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How to add weight to a Sport Coupe Pinewood Derby Car
The heavier your pinewood derby car, the faster it will go. Most race rules limit the weight to 5 oz so you want your car as close to the limit as possible. The Sport Coupe block will need about 1.5 oz of additional weight to bring it up to the 5 oz limit.
You should install the weights in your car before you paint it.
Before adding the weights to your car, put the car block, wheels, axles and any other accessories that you will be adding to your car on a scale. Then add the weights until the total is 5 oz. (paint will add very little to the weight of your car).
When your car is complete, weigh it again. If it is over 5 oz, drill a few holes in the bottom of the block about an inch behind the front axle to remove some wood.
Below are several suggestions for adding weights to your pinewood derby car.
Lead Wire Weights
Lead is inexpensive, dense and is easy to work with but lead is toxic. Always use gloves when working with lead and make sure that none of the lead is exposed after you install it in the block.
When weighing the car and weights, cut three weights so that they are approximately the same length. You can cut the weights with a hack saw, coping saw or wire cutters.
You will need:
- One set of Lead Wire Weights
- Drill and 5/16" drill bit
- Wood putty
- Sandpaper
- Hack saw, coping saw or wire cutters
- Clamp the car block on a flat surface.
- Using a 5/16" drill bit, drill three equally spaced holes straight into the back of the block. Be careful to drill above the rear axle slot. The depth of the holes should be slightly deeper than the length of the weights.
- Remove the clamp from the block.
- Insert the weights in the holes. The end of each weight should be at least 1/8" into the end of the block. This will leave room for the wood putty. Drill the holes deeper if needed.
- Weigh the block, wheels, axles and weights again. Adjust the amount of weight if needed for 5 oz.
- Seal the weight holes with the wood putty. Allow to dry in a warm place for 12 hours.
- Sand the wood putty until smooth and flush with the car block.
You can now paint your car and add the wheels and axles.
If the completed car is less than 5 oz. drill one or more shallow holes in the bottom of the car in front of the other weights and insert some of the leftover lead weight in the holes. Seal with wood putty.
Tungsten Weights
Tungsten is very dense but it is more expensive than the other weights. The density gives you a speed advantage because more of the weight can be placed farther back on the car.
You can use a combination of cylinders and a flat weight for optimum results.
You will need:
- Four Tungsten Cylinders
- One Tungsten Plate
- One Fine Tune Cylinder
- Drill and 3/8" drill bit
- Wood putty
- Sandpaper
- Screw driver
- Using a 3/8" drill bit, drill two holes into the bottom of the block behind the rear axle slot. The depth of the holes should be deep enough to hold one cylinder each.
- If more than two cylinders are needed, drill more holes in front of the rear axle. These holes should be deep enough so that the end of the weights will be recessed 1/8 inch into the bottom of the block. This will leave room for the wood putty.
- Weigh the block, wheels, axles and weights again (don't forget the flat weight). Adjust the amount of weight if needed by using part of the Fine Tune Cylinder.
- Fill the weight holes in front of the rear axle with the wood putty. Allow to dry in a warm place for 12 hours.
- Sand the wood putty until smooth and flush with the car block.
- Paint your car and add the wheels and axles.