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Old 12-07-2008, 03:24 PM #1
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Physics Project - build a PbGun?

I read the stickies and searched google. Some of the links in the stickies were dead so they were not much help. Also most of the links were for real legit guns or how to upgrade a gun.

I am just trying to make a device that shoots a paintball. I would like it to use an air (Co2 or compressed) tank but other than that it the specs don't matter. It can be made out of pvc pipe.

I have found the following links
http://www.gizmology.net/pbm.htm (more step by step directions needed)
http://www.spudfiles.com/forums/viewtopic.php?t=160 (vid down, no tank)
http://www.youtube.com/watch?v=z9gazqWU_aE (very cool, no tank, smaller version of above)

The project isn't official yet. just checking to see if i can do this for about $50

I have a compact 2000 to take parts from if needed.

Thanks
Peace.
-twodayslate

Also any science links etc; would be great.

edit://if you don't think this a good physics project tell me what is! thanks

Last edited by twodayslate : 12-07-2008 at 03:31 PM.
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Old 12-07-2008, 03:28 PM #2
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contact a machinist,

a good physics project would be a spoolie due to the dynamics involved
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Old 12-07-2008, 03:40 PM #3
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Quote:
Originally Posted by jonotwist View Post
contact a machinist,

a good physics project would be a spoolie due to the dynamics involved
a spoolie? don't think that is advanced enough.
thanks though

Last edited by twodayslate : 12-07-2008 at 03:46 PM.
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Old 12-07-2008, 03:44 PM #4
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Originally Posted by twodayslate View Post
a [url=http://mountainbikemilitia.com/images/graphics/spoolie.gifspoolie[/url]? don't think that is advanced enough.
thanks though


No, but seriously.
http://www.zdspb.com/tech/misc/animations.html

Look under Spool valve markers.
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Old 12-07-2008, 03:51 PM #5
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lol
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Originally Posted by benb1 View Post


No, but seriously.
http://www.zdspb.com/tech/misc/animations.html

Look under Spool valve markers.
Great link, thanks!
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Old 12-07-2008, 04:08 PM #6
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ie, matrix, quest, g3, ion, shocker, ect..........
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Old 12-07-2008, 05:01 PM #7
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I laughed.

Spools can be difficult to design well. Is this a HS project? Or a college design project? If its HS, I would advise a poppit valve, but if you have free machine time/its for college I would go for a spool. Thats just me though.

BTW, where are you in VA? VT fan?
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Old 12-07-2008, 05:18 PM #8
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I laughed.

Spools can be difficult to design well. Is this a HS project? Or a college design project? If its HS, I would advise a poppit valve, but if you have free machine time/its for college I would go for a spool. Thats just me though.

BTW, where are you in VA? VT fan?
not a fan of sports much so no reason to like virginia tech

this is a high school project.
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Old 12-07-2008, 08:52 PM #9
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For a HS level project, I don't think this is a good idea... sorry, but it seems way too complicated for HS. I'm currently a MechE major in college and I've already found out the hard way that simple projects executed cleanly with good scientific method following is the way to go.

Try dumbing down your project ALOT and forcus on the steps of the scientific method. A simple project would be something more along the lines of "which gas shoots a paintball fastest"? Your hypothesis could involve a challenge on the current compressed air standard of paintball.

-Next you want to develope a simple, yet efficient and consistant method to propel a single paintball, where you can control all variables, leaving only the gas to be the test variable.
To do this you could develop a very simple PVC spud gun, with a smallish volume chamber of around 40 cubic inches (or 2 feet of 2" PVC) and a electronic 1" operated solenoid sprinkler valve (you can get them for around $20 on ebay, look for rainbird brand, orbit is also good, look on spudfiles for more info on this)

-Now you want your barrel to be about 1/2 the volume of the chamber, and .75" sch 80 pvc is a size to go with because it is about .05" larger than a paintball, so a little paper towel as wadding will fill that gap, and to help with consistancy from test to test, precut all wadding ahead of time so you have the same amount. You barrel of .75" SCH 80 pvc should be about 45" long if you do the math.

-To finish off this test launcher, you must now make an easy way to inject gas into the cylinder, and a gauge which measures from 0-100 PSI (available at home improvement store) and use the SAME AMOUNT of gas every time. remember you must keep all variables constant except for the test variable - the type of gas.

-Now that you have a consistant, and SIMPLE testing launcher, you must obtain a few common compressed gasses. here is where cleverness and safety come into play.
--Since you will need less than 100PSI to propell the ball at standard paintball game speeds (300fps) you can get away with a gas like propane. (propane will not explode if used as the propelling gas, don't worry about that)
--Also you can use standard compressed air from a compressor.
--You can also use REGULATED CO2, non regulated is a nono unless you know what your doing, as more than 400PSI (CO2 comes out at 800PSI) will cause your PVC test launcher to burst.
--You will want a lite gas, so get a little party favor Helium canister.
--Find one more gas if you can, perhaps nitrogen if you can get ahold of it.

