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UV Halo View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote UV Halo Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2005 at 11:42pm
Hey Bruce, I don't think it's a matter of semantics because in every reference I have provided, the acceleration provided by backspin is in the vertical direction, in direct opposition to gravity.  If the acceleration was great enough, the ball would overcome gravity (at least momentarily) and rise. 

  However, with a flatline, most of the time, the balls only fly level for awhile, and then begin to drop.  This is because as the balls fly forward, the spin decreases, therefore the lift decreases, and the effects of gravity begin to take hold.

 If the acceleration were in the forward direction (which is contrary to every reference I have provided), then the ball would certainly hit harder.  Even the graphic on the nasa page I linked to shows that the force generated by backspin is in the up direction.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Clark Kent Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2005 at 11:56pm
There doesn't need to be actual forward acceleration for a FL ball to "hit harder" - there simply needs to be less negative acceleration, which would have to be due to decreased air resistance.  The question therefore is a very specific one.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote UV Halo Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 12:18am
True but, never has anyone, pointed out a reference that says a backspinning ball has less air resistance.  The only context of a ball somehow gaining lowered resistance in it's flight by it's design or path, is a golf ball, and specifically, it's the dimples on the ball that allow for this.

  Additionally, don't you think that backspin would be a concern for the ASTM, Tippmann, or even the goggle manufacturers, if the paintballs somehow hit harder?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Monk Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 8:29am
http://www.warpig.com/paintball/technical/zbody/index.shtml

Bam, even from a paintball related website.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KillerOne Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 9:28am
Originally posted by UV Halo UV Halo wrote:

Originally posted by KillerOne KillerOne wrote:

    HALO want everyone to assume he's an engineer - that e-mail is from NASA and We can All talk to the CDC too if you like - either way - This is all for fun and at the end of they day I've seen my flatline and the flatline of my buddys at work - it hits harder and goes farther.

I've been reading more of your posts - and wrote that if you dropped a paintball and then fired one at the same time from the same distance they would both hit the ground at the same time - thats about as good as the other stuff you have posted -

"Gravity accelerates all objects downwards at a rate of 9.8m/s  So, if you dropped and fired a paintball from 4.9m up, they would both hit the ground at the same time, of 1 sec (not accounting for drag)."

                    & ;nbs p;    --- UV HALO, TIPPMANN FORUM, MARKER GALLERY.



First off KillerOne, I never said I was an engineer.  I found and linked refereces, which to date, you have not provided.  Sorry but, the homepage of a NASA research center is not the same as the link to the page on the NASA website that describes the phenomena.  You seem to be intent on passing yourself off as a Marine with a B.S. in physics.  You even explicitly said so in the marker gallery:

Originally posted by KillerOne KillerOne wrote:



You talk from ZERO intel.  First. I am a marine. Second. I have a BS. in physics. 

This is Fun.
 


Second, do you doubt that the following equation is true:
Distance traveled = 1/2 (acceleration * time * time)

If you had a B.S. in physics you would certainly remember that.  I certainly remembered it from my Physics 100 level class.  Oh, and just to make sure I got my bases covered, the formula is on pg 23 of the Conceptual Physical Science, Second Edition, Hewitt, Suchocki, Hewitt.

Therefore, 4.9m = 1/2 (9.8 *1*1).

Third, do you doubt that if you drop, or fire an object horizontally, it accelerates downward at a rate of 9.8m/s in the absence of an atmosphere, (unless you give it some lifting force)?
This is illustrated and explained in section 4.4 Projectile Motion on pgs 86-87 of the above referenced publication.  Here is a question and answer from pg 87.
Q: "At the instant a horizontally held rifle is fired over a level range, a bullet held at the side of the rifle is released and dropped to the ground.  Which bullet, the fired downrange, or the one dropped from rest, strikes the ground first?

A: "Both bullets fall the same vertical distance with the same acceleration g due to gravity and therefore strike the ground at the same time."

This was also found
here (an EDU site for you):
" A dropped bullet will hit the ground before one which is fired from a gun.
As shown in the illustration of a horizontal launch, gravity acts the same way on both bullets, giving them the same downward acceleration and making them strike the ground at the same time if the bullet is fired horizontally over level ground
."

  So now we are fireing a round horizontally and dropping one from same height at the same time  - in that case, point taken. Though you didn't say anything about a horizontal variable the first time you posted.  Now you are good - I guess it is a matter of semantics. 

