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first attemp at pneumatic cannon>>>swooshhhhhh

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: FORE!!!! » Fri Jul 17, 2009 8:02 am

inonickname wrote:I'm gonna have to agree...you are spending a bit on this. My gun, which I will post tomorrow has had less than $100 spent on it (actually, perhaps more), including making a homemade 400 psi pump.

You can buy a $3 laser pointer from a store, carry out a simple mod on it to make it remotely switchable and put a nice case on it for aesthetics. Probably all under $5, presuming you had none of the parts (switch, wires etc to begin with)

By the way, with a ballvalve you will throw your aim off trying to open the valve fast.

Sorry to sound so critical, but it is actually quite a nice gun :cry:


ist all good ,about the ball valva i went to bunnings the other day and got a sprinkler valve and modded it with a blow gun,it awsome now steady as a rock...and accurate ill post a pic tommorow its 11.00pm ..
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Last edited by FORE!!!! on Fri Jul 17, 2009 8:05 am, edited 1 time in total.
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Unread postAuthor: frozebyte » Fri Jul 17, 2009 8:05 am

Are you using a laser red dot?
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Unread postAuthor: FORE!!!! » Fri Jul 17, 2009 8:08 am

frozebyte wrote:Are you using a laser red dot?


yup.
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Unread postAuthor: FORE!!!! » Fri Jul 17, 2009 8:23 am

frozebyte wrote:Don't think it was necessary to spend the 50bucks on a carbon fiber vinyl to strengthen your pvc pipe. That amount could've built you a nice copper gun or two.

Considered saving those for another project?


and the vinly was used for another project of mine not this one ,i wraped my laptop shell with it and had leftr overs... :wink:
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Unread postAuthor: frozebyte » Fri Jul 17, 2009 9:20 am

could've saved those leftovers for a sleek spudgun, i think the carbon fiber would make even a pvc gun look super sleek like a copper one :wink:

Oh i forgot you weren't a fan of small copper spuds, right? not nitpicking but you could quote twice in a post :]

Any progression for a next spud? can't wait :] you have pretty nice extras (cause you've got the cash)
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Unread postAuthor: FORE!!!! » Sat Jul 18, 2009 8:42 pm

just an update to my last post, the modded sprinkler valve and a damage shot...
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Attachments
19-07-09_1113.jpg
new valve,,had to mod it on side of caseing because of guide rod..
19-07-09_1114.jpg
full view
19-07-09_1115.jpg
the target entry hole next to bullseye,this was my first attemp at the target
19-07-09_1116.jpg
exit wound...
19-07-09_1117.jpg
20mm thick particle board
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Unread postAuthor: c11man » Sun Jul 19, 2009 10:46 am

see how much more powerfull the sprinkler is? i personaly have not used one but they are much better than a ballvalve but still not a piston valve.
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Unread postAuthor: jackssmirkingrevenge » Sun Jul 19, 2009 12:05 pm

Shame the chamber is still so big relative to the barrel, you're getting a lot of extra noise and filling effort without any real performance benefit.
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update

Unread postAuthor: FORE!!!! » Mon Jul 20, 2009 10:45 pm

updated with scope mounted on a aluminium bar,fits perfectly. :arrow:
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Attachments
21-07-09_1331.jpg
new decal
21-07-09_1330.jpg
view looking through scope lens,it has improved aiming tenfold .
21-07-09_1329.jpg
ergonomic...
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chamber lenght

Unread postAuthor: FORE!!!! » Tue Jul 21, 2009 11:54 pm

just wondering weather this would be an exceptable chamber lenght?
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Attachments
22-07-09_1437.jpg
x2 45 degree bends,, and x1 end cap
22-07-09_1438.jpg
full lenght ==chamber 700mm including tee elbow,,barrel lenght=950mm have i gone too far?
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Unread postAuthor: jackssmirkingrevenge » Wed Jul 22, 2009 12:21 am

Have I gone too far?


Not far enough in my view, capping the Tee with no extra pipe is enough.

Of course more chamber = more power but it gets to a point where you might increase chamber volume to 200% and get a power increase of 2%, ie not worth it. It depends what you want. I personally would chose silence and convenience.

Have you tried plugging a few numbers into GGDT to get an idea of what sort of performance increase/decrease you're talking about?
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Unread postAuthor: FORE!!!! » Wed Jul 22, 2009 12:29 am

yeah what numbers should i use for the valve type in ggdt for flow coef,im using a 1'' sprinkler valve

and should it be set to generic?
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Unread postAuthor: jackssmirkingrevenge » Wed Jul 22, 2009 12:39 am

Set to Generic, Flow coef 30 and opening time say 10ms.

Input all the correct data (barrel length, pressure, calibre, projectile weight etc.) and start with a chamber length of 10 inches.

Make note of the muzzle energy, then check it with 11 inches, 12 inches etc until you reach the length of the barrel.

This way, you'll get an idea of how performance changes with more volume and you can make an informed decision on what your ideal chamber volume should be ;)
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Unread postAuthor: FORE!!!! » Wed Jul 22, 2009 1:03 am

from these results how do i work out how many feet per second i can shoot my marbles at?

TRAVEL TIME =19MS
PRESSURE DROP=55.1PSI
MUZZEL ENERGY=50.1 J
MUZZEL VELOCITY=135 M/S

???AND I TEST AT 80 PSI
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Unread postAuthor: jackssmirkingrevenge » Wed Jul 22, 2009 1:09 am

If I'm not mistaken (don't have GGDT at work :roll: ) go to the configuration window and change your linear dimensions to inches.

Anyway it's not relevant for the purpose of this exercise, just make a list of chamber length and the corresponding muzzle energy.

Test at the pressure you typically use.
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