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Thread: When does recoil occur???

  1. #1
    Scott Lynch 1460V is offline Moderator
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    When does recoil occur???

    As a cannon shooter of a few years, an an artillery fan of many years I'd like some input from others. I have asked this question of several cannon shooters and gotten completely opposite answers. When shooting field artillery, specifically my 10 pounder Parrott, does the gun begin to recoil before the projectile has left the muzzle, or is the projectile long gone before the gun starts to move backwards? Knowing this would be helpful in knowing whether the gun needs to be exactly level and the trail sliding exactly level as it moves rear-ward. Also does it matter if you are shooting reduced charges and lighter projectiles as at the Fort or full service charges and full weight projectiles as at Grayling? Let the fun begin!!

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    Jim Brady Knap's Battery is offline
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    Some movement would have to start as soon as the projectile starts to move. I seem to remember reading that "Every action has an equal and opposite reaction." Guns aint magic whether it's a .22 derringer or a 20 inch Rodman, the laws of physics is the laws of physics.

    Of course I could be wrong!


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    Scott Lynch 1460V is offline Moderator
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    True but...

    True but we are talking about a 6 to 10 lb projectile attempting to move a 1800-1900 lb gun. Wouldn't there be a delay, and how much or how long?

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    let the number crunching ...

    Scott,

    When the charge ignites it creates a pressure "bubble" behind the projectile. As this is a contained volume, there is a delay before the projectile begins to move down the tube. As the projectile gains momentum (velocity) it begins to compress and move the air down the tube in front of itself. When the air column leaving the tube has reached the velocity of the following projectile, recoil begins to occur.

    Jim,

    Before you reach for the physics books (or Lefty does), think in terms of clearing a fouled musket with the air bottle.

    Take care and be safe
    pfb

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    Jim Brady Knap's Battery is offline
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    Ok but does recoil start before the projectile leaves the bore? I think that is the operative question here. Having the shell out of the bore before the barrel starts any movement that could have an effect on the flight path of the shell.

    :idea: If recoil doesn't start until the shell is out of the bore then things like rough ground or even a loose carriage wouldn't have an effect. But they do so things must start to move before the shell is clear of the bore.

    Hey! It could happen!

    Paul, Been a long time since I looked at a physics book. :roll:

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    Scott Lynch 1460V is offline Moderator
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    Recoil

    That is really the essence of the question. Because if the gun moves rearward before the projectile has left the muzzle then not only does the gun have to be level where it sits but also the area behind the wheels and the area where the trail rests must also be level for the projectile to hit where it is supposed to.
    I was always told that in high power rifles and pistols that the bullet was gone by the time the gun recoils except in the case of lightweight handguns firing large caliber fast bullets.

    As I stated in my first post, there are two schools of thought on this topic within the circle of my artillery friends. I would just like to know because I am not that experienced myself.

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    OK, recoil is a 2 part issue. Yes, recoil STARTS before the projo has left the tube. There is also a second recoiling effect AS the projo clears the bore and the gases effect the muzzle.
    Greg Ogdan, 11444
    110th OVI

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    Charlie Hahn is offline
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    There is a time function in the explosive event. The first part is set back where the forces propel the projectile and cannon in opposite directions. Due to mass differences, the rate differs, but happens as the powder burns, and starts instantly.

    The second recoil referred to, is at muzzle exit, and is referred to as set forward. This is where the projectile breaks it's seal and the gun gases pass the round at a speed much greater than the projectile speed. (The projectile acts as if it was flying backward at this point) The velocity of the gun gases have a greater effect on the gun at this point rather than the projectile due to the velocity difference.

    As both the cannon and projectile are in motion at this point the gun gases push on the air at about 10,000 feet per second, and add this force to the gun's mass which is already in motion, and give the second acceleration to the gun. Once the projectile clears the gun gases and hits the wall of air it buffets, and begins to slow.

    The total time of the event in our sport is about .005 of a second

    Charlie Hahn

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    cannoneerfour is offline
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    Re: When does recoil occur???

    Scott
    sitting around the campfire at Westerlo one night, talking to some of the 5th Mass guys, i asked the same question - in reference to how much a gun moves as it goes off. they told me they used one of their guns for a project where someone wanted to do a study using a high-speed camera to detail what happens when a cannon goes off. they told me you could see the projectile leave the muzzle before the tube moved at all. i think a wobbly carriage may let the tube move, but if the carriage is tight, the evidence is that the round is gone before any movement.

    hope things are well with you guys down there in the Snowy South

    ed moore

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    Re: When does recoil occur???

    prove it for yourself. Chock one wheel on the gun and fire at target. You'll see that the shell is thrown way off target. Our velocities at N-SSA loads are only maybe 600 FPS (if that), with a tube 6' long, that's a lot of barrel time. If the trail digs a hole and is on the slope created by the hole, it's essentially riding a ramp as the gun recoils, throwing shots lower or higher. If there's a stone behind one wheel, it acts like a small chock.
    Canted gun makes a difference because our trajectory is so high. Tilt to left throws shots low and left. opposite for right tilt. Much more dramatic at longer range. Use your gunner's level. It helps.

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