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Ranged Chrono Test


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#1 cockerpunk

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Posted 30 March 2009 - 03:01 PM

video -

data - http://spreadsheets....HdSU6mMTaMXfLLA

discuss!
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#2 Snipez4664

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Posted 30 March 2009 - 03:08 PM

Is there a way to compare this data with the paintball trajectory calculator predictions?
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#3 Leftystrikesback

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Posted 30 March 2009 - 04:06 PM

Is there a way to compare this data with the paintball trajectory calculator predictions?


The averages line up pretty well but there's no way to put 50 ft into the calculator and see what the speed is there, so it seems like you have to just stop the calculator at a distance close to what you want.

I wrote my own code that uses the same equations but outputs velocities in a vector. I can use that to compare velocities at certain distances. Are you just wondering how much the theory lines up with the tests? It's going to depend pretty heavily on how accurately your drag coefficient is defined. He uses Cd = 0.5 and so did I in my code (IIRC, I'm not at home to look at it) but it actually can vary with velocity which makes things much more complex. But defining it that way would make the results more accurate.

I guess it would be nice to see whether Cd = 0.5 is an underestimate or an overestimate, is that what you were thinking?

Edited by Leftystrikesback, 30 March 2009 - 04:08 PM.

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#4 Leafy

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Posted 30 March 2009 - 04:13 PM

do we know the minimum velocity at which a paintball will break? might be nice to add to the extrapolated data. and maybe add a bit of the extrapolated data to that graph so that it really shows the exponential decay of the velocity.

*edit how many times did you hit your 50' and 100' chronos before you got the paint to go through it? I only ask cause I notice that the paint "hits the ground" at 40 feet.

Edited by Leafy, 30 March 2009 - 04:16 PM.


#5 U83R 1337

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Posted 30 March 2009 - 04:34 PM

It would depend on the type of paint, temperature, how old the paint is, and what it hits

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#6 cockerpunk

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Posted 30 March 2009 - 04:48 PM

do we know the minimum velocity at which a paintball will break? might be nice to add to the extrapolated data. and maybe add a bit of the extrapolated data to that graph so that it really shows the exponential decay of the velocity.

*edit how many times did you hit your 50' and 100' chronos before you got the paint to go through it? I only ask cause I notice that the paint "hits the ground" at 40 feet.


note under the assumptions it is listed as zero barrel angle.

obviously we had to elevate the gun to get it to hit the chrono at range. but remember, we are dealing with ranges and assumptions about the ranges of values. the extrapolated data is part of an ongoing project i have with viper the scenario producer.
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#7 Leftystrikesback

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Posted 30 March 2009 - 04:56 PM

do we know the minimum velocity at which a paintball will break?


It definitely depends on the paint, but you can calculate a good estimate:
Every ball doesn't break after being dropped from 8 feet, so maybe after 10 feet would be like 90% breakage for an average paintball. How fast is a paintball going when it hits the ground after being dropped from 10 feet? I'm sure you can solve that for your self.
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#8 Leafy

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Posted 30 March 2009 - 05:39 PM

do we know the minimum velocity at which a paintball will break?


It definitely depends on the paint, but you can calculate a good estimate:
Every ball doesn't break after being dropped from 8 feet, so maybe after 10 feet would be like 90% breakage for an average paintball. How fast is a paintball going when it hits the ground after being dropped from 10 feet? I'm sure you can solve that for your self.


ok its about 25 feet/sec thats what I got without factoring in drag and using 3 meters as the drop height and 9.8 m/s^2 for the acceleration due to gravity.

#9 weeebeep

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Posted 30 March 2009 - 08:52 PM

would you be so kind as to try the same test featuring the tiberius first strike round? I would really like to see how fs holds up against traditional paint.

#10 brycelarson

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Posted 30 March 2009 - 08:55 PM

would you be so kind as to try the same test featuring the tiberius first strike round? I would really like to see how fs holds up against traditional paint.



that's on the list of tests for this summer.

#11 Snipez4664

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Posted 30 March 2009 - 09:27 PM

do we know the minimum velocity at which a paintball will break?


It definitely depends on the paint, but you can calculate a good estimate:
Every ball doesn't break after being dropped from 8 feet, so maybe after 10 feet would be like 90% breakage for an average paintball. How fast is a paintball going when it hits the ground after being dropped from 10 feet? I'm sure you can solve that for your self.


ok its about 25 feet/sec thats what I got without factoring in drag and using 3 meters as the drop height and 9.8 m/s^2 for the acceleration due to gravity.


Right.....Because when I play paintball, I do so wearing blocks of oak at right angles to those shooting me. It's much, MUCH easier to go the other way (hard to get breaks at 150 feet, therefore this velocity is about what it takes to break on a human).
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#12 Leftystrikesback

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Posted 30 March 2009 - 09:30 PM

Right.....Because when I play paintball, I do so wearing blocks of oak at right angles to those shooting me. It's much, MUCH easier to go the other way (hard to get breaks at 150 feet, therefore this velocity is about what it takes to break on a human).


