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Posted: Sat Feb 02, 2013 7:36 pm
by jsefcik
Apprecaite it guys, I'm going to futher my education through the army considering its all paid for ,I do want to continue my plumbing nd heating, I already have a 3 yr degree on it nd
Want to contiue that but if I dont get that on my asvab scores , and as a back up id like to get combat engineer!!

Posted: Sun Feb 03, 2013 12:41 am
by mark.f
jsefcik wrote:Apprecaite it guys, I'm going to futher my education through the army considering its all paid for , maybe ill become a liesnce gunsmith nd design hybrids then any otber spudder on the forum!!!


I want to do plumbing since I already have a 4 yr degree in it nd then move on
Image

Posted: Sun Feb 03, 2013 1:04 am
by jackssmirkingrevenge
*chuckle*

Posted: Mon Feb 04, 2013 12:28 pm
by POLAND_SPUD

Posted: Mon Feb 04, 2013 1:08 pm
by jackssmirkingrevenge
Interesting, I remember we had discussed this: http://www.spudfiles.com/forums/mass-fl ... 16641.html

I'm guessing the fact that a ping-pong ball has extremely low density is somehow related.

Posted: Mon Feb 04, 2013 2:47 pm
by MrCrowley
That arxiv paper is surprisingly basic, I'm sure there are more than a few members here who are capable of writing such a paper for a particular cannon. Though, our hypotheses are usually "I think I'll be able to shoot this through that given enough pressure" :D

Posted: Mon Feb 04, 2013 3:12 pm
by POLAND_SPUD
I remember that thread and I shared it precisely because of that thread... maybe you're right JSR it's because of small mass

Posted: Mon Feb 04, 2013 3:51 pm
by jackssmirkingrevenge
As I pointed out in the other thread, if there was any merit to the idea beyond firing extremely lightweight projectiles, we would see it more often.

I would surmise that the ping pong ball fired without the nozzle leaves the muzzle too quickly for enough pressure to build up behind it, so the advantage of the accelerated gasses is noticeable. If they tried the same setup shooting say golfballs instead I would expect the latter to have worse performance with the nozzle fitted.

Posted: Mon Feb 04, 2013 6:58 pm
by POLAND_SPUD
lol not safe for work
[youtube][/youtube]

Posted: Mon Feb 04, 2013 7:04 pm
by btrettel
I'm skeptical the convergent-divergent nozzle is necessarily helping here. They did no tests without it best I can tell. For all we know the gun would have performed better without it.

Posted: Tue Feb 05, 2013 2:19 am
by jackssmirkingrevenge
POLAND_SPUD wrote:lol not safe for work
The whole series is brilliant:

Makes you realise what sentimental saps environmentalists are.

Image

In the eternal words of Tim Minchin, so does cot death.

Posted: Tue Feb 05, 2013 8:30 am
by wyz2285
I'm thinking about buyingthese, and make a pneumatic launcher to use it. They're for 80 lb, I was wondering if I use too much pressure/muzzle speed will they fiy straight?

Posted: Tue Feb 05, 2013 10:47 am
by PaperNinja
my brother had something similar to those, they not only didn't fly straight, but the heads (maybe the tails? idk something) flew off whenever they hit the target. He got some solid-body plastic bolts similar to these that seemed to work a lot better (though they were a little heavier)

Posted: Tue Feb 05, 2013 10:54 am
by wyz2285
I thought about these but none ships to Portugal. Probably the tail, but I'm planning one remove the tail anyway so it would fit inside the barrel.

Posted: Tue Feb 05, 2013 12:36 pm
by Gippeto
Wyz...arrows are drag/spin stabilized....you need the fletching.

Arrow shooting airguns use an arrow with the nock removed (the part that holds the string) and slide OVER a smaller diameter tube. The air comes through this smaller tube.

Kind of like blowing the paper cover off of a drinking straw.