[Lord Odin]

Jack, do you see any similarities between what we saw in the drop video versus what you saw in the barrel?

To me, it looked like the balls flexed a little bit but it just depended on the ball. The shell kind of reminds me of a pencil. It has a little bit of flex to it but after a certain point, it just cracks. The balls that broke looked like they bent too much around the impact point for the shell to maintain its integrity.

[cockerpunk]

defiantly a buckling situation in terms of the role of failure. that makes perfect sense becuase typically a compressive test leads to buckling, or barreling of the part (anyone familiar with forging should understand the term barreling). very cool, thanks a bunch!

my thoughts are that a combination of the smaller volume of a ellipsoid and larger demands for surface area over a close to sphere its what causes the buckling to be catastrophic. meaning, the fill is being compressed by the shell, and the fill is just not very compressible, at the same time as that, the shell is going though an elongation of plastic deformation all around it, making it weaker.

eventually, you will either see a crack form and propagate due to either the shell being stressed laterally, or the internal pressure blowing out the back of the ball. probably a combination of both.

this leads me to think that shear forces on paintballs just are not a large factor in terms of failure of the ball. which makes sense becuase a sphere when presented with a shear force along its edge will tend to roll rather then shear. we also have cooberating evidence that shear doen't play a large part from the underboreing barrel break tests, and experince.

interesting ...

[Jack Wood]

Odin, it's hard to say. If I dropped 100 balls, you would see the start and propagation of the cracks/failure 100 different ways. The same with the barrel break. The only thin with the barrel breaks was that the paint always expelled forwards of the ball/shell.

Gordon, I would like you to see the barrel vids before you rule out the shear force idea. I too was very very skeptical that shear forces inside the barrel could be contributory at any level. But after yesterday, and viewing some of the vids again, I am not so sure. Don't forget that if the ball is bouncing, you are getting very localized and specific shear forces. Not like the underbore testing you did where I would expect it to be more uniform around the ball.

But what do you think of the quality? Pretty good, isn't it? Even on these crappy downloads. Knocks the socks off all the other captures you have seen before! Just wait til you see some of the barrel and breech stuff

This post has been edited by Jack Wood: 12 December 2008 - 02:34 PM

[Poe]

Jack,

Were the balls in the video new or old? I only ask because one looks like it has a dimple. Additionally what height were they dropped from and what surface (smooth/rough) were they dropped onto?

Were the balls that bounced in the barrel the same type and quality as the ones in the ball drop test?

I suppose balls stacked in the feed tube are experiencing more pressure then those resting at the bottom of a cupped breech... since force is the same but surface area is different. Were you able to see the cracks begin in the stack or could they have been there during or prior to loading?

Of the balls that cracked in the feed neck, where did the crack start?

Just out of curiosity what was the daily rate for that camera?

Amazing quality ....even if down-sampled. We all look forward to more videos. Thank you.

Gordon,

What were your comments in reference to? The ball drop or ball barrel bounce? If they are in reference to the ball drop then I think I understand what you are saying. As the ball decelerates the fill's inertia causes catastrophic tensile stress on the shell.

Other then bolt clip, nick or chop I can't imagine any shear stresses. Do you mean tensile stress caused by ball to barrel friction?

[moyster14]

Jack Wood, on Dec 12 2008, 02:33 PM, said:

But what do you think of the quality? Pretty good, isn't it? Even on these crappy downloads. Knocks the socks off all the other captures you have seen before! Just wait til you see some of the barrel and breech stuff

Honestly, I was pretty stoked just because it was in color. Not bad Jack, not bad. Can't wait to see the rest.

[Jack Wood]

Poe, the paint was fresh (or as fresh as we get all the way over here) DXS Silver, but we asked them for the most fragile (see: unsalable) paint they had for these test. We had to have paint that would fail easily, or we could have spent 2 hours just trying to get one instance of ball break, and then miss it!!. The paint had to be fragile enough to break consistently. It has been stored in close to zero degrees centigrade conditions for the last 2 weeks, hence the dimples. The only way we could get consistant breaks was to keep it chilled down. We were lucky that we have an unheated wharehouse that has been just above freezing for the last 2 weeks. We did the filming in there. As soon as we started to warm the paint, the incidence of failure went down to 1 in every 500 rounds. With the chilled, sable paint, we could get as many as 4-5 breaks per loader.

