I was looking for a quick, easy way to add weight to a Pinewood Derby car. You can use lead or tungsten, but they are relatively expensive ($1 - 2 per ounce), come in odd shapes, and you have to figure out a way to attach them to the car. Pennies, which are 97% zinc cost about $0.10 per ounce (or free if you find them under the sofa). An ounce of penny is the same weight as an ounce of lead, so why not go cheap. What you loose in increased volume needed for the same mass, you make up for with the utility of a uniform size and weight object.
Disclaimer: This is my daughter's car, so no comments about pink or the hearts, please!
Also, no pennies were harmed in the process of this Instructable!
Step 1: Supplies
Things you need:
- accurate scale.
- 3/4" drill bit and drill.
- some loose pennies.
- masking tape (optional).
- hot glue or epoxy (optional).
Step 2: Weight the Car
Pennies are exactly 3/4" in diameter and weight about 0.1 ounce each.
Weigh your car and then add pennies to the scale till you reach the desired weight.
I've been told there are two rules to the Derby:
- If your car is overweight, you are disqualified.
- If your car is underweight, you loose.
For our derby, 5 ounces was the limit, and her car started out at 4.5 oz, so we only needed to add five pennies to get close.
Yes, the car does say "I love you Dad and Mom" on the bottom. That makes it go faster.
Step 3: Drill Away
If you are unsure of your abilities to eye-ball the depth to drill, measure the thickness of the pennies you intend to use and mark your drill at the correct depth with masking tape. Five pennies are about seven millimeters in thickness. You want to be very careful here that you don't drill through the bottom (or top), or into your hand! You might take the wheels off and place it on a spare piece of wood.
My daughter wanted her pennies mounted on top, but I would put them on the bottom if you want it them out of site. If you need to add a lot of weight, you could add more than one hole. Most people recommend placing the weight toward the back of the car.
Step 4: Add the Pennies
Add the pennies and double-check the weight. Drilling removed a little bit of weight. If you decide to glue them in, it will add at little weight, so leave some room to spare. We ended up using six pennies.
With the pennies a snug fit, and the hole on top, we didn't even bother with glue. You can get the pennies out by slapping the car against your hand. This would allow you to remove weight if the track scale show a different weight at the race). Your track official may require them be glued. The standard rule is no loose objects, so it is a judgment call.
As the final touch, we put a penny from the year she was born on top. You could also use a new penny to help remember when the event was in years to come.
Total cost (minus drill bit): $0.06
There is my two cents! As promised. Cheap and easy.
Hope this helps you out!