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Old 06-27-2008, 08:52 PM   #21 (permalink)
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Pro-Team Products Bolt:



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Old 06-27-2008, 09:00 PM   #22 (permalink)
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do you think it works?
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Old 06-27-2008, 09:02 PM   #23 (permalink)
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seems too.....could be the placebo effect.
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Old 06-27-2008, 10:26 PM   #24 (permalink)
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I have a hard time seeing how that routes air to the bottom of the ball - the bolt that CP and I used was only open below the mid-line...

I would gladly put one up against an open face and a venturi if I happened to have one in my possession....
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Old 06-27-2008, 10:49 PM   #25 (permalink)
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i'll get you a pic of a Cooper-T bolt when my battery charges.
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Old 06-27-2008, 10:54 PM   #26 (permalink)
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This isnt the best picture, but you can just barely seen the channel that ran down the base of the bolt:
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Old 06-27-2008, 11:16 PM   #27 (permalink)
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HP, watch the intro video with the free body diagrams.

our results showed exactly what i had been thinking all along, that the instantaneous impulse from the "low blow" on the bolt will not produce enough spin, so that when the ball leaves the barrel it has enough spin to cause any effect.

the only time the bolt is subjected to a moment (rotational force) is the INSTANT the ball is against the bolt. the INSTANT the ball leaves the face of the bolt, the pressure inside the chamber will more or less stabilize. yes, there will be a transient performance of the pressure equalizing, but our tests showed no effect, so we can more or less assume that is the case.

if you can somehow name a force acting on the ball long enough, and strong enough to get a nearly flatline magnitude spin from the ball, be my guest. i can't find one.

if you have qualms with our test HP, do you own. or ship us a backspin bolt and well test it on cam for you. otherwise, Re has nothing to do with spin in the first place ... its a measure of how choatic the streamlines are and how much energy is lost to viscus effects. only forces would impart a moment (which is spin), and Re has nothing to do with force, it has to do with energy.

for the record - the venturi bolts tested were cupped, and yes, nearly half the ball was cupped into the one we used.

also, no flow, at any point in a paintball guns is laminar. none ... zero, nothing. to fast, though to small a passage.

Last edited by Cockerpunk; 06-27-2008 at 11:23 PM.
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Old 06-28-2008, 02:18 AM   #28 (permalink)
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Quote:
Originally Posted by cockerpunk View Post
HP, watch the intro video with the free body diagrams.

our results showed exactly what i had been thinking all along, that the instantaneous impulse from the "low blow" on the bolt will not produce enough spin, so that when the ball leaves the barrel it has enough spin to cause any effect.

the only time the bolt is subjected to a moment (rotational force) is the INSTANT the ball is against the bolt. the INSTANT the ball leaves the face of the bolt, the pressure inside the chamber will more or less stabilize. yes, there will be a transient performance of the pressure equalizing, but our tests showed no effect, so we can more or less assume that is the case.
It is possible that that moment is the critical issue. In effect, I'm thinking that if it is ever successful, the spin may be caused by basically the same mechanism as the flatline effect ... the ball rolling along the top of the barrel. HP cited the need for an oversize barrel, so basically the point of contact must be reduced in order to bias the spin. The moment at firing could drive the ball to the top of the tube, though i am not sure what forces would keep the ball there as it travels down the barrel.

I'm thinking the longer the barrel, the more the forces acting on the ball would tend to equalize out, so perhaps a very short barrel would produce the most marked effects?

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also, no flow, at any point in a paintball guns is laminar. none ... zero, nothing. to fast, though to small a passage.
Wouldn't this only be possible if the guns were constantly in a high-pressure, high-flow state? Wouldn't there be be *some* laminar flow at *some* point? Whether it affects the ball is of course another question.
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Old 06-28-2008, 03:41 AM   #29 (permalink)
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First off, good job. Nice to see some effort being put in, but a couple of points that bug me:

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HP, watch the intro video with the free body diagrams.

our results showed exactly what i had been thinking all along, that the instantaneous impulse from the "low blow" on the bolt will not produce enough spin, so that when the ball leaves the barrel it has enough spin to cause any effect.

the only time the bolt is subjected to a moment (rotational force) is the INSTANT the ball is against the bolt. the INSTANT the ball leaves the face of the bolt, the pressure inside the chamber will more or less stabilize. yes, there will be a transient performance of the pressure equalizing, but our tests showed no effect, so we can more or less assume that is the case.

if you can somehow name a force acting on the ball long enough, and strong enough to get a nearly flatline magnitude spin from the ball, be my guest. i can't find one.
You have absolutely no way of predicting the magnitude of the instantaneous acceleration of the paintball in that first instant. I think your theory is fine, but it's just that, a theory. Wouldn't the paintball see the greatest magnitude of acceleration in that initial instant? Might that not have a greater affect than you think?

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if you have qualms with our test HP, do you own. or ship us a backspin bolt and well test it on cam for you.
You can't make claims and expect people not to critic and comment on them. In this test, you essentially made a half-assed backspin bolt and then applied the results to all backspin bolts. It does seem sketchy.
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Old 06-28-2008, 08:46 AM   #30 (permalink)
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Quote:
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if you have qualms with our test HP, do you own. or ship us a backspin bolt and well test it on cam for you. otherwise, .
The test was flawed. That is what I was pointing out. I was very specific in pointing out where the error in the logic was. Did you miss the discussion on laminar flow, and turbulence?

The CooperT bolts were well documented to work, producing the same trajectory as the Flatline. It was not some voodoo science.

The complaint for the CooperT bolts was that the barrel had to be overbored. Meaning, if your paint was .688, your barrel would need to be .698.
Those barrels did not exist "off the shelf" so you had to have them overbored for you in order for the effect to work.

I took an alternate approach. I found a good .694 barrel that was overbore, but not enough. Instead of a flat trajectory, it was making corkscrews. Clearly the added friction was effecting the spin axis.


So I started cutting it shorter, and shorter. At a certain point, the corkscrews stopped, and the trajectory flattened out:


Like drg pointed out, with the CooperT bolts, barrels have the opposite effect as the Flatline. The Flatline barrel increases the spin, while the barrel used with the CooperT bolt slows it down. Thus, needs to be way overbored, or extremely short. Neither method was popular with people who liked there overpriced barrels.

SO I have no need to "Do my own test", as I've been doing them for the last 20 years. There are also some people who think the Flatline is also fake as well. But, it seems you do acknowledge the Flatline does work?

The test was well done, but based on a false premise. If your happy with that, then who cares? But just don't called the "Backspin Bolt" a myth, or busted in any form until you do a proper test.
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