The forces propelling a pinewood derby car are gravity and inertia, the opposing forces are friction and air drag. Therefore, pinewood derby car modifications are aimed at maximizing the potential energy in the car design and minimizing the air drag and the friction that occurs when the wheel spins on the axle, contacts the axle head or car body, or contacts the track guide rail.

Pinewood Derby Car and Friction

Friction due to air drag is a minor, although not insignificant, factor. The wheel tread can be sanded or lathed and the inner surface of the hub can be coned to minimize the contact area between the hub and body. Polishing the wheel, especially the inner hub, with a plastic polish can also reduce friction. Often one front wheel is raised slightly so that it does not contact the track and add to the rolling resistance.

Pinewood Derby Car Extensive Modifications

Axles are filed or lathed to remove the burr and crimp marks and polished smooth. More extensive modifications involve tapering the axle head and cutting a notch to minimize the wheel-to-axle contact area. Note that packs can establish additional rules for what, if any, modifications are allowed. In some areas, no changes can be made to the axles or wheels.

Pinewood Derby Car Energy

A second consideration is the rotational energy stored in the wheels. The pinewood derby car converts gravitational potential energy into translational kinetic energy (speed) plus rotational energy. Heavier wheels have a greater moment of inertia and their spinning takes away energy that would otherwise contribute to the speed of the car.

A standard wheel has a mass of 3.6 g, but this can be reduced to as little as 1 g by removing material from the inside of the wheel. A raised wheel can reduce the rotational energy up to one-quarter, but this advantage is less with a bumpy track.

Pinewood Derby Car Lubricant

A proper lubricant, typically graphite powder, is essential. Wheel alignment is important both to minimize wheel contact with the axle head and body as well as to limit the contact between the wheels and guide rail as the car travels down the track.

The center of mass of a typical pinewood derby car is low and slightly ahead of the rear axle, which helps the car track straight as well as providing a slight advantage due to the additional gravitational potential energy.

When building your Pinewood Derby car, never wait to add weights! However, the process is more complex than it might seem at first. Failing to take the right steps could mean the difference between winning the race, and crossing the finish line a split second after the fastest car. Here are some helpful tips for successfully adding weights to your car.

1. Avoid adding too much weight

The maximum weight that your car can be is five ounces. The key is for your Pinewood Derby car to be as close as possible to that weight-without exceeding it. This means that you should be cautious when adding weights, as adding too much will disqualify you for the main event. Fortunately, there are steps you can take to help you achieve your mission.

Pinewood Derby Car Weights

2. Keep the weights flush with the car’s surface

When adding weights to the car, avoid allowing them to protrude past the surface of the car. That would add friction, which could ultimately prevent you from crossing the finish line first.
3. Add the weights to the back half of the car.

This is a crucial step to take when building your Pinewood Derby car. Taking this approach will maximize the amount of momentum that your car has. In turn, that will boost the speed of your car and give you the best chance at crossing the finish line first.

4. Properly secure the weights

Weights won’t be worth much if they drop out during the race. How should you secure them? An effective method is to add a little glue around the surface of the weights. Then before you paint your car, add some putty over the holes where you inserted the weights.

5. Use denser weights

The actual type of weights that you use isn’t as important as how efficient they are. It’s highly advisable that you use weights that are as dense as possible. This will further help to reduce the amount of friction that the car produces-which will in turn make it faster. Regarding the actual weight of the weights, lighter is better. This will allow for more precision, so you can get as close to your target weight as possible.

6. Consider adding some weight to the front half of the car

You should typically add the majority of the weight to the rear of the car. But you might want to counterbalance that weight, by adding some to the front half of the car as well. For instance, you could add two-thirds of the weight to the back, and one-third of the weight to the front.

7. Keep experimenting until you get the weight right

After adding weights to your Pinewood Derby car, you might need to make some other adjustments. So weigh the car afterwards. When necessary, add more weights until you’re extremely close to the target weight.

While there are several possible methods for maximizing your Pinewood Derby car’s speed, adding weights is one of the most effective ones. These above pinewood derby car weight tips will maximize the benefit of adding a little weight.

•Maximum Overall Width (including wheels and axles) shall not exceed 2-3/4″;
 
•Minimum Width between the left and right wheels shall be 1-3/4″ so car will clear the center guide strip;
 
•Minimum Clearance between the bottom of the car and track shall be 3/8″ so the car will clear the center guide strip;
 
•Maximum Length (including wheels) shall not exceed 7-1/8″;
 
•Wheelbase (distance between the front and rear axles, center to center) may not be changed from the kit body distance of 4-3/8″.

Pinewood Derby Cub Scouts Regulations:

•Weight of Car: Car may weigh no more than five (5) ounces (total weight) as determined on the official scales during race day check-in.
 
•Width of Car: Car can not be more than 2-½ inches wide.
 
•Length of Car: Car can not be more than seven (7) inches long.
 
•Height of Car: Car shall not be taller than three (3) inches in height.
 
