[Panda Man]

I live very high above sea level. Does that effect how a paintball gun operates?

I know a gun filled with 600psi will be 600psi no matter what(how would the gun know?) But I'm talking about like paint or lube.

[Vhyrus]

C02 expands differently at different altitudes, but I assume you aren't using C02. I believe that air efficiency is slightly affected at altitude but I am not sure if it is more or less efficient. 600 psi is not always 600 psi, though. It is relative to your ambient air pressure (we call this gauge pressure vs. absolute pressure). The gauge is telling you how many psi above atmosphere it is reading. It should not matter for paintball though since even the operating pressure is at least 1 order of magnitude above atmosphere. The one thing that might actually be affected is range. Air is thinner at higher altitude, which means less air resistance on the paintball. I don't know how much farther a paintball will fly at high altitudes though, probably not a lot.

[asthmaticrhino]

It shouldn't theoretically, you should see an increase in efficiency, since the pressure difference is greater. This would probably be very slight, maybe a half of pod at max. And that's assuming the temperature is comfy. If its cold, a guns efficiency will suffer a bit.

[Troy]

Wouldn't a decrease in atmospheric pressure decrease air resistance and increase accuracy (due to a, slight, decrease in the effects from vortex shedding)?

[Akkadian_Tim]

Troy, on 05 April 2013 - 09:41 AM, said:

Wouldn't a decrease in atmospheric pressure decrease air resistance and increase accuracy (due to a, slight, decrease in the effects from vortex shedding)?

Not within any measurable amounts no. There are other variables still in play that would mess with accuracy +/- way more than this would. The effect for a paintball is statistically insignificant, and quite likely unmeasurable.

This post has been edited by Akkadian_Tim: 05 April 2013 - 11:44 AM

[Troy]

Akkadian_Tim, on 05 April 2013 - 11:43 AM, said:

Troy, on 05 April 2013 - 09:41 AM, said:

Wouldn't a decrease in atmospheric pressure decrease air resistance and increase accuracy (due to a, slight, decrease in the effects from vortex shedding)?

Not within any measurable amounts no. There are other variables still in play that would mess with accuracy +/- way more than this would. The effect for a paintball is statistically insignificant, and quite likely unmeasurable.

You think there are other factors that mess with accuracy MORE then vortex shedding?

[Akkadian_Tim]

Troy, on 06 April 2013 - 01:00 PM, said:

You think there are other factors that mess with accuracy MORE then vortex shedding?

Yes.

Consistency of velocity from shot to shot for one. The wider that range, the greater differences in trajectory. Paintball quality and consistency of paintballs from shot to shot. Any misshape or variability will impact everything else. Those are just two easy examples.

For the distance a paintball is capable of traveling, the effect of altitude/differing air pressure will be minimal to nonexistent. You'll see more variability from shot to shot with the other things I listed.

[Troy]

Akkadian_Tim, on 08 April 2013 - 10:30 AM, said:

Consistency of velocity from shot to shot for one. The wider that range, the greater differences in trajectory.

This has been proven to be false (within about +/- 8 fps, IIRC...).

Akkadian_Tim, on 08 April 2013 - 10:30 AM, said:

Paintball quality and consistency of paintballs from shot to shot. Any misshape or variability will impact everything else. Those are just two easy examples.

These have not been proven to have a larger effect then the probability cone created by vortex shedding.

Akkadian_Tim, on 08 April 2013 - 10:30 AM, said:

For the distance a paintball is capable of traveling, the effect of altitude/differing air pressure will be minimal to nonexistent. You'll see more variability from shot to shot with the other things I listed.

The interaction between the air and the paintball is, by far, the largest source of inconsistency... insomuch as it EVEN obscures the effects on the y axis of shot to shot speed inconsistencies. I don't believe that it's unjustified to suspect that a lower pressure could effect the air interaction with the paintball at a, mathematically, significant level.

[Akkadian_Tim]

Now if only I had a climate controlled, pressure adjustable dome of a world to be able to conduct these tests....



I do value science at heart, so I'd be the first to admit if my tests proved me wrong. And if I was right, I'd publish that too.

