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Pinewood Derby Tips?
PizzaFace asks: "My son and I have to start building his first Pinewood Derby racer, and I'm looking for tips. I've found conflicting advice online about even the basic science (e.g. high vs. low centers of gravity) so I'm hoping to tap into some of Slashdot's expertise." Might someone have some pictures of cool designs that might useful as a starting point?"
Since the last pinewood derby I had the pleasure to attend was over a decade ago, my memory is a little hazy. However, I do clearly recall all of the fastest cars having one common feature: They were almost planes. And I don't mean the flying vehicle kind. Plenty of people made very carefully crafted, glossy cars with carefully painted details, but they never won. All of the cars I saw do well were basically shells whose purpose was to hold the weights (which were always measured out to be barely below the upper limit) and the wheels together. Further, I recall many taking great trouble to rub some lubricant on their axels prior to every run. I can't speculate on the usefulness of such a thing.
Overall, I think the process is more fun if a lot of effort is taken in designing the car to look nice more so than making it fast, due to the blandness of competition stated above. That's not to say I didn't see a couple of nicely decorated planes, but when you got right down to it, it was still 2-dimensional.
You like splinters in your crotch? -Jon Caldara
Er, am I revealing woeful ignorance or are there a lot of other people out there who haven't the faintest idea what the heck this is? Couldn't an informative link have been provided?
OK, 5 minutes with Google later, it appears to be something coming from the Scouting movement; kids build cars out of a basic kit of a block of wood and wheels, and then race them down an inclined track. So you get competition, woodworking skills, and parent/child bonding as Grandad shows you how to work a lathe etc. (OK, you don;t use a lathe to make a wooden car but obviously since I don;t know what it is I have no woodworking skills)
~~~~~ BigLig2? You mean there's another one of me?
Here's my advice.
Ask your son to draw some pictures of what he wants it to look like. Go over them with him. Pay particular attention to any pictures that go on the sides -- that will tell you his interests in a way conversation can't.
When it comes time to begin actually carving the block of wood, take a dummy piece of wood and make sure he knows how to cut. Then let him cut the dummy piece. Then let him cut the car.
Use a scale and some lead shot (or whatever), break out a piece of paper for a real application of subtraction. How much lead shot do you add to get to the maximum allowed 5oz? (Wow, subtraction is useful in real life, dad?) Ask him how best to attach your weight. Perhaps he can think of other materials just as good? (Paint will add some, so it may be helpful to keep it possible to remove a little.)
Now, start painting. Maybe you sand first, maybe you don't. Chances are, he's getting tired of this project and just wants to see the final shiny piece. High gloss enamel spray paint in the color of his choice. Anybody older than the Tiger Scouts (if they're still around) is old enough to handle spray paint with supervision. Try to coach, not lecture. Help, not instruct. Ask the boy how best to apply the artwork from the first paragraph.
Overall, the goal is to spend quality time with the boy. Sure, the boy says he wants to win. You or I may have won when we were kids, but do we remember? I don't. All I remember is how little help I got. My first car started out as a team project but it ended up as the metaphorical "Team of One". For my second car, I was told that I knew where the table saw was. These are the times he'll remember. And the times you will wish you had back. Try to imagine what'll happen to your son when he's 18. What will you wish you had done? What will you wish him to remember? Does a trophy really matter?
In the end, which would have more value to a boy like yours: winning first prize in the Pinewood Derby Competition, or his dad taking him and his den out for pizza? My money's on pizza. Judging from the winners in my pack, the pizza would have been cheaper.
Have fun. I wish I was in your place.
My father ran for several years a council-wide competition as well as the pack-level races. Just to try out different things, he made a test car that had different styles of wheels, solid axle vs. nails, etc.
WRT the wheels, he milled perfectly flat across (maximizing contact area), a very small sliver on the inside or outside of the car, and a v shaped wheels. It ended up that multiple runs ended up with near identical times. Wheel shape really didn't come into play. Didn't matter because altering the wheel shape was against the rules.
Weighting does come into play, but not the position of the weight. Just get it close to 5 oz (the limit at the time). If you have races over multiple days, remember that scales sometimes do change slightly over time, so it may be better to be a tad under.
Solid axles did nothing once you cleaned up the nails and put graphite on them.
Some other things that we found out with test cars and through observing the races that really don't affect times:
-Paint jobs. Smooth, polished, waxed. Didn't matter. Have fun with it, put stripes on it or flames, but don't go crazy trying to get the perfectly smooth finish to minimize microflaws in the paint. Regular ol' Krylon works fine.
-Percise "aerodynamic" shape. The winner was almost always a flat car about 3/4 of an inch think. Pointed, rounded, or angled noses didn't matter, but they usually had some type of "areodynamics" to them just for looks. A square nose ran just as fast.
-Drag, turbulance around the wheels, etc really don't come into play. They are light, start off slow, and reach the bottom quickly that it dosn't come into play significanly.
Things that did help with the car:
-Not buying the premium "pine car" accessories like the weights, "better" wheels, axles, etc. Any weight will do. We used old brass hardware. Lead shot also works. Feel free to have fun with model car parts like windshields, tailpipes, etc. Keep in mind overall dimension limitations.
-As someone else pointed out, polish the supplied nails to remove the burrs or whatever they are from both the head and shaft. You want a very smooth nail. Easiest way is put them in a drill press, get some fine sandpaper and some water. Turn the press on and just polish away.
-Pop the wheels into a lathe or drill press and wet sand down the surface of the wheel to remove any moulding lines.
-Graphite, graphite, graphite. Don't use WD-40, oil, etc. graphite is the key. Put it on till everything is covered where a wheel may even rub (side of car, nail head, shaft) I think liquids or grease might even be against the rules (drips on tracks) as well as spacers.
-Getting a fast lane. This is just a chance. Some lanes run faster the others. They may be smoother at the joints or have a better finish or something.
Some other advice:
-Have fun.
-Take your time. Work with your son to figure out what you want to do before hand on paper. Have him draw out a couple of ideas and talk to him about the design qualities (aerodynamics, liitations of the wood, available tools to make it).
-Don't do it all. This is your son's project that you are helping. Give him some tips/help, but don't do it all for him. I remember when I was a scout seeing these wonderful looking cars magnificantly created and a flawless paintjob. It's very obvious when Dad does it all and the kid has didn't do anything. Son will get more value in the long run from spending time with you working then if you did it all and he wins. Looking back, I didn't win 1st, but I usually ranked high and I remember working with my Dad more then anything about the race.
-Both of you should remember it is only a race. It doesn't mean anything in the grand scheme of life. I remember kids crying because they lost. I'm sure some dad has gotten "track rage". It isn't worth it.
As a former Cubmaster, I used to hate Pinewood derbies. It was the fastest way to take 50 kids, (and their fathers) who were proud and excited about their works of art, and turn them into 49 loosers and 1 winner. Only one kid would go home happy.
After building ten different cars, I learned to focus on having fun. Make a unique car that you can be proud of. Make a car that will make you smile or laugh (a fire truck, a bananna or hot dog on weels). But JUST HAVE FUN!!!!
There is no reason to melt lead into the car. You can drill a hole, add lead buckshot, and seal the hole with wood putty.
Far less dangerous.