How to Build a 1st Place Pinewood Derby Car

by Brett & Kate McKay on August 17, 2009 · 50 comments

in Manly Skills, Projects

PinewoodDerby

When it comes to father/son bonding experiences, few can match the satisfaction of working on a pinewood derby car together. Most Cub Scout packs have an annual pinewood derby race. Little Scouts turn blocks of wood into super fast racing machines. In the process, they get a basic lesson in physics, tool handling, and competition. If you never had the pleasure of taking part in this glorious boyhood rite of passage, here’s how you can guide your son in building a pinewood derby car that will race to the head of the pack.

1. Remember, he’s supposed to do most of the work. Don’t be one of those uber-competitive dads who wrenches the project from his son’s little hands and takes complete control of the construction of the car in order to secure the blue ribbon. You can always tell which cars were built entirely by a dad, and everyone resents him. His kid ends up at the receiving end of that animosity, and worse still, feels like his dad doesn’t trust him. Your role in the car making process should be as minimal as possible. Once you fully understand these steps, your job is to simply offer guidance and encouragement and perhaps do any cutting that requires heavy machinery.

2. Check the rules. While there are general pinewood derby rules, some scout packs have local rules. You don’t want your son to spend hours working on his car only for it to be disqualified for not complying with the guidelines.

3. Trace the template on the block of wood. Included with the official pinewood derby set your scout pack will give you are a variety of car designs to choose from. You can get as creative as you want. Keep in mind that intricate designs often sacrifice speed for looks. Growing up, my dad and I always had success with very basic designs that looked like a wedge of cheddar on wheels.

The easiest way to get your chosen template on the block is to use carbon paper. With a sheet of carbon paper underneath it, place the template design on the side of the block of wood. Trace the design. Repeat on the other side. Make sure the front of the car is facing the same direction on both sides of the block.

4. Cut the block. Using a coping saw, cut just outside the template designs. You can sand down to the actual lines after you cut it.

5. Prepare the axle slots. Cars with longer wheel bases tend to be faster. So you might consider moving the two pre-made axle slots further towards the end of the block. If you decide to do this, make sure the new axle slots are exactly square with the side of the block or else the car alignment will be off.

6. Drill holes for the weight. Pinewood derby cars work on basic Newtonian physics. The cars race down a sloped track, propelled only by gravity. Thus, the heavier your car is, the more potential energy it has, and the faster it will go. When adding weight to your car, you have two options on where to place it: externally or internally. Externally is the easiest option. You just glue the weight on the top or the bottom of the car. However, this increases wind resistance. That’s why the best place to apply the weight is internally, inside holes drilled in the car. It’s best to place the weights near the rear of the car, so drill your holes there. You’ll probably have to drill 2 or 3 holes to get all the weight in. Pick a drill bit width that will allow space to insert the weight (see Step 13).

7. Sand. Start with heavy grit paper and work your way to a finer grit. Finish it off by going over the car with some steel wool. The car should be nice and smooth for the paint.

8. Paint and finish. Prime the wood surface of the car by applying a wood sanding sealer. Now you won’t have to put on several coats of paint. Spray paint is fast and gets the job done. But if you’re going for more elaborate designs, you’ll have to paint it by hand. After you paint it, sand it one more time with a fine grit paper. Apply decals to the car as desired (studies have shown that flames on the side will make the car go faster). Finally, go over everything with a clear-coat finish to give the car that glass-like look.

9. Check the wheels. Make sure there aren’t any burrs or extra plastic on the tread of the wheel. Blemishes like these will only slow the car down. If you see any, gently sand them down.

10. Polish the axles. The axles in pinewood derby cars are small zinc nails. If you want your car to be a speed demon, you need to reduce the friction between the wheel and the axle. The first thing you can do is polish the axles by gently sandpapering them. This will remove any burrs or blemishes that the spinning wheel can get snagged on.

11. Mount the wheels. This is a key step in building your speed machine. The wheels should be aligned to minimize the amount of friction on the wheel. Thread the nail/axle through the plastic wheel. Place the pointed end of the nail into the car’s axle slot. When you do, angle it so the head of the nail is pointing slightly toward the back of the car. This will reduce friction by causing your wheel to ride near the end of the axle instead of near the body of the car. Test roll the car to see if rolls straight. If it veers off in any direction, adjust the axles accordingly to straighten out the car. Adjustments should be made slowly with repeated trials.

12. Lubricate the axles. Dry lubricants are usually the only lubrication permitted. Powdered graphite is the most common dry lubricant. Just place some in the axle hole of the wheel and spin the wheel around a few times to ensure that the entire inside of the hole is covered with the graphite.

