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M82A1 0% (destroyed)

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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M82A1 0% (destroyed)

Unread postAuthor: Demon » Sun May 08, 2011 5:57 pm

[youtube]http://www.youtube.com/watch?v=ucWOZxKykJo[/youtube]

http://www.servimg.com/image_preview.ph ... u=15093793

http://www.servimg.com/image_preview.ph ... u=15093793

Only got the external aspect left :toothy10:
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Last edited by Demon on Tue Sep 20, 2011 12:43 pm, edited 4 times in total.
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Unread postAuthor: warhead052 » Sun May 08, 2011 7:00 pm

Wowwwwwwwwwwwwwww, thats nice! Very cool.
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Unread postAuthor: Gaderelguitarist » Sun May 08, 2011 7:17 pm

Very nice. Can't wait until it is 100%
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so many muchness
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Unread postAuthor: saefroch » Sun May 08, 2011 7:44 pm

That looks pretty amazing... care to enlighten us as to the sabot discarding system?
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Unread postAuthor: mark.f » Sun May 08, 2011 8:00 pm

Looking good! It seems that friction would keep the CPVC part from sliding forward... Works great nonetheless.
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Unread postAuthor: Demon » Mon May 09, 2011 6:04 am

That looks pretty amazing... care to enlighten us as to the sabot discarding system?


It's very simple: At he end of the barrel, there is a reducor with an I.D. just over the size of the projectile. That way, the sabot is stopped, but the projectile continues.
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Unread postAuthor: saefroch » Mon May 09, 2011 6:20 pm

*facepalmheaddesk*

Brilliant!
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Unread postAuthor: Demon » Mon May 09, 2011 7:15 pm

It seems I have accuracy problems ...

No matter the front barrel ejected sabot, discarding sabot or plain simple paper wadding, the 2.5 gram projectile can't stop curving to the sides
(approx 2 meters at 40 m eters). If it curves, it implies that it spins. But why ?

With my .43 gram airsoft carbine with a shorter barrel I got at 500 (same speed) much better accuracy (somewhere ten centimeters at 40 meters).

Any reason, solution ?

The projectile is spheric enough. Spinning is the problem.
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Unread postAuthor: jackssmirkingrevenge » Mon May 09, 2011 11:43 pm

Sexy indeed, good job!

I think the fact that you're using soft wadding material means that accuracy isn't going to be that great. Have you thought of adding a short sub-barrel at the muzzle that is exactly the same diameter as the projectile to guide the projectile correctly?
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Unread postAuthor: Zeus » Mon May 09, 2011 11:49 pm

I didn't think of this whilst we were in the chat but whay JSR said prompted me to think of it.

The sabot isn't releasing the projectile evenly thous it's trajectory is being altered. The fix JSR suggested would fix you're problem.
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/sarcasm, /hyperbole
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Unread postAuthor: jackssmirkingrevenge » Mon May 09, 2011 11:54 pm

Have a look at these ideas, you may be able to use a more rigid projectile without actually tearing the thing apart ;)
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Unread postAuthor: Demon » Tue May 10, 2011 6:02 am

I think the fact that you're using soft wadding material means that accuracy isn't going to be that great.


The blue foam sabot fits rather snug, I dont think to problems comes from there.

The problem is the projectile spinning on itself, causing a curve to the sides.

Would rifling the copper barrel help controling how it spins ?
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Unread postAuthor: jackssmirkingrevenge » Tue May 10, 2011 6:06 am

Demon wrote:The blue foam sabot fits rather snug


... yet it's very soft material and I can assure you it deforms considerably when pressure is applied.
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Unread postAuthor: Demon » Tue May 10, 2011 7:08 am

But It cannot impart spin along the vertical axis on it, can it ?

Rifled barrel, good or bad ?
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Unread postAuthor: jackssmirkingrevenge » Tue May 10, 2011 7:39 am

Demon wrote:But It cannot impart spin along the vertical axis on it, can it ?


I think your problem lies with the reducer - how close is the internal diameter to the projectile diameter?

Remember, golf ball in a drain pipe - if your projectile is free to bounce around, there's no telling at what angle it will leave the muzzle.

Rifling will not help if the projectile hits one side of the reducer and not the other.
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