| Pack 373's Pinewood Derby Pages |
| "A little, healthy competition is a necessary part of building strong character." |
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| Weight |
The weight of your car is a very important factor. It is necessary to get as close to 5.0 ounces as possible without exceeding the limit. Remember, potential energy (weight) is transferred to kinetic energy (speed) as the car travels down the track. The more your car weighs, the better your chances of reaching a higher speed. To help illustrate this concept, think of a 5.0 ounce car getting a 5 mph push off the starting line, a 4.0 ounce car getting a 4 mph push, and so forth. It is easy to see, using this analogy, that the more a car weighs, the more force acting on it at the starting line.
The official scales used on the day of the race may weigh slightly different than the scales used to initially weigh your car, so be prepared to add or remove a little weight. It is a good idea to have a small piece of weight attached to the underside or back of your car by a screw. Assorted sizes of Zinc, brass, or steel washers work well for this weight adjustment. On the day of the race, you can easily remove this small weight, or replace it with a heavier piece of weight to achieve the 5.0-ounce maximum weight. Also, be sure this removable weight is fully recessed into the body of the car so you do not exceed the length, width, or ground clearance limitations. Always cut the recessed area to allow for the largest weight you have available for attachment.
There are many different types of weight available:
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Zinc and alloys of zinc make good weights. They are available at your local Scout Shop, hobby store, or hardware store. They are usually flat or round so they can be attached to a recessed area or inserted into a hole easily. Zinc weights also have a high mass (more weight when compared to other metals of equal size) so you use less metal. This allows for more variety in your design. |
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Lead weights, such as those found in any tackle box, also make great weights. They are cheap, easily obtained, and if you like to fish, there is likely to be a pound or two in your tackle box right now. They come in round or bullet shapes so they are easily inserted into holes, and they are easily pressed flat by putting them into a vise or pounding out using a hammer. Care must be taken when using lead to avoid breathing or ingesting lead dust. Always wash your hands after handling lead. NEVER use molten lead to add weight to your car. The temperature of the molten lead is more than enough to cause the wood body to burst into flames. Also, the risk of burns from spatters or spills it too great. |
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Brass and Steel also make good weights, but are more expensive than Zinc or Lead to use. These weights also have less mass than Zinc or Lead, which means you will need to use more of it to achieve the desired weight of your design. |
The total weight of your car (body, wheels, axles, accessories, and weights) must be as close to 5.0 ounces as you can get it without going over. Since gravity is the only method of starting your car down the track, the more it weighs, the better your chances of reaching a higher speed.
Your car's design should take into consideration what type of weight, the amount of weight, and where the weight will be placed. The average weight of the Official Kit (wood body, wheels, and axles) is a little under three ounces, so plan on adding at least two or three ounces of weight to your design.
Many people have differing opinions on placement of the weight. The fact is, weight placement has little effect. However, those subtle differences mean hundredths and thousandths of a second in the course of the race. Since the average car goes from start to finish in less than three seconds, those hundredths of a second add up to winning or being eliminated.
Weight should be placed low in the car. This helps create a lower center of gravity, preventing wobble and tipping that causes the wheels to rub the center lane guide. That rubbing will slow you down and cost you the race.
Weight should also be placed as far to the rear of the car as you can get it without causing the car to "pop wheelies". This maximizes the potential energy of the car because the weight is placed higher off the ground and farther up the slope of the track when the car is placed into position at the starting gate.