I now have a very bad cold! Oh the sacrifices we make...................sob sob.............

And yes, the paint we used in all our tests was the same. We did have some RPS Marbs that was too fragile to get through any loader, so we never shot any meaningful footage this time with it. We used it last time, when it was slightly warmer.

On our breech shots you can see all the ball in the breech, and the centre vertical strip of about 10mm wide and the full length of the second ball. You could often see the cracks in the second ball as it arrived in that position, meaning it was brocken in position 3 or above in the stack (Pos1 = Breech, Pos2 = 2nd ball in stack, Pos3 = 3rd ball in stack etc)
The great thing for us was that by the end, we had a set-up that would shoot this paint, loader after loader, with zero breaks And yes, the major change in the set-up was with the loader

For this shot, I was using a red paving brick I found out in the road. It was sat on a jig that we had been using to mount the guns so that it was in front of the camera lens. This rig was about 4 1/2 foot off the floor. I had to get up on a chair and drop the paint onto it. I could only get about 4 feet above the brick to drop the balls. after a couple of attempts just dropping the balls, the results were not spectacular. So in the end I "launched" them down, gently, towards the brick for this shot and a couple more. The results look the same or very very similar to the dropped balls, but I just got more to break in shot.

Normal daily rate with operator is around $1.5k for this type of camera. We did get a deal this week because we did the operating ourselves, and we took it for 3 days, and it is close to Xmas

[cockerpunk]

great work!

yes, my comments were in regards to the balls dropped on the ground.

i think the comparison to barreling of your part when forging is a great model to look at that type of failure.

heres a video on forging and the first thing it shows is a barreling part - http://www.youtube.com/watch?v=tLRkOupbARM...feature=related

you can see even in that case, the outside is stressed (and cooled) to the point where it just sheds right of the sides, with cracks propagating with the axis of the load applied, just like paintballs.

[Poe]

Jack,

Thanks a tonne for all the info.

$1.5k per day is pretty salty. Glad to hear it was fruitful.

[brycelarson]

$1.5k US dollars or Pounds?

either way - thanks man, hope the research serves you well. It's good to know that someone at a manufacturer is actually doing something to advance their products other than advertising.

[Poe]

cockerpunk, on Dec 12 2008, 04:32 PM, said:

great work!

yes, my comments were in regards to the balls dropped on the ground.

i think the comparison to barreling of your part when forging is a great model to look at that type of failure.

heres a video on forging and the first thing it shows is a barreling part - http://www.youtube.com/watch?v=tLRkOupbARM...feature=related

you can see even in that case, the outside is stressed (and cooled) to the point where it just sheds right of the sides, with cracks propagating with the axis of the load applied, just like paintballs.

Apologies for the double post.

That model might not apply since it involves a two point, fixed area, compression force. The slag in that video was falling off because of how the metal was poured and handled prior to entering the forge. Since a paintball is liquid on the inside and that ingot was still solid maybe a better model would be a water balloon dropping?

Regarding the balls dropping.. Bricks have rough surfaces at this scale and I'm concerned the balls might have broken primarily due to small punctures at the impact site.

Jack,

Were you able to get any 'true barrel breaks' on film? By that I mean balls that broke in the barrel that were not damaged prior.

Thanks again.

[Jack Wood]

brycelarson, on Dec 12 2008, 09:48 PM, said:

$1.5k US dollars or Pounds?

either way - thanks man, hope the research serves you well. It's good to know that someone at a manufacturer is actually doing something to advance their products other than advertising.

To advance our products? Don't be stupid, we did it all for you guys Sorry, I mean, we did it all to make cool footage for marketing videos........no, no I mean.....yes, to make dem gunz better, right.............






PS. I converted to Dollars for you Yanks

[Jack Wood]

Poe, as said before, as close as we could possibly get with the time constraints to Pure, yes. They was definitely no visible fracture in the ball prior to firing. That is not to say the ball may not be "weakened" in some way by the loading cycle, but they were definitely "whole" at the time the power pulse hits them and through the first 1-2" of travel.