•Wheels and Axles: The car shall roll on four (4) wheels. The wheels shall turn about the axle nails. The axle nails shall be firmly affixed to the wood of the car body. Wheel treatment (hub and tread smoothing and polishing) may not result in substantial removal of mass nor in reducing the tread (track contact) width from the original wheels.

You can polish the axles. You may lightly sand the wheels to remove the molding seam on the tread. No other wheel changes are allowed. You may not use hubcaps, washers, inserts, sleeves, bearings, or bushings.

Discovered secrets for getting the most speed from a car and will guarantee that you will have a competitive pinewood derby car!

Maximize Momentum

As stated earlier, momentum must be maximized for top performance; and the key to momentum is weight. In each pinewood derby car race, there is a maximum allowable weight for the car is usually 5 ounces.

For a five ounce maximum weight, you will likely need to add 2 or 3 ounces of weight to the car. For the best performance add weight towards the rear of the car.

The type of weight does affect how easily the desired weight can be achieved. Denser weights (such as Lead or Tungsten) take up less space, so it is easier to reach the maximum weight. Also, since denser weights require a smaller volume of space, they allow creation of more aerodynamic cars

Pinewood Derby Car Aerodynamic Shape 

Low-profile cars will tend to outperform higher profile cars.

Cars should taper from a smaller surface area in the front to a larger surface area in the rear.

Edges running across the car should be rounded or tapered.

Wings, sails, flags and etc. tend to decrease performance.

Open holes or pockets can catch air and slow down a car.

Pinewood Derby Car Wheel & Axle Preparation

All of the frictional losses in a pinewood derby car come from the wheels and axles. Start by inspecting the parts in your kit. If a part has a serious flaw, replace it.

Next, prepare the nails.

Place the nail in the chuck of a drill and use a Mini-File to remove the flashing under the nail head and minimize the ridges on the shaft. Beveling the nail head slightly also helps.

Finally, polish the axles with an Axle Polishing Kit until they are bright and shiny.

To prepare the wheels, use some wet, fine grit sandpaper to polish the wheels. 

Pinewood Derby Car Wheel & Axle Lubrication

Lubrication is an extremely important key. The difference in time between a well lubricated car and a car without lubrication can be one half second or more.

Most people use graphite for lubrication. Graphite is carbon that has been ground up into a fine powder. There are many varieties and qualities of graphite available at hobby and hardware stores, so make sure to get a good brand.

While lubricating with graphite, make sure to work it in thoroughly. After lubricating, free spin the wheels several times to break in the lubricant, Since graphite works best after a break in period, don’t re lubricate between race heats.

Pinewood Derby Car Wheel & Axle Alignment

For your car to get to the finish line as quickly as possible, it needs to go straight. If it goes side to side down the track, it will travel a longer distance and it will continually lose speed as it bumps and rubs against the guide rail.

To minimize the amount of alignment adjustment needed, make sure that the axle slots (holes) are perfectly parallel to each other and make sure that the axles are inserted perfectly straight.

There are a some different alignment procedures, but the simplest method is as follows:

Determine which of the front axles appears to be the most firmly on the ground.

Remove the axle from the car and remove the wheel.

Use a tool to put a slight bend in the axle.

Replace the wheel and re-insert the axle with the bend upwards.

Roll the car on a smooth and level surface.

If it does not roll straight, slightly rotate the bent axle by grasping the axle head with a pair of pliers.

Repeat these steps until the pinewood derby car rolls straight.

The pinewood derby is a racing event for Cub Scouts in the Boy Scouts of America. Cub Scouts, with the help of parents, build their own cars from wood, usually from kits containing a block of pine, plastic wheels and metal axles. With the popularity of the pinewood derby, other organizations have developed similar events, and a small industry has developed to provide tracks, timers, scales and other products.

The pinewood derby was selected as part of “America’s 100 Best” in 2006 as “a celebrated rite of spring” by Reader’s Digest. Similar Cub Scouting events include the raingutter regatta with boats and the space derby using rubber band powered rockets.

Pinewood Derby Car Construction

The idea behind the pinewood derby is for the parent, usually the father, but occasionally the mother or grandparent, to spend time helping the child design, carve, paint, add weights, and tune the final car. However, it is often the case that the parent takes over the construction of the car, an aspect of the event that was lampooned in the 2005 film Down and Derby, and also in a 2009 episode of South Park.

The quest for a fast car supports a cottage industry that supplies modified wheels, axles, and blocks as well as videos and instruction books. While a pinewood derby car kit costs around $4, a set of modified wheels and axles can sell for more than ten times that amount.

Pinewood Derby Aftermarket Items

These aftermarket items are legal under some pinewood derby Pack rules since the parts originally came from an official Boy Scouts of America (BSA) kit. Complete cars can be purchased on eBay and elsewhere for around $100 to $200. Although these cars violate the spirit of the event, if not the rules, enforcement can be difficult.

