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#1 cockerpunk

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Posted 16 January 2009 - 03:08 PM

Discuss the Results of the PunkWorks compression testing.

video -

data sheet - http://spreadsheets....HdSUqJufMjmLEUA

this is the first release of data, as the conversion continues we will release more of the data collected.

Edited by cockerpunk, 23 January 2009 - 10:55 PM.

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#2 WihGlah

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Posted 16 January 2009 - 03:19 PM

first!!

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#3 cockerpunk

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Posted 16 January 2009 - 03:23 PM

first!!


i hadn't seen you around for a while - though we had lost you. nice to see your still around!

needed to make the thread in order to have the link for the video info bar, hence why this thread is here.
The ultimate truth in paintball is that the interaction between the gun and the player is far and away the largest factor in accuracy, consistency, and reliability.

And yes, Gordon is the sexiest manifestation of "to the front."


#4 WihGlah

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Posted 16 January 2009 - 03:35 PM

I've been waiting for these results!

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#5 Protoboy

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Posted 16 January 2009 - 03:42 PM

Sweet video, very interessting..:)

#6 maximumslinky

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Posted 16 January 2009 - 04:26 PM

is this it for the compression testing or will you be comparing different brands of paint in the future?
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#7 cockerpunk

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Posted 16 January 2009 - 05:33 PM

is this it for the compression testing or will you be comparing different brands of paint in the future?


there are 5 different grades compared.
The ultimate truth in paintball is that the interaction between the gun and the player is far and away the largest factor in accuracy, consistency, and reliability.

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#8 Lord Odin

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Posted 16 January 2009 - 05:54 PM

is this it for the compression testing or will you be comparing different brands of paint in the future?


there are 5 different grades compared.

Very cool stuff. B)

According to ProCaps' website, there are only 3 grades; Tourney, Value, and Winter. I'm quite surprised that the Triumph (value) is stronger than the Frostbite (winter).

Can you guys now measure the thickness of the shells to see if there is a relationship between shell thickness and compression strength?

#9 cockerpunk

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Posted 16 January 2009 - 06:26 PM

is this it for the compression testing or will you be comparing different brands of paint in the future?


there are 5 different grades compared.

Very cool stuff. B)

According to ProCaps' website, there are only 3 grades; Tourney, Value, and Winter. I'm quite surprised that the Triumph (value) is stronger than the Frostbite (winter).

Can you guys now measure the thickness of the shells to see if there is a relationship between shell thickness and compression strength?


i can do that if you want to see it
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#10 Lord Odin

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Posted 16 January 2009 - 06:39 PM

I think that would be sweet. I would have assumed that the Frostbite would have a thicker shell to handle the winter temperatures and also would have assumed that they were stronger as well. I think that test would confirm or deny those assumptions.

#11 brycelarson

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Posted 16 January 2009 - 07:32 PM

I think that would be sweet. I would have assumed that the Frostbite would have a thicker shell to handle the winter temperatures and also would have assumed that they were stronger as well. I think that test would confirm or deny those assumptions.


based on the fact that the winter paint changed less from room temp to cold - there's going to be a formulation change that might be more important than the thickness.

as Gordon said on the phone this afternoon while we were talking about these results - it's starting to look like the paint manufacturers are the smartest people in the industry :)

#12 maximumslinky

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Posted 16 January 2009 - 07:33 PM

is this it for the compression testing or will you be comparing different brands of paint in the future?


there are 5 different grades compared.



i saw the video test and results. i was just curious if you were gonna compare like different brands of tournament rec and winter paint, like to see the difference between the brands. im not trying to tell you that you should im just wondering if that was your plan
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#13 RubberCoconut

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Posted 16 January 2009 - 07:54 PM

great tests !!!!!!!!

interesting how similar silver is to gold
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#14 Troy

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Posted 16 January 2009 - 07:55 PM

I thought you were going to compare paint stored differently *single tear*
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#15 cockerpunk

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Posted 16 January 2009 - 08:37 PM

I thought you were going to compare paint stored differently *single tear*

we did. ill release that data in a bit.

bryce, i didn't release the temp test data either, keep your trap shut!

we are not product testers, so we wont be comparing brands. we are more looking at paintballs as a whole here and how exactly they perform, rather then comparing brands and how they perform.
The ultimate truth in paintball is that the interaction between the gun and the player is far and away the largest factor in accuracy, consistency, and reliability.

And yes, Gordon is the sexiest manifestation of "to the front."


