Pinewood Derby time

[UNGN]

Tomorrow is my son's Cub Scout Pinewood Derby.

Because our cars always are covered in graphite, we figured we would just paint the car black this year.

The wheels were turning, so we decided to make a GN:

There is too much cheating to go for speed, so we go for looks. I'm sure it will hold its own against the non cheaters, but the guys I work with are serious cheaters, and it would be 1/2 tracked by them.

We have the fendered pinewood cars down to a science (this is our 3rd) and can slap them out in no time. My 8 year old son actually gets to do more work because he gets to hog away all of the weight from the block before we glue the sides on.

 

[jurassic five 7]

Thats awesome looking! The same guy with 4 kids, aged out a good deal. They ALWAYS won, i dont know how, but would like to know...Oh ya, their ole man is a dirt track stock car racer, and that is ALL ABOUT who can CHEAT the best!

My coolest looking pinewood derby car was actually, we put a diecast model of a flatheaded semi on the front. It was the fastest by a lot down the slope, but once it got to the straight away, i came in last!

I really thought i'd win 'best looking' but i didnt. NO ONE had anything more cool looking then mine, BY FAR!

Either way, pinewood derby was fun and always the highlight of Boy Scouts!

-Adam

 

[UNGN]

I know guys with machining fixtures for the tires. They indicate on the ID of the tread, machine the OD of the tire then locate on the OD of the tire and put a close tolerance graphite bearing in the wheel.

You spin the tire with your finger and it will spin for a minute. no joke.

You can't really tell the tire has been modified (other than they spin for 50 seconds longer than they should when you flick them with a finger) and they have never been caught.

 

[turbojimmy]

Ours was last weekend. This is my first year in Scouts and I'm the 'Den Mother' (at least that's what they were when I was a kid) and everyone also realizes that I'm a car nut. So there were high expectations for our car.

I re-scaled and printed a perfect side shot of the GN as a template, cut it out, taped it to that block of wood, traced it and cut it out. It was looking pretty good (though not as good as yours) until I realized that I had done it BACKWARDS. Being a Pinewood Derby noob, I didn't know there was a front and a back on these things.

That was all it took for my son to change his mind. He drew a picture and I cut out a new one (my dad gave me the excellent advice to have some spare kits around). I did some reading on weight distribution and wheel preparation. I was totally shocked when he won every single race in his class. He won first place among the 'Tigers' (first year kids). We were promptly beaten in the championships by the older, more experienced racers. But it was a blast anyway - I had no idea it was so much fun.

The car that won was so much faster than all the others it was insane. The problem with the faster cars was that once they got going real fast the wheels began to wobble on the shafts. They all did it but this one. This thing was perfectly balanced and prepped - rock solid.

I can't wait to do it again next year.

Here are some pic. I don't know where I've gone wrong, but my son thinks that the more decals a vehicle has the better it looks. Hopefully he'll grow out of it.

Jim

 

[UNGN]

I re scaled the GN 3-view, too. The back axle lines up perfect, but the front axle need to be moved back a little.

Here is my Three View

I cut the sides out of 1/4" wide strips with a sabre saw. and the top is from 1/2" thick piece with the sabre blade set an angle.

The big thing you have to remember is to remove most of the material from the block before gluing the sides on, or it will be too heavy (and it will allow th CG to go back by the rear axle where it belongs). I ended up using a 1 ounce "gas tank" weight.

The next big thing to remember with a fendered car is wheel clearance in the inner fenders where the top inners of the tires can rub on the original block when you crank in negative camber. A Dremel with a sanding drum does a great job cleaning out the wheel wells.

I use a drill stop to leave about a 1/8" center web (to keep the car from breaking in 2), but just let him go to town drilling out both sides of the block, then cover the mess with the side pieces.

 

[turbojimmy]

I re scaled the GN 3-view, too. The back axle lines up perfect, but the front axle need to be moved back a little.

Here is my Three View

I cut the sides out of 1/4" wide strips with a sabre saw. and the top is from 1/2" thick piece with the sabre blade set an angle.

The big thing you have to remember is to remove most of the material from the block before gluing the sides on, or it will be too heavy (and it will allow th CG to go back by the rear axle where it belongs). I ended up using a 1 ounce "gas tank" weight.

The next big thing to remember with a fendered car is wheel clearance in the inner fenders where the top inners of the tires can rub on the original block when you crank in negative camber. A Dremel with a sanding drum does a great job cleaning out the wheel wells.

I use a drill stop to leave about a 1/8" center web (to keep the car from breaking in 2), but just let him go to town drilling out both sides of the block, then cover the mess with the side pieces.

Awesome work! Like I said, my "GN" didn't come out nearly as nice as yours. Sounds like you put a lot of thought and effort into it. I may steal your template for next year

Jim

 

[Quiky One]

Haha here is my pinewood derby car from 10 years ago. My dad and I built this thing and it dominated. I won the entire competition. The power 6 is engraved then filled with paint. It's kinda dusty....

 

[UNGN]

Haha here is my pinewood derby car from 10 years ago. My dad and I built this thing and it dominated. I won the entire competition. The power 6 is engraved then filled with paint. It's kinda dusty....

The Tires on that are Trick. I think I'm going to make a trick set for next year.

Our GN got 2nd in the Bears (first in the Bears won the entire Pack) and he got a trophy for "most realistic" so it was a good day.

The Webelow II that won the Pack overall for the last 4 years (with the same set of wheels) had his wheels fall off in the last race and he finally lost. Parents were all smiles that somebody different finally won.

