Jim wrote:
My son competed in his second Pinewood Derby a couple of weeks ago.
Last year he finished dead last. This year he finished 3rd from dead
last. I would like to ask for some diagnostic help from more
experienced Pinewood Derby racers. Last year and this year I read a
good bit of the material available on the Web and I thought we paid
attention to all of the important factors. Based on the behavior of
his car on the track in both years, I suspect that we had a weight
location problem.

Last year his car would begin down the track with the other cars in a
tight group or even a bit ahead. As the car hit the straight away it
would slow down significantly as the other cars shot away. Each Scout
runs 4 races (1 on each track) and every race was the same. The
outcome was the same this year, except that 2 other cars happened to be
a bit slower.

Does this sound like an issue of weight placement? Is this what the
car would do if there was too much weight towards the back of the car?

The material on the Web seems to be contradictory. The average advice
seems to be to place as much of the weight as possible towards the
back. One web site qualified this by saying that you should not put
the additional weight any further back than the rear axle. The Pack
information recommended weight centered around 1/2" to 1 " towards the
rear from the midpoint between the axles. Another web site recommended
the weight be centered 1/2 to 2/3 back towards the rear axle.

Last year I had read some old advice that was apparently applicable to
the old S tracks and we had placed a lot of weight in the back. This
year we tried to avoid that. We used a 2 oz bar weight countersunk
between the axles. We also drilled holes on each side about 1/2 inch
forward of the rear axle to add more weight. Since we were still
short, we drilled 3 holes in the back and added more weight there. We
ended up weighing in at 141.74 grams. I am afraid that the extra
weight in the back tipped the center of gravity too far back, but I
just do not know for sure.

We would appreciate any help or advice.


I am puzzled also about weight placement. I have 2 sons who were in
the derby race yesterday. This year we put the cg about 1 inch forward
of rear axle. Last year 1 inch aft of front axle. No difference in
number of races won or speed noticable between years. This year we
polished the axles on one and not the other and treated the wheels the
same yet on the heat where they raced against each other they tied,
twice since the first time they could not tell a winner but on the
second race the third car won. One car won 4 out of 9 and the other
(with polished axles I might add) won 1 out of 9 races. I tend to
think it is pure luck but there are 3 families whose kids always place
in the top 5 or 6 out of 35 or so every year. They claim they do not
do anything excessive except make sure the car runs straight. We are
friends so I believe them.

Thanks.

Jim