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Lenght of backs?

speedbird_666

Old Skool Is Cool....
Feb 1, 2003
636
0
41
Bournemouth.
think i might get a redz pepper stick...

and by the way who is Tom?

the inventor of the pepper sticks?
Pepper Sticks are great barrels by all accounts.

And Tom Kaye is the guy behind the creation of the Automag marker and more importantly introducing compressed air to the sport at a time where the only gas in use was Co2.
 

Skeet

Platinum Member
You are looking at what i'm saying out of context, i assumed that Teggy played supair, i've now found he doesn't.

I did not say that Tom Kaye was wrong, nor the laws of physics have changed, rather that with the typical ranges that we shoot at on a SupAir field these days the subjective accuracy does not vary radically with barrel choice alone.



No, not quite. Tom Kaye's research clearly states 'that best efficiency would be had with an 8-10" effective length barrel'

Note the word efficiency there, because you can fire a paintball with less than 8 inches of unported barrel, but to the possible detriment to efficiency. And to add further a further twist to the tale:

'Under some circumstances there is a good reason to use a short effective length barrel. Short barrels cut off the acceleration abruptly by venting and this has the effect of tightening up the shot to shot velocity variation. If you need this at the expense of efficiency then go ahead. Tighter velocity control usually translates into some improvement in accuracy due to better consistency'

The full article is here: http://www.automags.org/resource/tech/tomstech/01_barrel_eff.shtml

;)
But he also says, that in order to accelerate the ball to 300fps, in very short barrels, you need much higher pressure, which breaks the balls, which is no good!;)
 

speedbird_666

Old Skool Is Cool....
Feb 1, 2003
636
0
41
Bournemouth.
But he also says, that in order to accelerate the ball to 300fps, in very short barrels, you need much higher pressure, which breaks the balls, which is no good!;)
But what you were saying, or at least the impression that you putting across in you your previous posts is that 8in unported is almost mandatory:

From a standing start, you need 8 inches of un-ported barrel to accelerate a paintball to 300 fps.
I was just pointing out the fact that this was not the case.....;)

I had a Sly Barrel, with a 2.5-3in back. It shot corner to corner at tourneys with no problems at all, and I had no problem with breaking paint.

It's all academic these days, right now i use a .693 bore barrel and don't bother with bore sizing the paint. I play back corner normally, and it works very well for me.

I've had a number of kits such Full Freaks, Lucky 13s (Which you sold me skeet ;)), Complete UL boomstick sets, Sly sets, CP but i keep coming back to throwing an Eclipse Shaft 693 barrel barrel on my gun and being done with it.

:)
 

Skeet

Platinum Member
But what you were saying, or at least the impression that you putting across in you your previous posts is that 8in unported is almost mandatory:



I was just pointing out the fact that this was not the case.....;)

I had a Sly Barrel, with a 2.5-3in back. It shot corner to corner at tourneys with no problems at all, and I had no problem with breaking paint.

It's all academic these days, right now i use a .693 bore barrel and don't bother with bore sizing the paint. I play back corner normally, and it works very well for me.

I've had a number of kits such Full Freaks, Lucky 13s (Which you sold me skeet ;)), Complete UL boomstick sets, Sly sets, CP but i keep coming back to throwing an Eclipse Shaft 693 barrel barrel on my gun and being done with it.

:)
Quite...but how long are the unported sections on all those barrels?

I am not suggesting that that, say a Sly with a 3 inch back or a Freak with a 6 inch back, does not fit the bill.

Simply, that the first 8 inches of barrel are the most important for accelerating the ball to 300. If your barrel has porting starting at less than 8 inches along the length of the barrel, then, this will mean your barrel is less efficient.

At least...I think that is what I am saying...I'm not really sure any more!:D

Lucky 15's I think they were, Warped Sports ones...great barrel set!
 

SAMUEL.D.RYAN

one.man.band
Mar 17, 2007
1,513
76
73
Cambridge/Huntingdon
The "trick shot" barrel you were talking about is the BT apex barrel. I had a go with one on an x7 yesturday. It's good for the tricks, but the nature of the method of backspin means you can't turn up the trick angle very high before you break medium bored paint (we were shooting blaze i think...).

