The biggest source of friction is the wheels scraping on the center guide. That is the key to everything. The reason the bent nails help is not just because they drift to the nail head for lower friction, but because it moves them away from the center guide and makes sure they don't touch. The front wheels must be closer to make sure they are the only ones that touch. The rail rider concept makes sure that only one wheel ever touches. I think it is better to have the raised wheel be the only one that touches because now it is a bearing not scraping at all, since it is not in contact with the track. Finally the weight in back is so that the wheels bearing most of the weight never are wider and never touch. Also, this gives maximum moment arm for the front to steer the car as easily as possible. It would be best to make the front as light as possible so it takes the least effort to steer the car. However there is a limit, as too light leads to bouncing around which takes the energy out fast. So you want the least amount of weight on the front guide wheels that still keeps the car stable. Everything comes back to how it rides the rail. Lastly the cutout in the nails under the wheel don't reduce friction as stated but it does serve a different purpose. All derby's have multiple runs to determine the winner. With each run some of the graphite is lost and wheel friction goes up. The gap in the axle serves as a reservoir for additional graphite to replace what is lost over time. But it must be filled for that to work. This is my final secret. In order to completely fill the reservoir with graphite use chemical deposition. Make a slurry of graphite and rubbing alcohol and pour it into the axles. When the alcohol evaporates it will leave large amounts of graphite deposited everywhere. Yes, my sons won every year, yes I am an engineer, and yes I made my own track and did lots of trials at home. You don't take an untested prototype to market now, do you…

I actually had to cut out my cars. We figured out that an hourglass shape was faster than a rectangular shape. We figured out that a lower car was faster. Cutting a new wheelbase was allowed as well, so almost everyone would flip their blocks over and cut a longer wheelbase. This reduced wiggling that slowed the cars.

Our troop also allowed something known as a cheater bar. Due to the way the cars were started, cheater bars gave the cars that used them a slight head start. You could duplicate some of this effect (but not to the same degree as if you actually used the bar) if you cut out the bottom of the nose of the car, resulting in an elevated nose.

Wonder what narrowing the wheels would do, it changing out the plastic wheels for steel wheels

No, you were disqualified for cheating. ????

My dad and I did this exact same thing in 1970!!!

Let's drop the use of Ghetto bro.

Hacksaw to cut the body?

That doesn't look like science looks like cheating

My father wasn’t a tool guy. I built mine by myself.

It’s not just dads, single moms build these things too. I don’t want to make the fastest car, just teach me how to build the darn thing ?

Graphite on the axle..

I was in the Scouts back in the mid 60’s and fondly remember the Pinewood Derby. That said I think all of this has just gone too far. The spirit of the Derby was to be a competition between the BOYS. NOT between the fathers. That said I would like to see them have one Saturday set aside as the Car Building Day. All scouts come to their meeting place on that day and all are provided with their blocks, axles and wheels and the same basic tools. The Scouts have X hours to complete their cars which are then stored by the Scoutmaster until completion day. And the biggest change? NO parents are allowed in the room to assist their scout. If I was a Scoutmaster I guarantee this us his I would run it.

I agree with shaving the wheels – the only issue with that is in alot of cases it is consider illegal to shave the wheels. Alot of venues only allow truing up or sanding the wheels

Oh snap I filmed an interview with Scott while I worked with Wyoming PBS. He's on the James Webb team!

I never even got to touch mine when I was a scout. When my oldest was in scouts he had final decisions and did everything but saw work. We never won a heat but we looked great doing it. His last year for derby the scout master had a Best of Show trophy just for my boy cause they always looked sweet af.

I cant believe so much effort goes into this. lol crazy

Science? What’s science?

What you didn’t mention, is there is always a kid who actually did build their car themselves or with minimal help, either because they don’t have someone in their life who can do it for them, or because getting Dad to do your work for you in a competition between kids isn’t a lesson the parent wants to teach. Those kids inevitably loose because of course the adults are better at it than the kids, and they go home feeling like sh*t…

where were you in 2010 when i was makin pinewood derby cars I MEAN MY SON WAS yeah

Back in the 70's, o
ur scout master was an engineer and we focused on 1, 2, 3, 4, and 6. Our troop did well.