deburr the axles.
graphite the living shit out of the wheel/axle interface.
weight distribution depends on track design, short hill, long straightaway, or long hill, short straightaway?
what we discovered:
weight in the front will take an early lead off the hill, weight in the back and the car "catches up" on the straightaway.
The mom of 1 of our cubs had a digital scale, and we declared that scale to be the "official" scale.
She'd bring it to the weekly meetings leading up to the race.
Day of race, I'd bring tools to sand/drill fat cars, and extra weight for thin cars.
The cubs (and moms/dads) had up to an hour (which is how long it took me to set up the track) to tweak on race day.
I built our track.
The starting gate was 4 steel pins (1/2" diameter) sticking up out of the track at the top.
When you pressed the START button, solenoids would snap the pins below the track surface.
That also started the digital timer.
The finish line was four sensors above the track; a car moving through would stop the timer.
To remove any "lane advantage", every car raced in every lane, with all times added together.
Shortest total time was winner.
The Cubs raced, and we had seperate "class" for family members who also built cars.
The dads loved that shit, but we also had sisters and moms who had their own cars to race.
It was a 6-hour event, with lots of food, rediculous amounts of laughter, and some really fun car designs.
I still have most of our family's cars; I'll get a pic or 2 and post them up.