13. Add the weight and seal the holes. You have several options for weight. I always used lead buckshot. It’s definitely manly. Another option is zinc. Many Boy Scout and hobby stores sell zinc weights for pinewood derby cars. Cars cannot weigh more than 5 ounces, and it’s better to be slightly underweight than overweight because it’s easier to add weight than to remove it. Seal the weight in with some wood putty and sand smooth. Leave an extra hole empty in case you have to add more weight. Make sure to bring some extra weight along with some fast drying putty to the derby in case you have to add more weight to get up to that 5 ounce weight limit.

Do you have any more tips on building a fast pinewood derby car? Share them with us in the comments!

{ 50 comments… read them below or add one }

1 MountZionRyan August 17, 2009 at 11:49 pm

It’s my understanding that at that size and speed, air resistance has no part in it. Let him make it whatever shape he wants.

2 Muffin Man August 18, 2009 at 12:27 am

I always hated the kids that had the SUPER thin cars that would win every time. Always seemed like they were bending the rules by not constructing their car in the classic derby car shape.

3 Jeff M August 18, 2009 at 1:11 am

Pinewood derby cars work on basic Newtonian physics. The cars race down a sloped track, propelled only by gravity. Thus, the heavier your car is, the more potential energy it has, and the faster it will go.

This isn’t true. Newtonian physics says that things accelerate due to gravity at the same rate regardless of their mass. Ignoring the effects of wind resistance and friction, the kinetic energy at the lowest point in the track will be the same as the potential energy at the start. mgh=.5mv^2. The mass is on both sides of the equation, this it is irrelevant.

Now, if you really want to quibble about a small increase in speed, move the center of mass as far back as possible. Since the track is angled at the start, moving the center of mass of the car to the rear will also cause it to move vertically upward, which will increase the potential energy in a way that isn’t canceled out on the other half of the energy equation.

4 Will August 18, 2009 at 2:52 am

For weight, my dad and I used to melt fishing weights and pour the lead straight into holes drilled in the car. It may have been somehow toxic, but it sure made for some fast little cars.

5 Tor Hershman August 18, 2009 at 6:39 am

The Cub Scouts sucked and moi ’twere a Den Leader.

6 Allen Miller August 18, 2009 at 6:46 am

if the rules allow, covering the car with monocote makes for a shiny slippery car. We always used “Richard Petty ” blue.

7 Mike August 18, 2009 at 7:08 am

>>> “Test roll the car to see if rolls straight. If it veers off in any direction, adjust the axles accordingly to straighten out the car”

And just exactly how do you do this??? My experience with this resulted in either widening the grooves in the wood to where the nail wouldn’t stay put, or splitting the wood in one case on a too-thin body design. Super glue? No doubt about it, this step is where the winning cars are made (and the flames on the side of the car don’t hurt, either ;) ) Even if the car doesn’t win, you certainly don’t want to be the poor kid with the last-place car that comes dragging in 5+ seconds behind everyone all the other cars.

A tip on adding weight: get the car finished to the point where you’re ready to add the weight (cut out, sanded, etc. and ready to paint), then pre-drill the holes (if you are going to place the weight internally), then take the car, wheels, etc. to the post office, UPS store or some place with a postage scale and ask them to weigh it for you, adding weight until the whole thing weighs almost 5 oz. Now you know how much weight to apply in whatever fashion you see fit. Pre-drilling is the key – I was surprised at how little wood needs to be removed to drop the weight.

Another tip: last year, my son and I sanded the axles by putting the nail / axle into my drill, powering up the drill and gently putting the sand paper up next to it. Much better than manually trying to control the sand paper!

Final note: Check out the movie “Down and Derby” – http://www.downandderby.com/ – absolutely hilarious. You may want to preview it before watching with your Cub Scout if you don’t want him giving you dirty looks the whole time (depending on how competitive you are…)

8 John Burzynski August 18, 2009 at 8:19 am

Having run Pinewood Derbys for 12 years when my kids were younger, a couple of real life observations:

Primarily, weight is everything, period. We had a maximum of 5 oz., if you didn’t carry the maximum amount of weight, you didn’t win, simple as that. Cars seemed to do better with weight in the back of the car, but I have no proof of this.

Friction on the wheels and axles is the next key after reaching wieght…properly aligned wheels, no rubbing or burrs, all of what is stated in the article. We had cars do very well that only had 3 wheels touching the track, I assume less friction from one less wheel. If the wheels don’t track straight, they rub against the raised inside of the lane, and that slows the car very quickly.

