Air Cannon

By: Aaron Oswald

Introduction

Air guns have existed since the 15th century. In the 17th century, air guns were used to hunt big game deer and wild boar. These air rifles were charged using a pump to fill an air reservoir and gave velocities from 650 to 1,000 feet per second. Then a trigger was pulled to turn a valve that let the air out and push on the projectile that was being shot. It consists of one or more pneumatic chambers that are pressurized with compressed air. They were also used in warfare. Air guns are still used for hunting, pest control, recreational shooting and competitive sports.[1] The purpose of this investigation is to find out the relationship between air tank size and distance. My hypothesis is that if the air tank is bigger than the ball will go further because there will be more mass to push on the ball. I believe that this will work because force equals mass*acceleration, which means that I am adding more mass which will create a greater force on the tennis ball. I will measure my variables by determining the amount of space for air after it fills with varying amounts of water and I will measure the time it takes the ball to come back down to the ground.

Method

In order to start this project I needed to gather all of the proper materials.

Materials needed:

·         10ft of 2”pvc pipe

·         10ft of 2.5”pvc pipe

·         3 2” pvc pipe elbows

·         1 2” pvc Tee

·         1 2” reducing threaded tee

·          1 valve

·         Bushings for connecting the reducers to the nipples for the valve

·         Pipe nipples for the ends of the valve

·         1reducers

·         2 2”end caps

·         Pvc primer and cement

·         Valve stem

·         ¾ coupling air fittings for compressor

·         1 bushing

·         Air compressor(unless you want to spend all day pumping it up

·         Stop watch

·         3 gallons of water

·         Several Tennis balls

·         Pressure gauge

·         1 male to female elbow

Okay, so now that we have all of the equipment you can start building the air cannon. The first step would be to cut the pvc pipe to the proper sizes. You will need to cut 3 3” pieces to start with to connect the elbows and tees together. Then cut 2 pieces of 2ft for the air tanks and then use the two and a half inch and cut it to 6 ft for the barrel. Now connect the caps, air tanks, elbows and tees together as shown in picture with the primer and cement. Then connect the barrel with the bushing also using the primer and cement. Then all you have to do is screw on the rest of the pieces where they should go as shown in the picture. It is optional to use the two elbows that connect from the tee to the air valve. This just makes it easier to shoot at a 90 degree angle.

Now that the air cannon is built: we can start shooting tennis balls with it. To fill it up with water the valve will need to be removed or turned so that the water can get to the air tanks. To copy exactly the way I did it \fill it up to 50 psi for each shot. Do five trials for each amount of water put in. Put in 1 gallon, ¾ gallon, half a gallon, and no water at all.  Afterwards push the tennis ball all the way down the barrel and then begin filling up the cannon with air to 50 psi. Then get the stopwatch ready to start and release the air and measure the time the ball was in the air.

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Results:

 volume(cm^3) time distance(m) volume(cm^3) time distance(m) 6435.2 4.19 86.02489 6435.2 4.21 86.84809 4542.494108 3.84 72.25344 4542.494108 4.2 86.436 3596.141162 3.5 60.025 3596.141162 3.42 57.31236 2649.788216 71.5in 1.8161 2649.788216 71.5in 1.8161 volume(cm^3) time distance(m) volume(cm^3) time distance(m) 6435.2 4.12 83.17456 6435.2 4.05 80.37225 4542.494108 4.12 83.17456 4542.494108 3.94 76.06564 3596.141162 3.6 63.504 3596.141162 3.42 57.31236 2649.788216 72in 1.8288 2649.788216 72in 1.8288

Average:

 volume(cm^3) time distance(m) 6435.2 4.1425 84.08550063 4542.494108 4.025 79.3830625 3596.141162 3.485 59.5116025 2649.788216 71.75in 1.82245

Data file: text.:. Excel

Formulas used

·         0.0002642 Gallons=1cm^3

·         Distance=initial velocity*time+.5*acceleration*time^2

These results show that my hypothesis was correct. However, as the volume began getting higher and higher. The rate of change between volume and distance began to get smaller and smaller. This causes the graph to look a little bit like a square root function.

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Conclusion

In conclusion, my data fitted my hypothesis and proved it to be true up to the point that I was able to measure too. This means that the amount of air or volume does affect the distance of the projectile and that more air equals more distance. I believe that the data turned out the way it did because by increasing the volume of air I was increasing the mass of air that was accelerating out of the air cannon at close to the same amount than with less air. The main sources of error with this project are that there were probably slight differences in air pressure and starting and stopping the stopwatch wasn’t the same every time. Another source of error was that there was a little bit of water that would come out every time I launched the tennis ball. Some improvements that I could make on this project are to make several air cannons instead of just one which would get rid of the need of water. I could’ve also recorded the launches to get more exact times and to see what the initial velocity was. Overall I am pleased with the way this experiment turned out for how little money I had to spend on it.

Related websites

"Theory/physics behind the spudgun" Gives information about how to build air cannons and fun to look at what they have built

http://en.wikipedia.org/wiki/Air_gun - This gave some history about air guns and different ways that they have been made.

http://science.discovery.com/tv-shows/punkin-chunkin/videos/punkin-chunkin-air-cannons.htm - Fun to look at and see how big they can get.

http://www.myaircannons.com/ -Gives ideas on how to build your own air cannon and uses for them

http://www.americanaircannons.com/ - A place to buy parts for an air cannon

Bibliography

Bavetta. Air Cannon Design <bavetta.com>, 2002
Millis, Bill. “Not How To Build an Air Cannon”, Corin.com
< http://corin.com/bill/paintball/aircannon >. 1999

Wikipedia contributors. "Air gun." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 30 Oct. 2012. Web. 2 Nov. 2012.

"Theory/physics behind the spudgun". The Spudgun Technology Center. 29 August 2008 original: 25 June 2000. Web. 16 August 2011.

Wikipedia contributors. "Spud gun." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 26 Dec. 2012. Web. 18 Jan. 2013.

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[1] Wikipedia contributors. "Air gun." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 30 Oct. 2012. Web. 2 Nov. 2012.