The Scout is given a block of wood made of pine with two notches for wheels, four plastic wheels and four nails. The finished pinewood derby car must use all nine pieces, must not exceed a certain weight (usually five ounces), must not exceed a certain length and must fit on the track used by that particular scout pack.

Pinewood Derby Carving Tools

Blocks can be whittled with a hand knife or a bandsaw or Dremel carving tool for major shaping. Decals can be bought at scout shops or hobby shops. It is also possible to use standard model decals to replicate actual racing cars such as Richard Petty’s 1970 Plymouth Superbird, shown at right. The original style is based on open-wheel cars; however, fender or body kits are available, or wheels can simply be placed outboard of the body.

Other than the previous basic design rules, the Cub Scout is able to carve and decorate the pinewood derby car as he chooses. Many Cub Scouts also add weights to the final design to bring the car to the maximum allowable weight; coins, glue-in lead pieces, and melted lead are common ways to add weight.

Cars typically vary from unfinished blocks to whimsical objects, to accurate replicas of actual cars. The fastest cars tend to resemble low doorstops, with weight at the rear. Graphite is usually the only lubricant allowed, and it often helps to polish the provided nails.

Pinewood Derby Competition

The pinewood derby track usually has two to six lanes and slopes down to the ground, since the cars are powered by gravity. Tracks may be owned by the pack or rented. The race is run in heats, giving every car the chance to run on each lane. The racers can be grouped with others from the same rank (Tiger Cubs, Wolf Cubs, Bear Cubs, etc.), or can compete against the pack as a whole.

The first, second, and third place winners usually receive ribbons, medals or trophies. Some packs also award on the basis of car design. The first place pinewood derby race winners get to advance to the district level, then each of the district-wide pinewood derby race winners get to race each other from across the entire council.

So, you’re new to Pinewood Derby racing, You are not alone. There are millions of new Pinewood Derby racers every year. Most of them are asking the same questions… “What do I do?”… “Where do I start?”

First of all, Pinewood Derby racing at any level is much more competitive than most people think. No matter what pack you’re in or where you’ll be racing, there will be at least one or two dads that will go all out to win. You must be one of those in order to have a good chance at winning. We can help.

Pinewood Derby Basic Information

You may have noticed by now that there is an overwhelming array of Pinewood Derby tips, secrets, myths, facts, parts, supplies and kits designed to help you build a faster car. It is truly amazing at how involved and intricate Pinewood Derby car building can get. Remember, this is your first year. So, unless you have a lot of  time, it is unlikely that you will learn and absorb all of the complex and convoluted factors and techniques of  building a truly fast car. That will come in time.

For right now, our goal here is to give you some basic information on how to approach this new and exciting  venture. We will point you in the right direction on your path to building a super fast Pinewood Derby car.  Remember to have fun and, if this is for your son, allow him to participate as much as possible.

Do Your Pinewood Derby Homework

The very first thing that you should do is research… do your homework. That’s probably how you got to this page.  Too many times a new car builder will wait until a short time before the race to start the building process. They then don’t have time to properly research what they need to do so they just slam the car together as best they can. Then, they wonder why their car was beaten so badly on race day.

It is very important to get an early enough start so that you can fully research the pack rules, the district rules, how the races are conducted, who qualifies for the district derby, speed tips that fit within your rules, Pinewood Derby blogs and forums, etc.

Pinewood Derby Car Builders

Serious car builders start this project at least two months in advance. For those new to pinewood derby we allocate 3 months for the building of a new car for a particular race. It’s likely that you haven’t given yourself that much time. Don’t panic… the other dad’s in your pack are probably just getting started too.

Know the Pinewood Derby Rules

Make absolutely certain that you fully understand the rules. There are many sets of rules on the internet with certain important variations so don’t just go by any set of rules that you just found on the internet. Get your pack rules. Some packs will permit broad modifications to the wheels and axles. Some packs may only allow minor modifications. There is utterly nothing more disappointing than seeing your son’s car disqualified at check-in because you didn’t carefully follow the rules.

Some pack and district Pinewood Derbies have only one race division or class while others have several different divisions, such as “Stock”, “Modified”, “Outlaw” and “Open”. Cars in the Stock class usually must follow the basic rules with no deviations, often allowing little or no modifications at all. Modified and Outlaw class rules usually allow much more flexibility in the building of the car. The open classes are usually for the scouts family members who wish to race a car. This is a great class for dad to enter his own car.

Pinewood Derby Assistance

Find out who your Derby Committee Chairman is. Ask him for a set of the rules well before you begin building the car. Then get to know him. Converse with him and offer him your assistance. Offer to help him set up the day before the race. What you’re doing here is establishing valuable “goodwill” with the chairman. This will allow you to more comfortably ask for rule clarifications down the road. This new friendship may also provide helpful should there be any future rule disputes involving your car.

If at any point you are unsure whether a particular car building trick is legal, ask the pinewood derby chairman for clarification before you make that modification.