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SA/FA Pnushnikov/Caselman-build log.

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: SA/FA Pnushnikov/Caselman-build log.

Unread postAuthor: Hurricane Air Arms » Sat Apr 16, 2016 8:14 pm

Brian the brain wrote:I'm assuming you are referring to the ROF dropping slowly in full-auto mode?

about wasting air:
While it pancakes 10mm leadballs like other powerful airguns the semi/full auto action uses only a fraction of air to recock.
It's designed that way.

My design uses a balanced valve with very high flow ( the barrel is smaller) yet it requires little to knock it open at high pressures.
Therefore the springs can be weak and blowback can occur with a minimum amount of gas.
The only air that reaches the piston is what passes between the valve housing and the valvestem...basically fitting together but lacking an O-ring seal.

The piston-hammer-bolt assembly itself is designed to operate with a minimum input of force.Large diameter face to generate the most blowback force..

On the return stroke the blowback-piston is airtight.
When the piston reaches the back a poppet in the centre is opened so the piston( hammer) can be pushed forward immediately without having to compress any volume in front of it.
When the piston hits the valvestem it hits it with the head of the poppet wich is automatically closed, sealing the piston again.

This feature also means the travel of the piston/hammer/bolt assembly is restricted...or better yet tuned.
I can't see how a BFV would be significantly more efficient...BFV's mean dead space and restrictions between the valve and the projectile.

Any inconsistency in ROF is due to the pressuredrop from the tank.In a couple of vids it was already half empty.
With a full tank it's not noticable in operation because the mag only holds 9 rounds.
When I hooked it up to a larger tank it (blank) fired consistently for an extended time.

In the vid where it's spraypainted silver...the tank was near empty so it wouldn't recock in full auto.
But that vid was only to demonstrate the difference between full and semi setting...

I was assuming your charged the tank to full in all of those vids. But I can see what you mean.

My other question is because you have a weak blowback spring, how does your action manage to scoop up the first round from your magazine without a holdup? This is something I've always been curious about. What if the magazine spring was too strong that it didn't allow the bolt forward when chambering the first round? Or is the mag spring weak as well?

This is particularly important as I want to build a drum magazine but don't want any hold ups.
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Hurricane Air Arms
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Re: SA/FA Pnushnikov/Caselman-build log.

Unread postAuthor: Brian the brain » Tue Apr 19, 2016 12:57 pm

Weak is relative.
It's easy to cock but the spring is strong enough to load the ammo.

What I meant was, because of the balanced valve I don't need a bulky, powerful spring to knock open the valve.Normally at these pressures a hammervalve with an opening this big would be impossible to knock open....There would be between 800 and 1000 Newton pushing it shut if it wasn't counterbalanced.
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Brian the brain
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