Wind resistance seemed to have little or no effect. Some pretty ‘ratty’ looking cars with both high and low profiles won or did well…

Let the kids do as much work as possible, it is for them after all.

9 DMD August 18, 2009 at 9:40 am

Pennies work well for weight, too. I usually turned my pinewood derby cars into convertible roadsters with plastic finger puppet drivers and hid the pennies under the drivers.

10 Ryan Miller August 18, 2009 at 9:40 am

Dad and I would put the 4 wheels on a drill bit and buff them with some fine grain sand paper to knock some of the plastic flash off. Also, I did encounter one major design flaw. Make sure that the nose of the car comes to somewhat of a point. one year I rounded down the front, and the starting peg would drag down the front of the car, which made for very slow starts. Try building a pickup truck, it looked super cool

11 Luke D August 18, 2009 at 9:48 am

In the past my brother and I acquired more then our fair share of 1st place trophy’s in pinewood derby cars (12 in all). My experience is we always put the weight on externally on the bottom. You can buy small plates of weight from your local hobby shop and break off pieces to get the weight just right. The post office scale may not match the one at the competition exactly and some last minute adjustments may need to be made.
Outside of the weight the axles are the key to winning. Don’t just take some sand paper to the axle and think you got it good enough. We would start by putting the axle in a drill and using Emery cloth to get the large spots down. Then we would use a strip of cloth and some polishing compound and repeat the procedure using the drill. We also found that Silicone spray that dried clear was the best lubricant on the axles. Go ahead and put it on just before you leave home for the big race.
For years this was our family secret but after we were out of Scouts we passed on the secrets to most everyone and I must say our troop had someone win the regional competition every year.

Good Luck and have fun.

12 OkieRover August 18, 2009 at 10:22 am

You want your car to weigh the most it can. Add weights to make the vehicle weigh exactly the maximum allowed. The shape is unimportant. There is no significant drag created on an object this size at this speed. With that said you can have your little tike have fun with the shape.

I’ve seen snakes, an unmodified block of wood, plastic army men glued to the top, dragon’s heads, the sky is the limit.

We finished first in Bears and Webelos. In our pack all the winners are combined for a grand champion. And 1st and 2nd for Grand Champion overall those years. I built a car for the OPEN class and won first. And raced my son’s first place car the next year and got second.

13 Lewis Butler August 18, 2009 at 10:36 am

The shape of the track can help determine the best placement of the weight.

If the track is curved, then flattens at the bottom, the most potential energy will come when all of the weight is in the rear of the car. The weight at the end of the car will sit fractions of an inch higher than if it was in the front. Higher PE will result in a faster car. If the track is a constant slope down, than the distribution of the weight will matter less.

One rule, which you should also be careful with is the wheel, and their alignment. Like the post mentioned, the longer the wheel base the better. The other twist on this is to position one wheel slightly higher than the rest, so it doesn’t quiet rest on the track. This can help reduce a little bit of friction. This can be slightly tricky as you have to make sure your car will still go in a straight line.

When putting the weight in my cars, I preferred to drill holes in the top of the car, put the weight in, and use wood putty to cover the holes. It was easy, and I could sand the putty down prior to painting.

The last track I competed on was a curve that flattened at the end, so I wanted to get as much weigh in the rear as possible. I cut a hole in the center of the car. I left just enough wood for the car would be solid enough not to break and the wheels to be stable. This allowed me to distribute a little more weight to the rear, along with having a design which no one else at the PWD had.

14 Greg August 18, 2009 at 11:48 am

+1 on having only 3 wheels touching the track. From what I remember, this isn’t allowed at levels past your local one.

15 Ryan August 18, 2009 at 2:15 pm

One of my fondest memories of engineering school was the project we received for an “adult” pinewood derby competition. It was substantially more complicated than the cubscouts version (I would hope so) but it was a great learning experience to learn design, fabrication and assembly all with the pretense of doing something cool.
P.S. – Sorry, forgot to tell you great post!

16 Mr. Wil August 18, 2009 at 2:27 pm

+1 to:
Shape doesn’t matter.
Keep the weigh as close to 5 oz. as possible.
Sand and polish the wheels and axles unilt they look perfect.
Also:
Add graphite to the axle/wheel combo on the car as a last step then run it on a treadmill if possible, a PROVEN advantage.
Last but not least: have a “dad’ or “geazer” class to discourage hovering dads at construction time!

