Hmmm... I was a Cub Scout, but not a Boy Scout. It sounds like you're talking about the illustrious pinewood derby. Unless they've changed things a bit, your son's troop should provide him with a hunk of pine, which you whittle down into any shape car you like, drill a hole in the back to accept a CO2 canister, add some wheels and a couple of eyebolts in the bottom to hook it to a piece of fishing line so it doesn't go flying off the track when they pop the canister. Lots of fun, not too much work. They race them in a little tournament when everyone is done.
I believe the finish is up to the scout, but I'm guessing that they don't like people to substitute other types of wood for the pine (though I could certainly be wrong- it's been an awful long time since I was a cub scout!)
That might have been to your benefit, depending on your dad! :) Mine tried to pack the axle with graphite, and the wheels wouldn't turn at all when he was done. Ah well, at least he tried.
Tom Watson wrote in news: snipped-for-privacy@4ax.com:
Yep.
The point YOU need to remember in all of this is that the point of the activity is to bond with your child, make something memorable, and have a good time.
The kids _will_ remember if the rules are stretched. And they _do_ remember if Dad wouldn't let them do anything.
Some units have a dad's competition, for just these reasons.
Patriarch, who, with the help of his Den Mother wife, raised four pretty good sons. And built more than a few Scout projects.
Center of gravity should be about 1" in front of the rear axle.
If you use the stock block of Jummywood, do yourself a favor and drill out the axle holes a little with your DP before you try to drive the nails in. If you follow the directions that come with it, you'll split the damn thing every time. DAMHIKT.
If you chuck the wheels on your lathe to polish them, go easy. Melted wheels don't turn very well. DAMHIKT.
Yes, but don't make the mistake we did. My son wanted to do a turned rocket car. (He actually turned the first one (*) himself, more or less.) It was a cool concept, but I stood there (I'm a leader) and watched it lose several heats because the little point didn't trip the electric eye efficiently. It never won a close race. It always won by a landslide, or not at all.
(* had a teething puppy at the time, and the puppy ate the whole thing the day before the race, so Daddy made him a new one in a big hurry... flagrant cheating, but everyone involved knew what I had done, and why, and no one came to blows over it when it came in second overall... his original one might have placed that well...)
One year we had a block of wood with some Legos hot glued on it that took first place against everything. If you hold your mouth right and wiggle your pinkie toe while you set the car on the track, it has as much of an effect as all the engineering in the world.
Yeah, and on race day you be sure to really swoon over the crappiest looking cars there. Those are the ones kids actually made.
It really isn't a fair competition at all. The kid whose Dad has the best shop usually wins. Or the kid whose Dad is the biggest Pinewood Derby freak. Or both.
If you want to do something nice, find the kids with single moms and help them make cars. A lot of kids don't have any tools at all. (OK, that's slightly sexist. Some single moms are probably wood dorkers. So find the kids with pussy dads too.)
If you make (turn) a pedestal out of a piece of walnut, and you screw it to a faceplate, take care not to let him turn it all the way down to the screws. DAMHIKT.
Hmmm... I've read that the CG should be such that each wheel has equal weight on it, since friction is proportional to weight you want to balance it all around.
FYI this is normally illegal for the kids' cars, as it's considered an unfair advantage.
The Girl Scouts had their first derby this year, so they didn't have the advantage of seeing the track ahead of time. The prettiest car was one with a wooden rainbow glued to the top - well made, well painted, great idea. The rainbow hit the top of the stop box at the end, and it put a big dent in the rainbow. This year I plan on making "sizing boxes" to send around to the dens and troops, so they can make sure their cars fit.
The "best attitude" award went to the cubmaster's son. He cut a notch out of the front of the block, painted it yellow, and happily declared it to be a bus. He was in it for the fun, not the competition!
I was wondering about that. Why is that, exactly? Isn't the vector of force from the gravitational pull on the car the same, regardless of the weight distribution? Has anyone actually tested this with the weight on the front, in the middle, and at teh back, to see if it's really different? Didn't make sense to me as a kid, didn't make sense to me as a physics student, doesn't make sense to me now.
As the track starts out with a greater slope than at the finish, the back of the car drops further than the front. The further back the weight is, the more energy it will pick up in the run, and the greater speed.
That said, the most important thing is probably getting a clean run in which the wheels don't bounce the car from side to side along the center strip. Alignment, luck.
The theory is that having the weight further back on the car will keep the weight further up hill longer than it would by placing it further forward on the car.
Some dad/scout teams go too far with this theory and place the weight behind the rear axle. In my opinion this is wrong because:
It makes the front end way too light and makes it pop up at the slightest bump in the track.
It puts too much weight on two axles. I would expect this to increase friction and negate any gains there might be had with keeping the weight up hill longer.
I place my weights inside the block of wood using one or two cylinders that were drilled into the car while it was still a block of wood.
I have two boys in Scouts. One joined Boy Scouts this year and the other is still in Cub Scouts. The boys have always been responsible for the design and construction of the car. They use the power tools that I think they're ready for. They do almost all the sanding also. I kick in some sanding when I think they are reaching their limit. Painting has been a problem. Their fingers haven't been strong enough to press the nozzle on the spray paint. So they get a few sprays in and I take over for them while they supervise.
It isn't unusual for our cars to have 6 coats of paint (including primer). We end up with very nice looking cars. Some of them have been two-tone paint jobs. Our car two years ago looked just like an ice cream sandwich complete with dimples on the top.
Our highest finish was 2nd overall two years ago.
To help out the Cub Scouts in our Pack that don't have the tools that I do I open up the garage on a weekend and also offer supplies (sand paper, paint, etc) to help them out.
Thank you. What puzzles me is how many other people have given some sort of pseudo-scientific rationale about "reduced friction" in support of three wheels on the board. If the reduction of friction due to one wheel not meeting the track is significant enough to increase speed, it's significant enough to cause the car to veer into the lane guides.
I'm guessing you saw a lot of cars lose speed and races by swerving, too.
My Boy Scout troop (Not Cub Scouts) did a pinewood derby once for the heck of it. Basically no rules at all as long as the car wouldn't hurt someone or the track.
The boy who won strapped a 2lb bag of nuts to the top of the car. Winning a pinewood derby really is all about the weight, which is why they have the 5 oz rule to make it more of a challenge.
I remember these cub scout days. We placed or won two out of three years. That one year the car had an accident on the way to the race, ha! The secret for us was: graphite and making the wheels true. That was it! Straight wheels minimizes resistance to the track and graphite minimizes resistance in the axle. We just rolled the car on the garage floor to make sure it went straight.
Oh. Nevermind. You said "or the track." That's why they wouldn't let me use my rocket car. $1500 for the track, big whoop T do. It would be sooooooo cool!
(Yeah, I know, I know. We defintely don't have the budget to replace that thing.)
My cub scout troop must of been an oddity- I definately remember all or most of the cars having CO2 canisters in the back of them, so they
*were* rocket powered... made for some speedy races! They just had some fishing line stretched above the blocks on the track to keep the things from flying off the track.
Either you were an oddity, or that was a long time ago. We weren't doing it that way 22 years ago, and we don't do it that way now. The rules really haven't changed much.
There _was_ such a case at the Soap Box Derby. It was, in fact, an _electro-magnet_, which was powered-up only when the driver did something very specific to switch it on.
I would -not- rule out somebody having tried a PM magnet in the nose of a Pinewood Derby car.
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