 



Edited by KillerOne
US MARINES: Breeding Killers since 1775.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Clark Kent Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 10:27am

Originally posted by Monk Monk wrote:

http://www.warpig.com/paintball/technical/zbody/index.shtml

Bam, even from a paintball related website.

Most of the article isn't that helpful (a discussion of the old Z-Body), but it does have this sentence tucked away in the middle:

Originally posted by WARPIG WARPIG wrote:

One consequence of moving the low pressure out from the center behind the ball is that the pressure difference between the front and back is decreased, so the ball will not decelerate as quickly from drag.

Unfortunately, no reasoning or explanation is provided - just another claim/statement.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote UV Halo Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 10:51am
Thanks for the reference Monk!!

Unfortunately, it's like Clark says, just another claim.

I say this because there is literature that states a smooth spinning ball actually exhibits a reverse magnus effect. Let me give you a quote:

"This reverse Magnus effect has never been observed for a baseball, however experiments with smooth balls have exhibited transverse deflections in the opposite direction. The drag coefficient of a smooth ball falls off sharply as it crosses into the turbulence regime, enabling this to occur."

This was pulled from section 3.3 The Reverse Magnus Effect. You can read this yourself,
here.     
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce A. Frank Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 11:13am

Originally posted by UV Halo UV Halo wrote:

True but, never has anyone, pointed out a reference that says a backspinning ball has less air resistance.  The only context of a ball somehow gaining lowered resistance in it's flight by it's design or path, is a golf ball, and specifically, it's the dimples on the ball that allow for this.

  Additionally, don't you think that backspin would be a concern for the ASTM, Tippmann, or even the goggle manufacturers, if the paintballs somehow hit harder?

Take a look at the article for which Monk provided a link:

http://www.warpig.com/paintball/technical/zbody/index.shtml

Though the purpose of the article is to review the GS Z-Body, it prefaces the review with a fairly decent condensation of what happens to drag when a ball is spun.

Even this article does not give a quantitative analysis of velocity retained, but is reinforces my earlier postulation on the effects of reduced aerodynamic drag of a spinning ball.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Snake6 Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 11:44am
this is so funny watching yall argue about this, but it beats the OMG 1m a 1337 5n1p3r threads.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote UV Halo Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 2:49pm
Bruce,
It looks like I posted quicker than you did, if you notice my post above.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote A5 dude15 Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 4:54pm
this is pointless...everytime someone says something or presents any facts that benefits their argument the other side is too stubborn to just except that the other side made a good point.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce A. Frank Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 6:29pm

Originally posted by A5 dude15 A5 dude15 wrote:

this is pointless...everytime someone says something or presents any facts that benefits their argument the other side is too stubborn to just except that the other side made a good point.

It isn't pointless. It is not an argument with a winner and a looser. It is a discussion with presentation of facts and thesis on what may or may not be happening in the physics of the flight of a ball. It is a learning process with comments that enlighten some and spark others to do more research. Beats the heck out of the same old, "i ghot sum muny, wat shood i by?"

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sargent Duck Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 6:38pm
Originally posted by A5 dude15 A5 dude15 wrote:

this is pointless...everytime someone says something or presents any facts that benefits their argument the other side is too stubborn to just except that the other side made a good point.


I'm actually througly enjoying this. I was orginally going to be an engineer, but switched programs 3 years ago. This is bring back momories, and making me think about physics again, which I really enjoyed (of course, I do keep up-to-date with the string theory). This is actually one of the very few "enlightning" topics on this board, seeing as how the rest are "what barrel should I buy?", or arguing about snipers.
Ref: I want a nice clean game
player: but it's paintball!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Clark Kent Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 6:54pm
Ok, so I fired off some emails to some friends who are actual rocket scientists.  Maybe they can enlighten us.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote UV Halo Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 7:35pm
Thank all of you who have provided meaningful input to this discussion!!

I agree, that this is not a debate.   It is a discussion of the physics behind what we are experiencing in one of our favorite games.

I also feel that it's very important to reference what we find because it's always possible that the poster misconstrues an important part of the assertion.

Based on everything I've read, I think the truth of whether a spinning ball having less air resistance is dependent on how 'un-smooth' a sphere has to be before it gets the benefit of the magnus effect (in the forward direction).  Because, if a paintball is smooth enough, it get's the reverse magnus effect.