~Wil

17 Mike August 18, 2009 at 4:39 pm

AoM,

A Pinewood Derby Event is not only a great father/son bonding opportunity, but it is also a way for kids to creatively express themselves. People tend to ignore the design component of Pinewood Derby Event, focusing only on weight, wheels, etc. What are your chances of beating 50 boys who have taken the exact same measures to making their car go fast? Pretty slim. Very rarely do kids put forth similar effort to come up with a unique design, which will yield them a “best design” trophy just as big as the “fastest car” trophy. When I was a Cub Scout, I designed a car with my dad that was a Heinz 57 ketchup bottle. We molded the block to have the same ridges as a ketchup bottle, painted it Heinz 57 red, and slapped the appropriate labels on it. Every other car looked pretty bland in comparison. It was a slam dunk for the “best design.” I still have the car.

18 J. McElrath August 18, 2009 at 5:07 pm

Someone wrote (above) that “Newtonian physics says that things accelerate due to gravity at the same rate regardless of their mass.” I agree and never added any weight to pinewood derby cars. Believe me, I was so wrong. I lost a lot of races to those with crude, non-streamlined (but heavy) racers. Weight makes all the difference.

19 Ted August 18, 2009 at 5:23 pm

most of this is good solid advice, but the weight bit is wrong… very wrong. Ideally the car should be streamlined to minimize drag and air resistance and frictionless at the axles. The weight can be anywhere from ounces to whatever the track can support, and here’s why:

It’s true that heavier things DO experience more pull due to gravity, but they also have greater inertia in proportion to their weight. This means that while the Earth is pulling harder, there is just enough resistance to movement to completely negate that extra pull. Marbles and bowling balls fall at the same speed. In a vacuum a feather and a hummer will fall at the same rate.

back to ideal pine derby cars: obviously getting the axles frictionless is impossible, but you can get them pretty close by following the instructions above (polish, lube, etc). The only weight requirement is that the car has to be heavy enough for gravity to completely overwhelm the friction at the axles.

(I don’t know if anyone mentioned this in a comment yet because I didn’t read all of them, but I felt like throwing in my physics knowledge/two cents)

20 Andrew August 18, 2009 at 7:06 pm

I have conducted 6 years of pine wood derby races and my two oldest sons have each always moved on past the local pack level and onto districts, each having won first place in back to back years at this level. Here is a lot of what we do:
We build the car together. He does as much of the cutting is prudent for his age, more as he gets older. We use a band saw for clean cuts.
He does all of the sanding of the wood body, gluing, cutting of the weights. I press the wheels in, until the hit about third grade, then they have the strength to do it usually.

Wedge’s and wedge like shapes, and flat thin shapes, in my experience, dominant in speed. I know one commenter states that the weight is not crucial, but after seeing literally hundreds of pinewood derby cars race, it has always been the ones that are very close or just at 5.0 oz that do well, and noticeably so. However, this may well be an indication to overall attention to detail, which pays off. We use tungsten rods, never lead, with a wedge shaped car. Drill the holes in the wood blank in the back end of the car before you cut out the shape. This way you have a flat surface to drill against. Place your cut to fit tungsten rods and a few big drips of two part epoxy, cap with cut to fit dowels. Then cut out your shape, it comes out very clean. Additional holes can be drilled just in front of the rear wheels for more tungsten. Leave at least one small hole open and available for modifying the weight on race day. The race scale simply will not produce the same reading as whatever scale you used. It’s murphy’s law. I use tungsten putty in this last hole, which stays moldable but also stays in place. also, don’t hesitate to keep putting a little tungsten putty on the scale until you go over 5.0 oz, not until you reach it. Depending on the accuracy of the scale, there can be a difference of up to .1 oz, or even 0.9 oz although I hope not, between cars that show as 5.0 oz on the scale. Some question if this is the right thing to do or not. I’m not judging, you decide. Of course, the scale your race officials use could be extremely accurate (ours is, since it is a lab scale) and therefore this discrepancy in car weights won’t occur.
The rest of this is if your rules allow:
Don’t use the axle slots. The are never accurate, and frankly aren’t worth the effort to fix. Drill holes with a drill press instead. Extended wheel bases are a plus, and one front wheel raised so it does not hit the track are options we have used in the past.
Sand your axles and polish them with jeweler’s rouge. Put the axle nail in a drill or drill press and use that to spin the axle while you hold the material to it.
The wheels must also be prepared. Sanding out the burrs is a must, but if you have the skill and confidence, I recommend making a slight cone on the hub of the wheel as well.
Graphite. Graphite. Graphite. And spin the wheels on the axles. Graphite again. Don’t put them on the car until the very last step. When you do put them on, press them on. Use a padded drill press and a block of wood, a padded vice clamp, whatever, but do not pound them in with a hammer!
Finish: paint, wet-applied wraps, stickers, spray paint, sharpies, honestly, whatever. I know people are cringing here, but I have seen cars with all of these options do very well. Again though probably due to overall attention to detail, in general the cars that have been finished with at least some care are usually winners.

