A good night for the Dunn boys at the track.
3/19 - 3/20/2005
It's been derby week for scouts Nick and Mike.
We spent the previous weekend cutting, sanding, drilling and painting
the cars for the Cub Scouts Pack 633 Pinewood Derby. Both cars
were cut the same on the table saw, then with some time using a coarse
grit paper in the belt sander the two different shapes were formed.
Nicks got an additional cutout in the middle removing as much weight as
possible so we could add it back with lead on the rear of the car.
This was followed by drilling 3/8" holes in the body and gluing in slugs
of tungsten (heavier than lead) to get the cars as close as possible to
the allowed 5.0 ounces of weight.
Nick's car received 5 coats of metallic purple paint
from a balky spray can, while Mike's was wrapped in a flame 'skin' that
is applied like a decal using a sponge. Once that was done it
received a overcoat of clear poly.
Then we added the details, Mike's blacked out canopy,
and Nick's jet engines made of lead spray painted with copper paint.
Finally the finishing rub on decals were applied.
Tonight is the weigh in and tech inspection.
We spent the dinner hour de-burring and polishing the nail axles, and
drilling the rim area of the wheels (a feature of last years winning
car) and sanding their surfaces smooth. This takes
quite a while as we had to drill 6 holes in all eight wheels. Then
we mounted the wheels, lubed with graphite, and were off to the
On arriving we were informed that this year drilled
wheels would not be allowed. No one had informed anyone of this
rule before hand, but we were now faced with replacing all 8 wheels on
the two cars. We found 4 additional spare wheels, and pulled 4
more old wheels of the spare 'play' cars the pack has. Dawn rushed
to the gym with the sandpaper and drill so we could do our best to prep
Finally we have them all on, but the nails went in too
easy the second time. Of course, now Nick's car is overweight.
After some additional drilling on the bottom and trimming of the lead
'jet' engines we finally got the scale to display '5.0'. Mikes is
light, at only 4.8 ounces. We added some weight with double stick
tape to get to 4.9 and will just hope it holds. His canopy also
popped loose so we had to re-glue and trust that it's dry and ready on
Thursday as the car is now wrapped and stored in the quarantine box.
Derby night is here. Dawn is in charge
as I'm off doing Maundy Thursday services. She is the quarantine
parent who has to keep 37 kids hands off their cars until the
competition races are done. The racing is done by age group (Den)
starting with the first graders in Mike's Tiger Cubs den.
small group of only 3 kids and Mike's car wins every race by a
substantial margin. It's back to the quarantine area for his car
as the champion of his age group.
Nick races later in the 4th grade Weblos 1 den. This is a group of 10 kids and through the course of many runs Nick is
the champion of that den. So far the Dunn boys are doing good.
Once all 5 dens are done and have a champion it's time
for the finals to determine the winner. Dawn re-lubed the axles as
allowed under the rules, but didn't check the tightness of what were
already axels that had been removed once before.
In the first race it's Mike vs. Nick (the track only
has 4 lanes and there are 5 cars so they had to run various elimination
runs). Nicks car now has a shimmy as it goes down the track due to
slightly loose front wheels. Mike wins by the narrowest of
Nick continues to race, finally loosing twice and
finishing in third place over all.
Mike races all the others as well, and finishes the
night as the Grand Champion of the pack 633 - 2005 Pinewood Derby.
His car never lost a race the entire evening. There are no "x's"
on his number 63 sticker.
All 5 den champions get a trophy and Mike has the
bragging rights for the next year.
Now that we are past cub scouts I can reveal the secret to these cars
Based on my observations during our first derby I came
up with a theory of how to get just enough of an edge to win races.
Using the table saw I cut a 1/2" deep 1" wide channel down the center of
the bottom of each car. This is entirely within the rules as the
front is still a straight surface without any indents. As the
starting pin the car sets against is rolled forward flush to the track
to start the race a car with this groove releases just a fraction of a
second sooner than a car without it.
Looks like my theory worked out pretty good.