[cockerpunk]

Poe, on Dec 12 2008, 06:09 PM, said:

cockerpunk, on Dec 12 2008, 04:32 PM, said:

great work!

yes, my comments were in regards to the balls dropped on the ground.

i think the comparison to barreling of your part when forging is a great model to look at that type of failure.

heres a video on forging and the first thing it shows is a barreling part - http://www.youtube.com/watch?v=tLRkOupbARM...feature=related

you can see even in that case, the outside is stressed (and cooled) to the point where it just sheds right of the sides, with cracks propagating with the axis of the load applied, just like paintballs.

Apologies for the double post.

That model might not apply since it involves a two point, fixed area, compression force. The slag in that video was falling off because of how the metal was poured and handled prior to entering the forge. Since a paintball is liquid on the inside and that ingot was still solid maybe a better model would be a water balloon dropping?

Regarding the balls dropping.. Bricks have rough surfaces at this scale and I'm concerned the balls might have broken primarily due to small punctures at the impact site.

Jack,

Were you able to get any 'true barrel breaks' on film? By that I mean balls that broke in the barrel that were not damaged prior.

Thanks again.

a water ballon or tennis ball impact is a great model - but do you have the math that models it? im looking for something i can crunch some numbers on. if only for a quick approximation.

actually, the scaling you see is from cooling pre-hardening the outsides, which in tern makes the stronger (and more brittle), much like a paintball's shell. so when the still amouphus (due to higher temp) center begins to get shorter, and push out the outsides, it breaks the hardned shell off.

if the press continued its forge, you would see another scaling, and then probably another one (as long as the press could push that hard).

This post has been edited by cockerpunk: 12 December 2008 - 05:28 PM

[Lord Odin]

Jack Wood, on Dec 12 2008, 01:33 PM, said:

Odin, it's hard to say. If I dropped 100 balls, you would see the start and propagation of the cracks/failure 100 different ways. The same with the barrel break. The only thin with the barrel breaks was that the paint always expelled forwards of the ball/shell.

From the few that we did see break in the video, it seemed like they all broke closest to the side of impact, which is opposite of what you saw in the barrel breaks. Or at the very least, the breaks were random. Do you think this might be due to the balls being struck at a single point rather than the hemisphere like with a power pulse? I would think the force would be spread out further and would push in on the ball from all sides from the air. Perhaps that's whats causing the barrel breaks to blow out the other side.

I don't know if you still have the camera setup or not (doesn't sound like it) but it would be interesting to see a power pulse blast a paintball in open air. Delicately hold a ball in the air at two points (pencil eraser heads?) and a bolt directly behind it at point blank range. Just to see the effect of the blast on a ball without a barrel interfering.

Or maybe even place a ball in a short barrel that holds it in place similarly but the barrel stops before the length of the ball, so that it is just enough to hold it in place. I don't know if the first test would put pressure on the ball or if it would escape in all directions and not affect the ball at all. This might do a better job.

On a side note, the dropped ball looks very similar to what this tennis ball is doing.

http://livephoto.rit...sBallBounce.mov

This post has been edited by Lord Odin: 12 December 2008 - 06:57 PM

[Jack Wood]

If you just fire an open bolt gun without a barrel, you get the effect you are talking about. The bolt pushes the ball forwad and fires it in free space. No we didn't do this. But when we saw the breaks in the barrel, the ball didn't break until 1-3 inches down the barrel, so by that point, the pressure was most definitely uniform, or close, across the surface. We never saw a pure break that initiated at the instant that the power pulse hit it....

In fact, thinking about it, that has to be a key point. There MUST be some other contributary factor to the failure of the ball in a Pure barrel break other than the power pulse, otherwise in a pure barrel break that was ONLY due to pressure of the power pulse acting on the ball, the ball would surely start to fail at the instance the power pulse hit it. No? When the ball is stationary (ok, it may be moving slightly due to it being pushed forward by the bolt, but nothing compared to what it will be doing in a few microseconds time), and the pulse hits the ball, that will be when peak pressure would be reached. This should the moment that the ball sees its highest forces. If the power pulse alone were to be the cause of failure, would it not start to fail right there?

Mmmm, interesting.

