High Speed Video Footage - Pure Barrel Breaks

[Jack Wood]

http://www.youtube.com/watch?v=QS1XgVYIu1k

After a discussion in Punkworks, I dug up some footage of what I had previously called Pure Barrel Breaks. The breaks occur in the barrel, the ball is not fractured prior to launch.

However, I am reluctant to say that the ball is breaking purely down to the pressure behind the ball. Obviously that is a compnent part, but I am hoping that you can see there is another influence in these clips.

Jack

[Shane-O]

Very nice footage. How well did the paint fit in the barrel? Looks to me like it was an overbore situation and the ball struck the top of the barrel and broke. All the breaks were from the top of the ball.

[JackandBlood]

well without busting out the fluid mechanics book. Just looking at it ol' Newton's 2nd law. It appears the resultant forces are what's causing the breakage. If Fx is from the marker and -Fy is gravity then -Fx and Fy are causing the breakage. If the barerl is over-bore, or even matched bore, I still think Fy is not the normal force from the bottom of the barrel but instead is a pressure differential. So in this footage it looks like lift and a slight airfoil type effect is occuring. I guess this is the part where density of the pressurized fluid and density of air at ATM comes into play which is Bernoulli's eqn, which I am not looking for the book for =D. I'll have to ponder this some more.

[JackandBlood]

Eh I'll keep throwing out notions until i get an affirmative from Jack =). As the breaks seem to occur consistently at the portion of the barrel just after the threads, I'll go with mis-alignment of breech to barrel. If that were the case then the problem is an inherent disadvantage in the standard way in which paintball barrels attachment markers, via threading. Something we'll have to live with.

[JackandBlood]

Comeon am I getting warmer or what? Does this test show an advantage in older style breech-as-part-of-barrel configurations? I hesitate to say its an overbore problem because well, PE stock shaft barrels have been 0.693 forever and only recently 0.689 - still a huge overbore on many paints. I like to think that PE is above the practice of knowing a problem yet supplying stock parts that don't address the problem to further sell "upgrades". That is pretty much the only reason why I am contemplating alternatives to overbore as the cause.

[JackandBlood]

ok 5th (or whatever attempt) the breaks coincide precisely with the bolt at it's limit of its forward cycle. That would be when the bolt inlet and body outlet achieve 100% interface. Endorses the SLS notion of changeable bolt inserts or the venturi inserts in some bolts.

[JackandBlood]

6ths or whatever try. The opposite of the above notion. break happens as the bolt just barely begins it's rearward travel. Bolt face o-rings break seal at that point, back-pressure from newly opened passage (the feedneck). change in pressure contours as the bolt seal is broken causes the break. Maybe endorses longer dwell. Score?

throw me a bone

[JackandBlood]

fine it was the evil monkey. http://mimg.ugo.com/200901/22093/evil-monkey-in-closet.jpg