How does the puck function?

[Waldo1 0]

I've searched around and can't seem to find an answer, so I'll ask the group. I've built a couple of AKs and FALs, so a gas piston system is not new to me, but I'm stumped by the action/function of the puck during the firing cycle? What does it do and why?

 

Thanks,

 

Waldo1

[Spartacus 1,619]

Although similar to a standard AK gas system, my understanding is that a more efficient gas system was needed for the S-12. There is less peak pressure to operate the action with a 12G round vs. a rifle round and at the same time, more force is needed to extract the larger shell and move the larger hardware of the 12G action. Another key factor was the need to have a user adjustable system, since the 12G rounds vary widely in their power.

 

The puck fits with close tolerance (better seal) in the gas cylinder and is "shoved" into the end of the carrier rod to operate the action. This allows the end of the carrier rod (what would be the piston on a rifle cal AK) to "free float" in a loose tolerance gas tube of it's own. The operation of the carrier rod is not at all hindered by needing to ride inside of a tight gas cylinder.

 

Very simple, effective, and reliable system that is a hallmark of AK action based weapons.

 

That's my best explanation of the S-12 gas system, I'm sure others will be able to add some other info.

 

Welcome to the forum!

[volkov 318]

functions the same as a piston, but has a bigger surface area so it is restricted in the area it travels.. otherwise you'd have a gigantic gas tube and the to remove the bolt the reciever would have to be significantly modified if it was attached.

 

edit: spartacus beat me, and with a better answer

Edited May 3, 2010 by volkov

[Boba Debt 350]

The part I don't get is that my puck only seems to move about 1" or less.

 

So I guess it hits the rod hard like a hammer to make it cycle????

[mgconnor13 206]

the puck acts similar to a short stroke gas piston system. the gas pushes the puck, puck shoves the piston and bcg back to cycle it.

[hellraiser 6]

the puck acts similar to a short stroke gas piston system. the gas pushes the puck, puck shoves the piston and bcg back to cycle it.

 

 

 

 

 

 

 

 

yeah but the bcg moves back alot to cycle, and like bobba debt said the puck only moves an inch???

so dose it work like a hammer? you think thered be more signs of wear if it did?

[Gunfixr 76]

It's a short-stroke piston system. The regular AK uses a long stroke piston system.

 

The M1 Carbine, the M14/M1A, and the Ruger Mini 14 also use this system.

 

The piston (puck) moves only a short distance, imparting a thrusting force to the bolt carrier. It then stops moving, having bottomed out in it's carrier, and the bolt carrier continues on from the impetus alone.

 

Although not exactly the same, it is similar in concept to the swinging balls you see on peoples' desks. The one where there is a frame with several steel balls hanging in it on strings, and when one is drawn back and allowed to hit the rest, the one on the opposite end moves away due to the transferred impetus. If you took the center balls out, and had only two, then it would be pretty much the same.

 

ETA: Actually, there is less than 1/32" of free space between the fully forward bolt carrier and the gas plug. This varies from about 1/64" to just about 1/32", depending on where the gas plug is adjusted.

Therefore, the puck does not act as a "hammer". There isn't enough free travel, and the puck doesn't have sufficient mass. It is all push, given by the pressure behind the puck, a very sudden and hard push.

Like playing shuffleboard. You take the "pusher" (don't know what it's real name is) and give the disk a shove. It keeps on going down the board, even though you have stopped pushing it.

Impetus.

[The_Caged_Bird 474]

There you have it!

[hellraiser 6]

There you have it!

 

 

 

 

 

 

 

 

 

 

now i know, and knowing is half the battle!!!! thanks!!!

[Kliegl 304]

Using the word impetus in a technical discussion makes this engineer cry.

 

Kinetic energy? Momentum? Impulse?....maybe even....FORCE?

[G O B 3,516]

The air in the barrel ahead of the shot cup will push the floating piston into contact with the bolt carrier extension (what would have been the piston in an AK) so there is no hammer action - just a bigger push due to the larger piston area. The regular AK is also a short stroke piston design, the piston comes out of the short cylinder and travels with the bolt carrier, however it only acts as a piston until it exits the rear of the short cylinder - after that it is just mass (and a guide as it travels through the fluted part of the gas tube).

[The_Caged_Bird 474]

Using the word impetus in a technical discussion makes this engineer cry.

 

Kinetic energy? Momentum? Impulse?....maybe even....FORCE?

 

Good, from what I've had to deal with on jobsites what with having to go back and re-do crap that the engineer either just got it plain wrong or missed it, they deserve to cry every now and then.

 

IMPETUS!!!!

 

J/K

[Kliegl 304]

Hey man, when a doctor screws up, they kill a person. When an engineer screws up, they kill a hundred. BWAH!

 

Another thing to notice that is interesting about the short piston in this instance is that the mass of the puck is removed

from the kinetic energy and momentum that the spring has to absorb coming back, since the puck is stopped by the gas tube.

This means that the spring can be lighter and shorter and will wear out less.

 

However, it also means that the negative acceleration that the carrier will get is sharper, since there's less momentum.

 

If anyone has taken a Browning short action apart before, they have a giant inertia block that the short stroke piston hits

and that block has a sub-block, with its own springs, to further smooth things out.

 

The interesting thing about Soviet designs, with the over-the-top op rod, is that it's a novel way to access the bolt.

Brownings go on both sides, legacy US equipment goes on the right side, modern US is over the top gas impingement, and the

AK has an op rod on top, while the SKS has a rather interesting double spring double rod system (which is important, since

many SKS's throw brass STRAIGHT up)

[Gunfixr 76]

If that's all it took to make you cry, I feel sorry for you.

I am not an engineer, just guy who works on guns for a living. I know how the system works, and so tried to explain it in terms anybody could understand.

 

Next time, I'll just stay quiet, and you can explain it.

 

Between your crying, and others picking my explanation apart.

 

Every time I log on here, I get more reasons to take a longer time before I come back.

Further proof that no good deed goes unpunished.

[The_Caged_Bird 474]

If that's all it took to make you cry, I feel sorry for you.

I am not an engineer, just guy who works on guns for a living. I know how the system works, and so tried to explain it in terms anybody could understand.

 

Next time, I'll just stay quiet, and you can explain it.

 

Between your crying, and others picking my explanation apart.

 

Every time I log on here, I get more reasons to take a longer time before I come back.

Further proof that no good deed goes unpunished.

 

Hey man, there are more here quietly listening and learning from what you are saying than those who are jacking with you. I've learned quite a bit from your posts. Screw the haters, keep teaching, please.

[Kliegl 304]

If that's all it took to make you cry, I feel sorry for you.

I am not an engineer, just guy who works on guns for a living. I know how the system works, and so tried to explain it in terms anybody could understand.

 

Next time, I'll just stay quiet, and you can explain it.

 

Between your crying, and others picking my explanation apart.

 

Every time I log on here, I get more reasons to take a longer time before I come back.

Further proof that no good deed goes unpunished.

 

The biggest problem you have is that you thought I was serious. This is the big, bad internet.

This is a GUN FORUM on the internet. Grow a pair?

[Gunfixr 76]

 

The biggest problem you have is that you thought I was serious. This is the big, bad internet.

This is a GUN FORUM on the internet. Grow a pair?

 

The internet may be big, but it ain't that bad.

I know it's a gun forum.

I have a pair already.

 

I'm just tired of the bullshit.

 

To me, this wasn't a joking kind of thread. Maybe for you the lines are a bit blurred.

Since it's a GUN FORUM, maybe the "filler" could be saved for the "filler" section.

[Kliegl 304]

You're right, I should've just told you it's not the right term.