 

[Brer Rabbit]

Lol

U guys are out of control!

 

[malibuick231]

We done this two weeks ago and the same guy wins every year. I think he pays NASA to build his.

 

[BlackMetal]

Here's my old one, haha. I don't think we had any Buicks in the family back then otherwise I'm sure we would have made it a GN instead.

 

[turbojimmy]

The Tires on that are Trick. I think I'm going to make a trick set for next year.

My dad says someone told him to 'soak' them in a baggie of graphite for a week? Does this make any sense?

As far as NASA designing them, I wouldn't doubt it. The guy that won this year has two kids and they won 1st and 2nd place. Cars were extremely clean and simple designs with flawless paint and no indication of where the weight was placed. Some guys have a lot of time on their hands (or bought them from a 'professional' - we were warned about that).

Jim

 

[malibuick231]

I have a book on them they should balance 1in to 3/4in infront of the rear wheel.

 

[UNGN]

I have a book on them they should balance 1in to 3/4in infront of the rear wheel.

That is about where the GN balances. It's all air forward of the Rear axle inside the body.

25 years ago I worked out the physics on the weight placement given the track slope, etc. with a theoretical car. The higher and further back the CG of the car, the more potential energy it has.

In reality, if you go too far back, the car can bounce, which will slow it down.

 

[malibuick231]

It says on a rough track 1in and on a smooth track 3/4in.

 

[acoen]

[/QUOTE]We have the fendered pinewood cars down to a science (this is our 3rd) and can slap them out in no time. My 8 year old son actually gets to do more work because he gets to hog away all of the weight from the block before we glue the sides on.[/QUOTE]

One awesome derby car...Your car can be fast without cheating, but it takes time. A Few things to remember, center your weight as far back and as high as you can, the cars that push at the end of the arc in the track place first. Place the wheels in a chuck of a drill and true them up, same with the axles, grind down the dia of the hub, less friction. Graphite, graphite, graphite....Pack those bearings, don't use teflon, graphite works better. Use a little elmers glue on the body where the wheels rub, also camber your wheels in just a hair (not much), three wheels to the ground is better than 4. Also good to build a wood jig to make sure the car tracks straight (this is where we went wrong).....Also undercut the front of the car, our track had rotating pegs that started the cars. Our car was very thin and pointy on the front end, I undercut the front of the car to the front axle. When the pegs that held the car rotated out of the way our car got out of the hole first. We had a very quick year for our first year to run. When you place your axles and get them where you want them, epoxy them into place....The little guys will be hard on them and you want them to be set up for the last race.

My 6 year old came up with the design, paint. He sawed and glued and ran the drill while we trued the wheels. I told him, we want to be competitive and have fun. I told him most guys have much more experience, but with a little help we can be competitive...And we were and never cheated...Some guys will spend 50 bucks on a set of wheels and axles that are balanced and true....that isn't the point. Having fun and being competitive is. We had a good year all of the cars performed well....We share all of our secretes, being competitive is funnest part.

 

[turbofish38]

Here's a couple of pics of the trophies I won when I was a cub scout. The big one is 1st place from 1971. The two smaller ones are runner ups from 69 and 70. These are regional. IIRC about 100 troops in the region. Man things have changed in the last 35 years. All I can remember was one of my cars was modeled after the 3rd gen Corvette. My father had a lot to do with the winning cars. BTW my older brother took first in 68,69 and 70. My dad was a typesetter and lithographer and one of the tricks we used was to cut a channel under the body and he would used the old lead typesets as weight. I can remember spending a lot of time scaling those cars. We used one of those old postage scales to get it just right. And tons of graphite on the wheels. Never did make it past the regionals. Not even in the top 10% if memory serves me right. Weird.

 

[UNGN]

That was back in the old days when 9 year olds were melting lead in mom's sauce pan, spray painting in a closed garages until they turned blue and used all manner of finger removing power tools to build their cars.

 

[turbofish38]

That was back in the old days when 9 year olds were melting lead in mom's sauce pan, spray painting in a closed garages until they turned blue and used all manner of finger removing power tools to build their cars.

Funny you should mention melting lead. My dad gave us boys his old toys. One of them was a tin soldier play set. Now you'd probally have to be 100 years old to remember it, but at one time they made an electric ladle and you would melt lead and pour it into a mold and make your own tin solders. Well after we broke the ladle we made our own smelter and foundry out in the backyard BBQ grille. We lived out in the sticks and scrounged for our lead by vandalizing railroad signal box batteries and old junk cars that were burned out. Pretty soon we had thousands of toy soldiers. Than a neighbor gave us an old scuba weight mold and we went into buisiness making 2 pound lead weights. We must have had tons of lead stacked everywhere. The parents would have probally had a fit if they knew what we did over our summer vacations. We didn't burn the house down and no drain bramage from inhaling the lead fumes. Try doing that today. Sorry for the hi-jack.:smile:

 

[BLACK6PACK]

Dang Eric, those are OLD, looks like they engraved your name with stone tools!! :wink:

I took 1st place about 1981 at the local PD meet. Only about 50 cars in my class. My dad helped me build my car in 1980 and it didn't do squat. I built my own in '81, but I did use all the tricks my dad taught me. The next door neighbor's dad let us use all his stand up wood working tools (drill press, band saw etc). I still have scars to this day. we put what looked like a rasp (cheese grater) bit about 2" in diameter on the drill press. I was fine tuning all the lines on the car, the bit caught the wood and drug my hand right across the bit. Only my pointer finger and my thumb escaped unharmed, the other 3 fingers didn't have much skin on them.