Pinewood Derby Tips?

PizzaFace asks: "My son and I have to start building his first Pinewood Derby racer, and I'm looking for tips. I've found conflicting advice online about even the basic science (e.g. high vs. low centers of gravity) so I'm hoping to tap into some of Slashdot's expertise." Might someone have some pictures of cool designs that might useful as a starting point?"

Comments

Weight is everything

[Picass0]

The following assumes that adding weight to your car is legal within your rules.

1. weigh everything
2. make a note of your max. allowed weight. That's your target.
3. drill several hole in your pine body and fill them with enough lead shot to make your weight without going over.
4. Fill the holes in you pine body with wood putty.
5. sand and paint body of car
6. spray wheels with 10w-40 for less friction
7. go kick ass
8. 
   
   1st place, cub scout pinewood derby, 1980

A few points

[zero_offset]

The guy who said use graphite is absolutely right, it's the best way to get your axle to spin. That said, don't use "wheel nails" as he indicates -- use an actual axle running through a hole drilled into the body. Find the most rigid, lightweight "rod" you can for an axle. Get the graphite that comes in a squeeze tube, which makes it easy to squirt into the axle hole. Make the hole relatively tight (bouncing around is wasted motion) but not tight enough to restrict rotation or make it unreasonably difficult to add graphite. Be aware that graphite is powdery, messy stuff, so carry the car in a big ziploc or something along those lines.

Put all your weight in the middle, and as low as possible. If you put it up front, your rear wheels end up being a drag. Max out the weight as everybody suggested, it does help it run more smoothly. Just hollow out the shell as much as you dare, melt lead fishing weights into it, and goo the whole thing over with silicone to make it stay in place. I have a shoebox in a closet that I just happened to open a few months ago that has 25 year old cars in which the siliconed weights are still securely in place. The nice thing about lead is that you can actually re-melt it and experiment with distribution prior to siliconing it into the final location. For testing we'd just temporarily tape it in place using something strong like electrical tape.

I'll go counter to everything everybody else said: Aerodynamics didn't seem to matter at all. Many decades ago I consistently won with *everything* I built -- specifically, that included a big boxy "fire truck" design festooned with all sorts of plastic "equipment". I never took anything less than first place in the 20 or 25 cars I built and ran over a period of several years. I doubt the cars go fast enough or run far enough for aero to matter -- it's all weight distribution and free rotation of your wheels.

That said, most of my car bodies still followed a basic low-wedge shape, with a wide rounded-bottom groove down the middle. This was easy to build, sort of looked aerodynamic, and removed as much high-riding wood weight as possible, leaving as much low-riding lead weight available as possible. I've tried shaving weight off EVERYWHERE, in some cases even trimming wheels down to flat discs (leading to new rules in our group requiring the use of specific wheels from a kit).

"Real" car designs are boring, everybody does those. Go for the abstract. Confuse your opponents. :)