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Science fair project

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Science fair project

Unread postAuthor: spudmanb3 » Fri Oct 15, 2010 1:01 pm

I am in seventh grade and have had plenty of experiences with pneumatics. Recently I have been assigned a science fair project and for my topic i'm doing how launch angle affects distance. I will be using a pneumatic launcher with a half inch barrel and a half inch qev to fire it along with an adjustable stand. It ma be about a month and a half, but I'll try to post it asap. Any way I'm going to fire the launcher three times every five degrees from 0 to 85 degrees and taking the averages. after I'ved determined which two angles provide the most power I will test each five degrees 3 times and determine the best angle. I have heard that fourty-five degrees is the best launch angle but will be testing this. From your experiences is this true? if not what is the best angle and does my experiment sound like a good idea? ask for clarification of any details.



Oh and also, I almost forgot, what would be a good catchy title? Something like up and out or up, up, and away
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Unread postAuthor: Technician1002 » Fri Oct 15, 2010 1:13 pm

Be sure to use a projectile that flies straight. Marshmallows and other cylindrical shapes tend to tumble and catch the wind providing poor repeatability in tests. This is more of a problem at high speed with lighter weight projectiles.

A high sectional density projectile such as a steel BB works well for a repeatable launch. To find the projectile, try regulating the pressure to under 15 PSI. Use an accurate gauge or precision low pressure regulator instead of the small regulator supplied on cheap compressors. Poor regulation will affect your results.

Due to air friction and the slowing of the projectile over a long distance, most of the time an angle below 45 degrees is optimum. To show excess air friction on projectiles and it's affect on distance, shoot some foam packing peanuts or miniature marshmallows. Best distance will be obtained nearer to horizontal.

At low pressure and short distances a projectile toss is best near 45 degrees.

Pick up a copy of GGDT to model your launcher and use the ballistics model to test your theories, then see how well your launcher matches the predicted results.
Pick up a copy here and read the instructions. Try not to use it on Windows 7 or Vista. There are a couple of issues that can make installation difficult.
http://thehalls-in-bfe.com/GGDT/

A good title would be "Trajectory physics and the impact of an atmosphere"
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Last edited by Technician1002 on Fri Oct 15, 2010 1:48 pm, edited 3 times in total.
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Unread postAuthor: clemsonguy1125 » Fri Oct 15, 2010 5:23 pm

Yes I agree with tech completly, try to launch inside the school gym if at all possible, if you test outside you could use paintballs to mark the impact spot and a half inch sdr21 barrel works amazing for paintballs.
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Unread postAuthor: spudmanb3 » Sat Oct 16, 2010 10:43 am

I was planning on launching in the gym anyway, bu the paintball idea would make it possible for higher pressure outdoor tests. I will use the lightweight NERF darts if I launch inside because they surprisingly fly straight (do to the extra weight from the rubber on the head. The darts that I have are the ones with velcro on the end. I had these on hand because when I was around seven I played with NERF guns. These darts seem better than others because they are more aerodynamic than the suction cup ones, but are a tighter fit than the "sniper" ones.
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