Pinewood Derby Time...

[Art Mulder]

(Hey, it involves wood, and I helped build them!! It counts. )

And it's that time again for the annual Kub Kar (Pinewood derby) races at our church. This year I had to help make Three cars.

Last night was the "weigh-in" on the "official" scale. Next Thursday... We Race! Our max weight is 142 grams. Considering that I used a pretty old spring-loaded kitchen scale, I think I did pretty darn good, with one car at 139 grams, and another at 141 and the third pretty close to that (I forget what my kids said was the weight)

Here they are:
2009-kubkar1.jpg

On the left is my daughter's car, she's 8. (at our church the girls' group makes cars also, and then they compete against the boy's club.) Yeah, it's a watermelon. My wife is the artistic one and helped her with the painting. No, those aren't actual watermelon seeds, but they are actual seeds.

In the middle is my #2 son's car. He's turning 10 next week. We found a car that sort of looked like that (the shape) on the net and used that for inspiration. I helped him with the flames, I admit, but he did the other painting.

On the right is my #1 son's car. He's 12. I still did some of the cutting, and helped him lay out the pattern. but he did most of the sanding himself, and he did the drilling also, after I lined up the drillpress for him. And the paint is 99% his also -- the silver was rattle-can that I had, and I showed him how to do a sweeping motion and not get too close.

That thing on the top is the weight. He was thinking "tank" when we designed it together, or maybe "way cool super fast speedy tank" is more accurate. But when it came time to paint, he didn't feel like painting it like a tank. These pine blocks are really light, and when you cut so much away there isn't much left. What I hit upon last year is to use some 1/2" iron rod that I had sitting around, leftovers from the axle I made for my flip-top tool stand. Sure I found special "pinewood derby" weights on the net, soft lead and other ingot type stuff. But really, let's be reasonable. A 3' bar of 1/2" iron rod was less than ten bucks. For my eldest's car, we made it a part of the design. For the other two, I stood the car on end and drilled a hole in from the backside using a 1/2" forstner, and then epoxied the rod in place. You can just see the tip of the rod sticking out of the back of my daughters car. (I did do a test fit, but not 100% of the way in, and it jammed when I slipped it in with the epoxy. By that time it's too late to reach for a hammer unless I wanted to turn my daughters car into kindling. Right, forget that.) For #2 son, we cut the rod in half and drilled two holes. It was left sticking out on purpose, sort of as tail pipes, but the car was over weight so I ended up grinding them almost all the way down, so they're not visible any more in this photo.

And yeah, so there they are. Last year one son took 2nd overall, much to my surprise, he'd better not count on that this year.

...art

[Lee Schierer]

Nice work.

I used to bore a good sized hole with a recessed cover held by screws in the bottom and put in small lead fishing sinkers until the maximum allowed weight was reached. I always add a drop of super glue to the slot where the axles slip into the wood on each axle to hold them securely. Otherwise the wheels may drop off. Carefully file off the burr under the nail heads so they don't rub on the wheels and clean any flash off the wheels. Make sure all four wheels touch the ground on a flat surface so the car will roll straight. Lubricate the axles with powdered graphite right before the race.

[Eric Roberge]

Ditto to what Lee said. Just ran my son's a month ago and every little bit helps.

Good luck next week! I'm pulling for ya!

[Prashun Patel]

Art, yr cars are beautiful, and I know I'll be doing the same for my 5yr old son in a couple years.

I gotta say, though, (having just watched my neighbor's son's Cub Scout competition) this event turns into a competition among dads. They should make a rule about that (they should also have a pinewood derby just for dad's too).

[David Epperson]

Art, yr cars are beautiful, and I know I'll be doing the same for my 5yr old son in a couple years.

I gotta say, though, (having just watched my neighbor's son's Cub Scout competition) this event turns into a competition among dads. They should make a rule about that (they should also have a pinewood derby just for dad's too).

I was a Cub Dad and volunteer Leader for close to 15 years with my 3 sons. I helped them build their 15 cars, built 2 or 3 of my own (as well as an 18 wheeler kit), and helped probably hundreds of other kids learn to build their own (I would teach a clinic on Pinewoods every year in January or February during one of the annual lock-ins). Lot's of "tricks" to making those little rascals roll right. Hard to believe that max speed is only about 10mph, but at that the wheels are spinning at 3000rpm. Wheel and axle prep is most important, much more than aerodynamics. Weight location helps - as far to the rear as is stable allows the center of gravity to fall the farthest, and the farther something falls the faster it gets going.

Good luck and have fun.

[Lee Schierer]

I gotta say, though, (having just watched my neighbor's son's Cub Scout competition) this event turns into a competition among dads. They should make a rule about that (they should also have a pinewood derby just for dad's too).

Unfortunately Dads often do most of the work, but part of the goal is to get Dads to spend time with their kids. The pack I was a leader for used to have an adult competition for several years, which helped keep teh Dads from over doing teh kid's car. When I help my grandkids, they do the design, I help guide the cutting on the BS for basic cuts, Then set up a spindle sander and let them do the shaping and contours. The first time, I have to help guide their hands quite a bit, but they are holding the car. Then for the paint job, they do the painting, but I apply the masking for the fine details.

The fastest car I ever saw was one that was made mostly of metal with just enough wood to cover it. The thickness was about 3/16" to 1/4". It would consistently beat the other cars by more than a foot.

[Art Mulder]

I always add a drop of super glue to the slot where the axles slip into the wood on each axle to hold them securely. Otherwise the wheels may drop off. Carefully file off the burr under the nail heads so they don't rub on the wheels and clean any flash off the wheels. Make sure all four wheels touch the ground on a flat surface so the car will roll straight. Lubricate the axles with powdered graphite right before the race.