I have one last set of suggestions: Make your sure pack gives a trophy to every scout, because every scout wins by participating. Have an “artistic” category that will also have 3 top place winners, who get trophies that are just as big as the speed class. This makes it more exciting for everyone involved, and lets more kids express themselves without feeling like their car doesn’t look like what they want it to look like. Have three parents who’s scouts are in the speed category pick the winner of the artistic class. These parents should never be leaders in the Pack. I have seen swiss cheese with a mouse, pirate ships, cake, sponge bob, sharks, tanks, planes, alligators, fire trucks, baseball bats, hotdogs, etc. They are awesome, and deserve recognition.

Have fun! Enjoy the time with your son. Take the time to explain what you are both doing and why you are doing it. It is a great time to explain different sand grits, the chuck of a drill, what epoxy is, and for that matter, what tungsten is. Use the opportunity to its fullest.

21 nahum August 18, 2009 at 8:42 pm

I used to make Pinewood derby cars when I was in cub scouts. OK my dad used to make Pinewood derby cars. But anyway I remember one year this kid came in with a charmingly self made car that was about 2 oz (we all laughed at him. Seriously I think I’m joking but can’t really remember). Apparently the local butcher let him use his scale to weigh it and the local butcher wasn’t a straight shooter. Long story short the master helped the kid out to get up to weight by taping about 3 oz. of lead to the nose of the thing. My childish heart broke as my remarkably lifelike Morgan modelled pinewood derby car was absolutely fing trounced by this ridiculously hood-ornamented pine jallopy

My point is – put the weight on the nose for a sure winner. It’s like the pine wood derby equivalent of betting on a horse with foot wraps.

22 Will August 18, 2009 at 10:49 pm

“…your job is to simply offer guidance and encouragement and perhaps do any cutting that requires heavy machinery….”

Precisely what I did with my son. We made the block of wood look roughly like the picture on the box, and then he took over. The only thing I did other than cutting was to buy some weights that screw on the bottom of the car, and take it to the mailroom in my office to get an accurate weight on the postal scale. He won second prize one year, and first prize two years later. And this was from a group of about 200 scouts.

Basic answer: Let your kid have fun with it, and make sure he knows that, in this case, being #1 is not THAT important. My other son’s car didn’t even make it to the semi-finals.

And I like the idea of a “Dads-only” class. Then the overachieving dads can show off all they want, and leave the boys out of it.

23 Don August 19, 2009 at 2:37 pm

In our scout pack, we reserved the night a week ahead of the derby as a weigh-in night. On this night, we would drill the holes in the bottom of the car for weight, place the car on the scale, and then pour hot-lead into the holes until the car reached the 5-oz weight. If there was too much weight, an electric drill would be used to scrape away weight. Having all the cars very close to the 5oz limit makes for much more exciting racing.

24 KT August 19, 2009 at 11:16 pm

My tip is not enrolling your child in the Boy Scouts, an organization that openly discriminates against gay people.

25 KF August 20, 2009 at 7:09 am

Hey KT the website is called “The Art of Manliness”

26 Will August 20, 2009 at 6:30 pm

Oh, please, KT. Scouting is one of the finest organizations a boy can ever belong to. Get a life.

27 Beretta August 20, 2009 at 11:12 pm

Are you allowed to play with the wheels?

If so, physics suggests you should mill as much weight out as possible without them collapsing. This will reduce the moment of inertia (basically the rotating mass) and allow more of the potential energy to become linear kinetic energy instead of rotating kinetic energy.

The More You Know

28 Dan August 21, 2009 at 10:48 am

2 notes to add to the above, one from my experience from pinewood racing as a kid and one from my Engineering classes in college:

1) Evenly balanced cars do great! I came in 1st place with a car shaped like a wedge with the ends rounded off and the extra weight added to the front by way of a couple of thick screws which made it kinda look like it had headlights. The overall effect of weights in the front and a thick wedge back spread the total weight more or less evenly over each wheel, same amount of downforce/resistence on each axle/wheel.

