Pinewood derby build ideas

All right boys and girls time to build a Pinewood Derby car. My son's Boy Scout Pack just put out the official time and date, I have one month to help him build his and then compete. But there is also an outlaw class set aside for yours truly. Let's hear it your best ideas.

I know my dad has some great tips and tricks but new ideas are fun and welcome.

graphite for the wheels, you knew that. chock the wheels in a drill and spin em, while polishing with sand paper, then emery, then fine, then ultra fine, then a buffing wheel with compound. perfectly round and smooth wheels. do a similar run through the axle holes, make sure theres no casting marks on the contact surface. polish the nails too, paying close attention to the head where it will contact the face of the wheel. add a thin layer of aluminum foil the body on the inside of the wheel, where the hub makes contact with the wood. be sure to graphite that. nose weight is better for take off, but you start slowing down faster. rear weight makes the launch a touch slower, but you accelerate for a few inches longer then others. rear weight is fun cause you are usually a few inches behind until it flattens out, then you pass everyone. makes for good racin'. also, take nothing off the front of the car, leave the wheels as far back as is stable. this keeps the wheels on the decline longer, as they wheels are 'higher' behind the launch nail than others who shorten the front. i usually swap the kit around, build it 'backwards' to keep the wheels back.

aerodynamics are almost of zero use in this application. ive seen unbuilt, box stock kits (literally the wheels on a block of wood) beat cad designed cars cause the builder knew how to clean up the wheels and use the proper lube. the key is making sure the weight is dead on, dont leave an ounce on the table, being adjustable is good too, like being able to add washers under a screw until you creep up on the limit. sanding the wheels will also lower the weight, so be sure to do that before you set your ballast.

theres ways to cheat too, if your interested. my favorite was leaving the bottom unpainted, then after weigh in, setting it on a wet rag to soak up water. it would dry before the post race weight check, and you'd be clear. i have more if your interested.

-J0N

I have no proof, but I've heard 4.98oz allows for better roll at the bottom and giving one axle the slightest tweak, so the fourth wheel just barely touches reduces rolling resistance.

Isnt this the exact discussion that got the valve cover racing at challenge started?

I saw this in a store the other day and thought it was super cool.

I totally agree to spend your time polishing the axles. The last year my daughter won first place with a Pez car we made and we ate a lot of Pez candy.

Once again - axles, wheels, and graphite.

84FSP just built a couple cars recently. I think they did really well in the races.

If you happen to want one to look like an early GTI, he'd be the guy to ask..

In reply to jmthunderbirdturbo:

More cheats?? Of course we are interested!

Local rules sometimes do not limit the axle locations. Our local rules only say the car has to fit inside a measuring box.

In this case, I stretch the wheelbase to the absolute limit. Makes for a smoother ride, and straighter tracking.

I put the rear wheels at the exact rear of the car, with as much weight as I can rearward. The front wheels still fit inside the measuring box, but overhang the front of the body by as much as possible. Our starting "gate" is a vertical post in the center of the track which levers down. So, when the car body is resting against the post, the front wheels are actually getting a slight head start. Doesn't matter at the top end, but will break the finish line first in a photo finish.

Know your rules, but also the details of your track setup and design. Ours is usually setup with a fairly steep slope, then a long level straightaway. Weighting the car as Jon suggested always gives me a slower start, but an advantage at the finish.

Our track also has a raised center guide, but no outer guides. I make the car as wide as I can, so the axles are as far as possible from the raised center guide- reduces friction from bumping the guide.

I just checked the last car I built- the center of balance is less than 1/2" in front of the rear wheels.

Berkelying pinewood derby. I suck at making them. Last time my son had a competition we made 6 cars. Polished the axles, lightened the wheels, weights perfect, ALL OF IT. Nothing made an appreciable difference. Not alignments, tricycling, wheelbase. Nothing.

All the cars looked cool, and weren't embarrassing but they were all solidly mid pack. Grumble.

Edit for clarity: at the time I was the den leader for my son's troop and I wanted our derby cars to rule. I bought a band saw, a drill press, a digital scale, a vertical sander, the DVD and book on how to build the perfect derby car...... Even built a practice track. None of it made a difference.

The "outlaw cheater" that won weighed two lbs btw, in case you want to try that.

Back when I was a kid, many, many years ago, my father chucked my wheels in the drill press and turned the rolling surface at the slightest of angles so that just the inner or outer edges touched the track. He also somehow cut away the axle bores so that the center portion didn't touch the axle, just a tiny bit on each end. His plan with to insert tiny pieces of mechanical pencil lead as roller bearings but he didn't have precision enough equipment.