Now that you have a test - run it. You will get different velocity's for each gas, so test then and compare. The fastest is the best perhaps, but you can also bring up stuff in your conclusion like cost/shot and ****.

good luck. remember doing good on a physics project is not always about what you make (unless it's revolutionary, a spoolie IS NOT!), but how you make it. The professionalism you use in your experiment is what a teacher will see and be impressed by.

Sorry if this is not exactly what your project asks you to do - but I'm just assuming it is since it's the standard project, and you really didn't explain it well
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Old 12-07-2008, 09:38 PM #10
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Thanks, Xsport. Probably the best and most helpful answer I`ve read in a long time!
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Old 12-08-2008, 07:37 AM #11
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Quote:
Originally Posted by xsport37 View Post
For a HS level project, I don't think this is a good idea... sorry, but it seems way too complicated for HS. I'm currently a MechE major in college and I've already found out the hard way that simple projects executed cleanly with good scientific method following is the way to go.

Try dumbing down your project ALOT and forcus on the steps of the scientific method. A simple project would be something more along the lines of "which gas shoots a paintball fastest"? Your hypothesis could involve a challenge on the current compressed air standard of paintball.

-Next you want to develope a simple, yet efficient and consistant method to propel a single paintball, where you can control all variables, leaving only the gas to be the test variable.
To do this you could develop a very simple PVC spud gun, with a smallish volume chamber of around 40 cubic inches (or 2 feet of 2" PVC) and a electronic 1" operated solenoid sprinkler valve (you can get them for around $20 on ebay, look for rainbird brand, orbit is also good, look on spudfiles for more info on this)
I fail to see where this is less complicated than modeling a spool valved marker from PVC.

FYI: Gasses under the same pressure will expand at the same rate (assuming atmospheric conditions are the same). Maybe you missed that class...

My .02: Don't attempt to use paintball as a science fair project; it doesn't have the substance needed. If you REALLY want to use a paintball gun as part of your project: experiment with ballistic trajectories or unorthodox shaped projectiles.
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Last edited by Neppo1345 : 12-08-2008 at 07:48 AM.
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Old 12-08-2008, 07:43 AM #12
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Quote:
Originally Posted by Neppo1345 View Post
FYI: Gasses under the same pressure will expand at the same rate (assuming atmospheric conditions are the same). Maybe you missed that class...
Which is the result the kid should come up with...

Building a spud gun is easier than trying to design a well performing spooler. This kid thinks he's going to home build a spoolie for a HS project. It's not going to happen. Are you honestly going to say that a pvc air cannon is hard to make?
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Old 12-08-2008, 08:10 AM #13
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Which is the result the kid should come up with...

Building a spud gun is easier than trying to design a well performing spooler. This kid thinks he's going to home build a spoolie for a HS project. It's not going to happen. Are you honestly going to say that a pvc air cannon is hard to make?
I agree that building a spud gun is easy, albeit too easy. Anyone who knows how to use a hacksaw and 'pvc glue' can build one. I simply think that testing this hypothesis in this way is weak at best. It's like saying mythbusters is 'real' science.
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Old 12-08-2008, 08:39 AM #14
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Originally Posted by Neppo1345 View Post
I fail to see where this is less complicated than modeling a spool valved marker from PVC.
FYI: Gasses under the same pressure will expand at the same rate (assuming atmospheric conditions are the same). Maybe you missed that class...QUOTE]

But he may come up with some cool results. Doc Nickel did testing of different propellant gases many years ago. He found that some gases actually produced a different sound signature, but that compressed air and CO2 were still the best choices.
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Old 12-08-2008, 08:54 AM #15
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Quote:
Originally Posted by warbeak2099 View Post
Which is the result the kid should come up with...

Building a spud gun is easier than trying to design a well performing spooler. This kid thinks he's going to home build a spoolie for a HS project. It's not going to happen. Are you honestly going to say that a pvc air cannon is hard to make?
its easier than alot of people think,

if for physics im sure he would need to use some functon of a kind to apply it to a physics class, such as pressure, volume equating to velocity.

a spollie could be made with a butterfly valve, and pvc (essentially an elaborate spud gun)
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Old 12-08-2008, 01:58 PM #16
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Neppo1345 - I invite you to test your argument! (PS - it won't hold up the faster you try to propel the object!) In purely pnuematic spudgunning, we commonly use gasses like helium, which has a lower density (and I'm sure you know that), to approach mach1 in velocity. We usually dont test at lower velocity, so this experiment would be interesting to see the results.

