How to Build a Balloon Race Car for a High School Student
High school students build balloon race cars for illustrating science principles. A balloon race car can be made out of almost anything with a balloon strapped to it, but for simplicity and to save time, but to still give the car a home-built look, Legos or other blocks may be used.
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Things You'll Need
- Toy building set (such as Legos or K'nex) Craft glue Duct tape Balloon Straw Graphite (pencil lead)
Instructions
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Consider that the easiest way to make a balloon race car is to strap a balloon (already inflated) to a toy car of your choice, then let it go so that it is propelled forwards by the thrust of the air escaping out of the same hole that the balloon was inflated through. The ideal car would be lightweight and have little friction on the wheels. The wheels would have to be clear of the balloon to avoid interference from the balloon.
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Use plastic construction blocks like Loc Blocs, Legos, K'nex, Tinker Toys or other blocks/modeling systems to give the car a "built from scratch" appearance. Start with a long "backbone" of blocks that resembles a headless stick figure with the "arms and legs" going out at 90-degree angles.
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Attach the wheels at the ends of these limbs. The reason that the wheels are spread out is for stability so that the vehicle does not roll over if it should turn sideways due to the random angle of thrust from the balloon.
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Choose wheels that are the same size across from each other (side to side) and turn freely. Larger wheels would be a better choice since the mechanical advantage of the larger wheel on the ground versus the friction at the axle favors turning more than a small, harder to turn wheel (due to leverage).
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Lubricate the wheels (without oil) if desired. Graphite can be powdered and funneled into the areas where the wheels turn (if the builder is really a fanatic for speed).
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Inflate the balloon. The best balloons to use are the balloons that are the hardest to inflate (if short bursts of speed are desired) or the biggest (if distance is required). This is a good thing to experiment with, but if the balloon is rubbing the wheels at this point, make the lightest structure possible to keep the balloons off of the wheels. If the blocks/pieces that you are using are not keeping the balloon off of the wheels, glue a small block/piece in place above the wheels (if necessary) to keep the balloon up.
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Attach the balloon to a straw (using tape to seal any leaks and make it stay in place). The straw narrows the opening and controls the flow better.
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Add more weight if the car leaves the ground. At low speeds, aerodynamics should not be as much of a factor as the type of balloon, weight of the car and the friction on the wheels.
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Tips & Warnings
Lead should be washed off hands and all surfaces to prevent ingestion (the most common route of toxicity).