I think we can all agree that most of the surface area of a paintball is pretty smooth.  Smooth enough?  I dunno but, I lean towards saying yes.  That being said, what is the exception?  The seam.  Now, how big does the seam need to be to disrupt the lamniar flow around the paintball?   Evil has a pretty small seam, while from what I've seen, Team Colors has a ridiculous seam 'belt' that really keeps the paintball from being a true sphere (it's more like a very short, cylinder with spherical end-caps).  Even worse, we can't control the orientation of the seam relative to the direction of flight.  So, even if the seam is big enough to generate a laminar flow, it may not be disturbing the air in the proper manner to disrupt the laminar flow, or, it may disturb it in an odd axis, relative to the flight of the ball.  So, if all this is true, you may have one longer range shot (or one that hits harder should that flight be interupted), your next shot may be shorter (or hitting softer should it be interupted).

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Monk Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 7:43pm
Quote We resort again to thinking about a stationary (but spinning) ball in a moving stream of air with speed V. Looking at it from above the north pole, the side of the ball against the air stream will slow the air down on that side of the ball while the air on the opposite side of the ball will slow down much less (since that side of the ball is moving in the same direction). There will now be a difference in the Bernoulli effect on the two sides of the ball: more pressure on the side of the ball moving against the air stream and less on the side moving with the airstream. This pressure difference will cause a net sideways force on the ball perpendicular to the airflow and the spin axis. [Under some circumstances (a rotating smooth ball moving at relatively high speed) one can also observe a reverse Magnus effect. This is produced by a reduction in the pressure on the side of the ball turning toward the flow that is caused by increased turbulence on that side at high speed. A similar effect reduces the drag coefficient for smooth balls at high speed.]


http://carini.physics.indiana.edu/E105/spinning-balls.html

Its not very clear an definate though.

What I get out of this, there is a distance that the ball will be going at a high speed. During this high speed there is less drag then a ball not spinning at the same speed.

However, the spinning, at lower speeds will cause slightly more drag.

So the spinning ball will fly further than the stationary ball during the time of high speed. But it will hit a threash hold where the drag will take it down.

Lets say two balls are starting out at 300fps   
Drag on the nonspinning ball is 1/2 the total feet per second everysecond
Drag on the spinning ball is 1/4 the total feet per second every second until the ball gets less than 200fps, then the drag is lets say 2/3 the total feet per second.

The balls both hit the ground at 20fps.

I find that Both hit the ground at about 4 second. The ball with no spin come in at about 450 feet and the spinning at 640 feet.

In order for that to happen the spinning ball must be traveling faster during that first 400ish feet, and with speed comes force.

Your opponent is only 400-500 feet away. Its going to hit alot harder than that of a nonspinning ball.

Obvoisly the drag coefficients are not real life but they do show the principal.



Edited by Monk
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Clark Kent Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 11:25pm

I read the article you linked, and didn't see the points made that you describe (granted I read it pretty fast).  Can you point to a section?

(And, BTW, UV, I believe the Reverse Magnus Effect means that the ball curves the other way - not that it slows down less)

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Monk Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 11:34pm
I quoted the part about the drag.

But in order to understand it, you kinda have to read the whole thing.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Clark Kent Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2005 at 11:49pm

Ah, the last sentence.  Yes, the reverse Magnus does imply that under some conditions "regular" drag could be reduced for some projectiles.  That is interesting and helpful.  Although more details (including some type of quantitative scale) would have been nice...

But does that also mean that, since we do NOT see the reverse Magnus with paintballs (either due to conditions or nature of the ball), that this drag-reduction will not be seen with paintballs?

Hmm.

 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lightningbolt Quote  Post ReplyReply Direct Link To This Post Posted: 13 October 2005 at 8:21am

I tossed out some golf ball theory a couple of years back.  Mainly my top-spin theory in windy conditions. 

Still looking for feedback on the Apex in dive bomb mode in windy conditions.

I may try this while doing yard work this weekend-

-Take a sphere of some type and drill a hole thru the center of it

-run a long rubber band or string thru the hole and attach the string/band to 2 stakes which are driven into the ground making the string/ band tight.

-charge up the air compressor and blow air over the ball while it is both static and with the string wound up making the ball spin and take some pics.

The only thing is that i need something to make the air flow visible.

Any suggestions?

anyone else is welcome to try this too.

 

 



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