#16 Lord Odin

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Posted 16 January 2009 - 08:42 PM

I thought you were going to compare paint stored differently *single tear*

we did. ill release that data in a bit.

bryce, i didn't release the temp test data either, keep your trap shut!

we are not product testers, so we wont be comparing brands. we are more looking at paintballs as a whole here and how exactly they perform, rather then comparing brands and how they perform.

You're holding out on us? C'mon! ;)

I thought this was the whole test. Can't wait to see the rest of it.

#17 cockerpunk

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Posted 16 January 2009 - 08:51 PM

I thought you were going to compare paint stored differently *single tear*

we did. ill release that data in a bit.

bryce, i didn't release the temp test data either, keep your trap shut!

we are not product testers, so we wont be comparing brands. we are more looking at paintballs as a whole here and how exactly they perform, rather then comparing brands and how they perform.

You're holding out on us? C'mon! ;)

I thought this was the whole test. Can't wait to see the rest of it.


the key to seeing the rest is for someone to make conclusions based on the data, to analyze it.
The ultimate truth in paintball is that the interaction between the gun and the player is far and away the largest factor in accuracy, consistency, and reliability.

And yes, Gordon is the sexiest manifestation of "to the front."


#18 brycelarson

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Posted 16 January 2009 - 09:06 PM

yup, we've got more stuff - but we are still talking and thinking about it. We're often trying to decide how to best present data, how to sort and present it.

#19 cockerpunk

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Posted 16 January 2009 - 09:19 PM

yup, we've got more stuff - but we are still talking and thinking about it. We're often trying to decide how to best present data, how to sort and present it.


yup

added the thinknesses, beware tho, those are not rock solid numbers, so be careful using them to precisely.
The ultimate truth in paintball is that the interaction between the gun and the player is far and away the largest factor in accuracy, consistency, and reliability.

And yes, Gordon is the sexiest manifestation of "to the front."


#20 Lord Odin

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Posted 16 January 2009 - 09:33 PM

How many balls of each type and total were used in this test? Just curious about this.

Just so I'm not making wrong assumptions, could you please explain what the Vmean, Hmean, and Vmean/Hmean are?

I'm trying to hold off on making conclusions until I know what I'm looking at.

Edited by Lord Odin, 16 January 2009 - 09:34 PM.


#21 cockerpunk

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Posted 16 January 2009 - 09:35 PM

How many balls of each type and total were used in this test? Just curious about this.

Just so I'm not making wrong assumptions, could you please explain what the Vmean, Hmean, and Vmean/Hmean are?

I'm trying to hold off on making conclusions until I know what I'm looking at.


3 balls each with the seams horizontal and vertical. with a double check of seams at 45ish degrees.

Vmean is the mean of the vertical seam orientation, Hmean is the same thing. V/H is simply one divided by the other.
The ultimate truth in paintball is that the interaction between the gun and the player is far and away the largest factor in accuracy, consistency, and reliability.

And yes, Gordon is the sexiest manifestation of "to the front."


#22 BOBBYTUCSON

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Posted 16 January 2009 - 10:24 PM

awsome test and results. this is just another reason why techpb rules!! but now , will we have results on high , mid, low quality rps paint? id like to prove to my teamates that dxs is better than rps!! lol , i hope :) hope to see how evil does compared to gold
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#23 cockerpunk

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Posted 16 January 2009 - 10:25 PM

awsome test and results. this is just another reason why techpb rules!! but now , will we have results on high , mid, low quality rps paint? id like to prove to my teamates that dxs is better than rps!! lol , i hope :) hope to see how evil does compared to gold


no other brands, thats not the point.
The ultimate truth in paintball is that the interaction between the gun and the player is far and away the largest factor in accuracy, consistency, and reliability.

And yes, Gordon is the sexiest manifestation of "to the front."


#24 Lord Odin

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Posted 17 January 2009 - 09:32 AM

Let me see if I'm reading this right.

It seems to me that deformation, shell strength, and shell thickness are pretty similarly related with minor exceptions. The thicker the shell, the stronger they seem to be and more deformation they can withstand before failing.

All balls seem to be stronger with the seam horizontally than vertically, which would make sense to me. The seam should be the strongest point on the ball and if forces inside the ball are pushing on the seam, it should hold out longer than if it were placed vertically. The Gold looks like it has a strength that is closer to being uniform than the others because they are much stronger at the seam and would require more force to break them. I'm assuming that's what the Vmean/Hmean is looking for: strength uniformity.