If you're looking for reach, the flatline is your best option, but the original post said he wanted accuracy so i'd go with the other posts here
 

Teggy

I like to shoot things...
Sep 8, 2007
13
0
0
34
Sydney, Australia
thats some heavy reading...

i understand what you guys are trying to say then, about efficiency

accuracy and range wise they would be all about the same right? as long as paint to bore match was good?
 

Teggy

I like to shoot things...
Sep 8, 2007
13
0
0
34
Sydney, Australia
actually, just of out curiosity then

these barrels are taking the Australian market by storm



they only have 1 inch backs, but theres about 8 inches of un ported barrel

so would that mean they would have the same efficiency of a redz pepper stick with 8 inch backs?

and if so what would the accuracy difference be like then, factoring out the air efficiency, and paint to bore match, only taking into account how long the actual back is?

they are carbon fiber by the way, if that makes a difference

and apparently they say that any barrel cleaner can be used, even the fluffy barrel swabs and stuff
 

russyj

Leeds Uni Paintball Soc
Jul 22, 2007
130
0
26
www.luupbs.co.uk
Backs do make a difference, you need 8 inches to do the job properly and the same is true for barrels!

That was discovered by Tom Kaye of Automags fame and I trust his judgement.

After that length you are slowing the ball down again.
Right, 2 points to make here, which are really musings rather than statements/arguments, as my mate got me thinking about this kinda quesiton the other day...

1) Tom Kaye, brilliant man that he is, and a favorite of mine for having stuck his tongue in an x-mag to show how good the lvl10 was, did his research when balls were propelled with quite high pressure. Now I'm not sure I can justify what i'm about to say, but it makes sense in my mind - to fire a paintball at lower pressure, you need greater volume, and to my thinking a longer barrel back to what kaye proposed would be better for a high-volume low pressure firing method (angel ones and other ridiculously low (firing) pressure markers), as the high volume of gas would reduce in pressure less over X distance than a high pressure low volume burst, meaning it propels the ball for longer before loosing its "push". Think of it as a punch and a shove - punch is hard with low contact time, and a shove is not as hard but with longer contact time, both will knock you over (dont "knock" the analogy, I know its bad, but I'm tired). I'm sure the brains of the forum might lend some help as to whether i'm right or not, however I'm confident in saying a high-pressure low volume burst lends itself to a different sized back than a low pressure high volume burst. How much difference this would make I could not tell you.

I'd also like to note to all the disbeleivers of Tom Kaye that he did his work empirically i.e. he made up a load of barrels and tested different lengths himself. In this way I'd beleive anything he says more than any theory I or anyone else can come up with without testing.

2) Chatting to a mate the other day, it occured to me the field of paintball aerodynamics is seriously under-studyed. Sure, people have tested different barrels, but I havent heard of many computer models or flight dynamics simulations of paintballs. Which lead me to these musings (after a few bottles of heineken admittedly):

If you look at the fluids of paintballs, you can see two types - the thin watery paint and the thick tourny stuff. I was thinking about how paintballs spun and what the liquid inside would do. My thoughts were that the more viscous the liquid, the more it would "cling" to the inside of the shell, and tend towards an even coating of the inside of the shell under high speed rotation, leading to a more stable flight path. I'm not quite sure what kind of speed of spin you'd need, I'm sure it could be calculated but I'd need all kinds of numbers, otherwise it would just be a guess.

A thin liquid on the other hand would exhibit less skin tension between it and the paintball walls, and would thus tend to collect in the bottom until a VERY high spinning speed, at which point it would spread evenly over the internal surface.

I'm still not sure which I would expect to give a better flight trajectory. I'm thinking the thicker fill, as the fluid would react less erratically to movement (think a glass of water versus a mug of thick soup), but I still cant decide.

Before anyone points it out, I've done this with the knowledge that there is always a very small amount of air in a paintball. Even if you ignore this however, the internal fluid dynamics would lead to the same conclusions.

Anyway, thats one to ponder, but I am leaning towards the thinking that the fill of a paintball might actually make more of a difference to its flight trajectory than the skin, and possibly the size of the seams - big seams are often found in cheap paint, which has thin fills. Its rare to find a thick fill in a bad seam (unless its a bad batch) or the other way around, leading me to beleive my theory isnt one that has/can be readily tested... werd...
 

