued to Body

Okay, let's cut out the profile and sand it to a reasonable level of
smoothness (this isn't the final sanding). Now we have the basic VW
Beetle without any detail work.


Figure 8 - Cut and Sanded Body

At this point use the toy car to pencil in detail lines. I chose to highlight
the fender wells and the sides of the car, but you can do more detailing if
desired (see Figure 9).


Figure 9 - Detail Lines

Here is where my skill level starts to get weak. I know many of you are
very adept with a Dremel-type tool. Unfortunately, I flunked Dremel 101,
so I must stick with wood rasps and sandpaper for shaping. After an
hour of work, I ended up with the body shown in Figure 10. The body,
without wheels, axles, or weight comes in at 3.6 ounces.


Figure 10 - Shaped Body

With a paint job provided by a talented local painter, and the addition of
some window trim, the completed Beetle is shown in Figure 11.


Figure 11 - Completed Car

CONCLUSION

This was a fun project, which resulted in a nice show car. You can use
the same techniques to make a show car or a competitive car. Just
make sure to plan ahead and use the step by step process I have
outlined. If you do scale up a toy car, please send a photo and
description. I'll be glad to include it in a future edition of this newsletter.

(1) Available at Maximum Hobby - part number MW4308

(2) This is one mistake I made. I used a 1-1/4 inch bit, as I knew it
would allow BSA wheels to fit. However, this bit was not large enough to
accurately model the size of the wheel wells on the toy car. I should
have used a 1-1/2 inch (or larger) bit.

Read More at: Pinewood Derby Times Volume 7, Issue 11

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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