Different kit, Lee. Our kit is produced here in Canada, and we have pre-drilled holes for the wheels, and the "axles" are actually Robertson "square-drive" screws, as you can see in this close-up. (the "yellow-handle" #0 size Fobertson screwdriver, which is a bit less common.)

2009-kubkar-wheel.jpg

I've been to a few pinewood websites and they frequently talk about polishing the axles, and removing burs from under the nail head... but I really don't find that much of an issue with our kits. The screw shaft is already pretty polished and smooth (I still go over it with some fine sandpaper) and I've yet to find any burs under the screw heads.

And the graphite thing is a common bit of advice but people really need to be wary of it. Check your local rules! In our groups, graphite is FORBIDDEN. The reason given is that the powder falls off and gets on the track and makes a mess and affects the track. We use light oil (3-in-1, usually) for our cars.

Our group uses more than single elmination, triple I think. And in the finals the races are such that each car races on each lane, to hopefully allow for any variations between the lanes.

best,
...art

ps: yeah, and I admit I kinda wish I could make my own car to compete...

[Art Mulder]

The fastest car I ever saw was one that was made mostly of metal with just enough wood to cover it. The thickness was about 3/16" to 1/4". It would consistently beat the other cars by more than a foot.

We had someone win with a sliding weight two years ago. I think that was forbidden at the regionals, but I forget.

As for "mostly of metal", that's an interesting idea, but it seems to be pushing the rules to me?

[John Thompson]

When I saw this I was going to add some tricks but... they already got covered. If you can't use sliding weigh but can use weight... I found from experiemtation that placed just forward of center was best on our cars. That might depend on the design though.

As far as turning into "competition between the dad's" well... that is absurd and I can't imagine why someone would think that. Kind of like why I can't imagine a dad jump a fence at a little league game to protest a call by an umpire concerning his son... then get into a fight trying to be restrained.

Yep... I've seen it happen and it is sad but.... it is reality as it takes all kinds I suppose. BTW... the dad I saw do that was the school bully when we attended and it unfortunately carried over into his adult life which the work adult could be questioned...

Good luck and remember it's the kid's thing.. not the adults...

Sarge..

[Art Mulder]

Gloat time....

Between our boys and girls club there were 60 kids... and all three of my kids made the finalists (9 kids). My daughter took 2nd overall. I was actually kind of embarrassed. I didn't think we'd done anything that outstanding in our construction, but all these people were asking what my secret was...

[Jim Becker]

Those are great, Art! And it sounds like great results, too.

[David Epperson]

Different kit, Lee. Our kit is produced here in Canada,

2009-kubkar-wheel.jpg

I've been to a few pinewood websites and they frequently talk about polishing the axles, and removing burs from under the nail head... but I really don't find that much of an issue with our kits. The screw shaft is already pretty polished and smooth (I still go over it with some fine sandpaper) and I've yet to find any burs under the screw heads.

And the graphite thing is a common bit of advice but people really need to be wary of it. Check your local rules! In our groups, graphite is FORBIDDEN. The reason given is that the powder falls off and gets on the track and makes a mess and affects the track. We use light oil (3-in-1, usually) for our cars.

best,
...art

ps: yeah, and I admit I kinda wish I could make my own car to compete...

Different games, different rules. The BSA Pinewood rules would hold those wheels and axles as illegal. And graphite, or powdered Teflon are the two preferred lubricants, oil is discouraged or prohibited, and is in fact slower according to tests I did.
you can always make a car of your own, and a track as well (they aren't that difficult - I still have one packed away in the shop that I built).

David

[Art Mulder]

Kind of fun to dig up this old thread that I started back in 2009.

It's now 2013, and there have been a lot of "cars down the track" since that old thread. We have four kids, and my wife is now a counsellor at the girls club. (At our church the boys and girls clubs compete against each other with pinewood cars.

that adds up to a lot of cars that I've had a hand in helping my kids build over the years:
IMG_2845.jpg

Here's the four of ours that competed this year:
IMG_2837.jpg

Didn't make the finals this time... the competition is stiff. There are few dads who have really gotten into the science of pinewood racing. But we had a great time, as usual. And there is always next year!

Our club track set up in the atrium at church:
DSC_4700_2.jpg

And here's my youngest's car in it's first race, against a friend of his.
DSC_4719.jpg

Couple more shots and some discussion on building techniques at my website, if you're interested in more.

[David Epperson]

Hey Art. Thanks for bringing it up again

There are few dads who have really gotten into the science of pinewood racing. But we had a great time, as usual. And there is always next year!

I was one of those engineering Dads that really did get into the science of PD racing. I went and looked at your website. Nice pics.
But you mentioned something that I found interesting.

One thing to be aware of are notches at the front. You can put a notch at the front, if you like, but you will need to add something like this bit of bent wire shown in the photo. The problem has to do with how the car rests against the starting pin. A notch at the front would allow the car to be forward, which is not fair. So the wire is mandatory.

As it turns out, the notch allowing the car to start out forward, in fact works against the racer and is not an advantage. The amount of energy available to be converted into speed is determined by the height that the car's center of gravity "falls". Starting out lower reduces this and results in a slower finish. Mgh=Mv^2. You cannot get more kinetic energy out than the potential energy you had to start with.

I got WAY too into the science of this type of racing.

[Leo Graywacz]

Back in the day when my kids were in scouts I got into making a bunch of these cars just because it was fun to do. I brought them to the races and to my surprise I got a best looking award. I didn't even know I was eligible for it. Bandsaw and Dremel with a sanding drum is all I used, plus some hand sanding.