[cockerpunk]

Jack Wood, on Dec 13 2008, 03:06 PM, said:

If you just fire an open bolt gun without a barrel, you get the effect you are talking about. The bolt pushes the ball forwad and fires it in free space. No we didn't do this. But when we saw the breaks in the barrel, the ball didn't break until 1-3 inches down the barrel, so by that point, the pressure was most definitely uniform, or close, across the surface. We never saw a pure break that initiated at the instant that the power pulse hit it....

In fact, thinking about it, that has to be a key point. There MUST be some other contributary factor to the failure of the ball in a Pure barrel break other than the power pulse, otherwise in a pure barrel break that was ONLY due to pressure of the power pulse acting on the ball, the ball would surely start to fail at the instance the power pulse hit it. No? When the ball is stationary (ok, it may be moving slightly due to it being pushed forward by the bolt, but nothing compared to what it will be doing in a few microseconds time), and the pulse hits the ball, that will be when peak pressure would be reached. This should the moment that the ball sees its highest forces. If the power pulse alone were to be the cause of failure, would it not start to fail right there?

Mmmm, interesting.

interesting because we never saw a mid barrel barrel break in our test, with any barrel.

leading one to conclude that whatever was causing our barrels breaks (probably loading issues), was not factor X.

[brycelarson]

Jack Wood, on Dec 13 2008, 02:06 PM, said:

If you just fire an open bolt gun without a barrel, you get the effect you are talking about. The bolt pushes the ball forwad and fires it in free space. No we didn't do this. But when we saw the breaks in the barrel, the ball didn't break until 1-3 inches down the barrel, so by that point, the pressure was most definitely uniform, or close, across the surface. We never saw a pure break that initiated at the instant that the power pulse hit it....

In fact, thinking about it, that has to be a key point. There MUST be some other contributary factor to the failure of the ball in a Pure barrel break other than the power pulse, otherwise in a pure barrel break that was ONLY due to pressure of the power pulse acting on the ball, the ball would surely start to fail at the instance the power pulse hit it. No? When the ball is stationary (ok, it may be moving slightly due to it being pushed forward by the bolt, but nothing compared to what it will be doing in a few microseconds time), and the pulse hits the ball, that will be when peak pressure would be reached. This should the moment that the ball sees its highest forces. If the power pulse alone were to be the cause of failure, would it not start to fail right there?

Mmmm, interesting.

in a situation where the ball isn't snug in the barrel - that could be the first location of impact on it's path "bouncing" down the barrel - or it could be shear forces.

[Jack Wood]

I am sure you both said the breaks were in the first 1-2 inches? Are you thinking now that all the breaks you saw in your tests were actually loading fracture breaks and not pure breaks?

I am thinking along the lines of Bryce here. These were fragile balls. If they were not broken due to loading fracture, and they made it to the barrel in one piece, the next mode of failure was not "just" the power pulse. "If" we could get rid of the bouce and concentrated shear, then you would surely see less breaks, and then the next mode of failure would have to be the power pulse on its own.

What we need to do is remove the bounce issue, if at all possible, and see if that further reduces pure breaks in the barrel. At that point I imaging we would need even more fragile paint to try and see breaks caused by power pulse alone. A type of failure that I believe we didn't see in over 6000 fired rounds.

[Lord Odin]

I wonder how big of a factor temperature is in your tests. Between your testing and the Chilled/Freezing Data thread, it's probably safe to say that colder paintballs are more brittle. So they should break sooner rather than a few inches into the barrel. It seems though that the opposite is happening. I wonder if the colder shells are allowing the balls to slide rather than grip the sides of the barrel and the impact alone is what is causing the failure. I don't know if temperature affects its friction level or if that is even happening. It could be something else entirely.

I think you're right, Jack. An underbore and overbore test is needed to help remove the bouncing variable. It would also serve as a comparison for temperature between your test and CP/Bryce's, since their test barrel break test was done in optimal conditions. Fortunately for you, the more brittle balls should make for getting breaks a lot easier and a lot less rounds.

CP and Bryce, in your barrel break test, did the bore size affect where the ball broke in the barrel? Or were they always similar?

This post has been edited by Lord Odin: 13 December 2008 - 07:24 PM

[cockerpunk]

Lord Odin, on Dec 13 2008, 08:23 PM, said:

CP and Bryce, in your barrel break test, did the bore size affect where the ball broke in the barrel? Or were they always similar?

thats what i was saying before, in all our bores we got the breaks right at the breach of the barrel.