Perhaps you missed the part about conducting a well laid out science experiment. Simply constructing a spool vavle and saying "durr it works!!" is not a science experiment. Thanks for your short winded attempt at discrediting my contribution, perhaps you can contribute your own suggestion in more than... oh say 80 words?

And the fact that a spudgun is easy to make is irrelevant, the test is not whether or not the OP can construct a spud gun - my dog can **** out a spudgun for that matter. The spud gun, constructed the way I stated provides a consistant basis for testing the variable - whether it be a projectile, the compressed gas, or the experiment that excelled me through the science fair - testing the impact resistance of common household siding constructions, where both the gas and the projectile were constants, and the household sidings were the test variable. twodayslate your more than welcome to use that test as well.

Last edited by xsport37 : 12-08-2008 at 02:11 PM.
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Old 12-08-2008, 02:33 PM #17
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Quote:
Originally Posted by jonotwist View Post
contact a machinist,

a good physics project would be a spoolie due to the dynamics involved
he wants to do it for under $50. I dont know many machinists that will be willing to make as many parts as he would need that cheap
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Old 12-08-2008, 03:15 PM #18
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Quote:
Originally Posted by warbeak2099 View Post
Which is the result the kid should come up with...

Building a spud gun is easier than trying to design a well performing spooler. This kid thinks he's going to home build a spoolie for a HS project. It's not going to happen. Are you honestly going to say that a pvc air cannon is hard to make?
He only wants to make the gun shoot a ball or two. He doesn't want a well performing spoolie - just something that can shoot a paintball. I think he is going more towards the air cannon.

Correct me if I'm wrong OP.
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Old 12-08-2008, 03:48 PM #19
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Neppo1345 - I invite you to test your argument! (PS - it won't hold up the faster you try to propel the object!) In purely pnuematic spudgunning, we commonly use gasses like helium, which has a lower density (and I'm sure you know that), to approach mach1 in velocity. We usually dont test at lower velocity, so this experiment would be interesting to see the results.

Perhaps you missed the part about conducting a well laid out science experiment. Simply constructing a spool vavle and saying "durr it works!!" is not a science experiment. Thanks for your short winded attempt at discrediting my contribution, perhaps you can contribute your own suggestion in more than... oh say 80 words?

And the fact that a spudgun is easy to make is irrelevant, the test is not whether or not the OP can construct a spud gun - my dog can **** out a spudgun for that matter. The spud gun, constructed the way I stated provides a consistant basis for testing the variable - whether it be a projectile, the compressed gas, or the experiment that excelled me through the science fair - testing the impact resistance of common household siding constructions, where both the gas and the projectile were constants, and the household sidings were the test variable. twodayslate your more than welcome to use that test as well.
1. I never stated the idea of comparing the expansion rates of gasses was a bad idea. I simply said that going about it in that way is more show than science and introduces environmental variables and more experimental error. The alternate gas spud gun idea would be great for a project like "alternate propellant methods for less than lethal weapons" or something along those lines.

2. Yes, if you want to see high velocities a gas of lower density is preferred. I apparently forgot the 'Supersonic Pneumatic Cannon" chapter from my texts.

3. Throughout my academic career I have been short winded. The fewer words the better; less chance for misinterpretation.

4. The inverse of point no. 1: I never said a pneumatic cannon of that design was a bad test bed. It would be better for testing alternatively shaped projectiles or ballistic trajectories (as I stated in post No.11).

5. I would like to meet your dog.

In closing:

I offered my suggestions (alternatively shaped projectiles, ballistic trajectories) if OP still wants to use a pneumatic gun to test a hypothesis.

I stand by my feelings towards using a pneumatic gun to test gas expansion rates. Better to use a pressure vessel, piston, solenoid valve, and two photo gates. This will involve fewer experimental errors than by measuring shot to shot distances in a field somewhere.
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Old 12-08-2008, 03:58 PM #20
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Thanks for the great replies (especially xsport)!

So from what I gathered, making a spudgun would be easier than making a paintball gun for a physics project.
So it looks like I am not going to go with the paintball gun.

Thanks for the ideas and suggestions.

I will edit this post to tell you guys what I picked.

edit://May do how a hard drive works. IDK

Last edited by twodayslate : 12-08-2008 at 04:21 PM.
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Old 12-08-2008, 05:07 PM #21
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You can do whatever you want, but it's best if you enter your project with a mindset to challenge something, or prove something, rather than just to show how it works... unless of course that something is revolutionary in your mind.
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