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6mm piston valve air gun

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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Re: 6mm piston valve air gun

Unread postAuthor: Ragnarok » Fri Dec 20, 2013 8:57 am

DYI wrote:the maximum attainable velocity is not c_0 (the initial sound speed), but rather 2c_0/(γ-1)

I know (but the equation's actually in Section 11), but there's two problems with it in this context.

Firstly, it makes a fairly large number of assumptions that are inaccurate when applied to homemade pneumatics (of a relatively low pressure). For our purposes, Mach 1 is pretty functional rule of thumb.
Secondly, delving into all the depths of fluid mechanics is a horrendously over-complex way to try and explain that breaking the sound barrier is not quite so trivial that everything you think might be a sonic crack is.

Sometimes, the dumbed-down explanation is the stronger choice.
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Re: 6mm piston valve air gun

Unread postAuthor: jackssmirkingrevenge » Fri Dec 20, 2013 9:29 am

bravootome wrote:ok, than take a look at this man that shoots 60 bar with metal bb. It is way over speed of sound


"This man" is a member of spudfiles ;)

there are custom pneumatics guns that shoots over 2000 fps.


I've never really seen an airgun go over 2,000 feet per second, any links?
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Re: 6mm piston valve air gun

Unread postAuthor: DYI » Fri Dec 20, 2013 9:49 am

Mach 1 is certainly a functional rule of thumb - but that's more a coincidence than anything. Deviate from the standard design parameters a bit, and you'll climb up over it. I wouldn't say that my explanation was "horrendously over-complex" - perhaps giving the derivation would have been overkill in this context, but I just gave a rough explanation and a reference. The manner in which you told him Mach 1 was the limit implied absolute certainty on your part that it was a theoretical impossibility to exceed this limit, when in practice it only requires somewhat higher pressure than the norm.

I disagree that a "dumbed-down" explanation is ever the stronger choice, if it's not even an accurate approximation to reality. Using classical mechanics to explain why the Earth goes around the Sun is fine, but using it to explain the existence of gravity waves is not.
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Re: 6mm piston valve air gun

Unread postAuthor: Ragnarok » Fri Dec 20, 2013 11:38 am

DYI wrote:The manner in which you told him Mach 1 was the limit implied absolute certainty on your part that it was a theoretical impossibility to exceed this limit

Not at all. As I've said repeatedly, I believe it's possible. However, it takes more than scarce and unreliable evidence for me to believe it.

It's a holy grail that people are all too bothered about beating, and people who get borderline aggressive when challenged over it are those I would least trust to have been objective and scientific in evaluating the possibility.
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Re: 6mm piston valve air gun

Unread postAuthor: bravootome » Fri Dec 20, 2013 3:25 pm

least trust to have been objective and scientific in evaluating the possibility.[/quote]

actually you were only trying to prove that i am wrong as far as Bucharest is to 1 hours travell to London. Cuz i am here and i am shooting my gun, and i have been making at least 100 pistons and pilots, valves tubes, airtanks in the past 2.5 years and when i make an afirmation i dont just say it to show i am a vip. i Based my words by comparing penetration tests with custom guns and by my experience . U used wikipedia definitions and theories about sound speed to mind my words even they didnt apply in this case and even you know most airgun are capable to exceed sound speed, just to show yourself that youre a smart dude and that is not nice of you !
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Last edited by bravootome on Fri Dec 20, 2013 3:52 pm, edited 1 time in total.
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Re: 6mm piston valve air gun

Unread postAuthor: bravootome » Fri Dec 20, 2013 3:50 pm

jackssmirkingrevenge wrote:
bravootome wrote:ok, than take a look at this man that shoots 60 bar with metal bb. It is way over speed of sound


"This man" is a member of spudfiles ;)

there are custom pneumatics guns that shoots over 2000 fps.


I've never really seen an airgun go over 2,000 feet per second, any links?


the gun is custom made, i dont remember where i sow the video but i remember he used extreme high pressure. He has a site trough he sells his guns.
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Last edited by jrrdw on Fri Dec 20, 2013 4:01 pm, edited 1 time in total.
Reason: Removed text. Do no harm to people OR animals.
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