I don't remember that it was particularly fast, but it was a lot of fun.

I normally make my father's for the troop he works with. I generally make hot rod looking ones with nice paint that aren't terribly fast but a couple years ago I got lazy and made buses. They were surprisingly fast but possibly a bit overweight. We found that if you run them a bit on a treadmill after polishing the axles and wheels you can make sure everything is aligned well and the start to roll a bit smoother.

I think the most important thing to remember is to let your son do as much of the build as possible...it seems these days that too many fathers take over the whole thing, which misses the point.

stuart in mn wrote: it seems these days that too many fathers take over the whole thing, which misses the point.

First car I built was totally on my own, whittled it down w/ a dull Barlow pen knife. Rough sanded w/ whatever paper dad had on the shelf and painted w/ red barn paint. No axle, wheel or ballast work. Looked crude as the Flintstone mobile. Made the motherberkeleying podium.

Next year we cut the body shape on a band saw, sanded, sealed, painted, lead ballast, the axle tweak, even model car decals--- and... a berkeleying backmarker.

Folks saved a bunch of my old scouting stuff but that Flintstone mobile was lost forever.

Lotta fun.

My dad never lifted a finger when it came to my Pinewood Derby cars, or my Soapbox cars for that matter. He did not help with design, he didn't offer advice, he didn't supervise and no power tools were used.

It wasn't that he didn't care but we strictly followed the rules of the day (mid 1960's). That was a better lesson than how to minimize rolling resistance.

And I held my own against cars that were clearly not built by 8 year olds.

I couldn't agree more on the spirit of the event responses.

I have a really nice wood shop, and have 3 boys that have participated over the course of 22 years. I generally use the Pinewood Derby as an opportunity to teach some woodworking merit badges, and invite the entire pack. I have helped build over 200 pinewood derby cars.

But I am really serious about keeping my hands primarily off. I may help do the bandsaw work, but that is about it. On Derby build day, I usually have 15 Cubs around my shop using sanders of all all types and sizes. Because of my seriousness about enabling the kids to do it, out of all of those cars, very few have won. Only 1 made it to the regional championships (and won for appearance, not speed). Total win for the kid- he wanted a car that looked like a shark with an arm hanging out of it's mouth. I never would have thought of that!

I usually make the moms go to the house and have coffee.

In reply to SVreX: That's similar to how my dad does it. A lot of the kids my dad works with are from single parent homes so they all get together and build their cars in the church basement over a couple nights. The kids do most of the work with the leaders helping out cutting them on a scroll saw and they do the sanding painting ect. I usually do a couple ahead of time so he has a few examples and because he likes nice deep shiny paint that you can't do in a basement full of kids.

At our Troop, we also have a Dad's Derby. Prove your stuff- no awards.

We've found it to be a teaching opportunity, and it allows the kids' cars to be kids' cars (with less arguing about the ones built by machinist dads).

Sometimes the kid's cars are much faster.

I once heard about a Troop that had a really nice track which included a machined gate to release the cars.

One kid (or his dad) figured out that he could put a magnet in the nose of his car, and use the gate to slingshot his start.

We just finished our Pinewood Derby and my son placed 13th of 37 attendants. My son wanted a GTI like Daddy's race car which presented a few construction issues. Having then added sides and an addition roof section it turned out well. Pay close attention to the wheel, axle, and lube commentary above. Also the $12 digital scale from Harbor Freight was a useful addition. There are a few salient points on cambering wheels in to decrease rolling resistance that are also relevant.

We've had good luck with stretching the wheelbase and locating the weight as far rearward as possible without having the car pop wheelies (been there!) Make sure it weighs the full 5.0 ounces. Graphite, obviously. And tune the car so it runs straight. I always give it a push across the hardwood and see if it goes left or right. If it pulls one way or the other, I will turn one of the axles about 90 degrees with a pair of needle-nose pliers and try it again. Takes a little trial-and-error, but a car that tracks straight will lose less energy bumping off the center strip on the way down.

So in this Cub Scout pack there are 3 classes.

Cub Scout class, which has very specific and strict rules.

Sibling class, same rules.

Outlaw class, not very many rules. Adults only.

Now as some of you have stated the kid needs to do the building but I am NOT turning a 6 yr old loose on a bandsaw or with a pocket knife. Paint it, sure. Sand it, yea. No bandsaw sorry.