Grand Prix Racing - How To Make A Fast Pinewood Car

Tool the Body

Out of the kit, your car body begins as a block of pinewood. It is too heavy and too bulky to use as it is. Get a saw ready!

Lighten the block

The goal is to make a light but adequately strong chassis from the wood. A chassis is the frame of your car. You build the rest of your car body on the chassis. Make the chassis light so most of your car's weight can be added using free weights and positioned precisely. You can't reposition weight if it's all tied up in wood. It should be possible to make two chassis from the one block (one chassis of the two will need axle grooves cut in it). Use one chassis as a backup.

Your free weight and body shell (if any) attaches to the chassis. Slots may be needed in the chassis to anchor these parts. A well for placing hammered lead into or melting lead into can be cut in the bottom rear of the chassis. A well is not needed if you use heavy screws as free weight (you may find you need more screws than you have space for!).

For the serious competitor
Dry wood contains more than 25% water by weight. Before cutting, place your block in an oven at 325 degrees for a couple of hours. This drives off some of the water; reducing the weight of parts made from it. Weigh before and after. The difference in weight shows how much water weight was lost. If you bake your car parts after they are cut, check for warping of the parts. Don't bake sealed or painted wood parts. They have to be refinished and less moisture would be lost.

Build on top of a minimal chassis

A chassis is the base of your car. It should be thin and have space (a lead well) cut out to hold free weights and it has the axle grooves cut in it. There are a number of physical reasons for a thin chassis but some practical ones include the fact that thin pieces of pine are more easily worked than a whole block at one time. A whittling or pocketknife is all you need to change its shape or contour. Cutting a lead well all the way through the chassis is easier than trying to drill or chip it out of a block.

Other thin pieces (shaped panels) can be used to cap the lead well and build up the sides and top of your car. With thin wall construction, the car can have many air filled cavities so that the weight is not tied up in wood bulk.

Bottom view of long, thin chassis with maximally spaced axle grooves.
For the enthusiast
Using thin shaped panels cut from your block, you can make detailed interiors, opening doors and hoods like your favorite plastic models.

To cut out the chassis and axle grooves (if it's aligned well enough), use a band or scroll saw. The chassis should be planed or sanded with a rough 60 or 80 grit sand paper (by hand in a flat holder) to give it straight lines and rounded contours. Rounding off edges often adds a nice touch. Be careful working around thin outcroppings, they can break. If they do, use wood glue to join them better than before.

Alter the shape of your chassis to your liking, but keep the nose squarish because a narrow tip may not trigger an electronic timer right away. Each quarter of an inch counts at the finish line!

Side view of long, thin chassis with maximally spaced axle grooves.

Check pre-cut grooves

Note that many kits come with grooves for the axles already cut. If you can not "move" your axle slots to take advantage of a wider wheel base then you should at least check to see if they are straight.

  1. Get a carpenter's square, drafting triangle or something you know is really "square".
  2. Turn the block on its side on a table.
  3. Place one edge of the square flush with the table and pressed flat up to the block.
  4. Move it along the block until the other edge is along a groove.
  5. The edge and the groove should be parallel. If they are not, cut new grooves on the opposite side of the block.
Recommendation for most tracks
Design your car so the weight is very near the rear axle but make sure you extend the wheelbase as far as possible. If you do not, the car will likely zigzag down the track nullifying any advantage!

However, if you do not have access to an accurate miter saw, making any of these cuts could result in misaligned wheels. Ask your parent or leader to assist.

For the tool deprived
One way to get around "perfectly" square axle slots is to cut them half again as wide as the axle. This gives you "wiggle" room to align your axles perfectly when you glue in your axles (hot glue is recommended). You can also use thin wedges of wood (shims) to help align them, though it requires more patience.
For the serious competitor
Raise one front wheel and "steer" with the other to get a perfectly straight run. To "steer" the touching wheel, cut the front axle groove wider than the axle so you can turn it a bit while the hot glue is cooling. See the details on the page about putting the wheels on.

Free weight and buffer weight

To figure out how big the well for your weight must be, weigh your chassis, other car parts and buffer weight. A buffer weight is a small amount of weight (usually clay or lead chips) that is easy to remove from and add to the lead well or other hollow place of your car. Add the buffer weight on the worksheet in the link below if you think your car will be overweight. If under, just make room to add it at the competition. Use the worksheet to determine how much lead weight will be needed. (click the "back" button on your browser to return here)

If you decided not to use a chassis, cut the well using a drill or carving tools. If you made a thin chassis, fill it with lead and cap it with a body shell. The fit between the chassis and shell must be good to keep lead from leaking out from between them if you pour it. Get assistance when working with tools.

For the very careful enthusiast
Use a scrap piece of wood cut to fit the top of your lead well. Abut it to another scrap to cover the open back of your chassis and to a third piece to cover the open rear, bottom of the lead well. Tip the chassis as necessary to pour lead through the opening in front of the rear axle. It will fill in the back of the lead well first making a smooth block.
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Grand Prix Racing - How To Make A Fast Pinewood Car
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