You and your "logic" :rolleyes:

Edited by Leftystrikesback, 30 March 2009 - 09:30 PM.

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#13 Leafy

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Posted 30 March 2009 - 09:31 PM

do we know the minimum velocity at which a paintball will break?


It definitely depends on the paint, but you can calculate a good estimate:
Every ball doesn't break after being dropped from 8 feet, so maybe after 10 feet would be like 90% breakage for an average paintball. How fast is a paintball going when it hits the ground after being dropped from 10 feet? I'm sure you can solve that for your self.


ok its about 25 feet/sec thats what I got without factoring in drag and using 3 meters as the drop height and 9.8 m/s^2 for the acceleration due to gravity.


Right.....Because when I play paintball, I do so wearing blocks of oak at right angles to those shooting me. It's much, MUCH easier to go the other way (hard to get breaks at 150 feet, therefore this velocity is about what it takes to break on a human).


you dont? it can be the eigencammo.

but you're correct, but now how do we test human bounce? have one of you friends lay down on the floor and drop it on his chest off your roof?

#14 Snipez4664

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Posted 30 March 2009 - 09:47 PM

but you're correct, but now how do we test human bounce? have one of you friends lay down on the floor and drop it on his chest off your roof?


You shoot them, over a chrono. I'm happy to volunteer you for this duty. Remember, bouncers hurt the most!
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#15 Spitlebug

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Posted 31 March 2009 - 12:30 AM

but you're correct, but now how do we test human bounce? have one of you friends lay down on the floor and drop it on his chest off your roof?


You shoot them, over a chrono. I'm happy to volunteer you for this duty. Remember, bouncers hurt the most!


Bwhahahahahahahaha.

Seriously though, it would be interesting to get the final velocity at or around 150 feet (is that a standard field length?) so as to know the speed the ball is travelling and then get a rough idea of the centroid for accuracy at that range. This information may be pertinent to fixed and inflatible bunker design.

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#16 AndreS

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Posted 31 March 2009 - 01:21 AM

awesome test!

Edited by AndreS, 31 March 2009 - 02:45 AM.




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#17 brycelarson

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Posted 31 March 2009 - 09:41 AM

but you're correct, but now how do we test human bounce? have one of you friends lay down on the floor and drop it on his chest off your roof?



I don't think we can quantify bounces off a human target - there are too many variables. you've got joints, muscle and fat. I guarantee I'll get more bounces from my belly than from my elbows. We're looking at a massive density range depending on the location of the hit.

I would agree with the 25 fps number - for a mask, pod, gun or hopper hit - but obviously not for a chubby guy's belly.

#18 Lord Odin

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Posted 31 March 2009 - 11:16 AM

You could always make your own ballistics gel to simulate human flesh and bounce off of that. There are plenty of links on how to make it yourself. Just have to make sure you keep the formula the same for consistent viscosity for different batches. Wouldn't want one target to be softer/harder than another.

This looks like a good one.
http://www.firearmst...r2/article1.htm

Edited by Lord Odin, 31 March 2009 - 11:19 AM.


#19 cockerpunk

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Posted 31 March 2009 - 11:45 AM

but you're correct, but now how do we test human bounce? have one of you friends lay down on the floor and drop it on his chest off your roof?



I don't think we can quantify bounces off a human target - there are too many variables. you've got joints, muscle and fat. I guarantee I'll get more bounces from my belly than from my elbows. We're looking at a massive density range depending on the location of the hit.

I would agree with the 25 fps number - for a mask, pod, gun or hopper hit - but obviously not for a chubby guy's belly.


maybe your belly!

but mine is hard as oak and washboards!
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#20 Spitlebug

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Posted 31 March 2009 - 01:24 PM

maybe your belly!

but mine is hard as oak and washboards!


Yes, I am definately as hard as wood as well. :blink:

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#21 russc

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Posted 31 March 2009 - 11:47 PM

What's it at when you hit 15 feet? 270ish? I'm trying to convince the local field to drop the confusing mercy rule and just lower overall FPS from 300, seeing as they want to be renter friendly.

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#22 Leafy

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Posted 31 March 2009 - 11:48 PM

What's it at when you hit 15 feet? 270ish? I'm trying to convince the local field to drop the confusing mercy rule and just lower overall FPS from 300, seeing as they want to be renter friendly.


but i love getting people to surrender. especially groups of 3 while pumpin it.

#23 Texas Cheezburgr

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Posted 31 March 2009 - 11:48 PM

What's it at when you hit 15 feet? 270ish? I'm trying to convince the local field to drop the confusing mercy rule and just lower overall FPS from 300, seeing as they want to be renter friendly.