2) To minimize rolling resistence, in addition to drilling out as much of the wheel interior as you can (think of a 4 or 5 spoke alloy wheel rim) to reducing rotating mass, also try to grind away as much of the thickness of the surface of the wheel touching the ground as possible (even to almost a knife edge if possible). There is a reason the experimental solar powered and super fuel efficient cars you see in college engineering competitions have tall skinny wheels, to reduced rolling resistence as much as possible.

29 Niemsters August 24, 2009 at 10:31 pm

My Father’s a dentist and would use his tools to polish the axle and the wheels SUPER smooth. Besides that he’d let us to all the other work, and my brothers and I always seemed to win.

30 Mike August 27, 2009 at 4:52 am

My two sons are 17 months apart. We built many pinewood derby cars over the years. It was a fun learning process. They won first and second place in the district the last two years.
For us it was a good opportunity to work together and teach the boys how to safely use power tools. Here are some of our observations:

Thin cars weighted in the rear seem to run faster. We made ours thin and drilled three 3/8 inch holes in the rear (crosswise). We originally melted lead and poured into the holes, but we found that 357 wadcutter reload slugs fit nicely and work just as well (not the entire bullet; the reload slugs!!). You should be able to find them at a sporting goods store.

It’s important to use a drill press to drill the holes for the nail axels.

The axels are nails; they can be polished to a fine sheen using jewelers putty. We put the nails in a drill press and the boys held the jewelers putty against it gently as the nail turned in the press.

The wheels are plastic. We made a mandrel that would fit inside the wheel and attached it to the drill press. The boys would gently hold fine grain sandpaper against the tire until it was smoothe.

The lubricant that most people use is graphite. It works pretty good but not as good as molybdenum. You can find it at some hardware stores. It comes in a tube and it’s in powder form.

In our rules, it didn’t state that all 4 wheels should touch the track. If you drill one of the front holes for the axel a little higher, the front wheel won’t touch the track. Now you have reduced the friction of your car by 25%. We’ve tested this using two cars that had nearly the same speed and it DOES make a difference.

If you cut the block of wood into a wedge shape leaving just enough room for three 3/8 inch holes in the rear. Fill them with lead, your car should weigh close to 5 ounces. If it is OVER 5 ounces, get a drum sander attachment for your drill press which is slightly LESS than the width of your car and remove as much wood from the under side near the front. We tested the weight on post office scales.

We had some boys in our pack that didn’t have a father around the house. We always invited these boys (and any other boys) over to help them make their car. I did that each year for several years after my boys finished scouts.

31 Derby Leader September 1, 2009 at 11:04 am

The most difficult task for our PWD committee is creating and enforcing fair rules and getting the dads to follow the rules. We have them sign a form saying they let the scout do as much building as possible. Unfortunately, it’s clear that most of the speed winners are built by dads bending the rules. We’ll make a few rule tweaks this year. It’s too bad we have to play these cat and mouse games.

The approach I take with my son is to help him channel his creative energies on a fun design that he can build and paint. I was the proudest dad at the Derby last year when he won the best design award. Sure, his car didn’t place in the top three fastest cars in his rank. But it was clear to the impartial judges (no relationship to any kids in the race) that it was his design and efforts that made that “cool” car.

32 Dad now September 12, 2009 at 9:43 pm

I never won a race. My dad only helped on the day of the race. I wish I could have one at least one race every year. My advice is that the boys ultimately love to win. I would encourage dads to do all they can to help the boy win at least some races. Don’t wake up the hour before the race and try to act like you are involved. Spend some time with the boy and look at pictures and see what he likes. Spend the time to learn about how to make them go faster. So what if they are not perfect. I always admired the boys who went home with the fastest car trophies because someone actually woked with them.

33 MDH October 28, 2009 at 11:26 am

After several years of experience with Cub Scout Pinewood derby races as a youth and with my own son and from organizing and leading a “Powderpuff Derby” for our local Girl Scout organization for the past few years I have only two things to add to the list of comments.

VERIFY THE RULES
for all of the races that you hope to participate in. This means that if you plan on winning and going on to the District race (or whatever it is in your area) you need to check the rules for that race as well. In general, you have to race with the same car that you used at the local level without modification. The local race is typically the most lenient. Every year that I can remember has had at least one parent try to get by with some un-allowed modification and get mad when they have to try to correct it with minutes to go before the race starts. It is even worse to have to tell your kid that they don’t get to participate because you were too stupid to check the rules before trying to cheat the system. This probably isn’t exactly the type of moral values that you hoped your kid would learn from being in Scouts anyway.

