Saturday, January 24, 2009

Pinewood Derby Heads-Up

It's that time of year when kids and their parents are starting to work on their cars for the pinewood derby. I've noticed an increasing trend in people coming to my blog by some form of Google search like, "pinewood derby humvee."

Let me just remind you from last year's post: Humvees are NOT aerodynamic and will NOT win the race (if that's what you care about). If you don't care about winning the race and just want to make something that looks cool, then totally go for it!

After our resounding defeat last year, I explained the basic concept of aerodynamics to ES. This year, ES decided he wants to make a bullet train for his pinewood derby car. We worked on it a bit today - got the basic shape cut, sanded it down, and put the first coat of paint on it. I'll post pictures later when it's done.


Kat said...

I still have one of my son's derby cars. That was such a fun time.

Oz said...

My dad and I pretty much came to the conclusion that aerodynamic design has nothing to do with the car's speed. The important factors seem to be twofold, in increasing importance:

1) Getting as close to the weight limit as possible.

2) Wheel/axle friction. This includes proper lubrication and getting the axles in as straight as possible.

blunoz said...

Oz, Thanks for the pointers. This is only my second time doing the pinewood derby with my eldest son, so I'm no expert on this. I'll have to look into the lubrication and axles.

Oz said...

Just to slightly retract: we never actually won anything in the two years we did it. However, we did watch cars win that had no business doing so if wind resistance were the major factor. We finally figured that you could put the block of wood up there uncut and win if you could somehow improve on the "four nails" wheel system. Graphite works okay, but I'd do some research into anything that's not explicitly banned (In my pack, if I remember correctly, it was silicone and ball bearings.).

If you finish the car and find that you're underweight, don't waste money on the official BSA weight sets. Just carve a hole in the underside of the car and hot-glue some fishing sinkers in there until you hit 5 oz. Keep in mind, however, that your scale may vary slightly from the official one.

Oz said...

I seem to be becoming obsessed. If you have the cash and the desire, and if it's legal, it turns out they make precision parts. A quick search turned this up:

J120 Bowman said...

Agree with Oz. After two boys and 7 years of derbies, max weight and friction and wheel alignment. If the car is bouncing side to side on the track, it will not be fast. Straight and true down the track!

Good Luck and may the force be with you!

DukeRulZ said...

Though my son and I have aged out of the derby, I was proud to see the boy's from our church's pack hard at it last night.

They had some of last year's cars on hand and guess what the fastest car in the pack was? a 688 Submarine. Unfortunately, the scopes and masts didn't last through the year.