Was the distributed load test to see what would happen to the ball if pressure was added from all sides?

#25 brycelarson

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Posted 17 January 2009 - 09:47 AM

The seam should be the strongest point on the ball and if forces inside the ball are pushing on the seam, it should hold out longer than if it were placed vertically.


the seam is actually the weakest point on the ball.

#26 Lord Odin

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Posted 17 January 2009 - 09:51 AM

The seam should be the strongest point on the ball and if forces inside the ball are pushing on the seam, it should hold out longer than if it were placed vertically.


the seam is actually the weakest point on the ball.

From external forces but what about internal forces?

#27 brycelarson

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Posted 17 January 2009 - 11:58 AM

From external forces but what about internal forces?


since the internal forces aren't what cause barrel, loading or impact breaks - I don't know that it's an issue - and I don't see what you mean exactly.

In this test the balls always broke at the seam first - the break propagated to other places on the ball - but the seam was the weak point.

#28 Lord Odin

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Posted 17 January 2009 - 12:13 PM

From external forces but what about internal forces?


since the internal forces aren't what cause barrel, loading or impact breaks - I don't know that it's an issue - and I don't see what you mean exactly.

In this test the balls always broke at the seam first - the break propagated to other places on the ball - but the seam was the weak point.

I think I screwed up in thinking with internal forces instead of external. I'll try to explain what I mean.

If you place a ball with the seam horizontally, the pressure points are at the poles. As the force increases at the poles, the equator of the ball (the seam) is where it will naturally want to expand. According to the data, it takes a lot of pressure in this position before the ball breaks. So forces are acting on the seam from inside the ball.

Now when the ball is rotated with the seam vertically, the pressure points lie on 2 points of the seam. When its compressed, it still wants to expand at the equator but that line only intersects the seam at 2 points. So you have external and internal forces acting on the seam. The balls don't look like they hold up as well in this position and require less pressure before failure.

I agree that the seam is the weak point, now that I think about it. It just depends on where the ball is contacted and with how much force before it fails.

#29 cockerpunk

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Posted 17 January 2009 - 12:22 PM

does anyone have a background in marital science? if i start tossing terms out like site defect, void space and force multiplier, will people be confused?
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And yes, Gordon is the sexiest manifestation of "to the front."


#30 Poe

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Posted 17 January 2009 - 02:15 PM

does anyone have a background in marital science?
...


If only it was a science... maybe my wife wouldn't yell so much. :)

#31 cockerpunk

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Posted 17 January 2009 - 02:39 PM

does anyone have a background in marital science?
...


If only it was a science... maybe my wife wouldn't yell so much. :)


oh lol, firefox didn't pick that one up!

thats certainly true too, relationships are hardly a science.

does anyone have that kind of background? im looking up Wikipedia entries and im not finding a whole heck of a lot.
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#32 Merc4Hire

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Posted 17 January 2009 - 03:53 PM

awsome test and results. this is just another reason why techpb rules!! but now , will we have results on high , mid, low quality rps paint? id like to prove to my teamates that dxs is better than rps!! lol , i hope :) hope to see how evil does compared to gold


no other brands, thats not the point.


Why not make it part of the point?

not because I want to be smug about my favorite brand or whatever, but I thought the purposes of punkworks were to:

1) determine what factors work better, in a qantifiable way.

2) get a large enough sample of available factors for the info to be useful.

3) apply it by choosing to buy or make the stuff that works

4) discourage false perceptions and encourage manufacturers to make stuff that works.

{5) be secretly smug about knowing the real truth} {officially not a factor}


This is supposed to be applied science, knowing how much compression is necessary to break paint and how much is nifty, but the bottom line of all of this is people want to know what paint/ barrel combo is going to work best for them. Why shouldn't we know if the compression factors are different for other brands?

Wouldn't a more useful test be to determine which classes and brands of paint perform best? To me paint performance would be defined by 1) shoots straight consistently 2) doesn't break in my pod, hopper, breech, or barrel. 3) does break on opponents. 4) is less effected by weather, or predictably works well in known weather 5) is conistent case to case on the previous 4 points 6) cost per previous factors.

This test seems to address parts of #2 and #3 and (maybe#4 depending on what other data ou are holding), but wouldn't it be more applicable test be to fire a bunch of different brands of paint at a target that simulates a player, and record breaks on target versus breaks in gun, at specific temperatures and at a fixed range and fixed velocity mean? Then periodically repeat the test as new products become available, and to test for continued quality.

