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Scott Lynch 1460V
01-05-2010, 03:13 PM
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!!

Jim Brady Knap's Battery
01-05-2010, 03:34 PM
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!


Jim Brady
2249V
Knap's Battery

Scott Lynch 1460V
01-05-2010, 03:54 PM
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?

paul w/McGregor's 385V
01-06-2010, 08:03 AM
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

Jim Brady Knap's Battery
01-06-2010, 10:33 AM
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:

Jim Brady
2249V
Knap's Battery

Scott Lynch 1460V
01-06-2010, 11:09 AM
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.

Greg Ogdan, 11444
01-06-2010, 04:30 PM
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.

Charlie Hahn
01-20-2010, 08:52 AM
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

cannoneerfour
02-11-2010, 09:25 PM
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

John Wells 3rd US
03-30-2010, 08:58 PM
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.

R. McAuley 3014V
05-02-2010, 12:35 AM
While “recoil” is certainly related to Newton’s third law of motion that for every action there is an equal and opposite reaction, recoil is actually the phenomena which occurs when the expanding gas column which propels a projectile inside a cylinder suddenly clears the end of the cylinder and the gas rapidly expands, and it is this force that once it has transferred to the barrel causing it to move in the opposite direction which we call “recoil.” Therefore, it may be observed that a shorter barrel produces a far greater recoil than a does a longer barrel because the shorter barrel has less internal volume for the gas to expand and is thus under a greater pressure when it vents than does a longer barrel which because of its greater volume contains a lower pressure when it is vented (i.e. when the projectile clears the muzzle). Until this point, the internal expansion of the gas does not translate into any measureable motion within the barrel, and if any part of the explosive chain could be felt, depending on the relative mass of the barrel it would perhaps be the movement of the projectile's mass within the barrel affecting the equilibrium or balance of the barrel, but not causing or contributing to any kind of recoil force, least not until the projectile escapes from the cylinder. So it is the internal gas pressure at the moment it escapes and expands from the barrel rather than the mass of the projectile that equates to the force of the recoil. The weight (i.e. mass times gravity) of the projectile is but a small portion of the total recoil force. Theoretically, if a barrel was long enough to compensate for the full volume of the gas pressure, the forward motion of the projectile would literally stop and there would be no recoil.

R. McAuley 3014V
06-09-2010, 11:48 PM
Sir Alfred George GREENHILL, Kt., F.R.S. (1908) Notes on Dynamics: For the Advanced Class of the Ordnance College, Woolwich.

http://books.google.com/books?id=nO_mAA ... &q&f=false (http://books.google.com/books?id=nO_mAAAAMAAJ&printsec=frontcover&dq=Notes+on+Dynamics,+Greenhill&source=bl&ots=zAUFRAOgom&sig=slAbQLIHQ8iWcZLSnw3Wz3Uyoqg&hl=en&ei=a14QTM3TDIK88gaSlJCfCQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBIQ6AEwAA#v=onepage&q&f=false)

Page 24 addresses “long recoil” while on page 38 illustrates the calculations involved in working out the ‘problem of recoil when the gun in its carriage or cradle is mounted on a railway truck or in a boat, of total weight M-lb, and checked by a buffer or frictional resistance of R-lb between the cradle and truck or boat, ignoring the weight P of the powder charge.’

As noted ‘the experiment can be made also with a gun suspended as in (12), firing at close range at the ballistic pendulum. Supposing, first, that the resistance does not come into action till the shot has left the muzzle; the gun will begin recoiling with velocity (w/W)V, and finally, when the recoil has ceased, the whole system M will be moving with velocity (w/M)V, the time occupied in the recoil and the length of recoil will be [see equation] during which the truck or boat will move W/M of this length.’

Kevin Tinny
12-31-2019, 11:19 AM
Hello and please forgive replying to an old Thread:

Saw McAuley's post and thought about it and the "When Does Recoil Occur?" question.

For me, the question would be:
Does the gun MOVE WHILE the bullet is IN the bore ("barrel time")?
This might be different from the technical "recoil" aspect.

I like John Wells' pebble under the wheel suggestion.

NOT to disagree with McAuley, rather to learn, my experience with rifles off a well setup bench is that with a correct, uniform sight picture, the slightest bit of variation in one's body resistance will move the shot because of "barrel time". So my conclusion is that the gun moves WHILE the bullet IS IN the barrel.

McAuley IS the expert and I respect that.

What am I missing here, please? Thanks.

Kevin Tinny
Tammany Rgt, 4w NY 13667

Des
12-31-2019, 11:05 PM
From the high speed cameras that filmed our cannons firing it definately looked like the projectile was out of the barrel before the cannon moved

Kevin Tinny
01-01-2020, 07:14 AM
Thanks on the high-speed info:

I recall a UTUBE guy with ultra high speed camera footage of cannon firing.
Search UTUBE for: Try "Smarter Every Day" "Cannon Shock Waves..."

In every sequence that is clear enough, the first thing out of the muzzle was a large "initial" cloud of gas and then the projectile in the rear of the initial cloud. Then the main cloud of FIREY colored gas and particulates were last. If gasses beyond the muzzle contribute to recoil and a small amount blow BY the projectile IN the bore and seem to exit first ....?

Am still unsure about why one must "hold" a gun the same if the bullet is gone before gun moves.

I suspect there is a technical difference in physics and dynamics involved.
Hopefully brother McAuley can help.

Very respectfully,
Kevin Tinny
Edited for spelling.