1911Tuner
Moderator Emeritus
It came to me in a dream...and a 30-minute drive/45 minute conversation with a retired high school physics teacher confirmed it.
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Anybody figgered out why the slide moves only when the bullet moves...
and why the slide didn't move because the bullet COULDN'T move when it
was blocked by the rod and screw?
With the rod in place, the thrust vector remained balanced throughout the entire pressure curve. The harder the force acted on the slide, the harder the blocked barrel resisted it. As the pressure came down, so did the force
that resisted movement, and the slide would operate easily. Balance!
Without the rod in place, the bullet is free to move, and when it moves the
vector is no longer equal. The force obeys nature's law and follows the path of least resistance...the slide...and the slide moves. The combined mass of the slide, barrel, and bullet aren't enough to resist the force, and they are drawn backward with the slide, even while the bullet is still in the barrel. If the unlocking and linkdown are correctly timed, the bullet exits just prior to the beginning of linkdown. The bullet exits and the slide completes the cycle because of the momentum that's already established.
Hint: The unbalancing of the force vector doesn't occur instantaneously.
It happens gradually. The bullet, even with the frictional resistance,
is easier to move due to having less inertial resistance to acceleration than the slide. The bullet is screaming toward the muzzle, while the slide
is having trouble getting started. (Objects at rest tend to remain at rest until overcome by an outside force. Heavy objects resist a given force for a longer time than lighter objects.)
This explains why a light bullet at low velocity requires a lighter spring to reliably cycle the slide. It offers less inertial resistance to movement, and hence less opposite force available to move the slide. A heavy bullet resists movement more aggressively, and redirects the force back toward the slide. Remember that the slide tries to move as soon as the bullet starts to move. Momentum begins at that point, even though the slide can't yet move. Stored energy.
How does the vector become unequal? Simple. The bullet offers more initial resistance in its passage through the bore than the slide's inertial mass and the force of the recoil spring. Remember...Prior to firing, the slide and barrel are held in battery only by the tension of the recoil spring, and the locked breech only locks when there is a force acting on it in opposite directions. No force, no thrust on bullet or slide. No thrust, no solid lockup. (If it was truly locked...as with a bolt-action rifle...you couldn't simply rack the slide and unlock it. The lockup is created by the vector of thrust, and only when that vector becomes unequal will the slide operate.) As the vector of force begins to shift and gets the slide going, it gradually overcomes the bullet's frictional resistance, and starts winning the tug of war
If the mechanical connection (upper lugs) between slide and barrel is
removed, the slide is free to move independently of the barrel. here you have the "Straight Blowback"..which operates in exactly the same way as the recoil system, except that it requires a heavier slide and/or a stronger spring to prevent opening the breech while chamber pressure is high.
Why? Because the slide and barrel are locked together for the better part of the pressure curve, slide movement is delayed until much of the momentum has bled off in its attempt to pull the slide and barrel in opposite directions.
So...This gives rise to a new question:
Is the 1911 really a locked breech, recoil operated weapon...or is it actually a delayed blowback? Hmmmm?
Flame suit on!
Tuner----------->Outta here like a John Deere...
_________________________
Anybody figgered out why the slide moves only when the bullet moves...
and why the slide didn't move because the bullet COULDN'T move when it
was blocked by the rod and screw?
With the rod in place, the thrust vector remained balanced throughout the entire pressure curve. The harder the force acted on the slide, the harder the blocked barrel resisted it. As the pressure came down, so did the force
that resisted movement, and the slide would operate easily. Balance!
Without the rod in place, the bullet is free to move, and when it moves the
vector is no longer equal. The force obeys nature's law and follows the path of least resistance...the slide...and the slide moves. The combined mass of the slide, barrel, and bullet aren't enough to resist the force, and they are drawn backward with the slide, even while the bullet is still in the barrel. If the unlocking and linkdown are correctly timed, the bullet exits just prior to the beginning of linkdown. The bullet exits and the slide completes the cycle because of the momentum that's already established.
Hint: The unbalancing of the force vector doesn't occur instantaneously.
It happens gradually. The bullet, even with the frictional resistance,
is easier to move due to having less inertial resistance to acceleration than the slide. The bullet is screaming toward the muzzle, while the slide
is having trouble getting started. (Objects at rest tend to remain at rest until overcome by an outside force. Heavy objects resist a given force for a longer time than lighter objects.)
This explains why a light bullet at low velocity requires a lighter spring to reliably cycle the slide. It offers less inertial resistance to movement, and hence less opposite force available to move the slide. A heavy bullet resists movement more aggressively, and redirects the force back toward the slide. Remember that the slide tries to move as soon as the bullet starts to move. Momentum begins at that point, even though the slide can't yet move. Stored energy.
How does the vector become unequal? Simple. The bullet offers more initial resistance in its passage through the bore than the slide's inertial mass and the force of the recoil spring. Remember...Prior to firing, the slide and barrel are held in battery only by the tension of the recoil spring, and the locked breech only locks when there is a force acting on it in opposite directions. No force, no thrust on bullet or slide. No thrust, no solid lockup. (If it was truly locked...as with a bolt-action rifle...you couldn't simply rack the slide and unlock it. The lockup is created by the vector of thrust, and only when that vector becomes unequal will the slide operate.) As the vector of force begins to shift and gets the slide going, it gradually overcomes the bullet's frictional resistance, and starts winning the tug of war
If the mechanical connection (upper lugs) between slide and barrel is
removed, the slide is free to move independently of the barrel. here you have the "Straight Blowback"..which operates in exactly the same way as the recoil system, except that it requires a heavier slide and/or a stronger spring to prevent opening the breech while chamber pressure is high.
Why? Because the slide and barrel are locked together for the better part of the pressure curve, slide movement is delayed until much of the momentum has bled off in its attempt to pull the slide and barrel in opposite directions.
So...This gives rise to a new question:
Is the 1911 really a locked breech, recoil operated weapon...or is it actually a delayed blowback? Hmmmm?
Flame suit on!
Tuner----------->Outta here like a John Deere...