Finding the right weights for your pinewood derby car can be a pain. While lead is cheap and accessible, it is also poisonous. Tungsten is a dense option promising maximum control of weight placement on the car. But it is expensive, retailing from $5.50 to $7.50 per ounce in most hobby shops.
United States pennies are a fantastic Derby weight alternative to using poisonous lead or expensive tungsten. Pennies minted before 1982 are 95% copper and weigh 0.109 oz. each (3.11 g). This means that nine of these and a drop of glue equals one ounce of weight that is exactly 0.75” in diameter (19.05 mm) by just over one-half inch high (0.54” or 13.7 mm).
If you don’t have any old pennies lying around, no problem! In 1982 the US Mint shifted to using copper plated zinc for US 1 cent pieces. They weigh just a little less than their older counterparts at 0.088 oz. (2.5 g). This means that eleven of these newer pennies and a couple drops of glue will give you an ounce of weight. The diameter will be 0.75 inches with a height of 0.66 inches or 16.7 mm.
With a three-quarter inch wood drill bit and a handful of pennies, you can save a lot of money on derby car weights!
Derby Weight for 10 Cents an Ounce!
Here is a simple car I designed to use only US 1-cent pieces as the ballast weight source. Each hole is only about one-half inch deep, which keeps my entire wedge to well below three-quarters of an inch thick.
Here is the car with the pennies not yet added and hatch plate not yet in place. Although this has some decorative carving, you could make a simple super-fast wedge body in no time using this same principle.
Car Design Background and Build Tips
- It is a simple rounded wedge shape 5/8” thick from the mid-point to the rear. You could cut the entire block to be 5/8” thick and simply use coarse sandpaper to shape the hood if you’d like to avoid any complex curve cuts with a saw.
- A shallow scoop is taken from the hood to reduce weight and add a little style. You can achieve this yourself by wrapping sandpaper around a tapered dowel and sanding the indentation.
- There is a canopy cutout 1/8” deep. A flat canopy or carved one like I did will fit into this section acting as a cap to keep the pennies securely in place as weights.
- There are six holes drilled under the canopy area. Each is ¾” in diameter and 3/8” deep. I filled each with copper pennies and a couple dabs of glue to make sure they stay in place. This added exactly 3 ounces or weight to my car with the weight placed precisely where I wanted it.
- The canopy is then put into place using whatever method of securing desired. I use a tiny strip of super-thin double-sided cellophane tape so I can re-open it if I decide to shift weights around. I get rolls of this tape from the Dollar Store. It looks like “Scotch Tape.” Alternatively, you could use a tiny screw or glue.
The pennies have been added for weight and glued into place with a couple drops of glue per cavity. If the pennies are wedged in tightly, there really is no need to glue them unless you want to – as long as the hatch cover is secure, and they do not move around.
Here is our pinewood derby car all put together and ready to race!
Derby Car Side View. Note how the hatch cover is flush with the top of the car’s surface. If you just us a flat piece of wood, the car will be even more aerodynamic.
This is what the car looks like head-on. The scooped area of the hood lines up with the wolf’s triangular snout. While this looks streamlined, I should mention that while not a bad design, a flat surfaced wedge would provide less air resistance. If you follow the scoop shape you can see it adds surface area to the car’s top which means more surface for air to drag against. But this car was all about showing you weight placement. We will get into maximizing car shape for speed in another post.
My Own Critiques: This design could be more aerodynamic, but I wanted to show a decorative way to secure your weights. A simple wedge design would have been a bit less air resistant and a flat hatch over the weight holes would be more aerodynamic. But the 3d relief carving of the wolf’s head is very cool and adds just a tiny bit of air resistance.
Another consideration is weight placement. The above car will certainly win some races in a typical Derby, however if you use an equivalent tungsten weight, the car will have a better center of gravity and run faster on the flat track. Although not perfect, the following use of those same drilled holes filled with tungsten will run considerably quicker on the flat track.
It may seem odd placing the most weight in front of the rear axel, but you will learn why in our post on weight distribution.
The price difference is $0.30 of pennies versus $16.50 for tungsten so that might factor in as well.
Speed with Style
This car was designed for a Wolf Den and we wanted more than just a fast car. We wanted a fast car that also looked good crossing the finish line and on the stepped display showing off first, second, and third-place winners.
As you will see in another post, any tiny bit of aerodynamic advantage we gave up, we more than made up for by using ideal weight distribution and a few other tricks of the trade.
There’s More to Weight Than Ounces and Grams
In the weight distribution post, I will show you how to do even better! But for now, here is a revised version of my simple car design following some of my own critiques.