Don't get me wrong though, this is a very cool test. I just have a hard time seeing how we can use the information you gathered to make our stuff work better. How can I use this to help me make better paint purchasing decisions?


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#33 cockerpunk

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Posted 17 January 2009 - 04:58 PM

awsome test and results. this is just another reason why techpb rules!! but now , will we have results on high , mid, low quality rps paint? id like to prove to my teamates that dxs is better than rps!! lol , i hope :) hope to see how evil does compared to gold


no other brands, thats not the point.


Why not make it part of the point?

not because I want to be smug about my favorite brand or whatever, but I thought the purposes of punkworks were to:

1) determine what factors work better, in a qantifiable way.

2) get a large enough sample of available factors for the info to be useful.

3) apply it by choosing to buy or make the stuff that works

4) discourage false perceptions and encourage manufacturers to make stuff that works.

{5) be secretly smug about knowing the real truth} {officially not a factor}


This is supposed to be applied science, knowing how much compression is necessary to break paint and how much is nifty, but the bottom line of all of this is people want to know what paint/ barrel combo is going to work best for them. Why shouldn't we know if the compression factors are different for other brands?

Wouldn't a more useful test be to determine which classes and brands of paint perform best? To me paint performance would be defined by 1) shoots straight consistently 2) doesn't break in my pod, hopper, breech, or barrel. 3) does break on opponents. 4) is less effected by weather, or predictably works well in known weather 5) is conistent case to case on the previous 4 points 6) cost per previous factors.

This test seems to address parts of #2 and #3 and (maybe#4 depending on what other data ou are holding), but wouldn't it be more applicable test be to fire a bunch of different brands of paint at a target that simulates a player, and record breaks on target versus breaks in gun, at specific temperatures and at a fixed range and fixed velocity mean? Then periodically repeat the test as new products become available, and to test for continued quality.

Don't get me wrong though, this is a very cool test. I just have a hard time seeing how we can use the information you gathered to make our stuff work better. How can I use this to help me make better paint purchasing decisions?


well first and foremost, we are not product reviewers. only when a product claims to be different or advantageous in some way that we have evidence that it is not, is when we become product testers. i genuinely despise reviews, we are not the consumer reports of paintball.

but point per point -

1. we can do this without testing brand of paint, we need only look at the quality of the paint.
2. we can do this without testing brand of paint, we need only look at the quality of the paint.
3. we can do this without testing brand of paint, we need only look at the quality of the paint.
4. we can do this without testing brand of paint, we need only look at the quality of the paint.
5. that secretly is the point of all this - good call.

me and bryce have talked alot about this issue, and to maintain objectivity and analysis on the science, and not the products themselves, we wont want to do brand vs brand testing. you are welcome to do that, but we will refrain from doing that.

unless of course the brand changes an important factor, like the method by which a gun works. we can't test a spool vs a poppet with dye guns, we need to change brands.

the bottom line assumption is that in terms of paint is that we tested a wide range of paintballs, grades, qualities and types, that is enough for us to make generalizations about all paintballs, unless the producers of paintballs start marketing something new. to my knowledge no paint company markets anything other then higher quality, cheaper price, thicker fill and such.

also, to prevent any type of product testing, we tend to tell our sponsors that we will only test there goods, we will never test sponsored goods vs un-sponsored goods. so, in theory, we could do a paint test, but all the paint companies tested we would buy, or they would all donate to us.

so, there are alot of reasons why we wont be doing brand comparison tests.

EDIT what i am try to say is that brand in and of itself is not a factor. only when one brand is fundamentally different then the next is it a factor, and then its the fundamental difference that is the factor, not the label on the box. if one brand made paintballs not with encapsulation machines, or with a non-gellitine shell, or something of that nature, then we would defiantly take a look.

Edited by cockerpunk, 17 January 2009 - 05:07 PM.

The ultimate truth in paintball is that the interaction between the gun and the player is far and away the largest factor in accuracy, consistency, and reliability.

And yes, Gordon is the sexiest manifestation of "to the front."


#34 Merc4Hire

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Posted 17 January 2009 - 06:52 PM

thanks for the response. kind of my point though is that it is very seldom that you can do a direct quality tier comparison between brands. You can't buy brand x midrange paint, with a shell strength of aprox 77% stronger than gold and buy rand y midrange paint, with a shell strength of aprox 77% stronger than gold, and expect them to behave similarly. There are so many other factors that affect performance. Turns out brand y is sloppy and the diameters vary by a lot more than brand x....

