Gas sealing with PRBs in rifled barrels

[coloradoclyde]

"Knowing Physics, I'm pretty sure "compressed air" has to have something to be forced against in order to become compressed...not an open empty pipe."

Then how do you explain Bernoulli’s theory?

 

[Stumpkiller]

Man can't fly. It's a hoax.

Cloth is, in fact, a flimsey material. But wet it with wax or water based lube (which is practically uncompressible) and jamb it between two metal surfaces and it becomes a very suitable gasket. That's why a cloth patch can impress into the lead surface - the liquid makes it less compressible than lead when subject to sudden, high pressure.

 

[coloradoclyde]

Yep, cloth is such a flimsy material that the wind (I.E. AIR ) will never be able to push against it (SAILS) with enough force to get those big heavy ships all the way across the Atlantic to the new world, besides the Earth is flat anyway.
otherwise no argument.

 

[coloradoclyde]

"That's why a cloth patch can impress into the lead surface"

Perhaps thats part of it but lets not forget the velocity of the explosion (not to be confused with the projectile)

OK I will get off my soap box now :v

 

[Stumpkiller]

Have you ever sailed in a 2,000 fps wind? ;-)

 

[roundball]

Why would we think a greased, cloth patch would seal all gases when we know in a modern, internal combustion engine the rings don't seal all gases???

This is why you have to change your oil in your truck as it gets dirty from carbon...

Pretty good analogy...and you being such a student of history, recalling my OP do you remember seeing the referenced video...it was several years ago back around the time when there were a lot of documentaries on the History Channel like the American Revolution, Tales of the Gun, etc, etc...it was along the same lines as the videos the other member just posted, only I recall it being brighter / clearer.

 

[roundball]

Great videos Viking, thanks.

As an aside, the one about the modern pistol bullet is a real shocker

 

[coloradoclyde]

WEll..there was this one time (at band camp) when Gilligan my first mate was behind me and sneezed.. does that count? :rotf:

 

[azmntman]

They were called polypatch and were great, never expeirenced them coming loose but could happen.

 

[Rifleman1776]

simple patch

We do not use a "simple patch". In most cases a cloth is chosen that is very durable and of a tight weave. That cloth is then sealed/lubed with some kind of grease or oil making it a type of gasket. The sides of recovered patches are not burned. (assuming proper ball/patch fit) If hot gasses blew by that (not)"simple patch" the cloth would be burned.
In this game we seek the best fit and seal possible in an attempt to wring the very top performance we can from our antique style guns and projectiles. Working to obtain that 'seal' is a major step in that endeavor.
I think the vids prove me correct. We do not see flame coming out of the muzzle ahead of the ball. What does come out is a matter of conjecture.
And, BTW, I'm disputing the experts here, gasses can be compressed in an open end tube. They don't remain in there very long but they do compress before exiting. What detrius we see, I dunno but it is something ahead of the ball.

 

[ApprenticeBuilder]

What I still seem to be missing in the latest vids is the fact that there is no evidence of combustion/flame ahead of the projectile, this would lead an individual to believe that the patch does indeed seal the bore.

What it looks like is the pressure wave ahead of the ball.

 

[Rifleman1776]

What I still seem to be missing in the latest vids is the fact that there is no evidence of combustion/flame ahead of the projectile, this would lead an individual to believe that the patch does indeed seal the bore.

What it looks like is the pressure wave ahead of the ball.

Amen, Bro. :applause: :bow: :v

 

[ApprenticeBuilder]

Maybe, at the moment of ignition there is a faint amount of blow by in the instant before the ball bumps up, but there is surely no evidence of flame ahead of the projectile.

I would think that if there was flame escaping the patch then the patch would be charred/shredded beyond the centerline of the ball. I don't see it with my patch ball combination, if I did I would increase ball diameter or patch thickness instead of using fillers/wads.

Water based lubes are non-compressible.

 

[Rifleman1776]

Maybe, at the moment of ignition there is a faint amount of blow by in the instant before the ball bumps up, but there is surely no evidence of flame ahead of the projectile.

I would think that if there was flame escaping the patch then the patch would be charred/shredded beyond the centerline of the ball. I don't see it with my patch ball combination, if I did I would increase ball diameter or patch thickness instead of using fillers/wads.

Water based lubes are non-compressible.

We are mostly in agreement.
But, I don't believe there is any "bump up" or obduration/obturation. I acknowledge that is a huge jug passing issue.

 

[Billnpatti]

I'm going to toss out an idea, sort of a SWAG. I think that what is quite possibly happening is that the hot gasses do not pass the PRB until the ball exits the muzzle. I think it may be that because of the lesser masses of the hot gasses allows them to be more rapidly accelerated past the more massive ball. This happens the instant the ball exits the muzzle giving the impression that the gas is ahead of the ball prior to the ball's exit from the muzzle. Like I say, I do not actually know and this is just another 2 bit idea. :2 I could be, and probably am wrong but I just wanted to toss it out there for consideration.

 

[okawbow]

Someone needs to do the same video with a clean bore.

I also think that little if any hot gas escapes ahead of a properly patched ball. If it did; accuracy would suffer. Just like accuracy suffers when the patch is burned or shredded.

 

[Coot]

I would think that if there was flame escaping the patch then the patch would be charred/shredded beyond the centerline of the ball.

I am not so sure. You can pass your hand thru a candle flame without getting burned as long as you move it fast enough. The patch is only in contact with the burning powder/hot gasses for an instant, not long enough to burn thru the bottom (center) of the patch. Easy enough to experiment by shooting a very loose patch/ball combo (loose enough to guarantee blow by) & see what the recovered patches look like. Inquiring minds want to know ..............

 

[Rifleman1776]

Someone needs to do the same video with a clean bore.

With a clean GLASS bore.
That would be an interesting experiment. Also it would allow study of the ball to determine if obturation happens.

 

[Larry Pletcher]

Since we have been looking for evidence dealing with gases and the fired ball, here is a photo to think about. In one of my failed attempts to catch a patch separating from a ball, I got this one. You can see a shadow left on the ball by a spark.The ball isn't moving in the flashes duration, but the spark is.

In this photo we marked a ball with a Sharpie Marker to see if it would show up in the photo. Fired from a smooth bore. There is a felt wad behind the ball.

Next is the photo we tried to take. This is about 20 inches from the muzzle with Swiss powder.

If you wondered why Swiss was used, this last pic shows the reason.

The ball is in the photo, but is obstructed by the sparks. This photo is 60 inches from the muzzle. Smoke was not an issue, but sparks were.


Regards,
Pletch

 

[Larry Pletcher]

Since we have been looking for evidence dealing with gases and the fired ball, here is a photo to think about. In one of my failed attempts to catch a patch separating from a ball, I got this one. You can see a shadow left on the ball by a spark.The ball isn't moving in the flashes duration, but the spark is.

When I said there is a photo to think about, one needs to think what is happening during the 1/40,000 second the flash is operating.

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The ball is stopped by the flash, but the sparks are not. They provide their own light from the camera's point of view. The "overtaking spark" may have made its shadow on the image of the ball well after the ball left the scene. This may teach us to be very careful as we try to interpret what we think we see in images - moving or still.

I have to caution myself when I look at these images and videos to make sure I don't jump to conclusions.

Regards,
Pletch