Pinewood Derby Time...

[Art Mulder]

As it turns out, the notch allowing the car to start out forward, in fact works against the racer and is not an advantage. The amount of energy available to be converted into speed is determined by the height that the car's center of gravity "falls". Starting out lower reduces this and results in a slower finish. Mgh=Mv^2. You cannot get more kinetic energy out than the potential energy you had to start with.

Science rules, David!

Note that on our track, the starting pins tip forward to start the race. So we've realized that a car with a notch + wire, or a car with an upward-sloping front end has an advantage in that it allow the car to get going just a fraction of a second quicker than a car with a flat front.

[Lee Schierer]

Science rules, David!

Note that on our track, the starting pins tip forward to start the race. So we've realized that a car with a notch + wire, or a car with an upward-sloping front end has an advantage in that it allow the car to get going just a fraction of a second quicker than a car with a flat front.

It also helps to keep the majority of the weight toward the rear of the car because it is slightly higher than the front at the start therefore there is slightly more potential energy to work with. However too much rear weight makes the car unstable and like to jump the track.

[David Epperson]

It also helps to keep the majority of the weight toward the rear of the car because it is slightly higher than the front at the start therefore there is slightly more potential energy to work with. However too much rear weight makes the car unstable and like to jump the track.

Yeah. There's a fine line - with the "Standard" wheelbase - of being too far back. We had one pack that skirted that issue by changing the wheel/axle locations, moving the axles to within 1/4" of the front and rear of the body. It made for a funny looking car, but allowed the weight to be shifted even farther to the rear and remain stable. My opinion was that it was outside of the spirit of the rules, but I wasn't in charge, so the design was allowed. Even though those cars no longer fit in the sizing box due to the wheels extending past the front and rear.

[Art Mulder]

... Even though those cars no longer fit in the sizing box due to the wheels extending past the front and rear.

Hmm, I would have been voicing my complaints if they'd tried that here. That is one of the reasons that all our cars have to be turned in the week before the competition. At that point they are weighed, and checked with the sizing box. If they pass, they're locked away until the race -- too many cars competing to do all that checking on race day. If they don't pass, that gives the dads a week to fix their mistakes (and we all know it is the dads who messed up! )

Sometimes rules need to be fine tuned. For instance... Kids are supposed to make a new car every year, but every now and then they let someone run a "repeat" car, due to family issues. This year we had a repeat car that won a design trophy -- for the second year in a row. Oops. The judges did not realize that this car was a repeat, and since it was such a rare occurrence no one had written a rule for this. Next year I bet this will be different!

[Art Mulder]

It’s race time again here in London, so time to resurrect this old thread and post some more photos…
NOTE: faces are blurred for privacy reasons -- well, except for my own family members


(I wrote a web page last year, with a lot more photos and details which you can see here: www.wordsnwood.com/2013/kubkars/)


Every year we have Pinewood Derby / cub car / Kubkar races in our church. And it is always a noisy, boisterous and fun evening. Both our boys club and girls club build cars, so there is a lot of fun "boys-vs-girls" rivalry going.


Our family produced five cars this year, pictured here. Only two were in the actual "competition". Three of them were in the leader/counsellor/adult category which is just run for fun and bragging rights after the real races — no trophies there.


From L-R we have a rocket/missile thing, flat green thing, seahorse, Minecraft Slenderman, and a Pink Marshmallow Peep



Yours truly with our two oldest sons against the side wall taking in the action.



Here are my two oldest son’s cars lined up and ready to race



My oldest was manning the track-end for a while. They have some foam to catch the cars as they leave the track. You can see one black car in mid-bounce. All eyes are on the end, though the electric eyes on the track are the ones that determine the winner:



Here is my wife’s car (on the left) out of the starting block.
They rebuilt the track launching system this year. Instead of a manual system where the pins tilt down out of the way, they now have an air-driven system. You can see the red air hoses at the bottom. The 3 track pins are now on a piston and drop down vertically into the track very quickly.



There were 69 kid’s running cars, and we run triple-elimination (you need to lose three times to be out), so there were a LOT of races!





See You Next Year!

[Rob Luter]

......As far as turning into "competition between the dad's" well... Good luck and remember it's the kid's thing.. not the adults.....

Good advice. When I was a kid I lived in suburban Detroit and we had a number of dads in our Cub Scout pack that were car company guys. It was always pretty easy to tell which cars were made by the kids and which ones were produced in an R&D lab at Ford or GM. It pretty much spoiled it for everyone.

[curtis rosche]

When I made these cars, we would use a router to hollow out the bottom, then place the car upside down on the scale, and melt solder into the bottom until it was the right weight

[Leo Graywacz]

We did the same thing with lead. But instead of weighing while pouring we'd just pour and make sure it was over weight. Then drill the lead out until it was 5.0 oz