On this page are design tips and links
to assist you in building your Grand Prix car. Some of the links refer
to Pinewood Derby cars. The two events are similar in nature and design
tips for one apply to the other.
The following design tips are used with
permission from "The
Ultimate Pinewood Derby Site", by Randy
Worcester and may not be reproduced without his permission.
- Have your son draw a design on paper
then cut it out and use it as a template. I use the paper with the
little squares on it to make it easier for him. Draw a side and top
view on the paper by tracing around the block of wood.
- Keep the car a full seven inches. It
has to do with the physics of velocity and length of travel of the
weights.
- Use the full 2 3/4 inches (outside wheel
to outside wheel) that the rules give you. This will allow the wheels
to travel farther before hitting the center strip.
- Leave a lot of wood in the back to put
in the weights.
- Use the groove closest to the end of
the block of wood as the rear axle. Trust me, it helps. If you are
interested in discussing the physics, please e-mail me.
- Do not make the front of the car pointed.
It is hard to set up against the starting dowels.
- Be aware of how sensitive your electronic
timers are. You want the car to set them off at the end of the race
and not before.
- Use your imagination. Be creative. Shape
has the least to do with winning. A beaver driving a log or even a
pickup truck is more interesting than a wedge and will be just as
fast. The aerodynamics of a small block of wood doesn't mean much
in thirty feet.
- Debur the wheels. Take off the flashing
and seam that was produced when the wheel was molded with a 600 grit
or better sandpaper. Inside as well as out. Sand any bumps off the
wheel the sandpaper. Metal polish will restore the gloss. Be careful
not to break any rules your race has regarding wheel modification.
Don't sand too much or you'll create a flat spot. Sand by hand not
in the drill. Heat from the high speed of a drill will damage the
plastic wheel.
- Polish the axles. First with a 400 grit
if you have a really bad spot. Then a 600 grit, and then a jewelers
rouge. Finish off with a chrome/metal polish.
- Have only three wheels touching the
track. Raise a front one slightly. There is less friction with 3 wheels
rolling than 4.
- The head of the axle should be tapered
about 15 degrees so it rubs against the wheel less.
- Wax the wheels with furniture polish.
Make sure the polish does not contain a solvent of any sort.
- Use graphite only on the wheels and
axles. Oil damages the paint and collects dust.
- Break in the wheels by spinning them
with lots of graphite.
- Put a small drop of white glue where
the axle goes into the car body and put powdered graphite on it there.
That causes less friction if the wheel should rub against the car
body.
- Put the axle in at a downward (5-10
degrees) angle. This provides two benefits. The first is the only
the inside edge of the wheel is in contact with the track. This seems
to make the car go straighter with less wobble. The second benefit
is that the wheel rides to the outside of the axle and doesn't come
in contact with the body.
- Axles must be in straight front to back.
That is square to the body. True the axles, don't trust the slots!
If you have one, use a drill press to ensure all axles are straight.
One of the front and two of the back should be measured to be the
same height.
- After pressing in the axles, test the
car for crooked wheels...roll it on the floor. If the wheels are on
straight, the car should roll 8-10 feet in a fairly straight line.
Should the car turn left or right, you need to tinker with the axle
placement without removing them from the car body, until it rolls
straight.
- Do not put the axles in at the top of
the groove. Put them in at the middle. This lifts the car of the track
a bit more and reduces the chance of rubbing on the center strip.
- Glue the axles in place. Nothing is
worse than having the wheel fall off as you cross the finish line.
- Once you match a wheel and axle together
with graphite, keep them together. They wear into each other as a
matched set.
- Get the weight as close to the 5 ounce
limit as possible. Add the last little bit of weight with lead tape
from the golf shop. This can be trimmed with scissors at the last
minute. Remember, the official scale may not weigh the same as yours.
- Everyone has an opinion on where to
put the weight. My belief is that the weight needs to be predominantly
in the rear so that gravity can act upon the weight further up the
incline and for a longer period of time A car with more weight to
the rear generally grabs more speed down the slope. Many suggest having
the center of gravity at 1 to 11/2 inches in front of the rear wheels.
But be careful not to put too much in the rear or you'll pop a wheelie.
- What kind of weight? I think the melted
lead is dangerous and unnecessary. Tubular weights can be sunk in
the sides; flat weights, like those sold at hobby & council stores
can be attached to the car bottom if it is carved in a bit. Incremental
weights ( with pre-marked grooves) are easier to snap off into the
size you need. Some folks just use BB's, nuts & bolts, etc., but
these must be glued so that they can not move. No movable weights
or mercury are allowed.
- We use the round weights found at the
hobby shops and craft stores. This allows us to stick the weights
out the back of the car. We paint them and tell everyone that they
are jet engines or tail pipes. What they really do is allow us to
get the weights as far back as possible.
- Keep the weight low on the car and in
the center (Left/Right of the car). Put the weight just in front or
behind the rear wheels for less wheel chatter.
Does
weight effect the speed of a Pinewood Derby car? (1998 - 1999 School
Year Science Fair)
Does
the location of weight effect the speed of a pinewood derby car?
(1999 - 2000 School Year Science Fair)
Pinewood
Derby Car Design
If you have any other tips you'd like to
share, send them to "Commander
Bill" and we'll share add them to this page.
