Pinewood Derby Time...

[Art Mulder]

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

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:
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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 (http://www.wordsnwood.com/2007/p.fliptop/). 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.)

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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. :D

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...

:D:cool::D:cool:

[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,

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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:
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Here's the four of ours that competed this year:
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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! http://familywoodworking.org/forums/images/smilies/023.gif

Our club track set up in the atrium at church:
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And here's my youngest's car in it's first race, against a friend of his.
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Couple more shots and some discussion on building techniques at my website (http://wordsnwood.com/), 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! http://familywoodworking.org/forums/images/smilies/023.gif


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.:D

http://fototime.com/BC1BFF8C8F79108/orig.jpg

[Art Mulder]

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.

Science rules, David! :D

Note that on our track, the starting pins tip forward to start the race. So we've realized that a car with a notch + wire, or a car with an upward-sloping front end has an advantage in that it allow the car to get going just a fraction of a second quicker than a car with a flat front.

[Lee Schierer]

Science rules, David! :D

Note that on our track, the starting pins tip forward to start the race. So we've realized that a car with a notch + wire, or a car with an upward-sloping front end has an advantage in that it allow the car to get going just a fraction of a second quicker than a car with a flat front.

It also helps to keep the majority of the weight toward the rear of the car because it is slightly higher than the front at the start therefore there is slightly more potential energy to work with. However too much rear weight makes the car unstable and like to jump the track.

[David Epperson]

It also helps to keep the majority of the weight toward the rear of the car because it is slightly higher than the front at the start therefore there is slightly more potential energy to work with. However too much rear weight makes the car unstable and like to jump the track.

Yeah. There's a fine line - with the "Standard" wheelbase - of being too far back. We had one pack that skirted that issue by changing the wheel/axle locations, moving the axles to within 1/4" of the front and rear of the body. It made for a funny looking car, but allowed the weight to be shifted even farther to the rear and remain stable. My opinion was that it was outside of the spirit of the rules, but I wasn't in charge, so the design was allowed. Even though those cars no longer fit in the sizing box due to the wheels extending past the front and rear.

[Art Mulder]

... Even though those cars no longer fit in the sizing box due to the wheels extending past the front and rear.
Hmm, I would have been voicing my complaints if they'd tried that here. That is one of the reasons that all our cars have to be turned in the week before the competition. At that point they are weighed, and checked with the sizing box. If they pass, they're locked away until the race -- too many cars competing to do all that checking on race day. If they don't pass, that gives the dads a week to fix their mistakes (and we all know it is the dads who messed up! :rolleyes:)

Sometimes rules need to be fine tuned. For instance... Kids are supposed to make a new car every year, but every now and then they let someone run a "repeat" car, due to family issues. This year we had a repeat car that won a design trophy -- for the second year in a row. Oops. The judges did not realize that this car was a repeat, and since it was such a rare occurrence no one had written a rule for this. Next year I bet this will be different!

[Art Mulder]

It’s race time again here in London, so time to resurrect this old thread and post some more photos…
NOTE: faces are blurred for privacy reasons -- well, except for my own family members


(I wrote a web page last year, with a lot more photos and details which you can see here: www.wordsnwood.com/2013/kubkars/ (http://wordsnwood.com/2013/kubkars/))


Every year we have Pinewood Derby / cub car / Kubkar races in our church. And it is always a noisy, boisterous and fun evening. Both our boys club and girls club build cars, so there is a lot of fun "boys-vs-girls" rivalry going.


Our family produced five cars this year, pictured here. Only two were in the actual "competition". Three of them were in the leader/counsellor/adult category which is just run for fun and bragging rights after the real races — no trophies there.


From L-R we have a rocket/missile thing, flat green thing, seahorse, Minecraft Slenderman, and a Pink Marshmallow Peep
http://i.imgur.com/XjsQ78T.jpg (http://imgur.com/XjsQ78T)


Yours truly with our two oldest sons against the side wall taking in the action.
http://i.imgur.com/gKpYiZM.jpg (http://imgur.com/gKpYiZM)


Here are my two oldest son’s cars lined up and ready to race
http://i.imgur.com/4RnBcp6.jpg (http://imgur.com/4RnBcp6)


My oldest was manning the track-end for a while. They have some foam to catch the cars as they leave the track. You can see one black car in mid-bounce. All eyes are on the end, though the electric eyes on the track are the ones that determine the winner:
http://i.imgur.com/bRzEXjD.jpg (http://imgur.com/bRzEXjD)


Here is my wife’s car (on the left) out of the starting block.
They rebuilt the track launching system this year. Instead of a manual system where the pins tilt down out of the way, they now have an air-driven system. You can see the red air hoses at the bottom. The 3 track pins are now on a piston and drop down vertically into the track very quickly.
http://i.imgur.com/HmmXEKW.jpg (http://imgur.com/HmmXEKW)


There were 69 kid’s running cars, and we run triple-elimination (you need to lose three times to be out), so there were a LOT of races!
http://i.imgur.com/3ENDlZn.jpg (http://imgur.com/3ENDlZn)




See You Next Year!
http://i.imgur.com/udzyEGS.jpg (http://imgur.com/udzyEGS)

[Rob Luter]

......As far as turning into "competition between the dad's" well... Good luck and remember it's the kid's thing.. not the adults.....

Good advice. When I was a kid I lived in suburban Detroit and we had a number of dads in our Cub Scout pack that were car company guys. It was always pretty easy to tell which cars were made by the kids and which ones were produced in an R&D lab at Ford or GM. It pretty much spoiled it for everyone.

[curtis rosche]

When I made these cars, we would use a router to hollow out the bottom, then place the car upside down on the scale, and melt solder into the bottom until it was the right weight

[Leo Graywacz]

We did the same thing with lead. But instead of weighing while pouring we'd just pour and make sure it was over weight. Then drill the lead out until it was 5.0 oz