
Lorentz forces and cheating at the Pinewood Derby - mafuyu
http://ch00ftech.com/2015/10/12/lorentz-forces-and-cheating-at-the-pinewood-derby/
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jaredhansen
This is one of the most enjoyable things I've ever seen on HN. It's just ...
_fun._

I remember doing PWD with my dad when I was a kid, shaving #2 pencil cores to
get graphite for the axles, making a batmobile one year, and generally doing
things that probably had no influence on making the car faster, but that
involved a lot of Time In The Shop Experimenting. PWD is the kind of thing
that makes hackers out of impressionable youngsters.

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te_platt
From the article:

"They also didn't have any protection circuitry on them, but I figured that if
my car burst into flames halfway down the track, it would totally be worth
it."

That's the spirit!

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NoGravitas
When I was in Cub Scouts (30 years ago), the rules for Pinewood Derby were (at
least as I understood them), fairly strict. You had to use the stock wheels
and axles, and carve the car out of the provided block of wood, but you could
weight the car any way you liked, up to the specified weight limit.

Given these constraints, there was one optimal design that would always win:
essentially, a skateboard about 1cm thick, weighted exactly up to the limit
with cast lead, with the bottom of the skateboard waxed. Everyone knew that
was the optimal design, but it looked boring, and its performance was
completely predictable, so almost no one used it. But every year, there was
_one_ kid who (or whose father) cared more about winning than about having a
cool PWD car...

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cafard
I beat you by a fair bit on seniority--going on 50 years. I was the kid whose
dad figured out that looks were nothing and weight was all. Somebody who
optimized for weight _and_ aerodynamics might have beaten us, but that
somebody didn't show up in our troop.

~~~
mcherm
That's interesting, because my first year, I optimized for aerodynamics (and
maximized the weight) but lost severely.

In later years, I realized that it had more to do with the wheel friction, and
I made cars that were more interesting than perfect teardrop shapes and which
also went much faster due to careful attention to wheel placement and
lubrication.

~~~
baakss
I missed this... but yeah same thing here. We won every year lubricating the
wheels and axles.

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strictnein
My son just joined the boy scouts (or Tiger Cubs or whatever it's called when
they're in the 1st grade). I need to review this for... uhmm.. research
purposes.

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CIPHERSTONE
Just a comment, as fun as PWD can be, don't be that parent that clearly did
all the work. The purpose is not to make a car NASA would be proud of, but to
make the car with your son to end up with a car he made and is proud of.

Usually this results in a car that looks like and reflects the age of the
scout (e.g. a Tiger Scout's (Kindergarten) car does not look like a Webelos
(5th Grade) car.

Seriously suggest to your pack leadership that they add three races:

-Adult/Sibling -Adult Scouter -Adult Vintage

The first give you and your other non-scout kids an opportunity to be a part
of things. You can make your NASA approved car that ultimately loses to the
simple block of wood that five year old suzie makes.

The second gives the scouts a chance to cheer on their den leaders.

The third let's them see what PWD cars from pack in the day looked like.

Just some suggestions from an old Cubmaster.

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strictnein
Oh, I won't be, my comment was mostly tongue-in-cheek and also remembering how
my the creations of my father and I never did that well.

Obviously you have to help a 6 or 7 year old to a degree, but I plan to be as
hands-off as possible, when the time comes.

I like your idea of multiple races. I'll have to go and find my old PWD cars.
They're somewhere...

~~~
CIPHERSTONE
It's really a blast to see the old cars, and the adult race is fun because
then you can see some really great adult designs.

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panglott
The simpler explanation is that the VW Diesel that won was cheating the system
too ;)

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ChuckMcM
That was a lot of fun! A long time ago I designed an electromagnetic "coil
gun" for BBs (.177 cal steel balls) as an exercise in electromagnetic fields.
While it was mostly worked out in the 19th century it often felt to me like
messing with more primitive forces than just charge and magnetic fields.

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elwell
I still remember winning "Best of Show" when I was a Tiger Cub. Took me a
couple decades to realize this was a booby-prize.

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hinkley
I suspect the real reason you lost is due to the aluminum track rails and eddy
currents. You'd need a way to switch the thing off almost immediately.

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dyladan
google cache
[http://webcache.googleusercontent.com/search?q=cache:k-OXSfS...](http://webcache.googleusercontent.com/search?q=cache:k-OXSfSOTWYJ:ch00ftech.com/2015/10/12/lorentz-
forces-and-cheating-at-the-pinewood-derby/&hl=en&gl=us&strip=1&vwsrc=0)

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matthuggins
Mirror? The site is down.

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craigmcnamara
My brothers and I we're in the scouts and my dad was a den leader. In pinewood
derby season we would design the cars how we want, rasp, sand and paint them
until they looked perfect to us, scouts, not parents. When that was done, my
dad drill cavity in the car (one year he went through the top of a car into
his hand), fill the cavity with molten lead to max weight, then we'd wood
putty, sand and touch up the paint. My den had great looking cars and we
dominated these races.