I get why you hate reviews, but a direct comparison test is really useful. There isn't a lot of room for opinion when you say that the numbers show that running the same.685 cp barrel at 280, it took brand x's $40 a case an average of 2 cases to get a barrel break, and brand y's tended to break about every 3 hoppers worth. You don't have to say that you like procaps better than rps, you can say that with the same setup, one broke more paint, one bounced more, and one had a better standard deviation on the target. you did it with barrel bore ratio's. Or your tests might show that in price tier they really were about the same on the target even though a bunch of factors were different. To me that means a lot more than rating just one factor of the paintball, and is easier to test. Without testing every factor about the quality of the paint, you assume that shell strength is the only thing that determines quality of paint, and you know better.

Before you can say that a certain factor determines quality, such as shell strength, you have to compare several paintballs that are about the same in that factor and see what they do over the chrono and on the target. Otherwise you are just picking something easy to measure and generalizing. ie from our sample, people who are 6' tall can lift more than people who are 5'7" look at the numbers, decide for your self, 6' people are better.Conclusion: date a tall person.

I also understand your obligations to sponsors and your care to avoid letting those make skewed tests. I respect that a lot. Your barrel test is great. however the length comparisons only seem to directly apply to barrels that arrange their porting and control bore lengths similarly to CP. Things like starting the porting at the end verses the middle would seem like a ,fundamental difference'. Your tests are excellent, but they don't cover everything yet. I don't expect you to get every single little thing eliminated. It just isn't definitive yet.

I really hope I haven't offended you, I think punkworks is one of the coolest things to happen to paintball in since about 2003, and wish it had been around since the eighties.


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#35 cockerpunk

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Posted 17 January 2009 - 07:17 PM

thanks for the response. kind of my point though is that it is very seldom that you can do a direct quality tier comparison between brands. You can't buy brand x midrange paint, with a shell strength of aprox 77% stronger than gold and buy rand y midrange paint, with a shell strength of aprox 77% stronger than gold, and expect them to behave similarly. There are so many other factors that affect performance. Turns out brand y is sloppy and the diameters vary by a lot more than brand x....

I get why you hate reviews, but a direct comparison test is really useful. There isn't a lot of room for opinion when you say that the numbers show that running the same.685 cp barrel at 280, it took brand x's $40 a case an average of 2 cases to get a barrel break, and brand y's tended to break about every 3 hoppers worth. You don't have to say that you like procaps better than rps, you can say that with the same setup, one broke more paint, one bounced more, and one had a better standard deviation on the target. you did it with barrel bore ratio's. Or your tests might show that in price tier they really were about the same on the target even though a bunch of factors were different. To me that means a lot more than rating just one factor of the paintball, and is easier to test. Without testing every factor about the quality of the paint, you assume that shell strength is the only thing that determines quality of paint, and you know better.

Before you can say that a certain factor determines quality, such as shell strength, you have to compare several paintballs that are about the same in that factor and see what they do over the chrono and on the target. Otherwise you are just picking something easy to measure and generalizing. ie from our sample, people who are 6' tall can lift more than people who are 5'7" look at the numbers, decide for your self, 6' people are better.Conclusion: date a tall person.

I also understand your obligations to sponsors and your care to avoid letting those make skewed tests. I respect that a lot. Your barrel test is great. however the length comparisons only seem to directly apply to barrels that arrange their porting and control bore lengths similarly to CP. Things like starting the porting at the end verses the middle would seem like a ,fundamental difference'. Your tests are excellent, but they don't cover everything yet. I don't expect you to get every single little thing eliminated. It just isn't definitive yet.

I really hope I haven't offended you, I think punkworks is one of the coolest things to happen to paintball in since about 2003, and wish it had been around since the eighties.


rigtho, we do general tests. and we make general recommendations based on those test. we can learn alot from these general tests, and if we have a standard type of test and a standard of equipment used to measure that test, we can repeat certain types of tests and compare test resealts that might be separated by a large amount of time. such as the "standards" we have used for accuracy and ball brittleness (rig has yet to be reveled).

obviously finding the exact optimum would require a 6 or 8 dimensional matrix of testing, with all manner of extreme precision measuring. it requires that you spend time with your setup to get the ideal. we can't test every setup with every paint with every loader and barrel and bolt and air tank and dwell setting and ....