GLUE THE AXLES
to the block after making sure that they are installed the way you want them. Be very careful not to get glue on the actual wheel. Almost as bad as having to tell a kid that their car can’t race because Daddy is a cheater is when a wheel falls off early in a race or even before the racing begins. Typically the axle will not stay in the groove very well after that and the car will have problems racing for the rest of the day if it still works at all.

34 Mountain Hermit October 30, 2009 at 5:02 pm

My solution for a winning pinewood derby car is to drill a hole all the way through the block of wood. Make it kind of like a jet car. Sand and polish the bore smoothly. This creates a lot less friction. Of course the car will be lighter, so you have to add a little more weight, and in doing that you have to be a little creative. You also have to be a little creative with the body design & cutting. Because now you have this big ‘ol hole down the middle of it. The next thing you do is chuck the wheels up in your drill or lathe.
And you sand the surface that touches the track to a an edge. Less wheel surface, less friction. I have done this on my pinewood derby cars when I was a scout and took 1st place every time. I have also done this with all 3 of my boy’s cars and they took home 1st & 2nd place trophy’s.

35 Grandpa November 1, 2009 at 3:24 am

Two sons – two Pinewood Derby cars – two second place finishes. Let the kids do the work? Sure – losing builds character. Dad builds winning cars. I endorse the views on weight and friction. I spent a lot of time polishing the axle nails. Would have come first with the second car except that the father of the kid with the winning car ran an industrial abrasive company and probably knew more than I did about friction. This was over 40 years ago and both cars still survive, the proud possessions of the two sons who raced them.

36 Paul November 5, 2009 at 11:51 am

I have used a dremel tool to polish the axles. Place the axle in the dremel tool and start with 400, then 800, then 1200, then 1600 and finally 2000 grit WET sandpaper. It takes a litle while but the axles will come out with a mirror like finish. When building a wedge car, be careful when placing the weight at the rear. We built a wedge car with all the weight at the rear and halfway down the track the front end would start to come up off the track and dance around causing us to lose speed. Just a bit of weight on the front end would cure this problem.

37 Gary D. McAulay November 5, 2009 at 4:58 pm

I have researched the history of the Pinewood Derby fairly extensively, and it’s both funny and sad that overly-competitive fathers have figured in the race since the very first one, held in Manhattan Beach in 1953. However, in the end, it’s about the time a dad spends with his son working on a project together. While there may be a few exceptions out there, every former Cub that I have interviewed, including the boy who won that first race, has only a vague memory of any wins or trophies. They all have clear and obviously cherished memories of working on their cars with their dads (or moms), which is, after all, a main purpose of the project.
A tip of the hat, too, to Don Murphy, who created the race and demonstrated that the manly act of volunteering as a scout leader can affect the lives of a million children.

38 deaton December 25, 2009 at 8:40 pm

all good advice here, and a great article. one thing that does need to be mentioned, if it has not been covered yet, is that the whole elongated wheel base strategy is not actually allowed for the district events and up (at least not when I competed 10 or so years ago.) this might have been just where and when I competed, but all the same, make sure that whatever you do is still allowed within the rules.

39 Andrew January 2, 2010 at 9:46 pm

For many, Jan and Feb are pinewood derby months. Does anyone have any other hints to share?

40 Mike January 7, 2010 at 4:33 pm

I was torn about the division of labor, and how much time and effort we should invest in regard to building our first car. So I sat with my son and we worked on building a car. It was our first Pinewood Derby race. We came in last, and needless to say my son was sad. To boot there were two families in my town that always placed 1st and 2nd. Well… not for long. I did a little research about inertia, mass, and some of the other topics discussed above… and viola… the next year there was a new sheriff in town. I did the cutting, my son did the sanding and painting, and I placed the wheels on and balanced the car. We placed first.
The gauntlet had been thrown down.
Every now and again when I see this other father around town he’s always crowing about the next pinewood derby.
It would be funny if it was’nt so sad.
I think the day before a race the kids should get two hours to build a car, and it should be in a pack setting with some limited guidance from a parent. That way they could learn about physics, and design. That would save them from having an overbearing father steal away the creative joy, and scientific curiosity they would otherwise develop.

41 DoesItMatter January 11, 2010 at 10:24 am

KT…. This is a website about how to build a pinewood derby car, not a political debate. If you want to start an organization for boys that encourages the homosexual lifestyle, do it, but don’t shove your crap down other people’s throats. The boyscouts is the best organization out there to teach boys to become strong, responsible leaders while at the same time teaching them valuable skills and having fun.

All that aside, my experience has been that the design of the car has nothing to do with its speed. Axle/Wheel polishing & truing, weight placement (slightly forward of the rear axle) and graphite are the keys to winning. To far back could cause your car to shimmy if the weight isn’t perfectly centered.