Skeet

Platinum Member
Right, 2 points to make here, which are really musings rather than statements/arguments, as my mate got me thinking about this kinda quesiton the other day...

1) Tom Kaye, brilliant man that he is, and a favorite of mine for having stuck his tongue in an x-mag to show how good the lvl10 was, did his research when balls were propelled with quite high pressure. Now I'm not sure I can justify what i'm about to say, but it makes sense in my mind - to fire a paintball at lower pressure, you need greater volume, and to my thinking a longer barrel back to what kaye proposed would be better for a high-volume low pressure firing method (angel ones and other ridiculously low (firing) pressure markers), as the high volume of gas would reduce in pressure less over X distance than a high pressure low volume burst, meaning it propels the ball for longer before loosing its "push". Think of it as a punch and a shove - punch is hard with low contact time, and a shove is not as hard but with longer contact time, both will knock you over (dont "knock" the analogy, I know its bad, but I'm tired). I'm sure the brains of the forum might lend some help as to whether i'm right or not, however I'm confident in saying a high-pressure low volume burst lends itself to a different sized back than a low pressure high volume burst. How much difference this would make I could not tell you.

I'd also like to note to all the disbeleivers of Tom Kaye that he did his work empirically i.e. he made up a load of barrels and tested different lengths himself. In this way I'd beleive anything he says more than any theory I or anyone else can come up with without testing.

2) Chatting to a mate the other day, it occured to me the field of paintball aerodynamics is seriously under-studyed. Sure, people have tested different barrels, but I havent heard of many computer models or flight dynamics simulations of paintballs. Which lead me to these musings (after a few bottles of heineken admittedly):

If you look at the fluids of paintballs, you can see two types - the thin watery paint and the thick tourny stuff. I was thinking about how paintballs spun and what the liquid inside would do. My thoughts were that the more viscous the liquid, the more it would "cling" to the inside of the shell, and tend towards an even coating of the inside of the shell under high speed rotation, leading to a more stable flight path. I'm not quite sure what kind of speed of spin you'd need, I'm sure it could be calculated but I'd need all kinds of numbers, otherwise it would just be a guess.

A thin liquid on the other hand would exhibit less skin tension between it and the paintball walls, and would thus tend to collect in the bottom until a VERY high spinning speed, at which point it would spread evenly over the internal surface.

I'm still not sure which I would expect to give a better flight trajectory. I'm thinking the thicker fill, as the fluid would react less erratically to movement (think a glass of water versus a mug of thick soup), but I still cant decide.

Before anyone points it out, I've done this with the knowledge that there is always a very small amount of air in a paintball. Even if you ignore this however, the internal fluid dynamics would lead to the same conclusions.

Anyway, thats one to ponder, but I am leaning towards the thinking that the fill of a paintball might actually make more of a difference to its flight trajectory than the skin, and possibly the size of the seams - big seams are often found in cheap paint, which has thin fills. Its rare to find a thick fill in a bad seam (unless its a bad batch) or the other way around, leading me to beleive my theory isnt one that has/can be readily tested... werd...
1. Air pressure behind the ball is what causes this acceleration to happen. This pressure varies between the different guns but is generally between 50 to 125 pounds per square inch at its peak. The air pressure peaks right when the ball starts moving down the barrel, after that, the ball moving down the barrel creates a bigger chamber so the pressure drops. This is why low pressure guns are a myth, in reality all guns shoot at considerably lower pressure than 200 psi.

If you reduce the distance over which the air has chance to accelerate the ball, you will require higher pressure, so reducing efficiency and increasing the risk of ball breakages:D

2. http://www.automags.org/resource/tech/tomstech/03_spinning.shtml

It's not really Aerodynamics as such, as in Aircraft or car drag coefficients. Though clearly, a balls aerodynamics is a factor.
When you are talking about projectiles, like paintballs and bullets its Ballistics, trajectories and Ballistic Coefficient's etc. I know a bit about Ballistics;)

The Ballistic Coefficient of any projectile, is a representation of it's aerodynamics, weight and shape...sort of.

I think it was John Sosta who put his tongue in the breech of an LX!