often times the ideal is impossible to achieve (the fundamental problem that faces engineers across the world), so using a series of general ideas and relationships made off our test will give the best indication of what to use.

we dont use hard and fast rules here for a reason, we say things like "underboreing by about .003 or .004" or "we did not see a statistical difference" and "depending on the porting pattern, 12 to 14 inches one piece underbore is probably your most efficiency barrel"

and above all else we look at the scale of the outputs we get, and we try to understand that in a real world way. often we can see a resualt, but it just isn't large enough to be useful and such.
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#36 Lord Odin

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Posted 17 January 2009 - 10:44 PM

I wouldn't rule out product comparisons completely. They do have their place, especially in paintball testing. The testing that is being done is exactly what you guys are intending it for: to find the underlying causes and effects to explain behaviors generally. However, those results aren't always applicable. For example, lets hypothetically say that shell thickness is found to be the main contributing factor to accuracy. It explains it but people aren't able to apply it because of a lack of information. Paintball manufacturers don't publish their specs of their products and people have no way to tell which brand is better or worse. That can apply to anything from barrels, to bolts, to tanks, etc. By comparing products, people can see where they line up with each other and what their specs are.

Like you said CP, right now, you're simply after finding what the causes are and paving the way with creating testing standards. Once you know what does what, those tests can be repeated so that product comparisons can be done later on.

#37 cockerpunk

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Posted 17 January 2009 - 11:14 PM

anyway, back to the test at hand.

i think my leading questions would be these -

1. does seam orientation matter? what mode of failure are we looking at, and how does the seam effect that failure?

2. on page two, how does the method of loading change the load capability?

3. general thoughs in this one - note how much deflection a paintball can take under normal (ie non-impact) loading. how does this related to bore size choices?

after we explore those different questions and any others that arise in that discussion, well post some more data.

Edited by cockerpunk, 17 January 2009 - 11:16 PM.

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#38 Troy

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Posted 18 January 2009 - 08:52 AM

Since I'm one of the first to respond to CP, I'll grab some of the low hanging fruit... the orientation of the load on a paintball is very critical, if any of the paintballs are loaded vertically, they are FAR more likely to fail, then if they are loaded horizontally. With deflection numbers of at least .09 its no small wonder why we didn't see any statistical difference with a .003 underbore, which represents only about 3% of the amount it can be deflected until it brakes.

Troy's notes:
1) This test is very relevant to bolt strikes and underboring, but unfortunately not on how paintballs perform in the stack. Because a paintball is loaded in the stack with three points of pressure it's still unclear how or if the seam effects paintballs in the stack. I think we have reason to believe that this is a very critical point where many failures occur, so it would be fairly important to test it. If I were you, I would use a clear cylinder the width of a typical feedneck and press a paintball between two ball bearings with different seam orientations in 3D.
2) There certainly weren't many repetitions in your test, I would have liked to see a lot more.
3) I would be interested how much resilience is added to a paintball if it is in a bore. I'd like to see a paintball being pressed in between the two bolts in the middle of a freak bore, and see how much more pressure needs to be applied to break it.
\m/

#39 Merc4Hire

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Posted 18 January 2009 - 04:16 PM

Ok troy that was pretty astute, and I like all 3 of your points. I stand corrected on the practical application


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#40 Leftystrikesback

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Posted 18 January 2009 - 05:50 PM

does anyone have a background in material science? if i start tossing terms out like site defect, void space and force multiplier, will people be confused?


I'm focusing on the subject for my masters. I'd certainly like to hear your thoughts, though I'm not sure how you're going to toss out those terms since the gelatin shell of a paintball is not crystaline.

Do you have any photos of the cross sections of the paintballs so that we can look at what the seam looks like? From paintballs that I've cut in half, the seam is actually thicker than the rest of the ball. This is interesting, because you would think that would mean that it is the strongest part of the ball, which Bryce mentioned is contradictory to this test, since the seams were the main sites of failure.

But the reason the seam is there in the first place is because it is where the two halves of a paintball are 'stuck' together while they are warm and soft. So it makes sense that the seam is thicker, and also makes sense that it would fail there, since there could be imperfect bonding between both halves, leading to a weak spot along the seam.

Also, do you think we should be assuming the paint inside pressurizes turning the ball into a pressure vessel? I have no idea if that is a valid assumption but thinking of things this way seems like it explains the vertical seam failure.