The overall speed is not really slowed that much at all. Just gravity pulling it down.
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#24 UV Halo

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Posted 08 April 2009 - 09:33 PM

note under the assumptions it is listed as zero barrel angle.

obviously we had to elevate the gun to get it to hit the chrono at range. but remember, we are dealing with ranges and assumptions about the ranges of values. the extrapolated data is part of an ongoing project i have with viper the scenario producer.


By "elevate" do you mean you incline the barrel upwards or, raised the height of the gun/stand? If you did increase the inclination, did you measure how much so and was the inclination the same between the 50ft and 100ft tests? What was the height of the breach?

I took the time to create some google spreadsheets of the predicted numbers from the paintball trajectory calculator. Upon comparing them to the test data, I found some interesting things:

Looking at the 50ft Ranged test, 286 is the most frequent muzzle velocity with three shots. As you can see below, the predictions at least approximately hold true when compared to the average and measured velocities:

48.69ft @ 207.4fps
50ft @ 203.6fps (205, 204, 202)
58.71ft @ 194.2fps


Looking at the 100ft Ranged test, 299fps is the most frequent muzzle velocity with four shots. But, in this case, the predictions only holds true for one of the shots:

100ft @ 160.3fps (157, 160, 165, 159)
96.37ft @ 158.7fps
104ft @ 151fps


[EDIT]: I blew away my question about 40ft as I see Leafy was referring to the extrapolated data and not reality.

Edited by UV Halo, 08 April 2009 - 09:34 PM.


#25 cockerpunk

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Posted 08 April 2009 - 10:10 PM

its not too bad though ... interesting ...

the extrapolated data is a bit of my fun time, im not sure how realistic it is though, might need to compensate for the launch angle to do it.
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#26 russc

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Posted 08 April 2009 - 11:45 PM

What's it at when you hit 15 feet? 270ish? I'm trying to convince the local field to drop the confusing mercy rule and just lower overall FPS from 300, seeing as they want to be renter friendly.


The overall speed is not really slowed that much at all. Just gravity pulling it down.


Nope. You're wrong on that one.

I tested a 295-300 fps shot at 15 feet. Initial over a yellow chrono, second chrono was a red one. I made sure they were both reading approximately the same speeds.

At 15 feet, the 300fps shots had dropped to about 255-260. With that info I managed to convince the owners to drop the surrender rule and go to an overall speed of 275. 270-275 drops to 255-260ish at about 2-3 feet.

Edited by russc, 08 April 2009 - 11:45 PM.

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#27 brycelarson

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Posted 09 April 2009 - 08:42 AM

yeah Russc - the faster a projectile is moving the faster it decelerates. It's not a linear thing.

#28 cockerpunk

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Posted 09 April 2009 - 09:33 AM

indeed, drag is modeled as a square often, but for some flows a better approximation is to the fourth.

means when you go faster, your drag force increases ALOT faster then your velocity.

thats why i curve fit to an exponential and not a line.
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#29 Snipez4664

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Posted 09 April 2009 - 10:17 AM

Although I believe that in the regime we're in for a sphere its pretty much a square relationship? There are some Cd effects after the wake separation in back changes (at what, Re=~50k OTOH?) but those actually push back towards linear IIRC.

I don't recall what fit you used, but 2nd order or maybe 3rd would be fine. Less physical analogue the higher you go though.

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#30 NECanes Coach

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Posted 10 April 2009 - 02:55 PM

Awesome test.

Have you tried/considered shooting various guns to see if there is any difference in the behavior?
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#31 Leftystrikesback

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Posted 10 April 2009 - 03:48 PM

Awesome test.

Have you tried/considered shooting various guns to see if there is any difference in the behavior?


The only gun there will be a difference in would be one that spins the ball significantly (apex, flatline... maybe backspin bolt? :) ). The spin mostly affects lift on the ball, but it would be interesting to see if anything happens to velocity with those barrels.
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#32 cockerpunk

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Posted 10 April 2009 - 03:51 PM

Awesome test.

Have you tried/considered shooting various guns to see if there is any difference in the behavior?


yes, what guns would you like to see?

when we pull this rig out again for the first strike rounds, we can probably do a few other guns too. what would you like to see?
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#33 brycelarson

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Posted 10 April 2009 - 05:07 PM

Awesome test.

Have you tried/considered shooting various guns to see if there is any difference in the behavior?


yes, what guns would you like to see?

when we pull this rig out again for the first strike rounds, we can probably do a few other guns too. what would you like to see?


I'm going to guess that poppet v spool will be the answer - so I suggest Ion / SP1 vs cocker vs emag.

I know that all of those guns will be present at our next testing anyway.

#34 cockerpunk

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Posted 10 April 2009 - 05:12 PM

maybe i can get that shoebox shocker back and really put that one in the ground.
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