Tip! If I wanted more weight distributed to the back, it would be easy to have made each hole 1/8” deeper and need only four weight cavities instead of the six shown. The car would have been a touch thicker, but I would compensate with a more severe downward angle on the hood making the car a full wedge. I also could have placed the cavities further back, but I wanted this design for a reason.
This Steep Wedge design is still using everyday US one cent pieces for weight. That weight, however, has been moved back on the body and stacked in order to reduce the amount of square area the weight’s potential energy spans.
It’s hard to see in the picture but the two weight holes in back are 1/16″ shallower than the front to keep the weight more in front of the axel and also to avoid the axel nails.
That sounds kind of complicated but it’s really simple once you see a couple examples. This website has a post dedicated to maximizing weight placement that will tell you all you need to know.
Proof of Concept
After writing this post I decided to build one of each car and race them against each other on a side-by-side two lane test track. The exceptions were that I did not carve the wolf’s head. Instead I drilled them as shown in the above layouts and placed a piece of 2” wide painter’s tape over the weight cavities once the pennies were in place.
Running four heats, here are the results…
|Distance Won By
As you can see, the steep wedge (my second design) won every time. This is partly due to the aerodynamics, but more because of the weight placement.
The testing was not extremely scientific, but the basics were covered as follows:
- Each car used lightly polished nail axels from my stock.
- Each wheel was rounded and balanced but not shaved or weight reduced.
- About the same amount of graphite was applied to each axel on both cars.
- I used wax paper to shim the axels for a straight run.
- There was no rail-riding, bent axels, or other advantages applied to either car.
- After the first two heats, I swapped the axels and wheels of each car to make the conditions as even as possible. I then shimmed the axels to get a consistently straight run from each car. Finally, I applied more graphite and used compressed air to blow any dust off the track just like before the first heat.
As an afterthought I pulled one penny from each of the backmost weight cavities and moved them to just ahead of the front two cavities, securing them with a piece of cellophane tape to the top of the car. This is not ideal as it is always best to place weights at the bottom of the car, but I just wanted to see if I could stop the tendency to wheelie.
It worked but could have worked better. There was no pronounced wheelie, but I think it would have at some point had I kept going. The steep wedge consistently beat the original sportier car by one plus lengths (7”+), however moving all the drilled holes just a bit further forward along the car would have been better.
What Was That About Keeping Weight Low?
If it’s best to keep the weight low on the car, why do I drill in from the top? Good question! I like to embed my weights within the car to keep them separate from the visible design. There is nothing wrong with drilling or routing from the bottom of the car and sticking the weights in that way – as long as they are well secured.
To keep my weights securely in place without having to worry about breaking through the bottom layer of wood if I drill too deep, here’s what I do…
- Drill to a point that leaves about 3/32” to 1/8” of wood at the bottom of the car below the weights.
- Sand the interior sides lightly. Do not sand the bottom. Get rid of the sawdust. You are creating a very slight gap that will allow glue to surround the pennies and hold them in place from the sides.
- Now put a tiny drop of water on your finger and run it along the inside walls and bottom of the weight cavities. The wood should be just slightly moist. Do not let it get fully wet. The small amount of moisture will draw the glue into the wood and create a much stronger bond that the wood alone.
- Add a few drops of white wood glue to the hole. I use “Titebond” wood glue, but any wood glue should work.
- Using your finger or a cotton swab, spread the glue around the sidewalls of the hole. It should be very thin with a thicker coating on the bottom of the hole.
- With the car placed on a flat surface, insert one penny into each hole and press it to the bottom so it lays flat. There should be just enough room for the glue to seep around parts of the penny. Wipe off any that gets on top of the penny – especially at the edges. This will dry super-strong and make it so your next penny does not fully seat flush against the first.
- Allow the penny to dry in place.
I typically repeat this for each penny so at least the bottom two or three are glued into place – especially to the side walls. This adds a lot of strength to the overall arrangement and keeps the weight of the pennies from being a burden on the thin piece of wood beneath even if the car falls form a height of several feet to a hard surface. If there are smaller kids or pets around, this can happen.
More About Pinewood Derby Weights
If you want to see the benefits and drawbacks of weights such as lead, zinc, and tungsten – check out this article: Weights for Pinewood Derby Cars. It is on this site and loaded with helpful information on how to get the very most out of your car through proper weight material selection. Yes. It really can make a difference!
You can also check Pinewood derby weight below-
When you are ready to place your weights to maximize speed, this article will help: Pinewood Derby Weight Placement. It is also on this site and chock-full of hints, tips, and little-known secrets to getting every last bit of speed through proper weight distribution. I hope you like reading on Pinewood Derby Weights for Pennies an Ounce.
Last update on 2023-10-26 / Affiliate links / Images from Amazon Product Advertising API