I almost forgot my promise to give a report on the race! Things went very
well, and very bad. I carved a spot on the back for the cartridge to sit,
kind of like an el camino, but more aerodynamic. I taped the canister down
with packing tape (no, the cooling of the cartridge during discharge did not
freeze the adhesive). The trigger was the weak point in the design, and
where I failed. I taped the metal end of a pen on the back to guide a nail
that I hit with a hammer. It looked like a nosle on the end of the
cartridge. When I tested it, I taped the body of a pen to the bottom and
threaded it with a 40 ft. length of string to control the path (this worked
beautifully). First, the failure: When my heat started, I had a hard time
hitting the nail at the right angle to puncture the cartridge (yes, I tested
it, and the tests went fine, but the race was on a track that was elevated
at the start with a downward slope, and I tested it on the ground). While I
fumbled with the hammer, my opponents were already down the track. Yes, it
was very frustrating, because when I did finally hit it right, it took off
perfectly. It was by far the fastest car there. It stayed on the track
(which was a concern) and noone was harmed in the making of this email. I
am satisfied that I did have the winning car, even if it didn't win. Next
time, I think I'll use a roofing nail, which has a big flat head that will
be much easier to hit right. All things considered, this was very fun.
From brainstorming, to designing, to testing, and finally demonstrating,
this was a project I would encourage. Pinewood derby kit from the Boy
Scouts: $3 Package of 5 co2 cartridges from WalMart: $5 Tape, string,
cannibalized pen, and sandpaper: $almost nothing. The Ooo's and Ahhh's
from the crowd: Priceless.