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Kick'n'Blow

A place to ask general spud cannon related questions.
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Unread postAuthor: LeMaudit » Mon Apr 27, 2009 3:25 pm

Great look :-) And great reading too !

Y'a know, that means the mechanism I had in mind should worth a try :-)
I do plan to have a much stronger spring that a small rifle if possible, cocking it using power force.

I still need to investigate this "against spigot" and understand why not. I sure could push the arrow earlier instead of hitting it, but I would loose some acceleration on the full barrel length with the compressed air.
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Unread postAuthor: Big-E » Mon Apr 27, 2009 3:38 pm

I think it's because of the dead space before the acting surface of the projectile, but with a catapult, I don't know, it may offset that a bit. you could always try it and see if it works.

And don't sweat the spring, the whole point of bb guns working like this is so they would work with weaker springs. Of course, your projectile is heavier than a .177 BB
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Unread postAuthor: LeMaudit » Mon Apr 27, 2009 4:09 pm

I would guess roughly 10 times heavier than a pellet :-) It will be steel, machined like a harpoon head, maybe 3/4" inch length and 1/2" diameter with sharp triangle sides. Plus a light body.

It's heavy and that's why I may need the push from the start. The strong spring will also provide higher compression level. But I'll keep all the advises in mind.
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 27, 2009 11:49 pm

LeMaudit wrote:Can you please elaborate on that? I would have thought initially that because of the relatively loose friction, only with a O-ring at the end, it would have being better energy efficient. And also would have keep the arrow from falling, which is a plus. But I would like to learn :-)


Weapons built on this principle like the Blacker Bombard and Projector, Infantry, Anti-Tank tend to have extremely poor performance in terms of velocity and range.

Now, what throws an arrow-like projectile extremely well?

Image

:D

With the projectile inside a sabot in a wider barrel, you get a much larger surface area for the air to push on and therefore much more energy is available. Calibre is important when it comes to dealing with air, remember that 100 psi in a 20mm barrel has as much energy as 400 psi in a 10mm barrel.
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Unread postAuthor: LeMaudit » Tue Apr 28, 2009 7:27 am

Now, what throws an arrow-like projectile extremely well?


Many thanks for the explanation and links. Hmmm... I never thought about a sabot. Maybe overkill, but I'm not afraid about that :-) Overkill is more fun to machine ;-)

I sure will think about that solution, as it solves many problems. minimum dead space, useful arrow back (fins?), less friction, more pushing surface...

I still like the idea of the Kick'n'Blow, but it would become more a Push'n'Blow, like those BB guns. I think this mechanism is interesting to build the compression before starting releasing the air. And it is a simple trigger too.

I think I need to play with GGDT, because now I"ll have a much heavier arrow :-D
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