42 Brad January 28, 2010 at 2:15 pm

Case in point. I had a boy show up on race day with a “hand carved and painted with magic markers” car. He didn’t have a dad at home. He did all this work. He was 7 years old.

*** 15 minutes before racing, I put his wheels on straight for him, added graphite. Got his car up to 5oz, mainly by putting a giant fishing weight on the back of his car with hot glue. HE FINISHED 4th OVERALL !!!! I was very proud of him. I wish he had a dad to help him more, but the lesson was simple. Let your son design and do whatever he wants to his car. All dad has to do is get the weight to 5 oz, get the weight in the right spot and put the wheels on straight with some graphite. PLEASE don’t overdesign YOUR SON”S derby car. Let him run the show.

43 mick donahue March 7, 2010 at 1:59 pm

My son who is 8 and i our in our first derby race
thanks for all your insite and tips

i was wondering if any know where to get this “molybdenum” lubricant does it go by another name?

i car was built from a kit thru our church group, we have wood screws for axles and all of what i read and see is with nails, does this make any difference, is removing the wheels and axles and re-polishing and lube between races ever done?

we have enjoyed our building together and have a good looking car, no idea if its fast or not
i we are just under 5 oz.

thanks for you tips

44 spock March 18, 2010 at 5:36 pm

For those who are arguing about the physics of the race, you are each sort-of right. It is true that if you were to drop two cars of different weights (in a vacuum), the speed at which they fall would be identical. The same would be true if the sloping car track had no friction. The thing is – the car going down a slope is not frictionless, and is slowed by the friction of the wheels/axles. So…max weight gives the max inertia = good, and make the wheels/axles as slippery and straight as possible.

45 James April 18, 2010 at 12:28 am

Our district race is very lax… extended wheelbase is allowed. Even those razor thin wheels. Clearly they need better control. Our pack rules are better, but when we got to district, we couldn’t compete with other cars that didn’t have to follow the rules we did. They should mandate a universal set of clear rules, especially regarding wheels, axel position, etc. Too much crap being sold on the internet that is not official stuff from the kit.

46 Ryan May 7, 2010 at 2:56 pm

Wow, this article could have been written by my dad 20 years ago. This is exactly what we did and I won 1st place twice. If you’re not first, you’re last.

47 bingbag May 11, 2010 at 8:35 pm

cheese:)

48 James July 1, 2013 at 2:58 am

Re: physics.

For a set allowable mass, you want to minimize the rotational moment of inertia of all rotating parts. http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html#cmi the three factors are mass, diameter and shape. For a fixed mass and diameter, a sphere is actually more economical than a cylinder or hoop in that order (in theory, a “mag wheel” would be somewhere between a cylinder and a hoop). Practically speaking, thin disc wheels (a very thin cylinder) with holes drilled in work because you’re real-world options for spherical wheels will be heavier by more than 20% which is about the relative advantage of the shape factor. Removing weight nearest the circumference of the wheel is most effective, but care needs to be taken so as not to unbalance the wheel. Discs punched out of a flattened aluminum can would be good, and a light-weight axle (nylon/teflon?) would be theoretically advantageous if you can get the wheel alignment accurate.

If the track finishes along the floor (horizontal) then setting weight as far back as possible (higher up when the car is in the starting block) without ruining the car’s balance is also sound physics.

I’d walk a kid through the physics first, and then let him make the design choices.

I had to do challenges like this as part of my Engineering degree, and most times, someone who sacrificed the physics a bit for accuracy in fabrication would win the race, but the design most coherent with the physics principles would get better marks. Most importantly, these competitions are a great way to get kids interested in learning some physics, craftsmanship and love for their dad.

49 D. Martin August 2, 2013 at 11:55 am

The physics of mass not mattering makes does seem correct. Jeff put it best in the language of physics: mgh=.5mv^2 and the mass cancells out. However, higher mass will have more momentum, which (correct me if I’m wrong) will better resist any effects of drag from the track or misalignment. (what spock said)

When I was making derby cars, we would glue on pieces of balsa to either side to create wheel wells/fenders around the tires and get a more real-car look out of it.

50 Mike September 12, 2013 at 12:35 pm

I don’t know if this was mentioned previously, but a penny weighs 0.1 ounce exactly. My son and I would use the scale at the post office to get the car weight as close to 5 ounces as we dared before the weigh-in on race day. I’d be sure to bring a few pennies and a tube of super glue with me to the race so that we could get the car up to 5 ounces exactly if it was still a little light on the official scale.

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