How to Make CO2 Cars Fast
CO2 dragsters, which run on compressed carbon dioxide, are far more than simple toys; at the highest echelon of competition building, these little dragsters require an in-depth understanding of several different areas of engineering, ranging from mechanical engineering to advanced aerodynamics. And the fun doesn't stop at the drafting table. Many CO2 racers are just as comfortable with a jigsaw as a slide rule. While most of the CO2 car's speed happens in the design phase, there is at least one thing you can do to improve aerodynamics after the car has been built. It's called golf-ball dimpling.
Things You'll Need
- Multi-speed drill
- 3/16 drill bit
- Masking tape
- 1,000-grit sandpaper
- Automotive-grade gap-filling primer
- 2,000-grit sandpaper
- Paint
Instructions
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1
Insert the drill bit into drill. Measure 3/16 of an inch from the pointed tip of the bit, and wrap the drill bit with masking tape at that point. The tape will serve as a depth guide for your bit, ensuring that your dimples are no deeper than they are wide.
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2
Mark a line down the center spine of your car with a pencil, and place a reference dot on that line every 5/16 of an inch starting at the front.
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3
Measure 5/16 of an inch on both sides of the center line at 10 or more points along the line's length. Play connect-the-dots to draw two lines on both sides of your center line, running parallel to it exactly 5/16 of an inch away. Continue this procedure until you end up with a series of evenly spaced lines running the length of your car.
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4
Place a piece of thin string over the reference marks on your center line (perpendicular to the center line, so the string lay sideways across your chassis) and wrap the string around the chassis. Make a reference mark on each of the longitudinal line where the string touches it.
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5
Continue the string-marking technique if the shape of your chassis allows. Otherwise, you'll need to place 5/16-inch-separated reference marks along each of your longitudinal lines, starting from the front and working your way back. The idea is to wind up with a perfect grid of reference marks, with no one mark being closer than 5/16 of an inch to another.
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Drill a dimple into each one of your reference marks. If you've measured correctly, you'll wind up with exactly 1/16 of an inch between dimples. Adjust your spacing as necessary to ensure that you leave enough space between the dimples so that no two can touch. Cover the entire car with dimples.
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Lightly sand your car with the 1,000-grit sandpaper to remove any rough edges and splinters, but not so hard that you take the ridge off the edge of your dimple holes.
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Spray the car with two to three light coats of automotive grade gap-filling primer (available in a spray can from your local auto parts store), allow to dry and lightly sand with 2,000-grit sandpaper. The car is now ready for whatever type of paint you choose to use.
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Tips & Warnings
Dimpling is a well-documented way of reducing aerodynamic drag for anything moving through the air. A dimpled golf ball will travel almost twice the distance of a smooth ball the same size, due solely to the reduction in drag that the dimples provide.
Some car designs may require a little more creative approach when laying out the dimples.The grid-marker method works well if you're running a bullet-shaped "shell" car, but you may be just as well served laying them out freehand if your racer is a little curvier.
References
- Photo Credit Jupiterimages/Photos.com/Getty Images