Hoop stress would be acting to force the two halves of the paintball apart when the seam is in the Vertical position. In the horizontal seam situation, hoop stress goes along the seam (in the strong direction) and radial stress would be acting on opening the seam. And if the squished paintball can be approximated as a cylinder pressure vessel (and a cow as a sphere :) ) then hoop stress is much greater than radial stress, and we get our result that the paint ball fails sooner when the seam is positioned vertically.
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#41 brycelarson

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Posted 18 January 2009 - 06:29 PM

ok lefty - you seem to know this stuff - tell me this:

we have a sphere (imperfect though it might be). If you dent in one part of a sphere - does that force apply itself evenly around the entire surface of the sphere? - or is the outward force create directed in some direction related to where the sphere has dented in?

#42 Leftystrikesback

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Posted 18 January 2009 - 08:32 PM

It depends on what you're asking... I'll answer it in two different ways

First lets ignore the fill, if you dent a hollow sphere, the stresses are concentrated around the edges of the dent and won't affect the rest of the sphere at all

Now lets talk about a hollow sphere with fill.
We need to make some assumptions though; there is no air inside the ball, only paint, and the paint is incompressible.
Given that, which is probably true, the force will be constant around the surface of the sphere except for the spot where the dent is, where there is some additional stress due to the deformed dent.

Here's why; you dent the paintball in some spot, which decreases the volume on the inside of the paintball. But the paint is incompressible, so it can't change its volume, so to compensate it's pressure goes up and the paintball's shell slightly expands to correct the change in volume. Also, pressure in a static fluid is constant everywhere (ignoring gravity) so the original force used to dent the paintball is transformed into a constant pressure in the fluid, which is applied evenly everywhere. This is true for any shape, but pressure needs to be translated into a force, and in a perfect sphere this constant pressure turns into the same force at every point on the sphere.

but when you change the shape, so the ball is no longer spherical, things change drastically. That's what my point was in my last post, if you look at a cylindrical pressure vessel (any cylinder that holds pressure) the constant pressure on the inside translates into different forces (stresses) going in different directions across the surface. now I'm not suggesting a compressed paintball is cylindrical, but it's not spherical either so non-uniform stresses will pop up.
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#43 cockerpunk

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Posted 18 January 2009 - 08:51 PM

lefty - great call.

the reason i was asking about void space and such is becuase i believe the seam is the site of most paintball failures, or the reason for them. polymers like gelatin with have some amount of crystalisity, not a true matrix like an alloy, but there mers will be aliened in a strong way.

this is because the seam is chaotic, and becuase of that the mers of the polymer are not properly set up to take loading. there is probably also holes and voids where the two sphere halves to not line up exactly right.

either way, i believe the initial cracking takes place at the seam due to voids caused by irregular formation and alignment of the mers multiply the stress. the intial cracking may happen even when loaded horizontally, but the true failure of the structure is when the crack propagates catastrophically though a large enough section of the shell. again, i see the seam as another source of voids, and stress multipliers along it as a a source for the initial cracking to propagate easily through.

for whatever reason though, the seam plays a critical role in terms of failure of the paintball. of that there is no doubt IMO.

and to those calling for more data points, understandable. but when you see the true scope of what this test was about, you will see how it all took something like 8 or 9 hours of work. the trends we are talking about are pretty large IMO so further data points, while nice, are not necessary.

you guys also hit the nail on the head. while we can understand that in an impact type situation, there will be alot less deformation then in this case. this test is primarily about stead state loading, and the LARGE deflections we saw was primarily becuase of the mers in the polymer shell creeping. and underbore portion of a paintball is much more stead state then an impact at 50 or more FPS. however, its easy to see that when we recommend a .003 to .005 underbore, thats like 5% tops perhaps of the total crush strength of the ball, and with a nice destrubted load like we tested too, we saw that percent even get lower. so an underbore again simply puts minimal stress on the paintball.
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#44 Leftystrikesback

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Posted 18 January 2009 - 09:21 PM

In a polymer, the strength is influenced by both the length of the polymer chains (longer is stronger) and how they are mixed/tangled (more tangling is better overall). If polymer chains are lined up, the polymer will be strong in the direction of the lined up chains, but weak in all other directions. If the chains are not lined up, and the material is stretched in some direction, the chains move to line up in that direction strengthening the material. So more tangling leads to better strength overall, I think this is the key.