[Troy]

Akkadian_Tim, on 08 April 2013 - 01:16 PM, said:

Now if only I had a climate controlled, pressure adjustable dome of a world to be able to conduct these tests....



I do value science at heart, so I'd be the first to admit if my tests proved me wrong. And if I was right, I'd publish that too.

Here are the results of my last test, the 2nd and 3rd slides are an ANOVA of velocity verses accuracy and we found no significant correlation between the two for the sample group tested.

Another bit of data I'm drawing from is my analysis of rntlee's data here. I found no, significant, correlation between velocity and shot height there as well (which, frankly, SOUNDS absurd).

My working hypothesis is that the vortex shedding has such a significant impact on the paintball's flight that even, seemingly obvious, factors like exit velocity don't have a significant impact on accuracy. I will admit that we have seen significant increases in accuracy with better paint, but even that effect is slight relative to the impacts of vortex shedding. I did note, however, in my test linked above that there was, in fact, a significant correlation between the ratio of off seam diameter paint and accuracy... so, believe it or not, slightly oblong paint shot better for us for some reason.

So yeah, accuracy isn't, nearly, as straightforward as I would like it to be. There's still a bunch of crap that we don't know. And yes, a pressure controlled dome would be awesome.

[Akkadian_Tim]

Very interesting data. Makes me wonder, from a practical standpoint, what things do matter, because conventional wisdom and a basic understanding of physics seems to be contradicted.

Basic physics would suggest that consistency (precision) would translate to accuracy. A ball with velocity X vs velocity Y should have a different trajectory, and ones with the same velocity should be more precise as their trajectories would be more consistent. At least that's how it works in the classroom. The fact that it's not really all that significant is interesting.

[brycelarson]

Troy's math is better than mine - but I found using accumulated accuracy testing (climate controlled, indoor) up to about +/- 15 fps there was no detectable variation in accuracy. Simply put - paintballs are too shitty a projectile to see the consistency variations.

So, Tim - no, consistency does not have a larger effect than the interaction between ball and air.

edit - we were typing at the same time. I'll add more now that I see your post.

Based on several tests there are multiple factors that seems to effect accuracy - but we don't have enough data to determine the magnitude of these:

• surface finish
  
• seams
  
• roundness
  
• spin
  
• dimples
  
• contamination (oil, dirt etc)

This post has been edited by brycelarson: 09 April 2013 - 11:35 AM

[Troy]

Akkadian_Tim, on 09 April 2013 - 10:47 AM, said:

Very interesting data. Makes me wonder, from a practical standpoint, what things do matter, because conventional wisdom and a basic understanding of physics seems to be contradicted.

Basic physics would suggest that consistency (precision) would translate to accuracy. A ball with velocity X vs velocity Y should have a different trajectory, and ones with the same velocity should be more precise as their trajectories would be more consistent. At least that's how it works in the classroom. The fact that it's not really all that significant is interesting.

It doesn't make any sense to me, either, but that's the story the observational data seems to be telling us. To me, it makes sense that if vortex shedding puts, let's say, +/- 10 inches of spread, and differences in consistency rendered +/- 2 inches of vertical spread, that it would be cumulative and we would be able to see a correlation between speed and accuracy. However, time and time again we see nothing. We've got tons of data collected from different people all over the US that says the same thing. Something weird is going on.

I'm thinking (and I am, freely, just talking out of my ass here... there are people with a WAY better understanding of this problem then I have) that there HAS to be some kind of relationship between the magnitude of the force applied on the ball by a vortex and the speed. It makes sense in my head that a ball with more energy could "spawn" vortices with more energy. Therefore, as velocity increases, statistically speaking, so does the magnitude of randomness. In that way, the correlation between the speed and the vertical position is ruined by the increase in randomness magnitude (which may, or may not expand linearly).

Furthermore, there is additional speculation that decreases in speed over the crono MIGHT not be due to the marker putting less energy into the shot, but may be due to the ball bouncing around in the barrel and having a random spin on it.

The interaction between the above two factors MAY be why we can't observe any correlation between velocity and accuracy.

[Lord Odin]

Based on limited research of baseballs being hit in higher altitudes, it would be at most around a 10% increase in distance. So I don't see why it wouldn't affect paintballs less differently.

I think this would be a good test.