........
|
||||||||||||||||||||||||||||||||||||||
........
Last edited by thx997303; 10-22-15 at 15:55.
This is not that hard folks... impingement is like a stream of water from a firehose hitting something. Like a trash can lid. It's not contained, and it's not expansion of the water that creates force, it's the fact the water has mass and is moving.
Yes, cupping the impinged object (imagine flipping the trash can lid over) does transfer a bit more force, but it's not an expanding action. It's just that more of the water is forced to exit 180 degrees from direction of travel rather than allowed to slip out at 90 degrees.
Gas has mass, and is moving, and does create force. Otherwise jet planes would fall out of the sky. The jet engine gas/air flow blowing cars over is a prime example of impingement.
Pistons and cylinders, even the linear, indirect, insideout, whatever Stoner design, depend not on the direct force of the gas, but instead depend on the expansion of the gas in the chamber formed by the piston and cylinder.
Key difference: Impingement the gas is moving in the direction they want the impinged object to move. Where with the piston expansion approach, the gas direction is immaterial, it just has to enter the chamber formed by the piston/cylinder.
There might be a slight piston/cylinder effect in the various impingement designs as well, but it's mostly impingement. Like the firehose water hitting our trashcan lid and pushing it. The fact there is not a precision fit (rings) between the gas tube and cup bears this out. Likewise, the shortness of the cup vs the stroke of the carrier.
So as arcane as this debate is (angels dancing on pinheads), from a physics point of view, the AR is not impingement. The fact that the gas enters at 90 degrees to the desired movement makes that crystal clear. Which means it's a piston cylinder interaction which generates the forced based on expansion/increasing volume of the gas.
If this is a discussion of labelling, tradition, and ease instead of technical terms, perhaps it's more suited to AR General Discussion rather than Technical.
Or maybe that's the whole cause of argument. Everyone (besides hans) realizes that an AK, AR15, and whatever DI gun operate in the same way. Gas is routed from the barrel into a piston which causes the bolt/carrier to move rearward, a case ejects, the spring pushes the bolt/carrier forward and chambers a new round.
The traditional "piston" guns refer actually to the location of the piston above or below the gas port of the barrel and a rod between that piston and bolt to mechanically transfer the energy in the case of a "short stroke", or an extension of the bolt carrier itself as in a "long stroke". Using a gas tube to move that interaction further back has been traditionally called "di", though not often technically correct as pointed out earlier. But that's the terminology someone chose. Stoner's system breaks with traditional DI systems by moving the piston again.
For technical purposes, it's just as wrong to call it DI as Piston, as the key definition, the location of the gas expansion chamber, is different.
"I never learned from a man who agreed with me." Robert A. Heinlein
Actually your last example of the internet commando is the strawman. We are discussing whether or not an Ar15 is a DI rifle. We are not discussing if it has deficiencies that piston operated uppers claim to overcome.
Also, the deficiencies are typically, shits where it eats, bcg gets hot and bakes on carbon, too hard to clean, not reliable when dirty. None of which have any direct bearing on what the system is called, but come from a lack of actual experience with the system. You could call it the apple and android system and those arguments would still be made.
Another major problem is not that is is a DI vs piston one, as they are both pistons, the debate should be:
Where do we want to vent our spent gas?
Which part to we want to get hot?
How much axial wobble of the bolt carrier can we stand?
and
How well can we retrofit something different to an existing design?
So, you want me to aid your argument? Can't you make your argument on your own?
I'm going to say that based on your previous arguments, in that picture, there are male pistons and female pistons and stationary pistons and cylinders and who knows what else.
We're discussing existing, working designs. Not your little paint drawing.
I sort of agree with this definition, just not sure we can prove how much is force from expansion vs impingement in the Hakim and similar.
That's a common misconception. If this were the case the ideal sail angle would be 90 degrees. Most sails actually "suck", the sail is an airfoil. The longer path of the wind around the sail creates a low pressure zone ("lift" in the airfoil context) that moves the boat forward. Just like plane wings.Another true 'direct impingement' design is a sail boat, any guns out there with a sail?.
Better example of impingement is jet engine exhaust flow blowing over a car. Or blowing something along the ground with a pressurized water stream (firehose, etc)
I'm just trying to demonstrate the absurdity of calling the bolt a piston. What I was trying to demonstrate is that the situation with the AR is no different than the way the adam's arms piston works. But you knew that already, which is why you won't just answer the freaking question.
876.jpg
Bookmarks