I think what happens in the seam is that only some of the chains have tangled between the two halves, so the bond of the polymer in the seam just isn't as strong as in the rest of the paintball. That probably happens because the halves aren't held together long enough or are cooled too much to maintain their shape or something like that in the manufacturing process.

This is kind of what you're saying I think, I just don't agree with the term void because it implies a missing atom somewhere. In a polymer, a missing atom in the chain just means a shorter chain... which I guess does have a similar effect on the material strength but is a completely different mechanism. Let's call it a gap?

Edited by Leftystrikesback, 18 January 2009 - 09:27 PM.

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#45 Lord Odin

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Posted 18 January 2009 - 09:43 PM

If I may, I'd like to interject a question. If most of the breaks begin at the seam and the seam's strength is only as good as the bond between the two halves, then why are the thicker shells stronger than the thinner shells? Are the thinner shells cooling too rapidly to create a strong enough bond?

Edited by Lord Odin, 18 January 2009 - 09:44 PM.


#46 Leftystrikesback

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Posted 18 January 2009 - 09:46 PM

well a thicker shell should mean that the seam is thicker too (I assume). Lets say there are the same number of bonds/area due to the manufacturing process, a thicker seam would still mean more bonds overall, right? So the seam would get stronger in proportion to the thickness increasing (assuming seam thickness also increases), but still be weaker overall.
That's my justification, maybe there are others

Edited by Leftystrikesback, 18 January 2009 - 09:48 PM.

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#47 Troy

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Posted 18 January 2009 - 10:21 PM

well a thicker shell should mean that the seam is thicker too (I assume). Lets say there are the same number of bonds/area due to the manufacturing process, a thicker seam would still mean more bonds overall, right? So the seam would get stronger in proportion to the thickness increasing (assuming seam thickness also increases), but still be weaker overall.
That's my justification, maybe there are others


Hydrogen bonds occur between the different chains, which overall, increases their strength, but you're pretty much right, the chain tangling is the greatest source of strength in a polymer chain. Polymer chains are crazy temperature specific (that's why you have different kinds of waxes for skis for different temps, and margerine doesn't melt at room temp), and the temps that they need to be heated up to to wrap each other up is probably a fairly specific one... I'm betting that the temp that they have to combine the two halves together doesn't allow enough molecular movement to let the two halves interlink very well. Just in like a weld in high strength aluminum, the two materials don't interlink very well, you end up adding in materials like scandium that form dendrites between the particle grains that increase interlinking between the two materials.

I'm going to deny the assumption that there isn't air in a paintball, as I've seen plenty of paintballs with very clear bubbles of air. I would imagine that paintballs that were properly filled would break after much less deformation then paintballs with air. I imagine the slight air pockets are a source of great elasticity.

Anyone that has changed out the hydraulic fluid on their mountain bike (or perhaps motorcycle), can tell you about all the damn air that can hide in a liquid. Based on the pressure of the fluid the air can easily dissolve in the fluid and make the paintball much more prone to compression then if it had a noncompressible fluid fill without any air introduced.
\m/

#48 Leftystrikesback

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Posted 18 January 2009 - 10:34 PM

I wish I had the money to put hydraulic disc brakes on my mountain bike... ah all the things I'll be able to do once I graduate...

But yeah you might be right about the assumption that there are no air bubbles in the fill. I can't think of a good way to test this... Poke a ball in the top with a pin and see how much you can squeeze it till paint comes out?

Edit: about the temperature dependence, I would imagine getting the gelatin to the right temp to create good bonds would also make them unable to hold their shape, so could be a trade off between well bonded halves and round balls with no dimples...

Edited by Leftystrikesback, 18 January 2009 - 10:37 PM.

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#49 Lord Odin

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Posted 18 January 2009 - 10:37 PM

I wish I had the money to put hydraulic disc brakes on my mountain bike... ah all the things I'll be able to do once I graduate...

But yeah you might be right about the assumption that there are no air bubbles in the fill. I can't think of a good way to test this... Poke a ball in the top with a pin and see how much you can squeeze it till paint comes out?

What about a microwave? Place a ball inside a tupperware container that isn't completely closed and turn it on. If there is air in the ball, shouldn't it cause the ball to expand and/or pop? Or would this happen regardless if air was in there or not?

#50 Leftystrikesback

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Posted 18 January 2009 - 10:39 PM

Could be a good idea, time to microwave some paintballs? although it could boil the water in the fill and the vapor might blow up the paintball too. I still want to put one in the microwave haha.
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