Flatline Theories...

Lightningbolt wrote: Clark, What's your take on top-spin while shooting in windy condition's? Specifically shooting stright into the wind. Increased distance over a ball without spin? Better retained velocity down range over a  ball without spin? Any thought's?

First, shooting into a head wind will do two things, slow the forward velocity and the interaction of the lift and the headwind will cause the ball to rise rather than maintain a more flat trajectory.

Similar the the phenomenon of shortened takeoff distance in a head wind or the need to trim more nose down as you increase the speed in an aircraft. Higher relative speed of a lifting body caused greater lift. 

Edited by Bruce A. Frank

LordJovian wrote: Have no proof?!?! Haven't you read any of these posts?!

The question about proof is not about the mechanism that generates lift and the resultant flater trajectory. It is whether the back-spin of the smooth surface of the paintball actually creates reduced drag allowing the ball to retain greater terminal velocity. (as in "hits harder")

Though the references linked through this topic suggest that such retained velocity is possible, there is nothing that clearly states that forward velocity has a lower delta for the smooth back-spinning ball than it is for the non-spinning ball. So far no one seems to be able to put a definitive conclusion on that part of the question. Consenses is that empirical data is required.

LordJovian wrote: The ball is spinning backwards, creating lift.

True.

In order for the ball to fall to the ground, it must lose its velocity traveling paralell to gravity.

Not true.  Even if the ball maintained perfect horizontal velocity, the rotation would gradually slow/stop due to friction, at which point gravity would overcome the spin-induced lift.  It's the old cannon-ball drop.

Lift allows the ball to "cut" through the air better. Instead of the ball standing still and basically "slamming" into a wall of air, it's spinning like a drill and "swimming" through.

Not true.  Lift has nothing to do with "cutting" through the air - it has to do with the Berboulli-derived Magnus effect, which used friction to change the orientation of the back pressure on the ball, causing a change in direction.  Entirely different.

And a spinning ball does not "drill" through the air.  If anything, the spinning ADDS friction, made the air more of a wall.  The way that rotation adds velocity retention is by reducing back pressure with rotation-induced turbulence.  Entirely different.

This is evidenced, for instance, by the simple aerodynamic fact that a rough rotating sphere retains velocity BETTER than a smooth sphere - witness a golf ball.  The rough surface creates MORE friction, which is a hindrance, but it also creates more turbulence, which is a benefit.  With the correct balance between Reynolds number, rotational velocity, and travel velocity, the dimples on a golf ball help it retain velocity better, despite the increase friction.

You don't need any complex equations to realize this- logic is a beautiful thing. How, HOW, do you explain the increased range?

The increased range is easily attributable to the Magnus effect, which causes lift on a backspinning sphere.  If there is a velocity effect as well (unclear), then such velocity effect has nothing to do with "drilling" - rather the opposite.  In fact, a Flatline user could probably increase range significantly by roughing up his balls a bit, or using specially made dimpled balls.

Instead of throwing mud about drag, why don't one of you explain how it works, or how it doesn't really work at all.

I think drag has been thoroughly dissected in a couple of posts by now.

LordJovian wrote: You're arguing about how a swallow could or could not carry a coconut.

Is that an African or European swallow?   (Sorry, couldn't resist.)

Edit:  On a more serious note; if I understand the major arguments here, then the questions have already been answered in the following link.

This site, and other pages on it, have been referred to before, but after reading it all the way through, I realized it answers the two major questions being asked here.  To try to keep things relatively straight, I will emphasize sections of quoted text in red print and any personal observations specific to the quoted sections in green print.  Now, on to the questions!

1. Does the paintball gain speed from the backspin after leaving the flatline barrel?

• No.  "Unless acted upon by some external force (push) an object will not change its speed or direction. We already know from experience that paintballs do all sorts of strange things in the air. They drop; they curve. So they must be acted on by other than forces imparted to it by the marker when in the barrel. However, none of these forces will act to increase the speed of the ball in the direction of motion once it leaves the marker. In other words, the paintball is not going to magically pick up speed once it leaves the marker. I know I keep repeating this, but for some reason this is usually where many people seem to go wrong in their thinking."
  

2. Does the paintball from the flatline maintain speed longer once fired?

• Yes, but this could be argued.  For the sake of fairness, I will quote all of the relevant sections and explain the conclusion I reached based on the data presented. 
  
• First, a laymans definition of the Reynolds number which I found here. "The Reynolds Number is important in analyzing any type of flow when there is substantial velocity gradient -  shear. The Reynolds Number indicates the relative significance of the viscous effect compared to the inertia effect. The Reynolds number is proportional to inertial force divided by viscous force."  The site goes on to list the five factors in the equation as characteristic length, velocity, density, dynamic (absolute) viscosity, and massvelocity.  Note that actual spin (rpm) is not included anywhere in the calculation. 
  
• Now, the information from the paintball physics site: " Lets take a closer look at one of the curves; the smooth sphere data by Achenbach is of particular interest to us. The adjacent graph shows just this data and defines some of the terms used to describe the Reynolds number regions. At the critical Reynold number, the drag on the sphere suddenly drops by nearly a factor of five. Referring back to the drag equation, this means that a ball above the critical region will have reduced drag and fly further. Of course, once the velocity drops below the critical Reynolds number, as we will see it must, then the ball will slow down very rapidly, appearing to drop very fast (relative to the horizontal distance traveled)."  Note, that this is exactly what paintballs fired from a flatline appear to do.

  "So where does a paintball fit into this scheme. The Reynolds number of a typical paintball with a velocity of 280 ft/sec is around 9.4 x 10⁴. From the curve, we can see that this clearly falls into the subcritical region. As far as drag force is concerned (and perfectly spherical paintballs), there is no free lunch for well formed paintballs."  Note, that this appears to directly contradict my previous observation.

• First, let me say that I believe at least part of the reason that shots from a flatline seem to hit harder than shots fired from a normal barrel is psychological.  As Bruce pointed out above, when people get hit (break or not) at ranges where they can't do the same, they tend to conclude that their opponent is firing hot.  The loudness factor of most flatlines also probably helps to create the impression of illegal velocities as well. 
  

• Second, I belive that flatlines also seem to hit harder (and have a better chance of breaking paint at longer ranges) because of the angle at which the ball strikes the target.  Remember that the flat trajectory allows for direct hits at ranges where most markers can only get glancing blows due to the arc of the round.  The paintball physics site touched on this subject here while referring to paintball-drop testing.  "It would appear that most paintballs will break at distances somewhere between 6 feet and 10 feet. What are the speeds associated with these heights? Well the trajectory program won't allow a zero velocity, but if we make the number very small and use an angle of 0 degrees, we can obtain the speeds that the paintball will reach just as it hits the ground. From 4 ft, 15.8 ft/s; 6 ft, 19.3 ft/s, 8ft, 22.1 ft/s; 10 ft, 24.6 ft/s. So the speeds are not very high. Remember, we calculated that even a maximum trajectory would have a speed of 60 ft/s as it hit the ground. However, a big factor here is the type of surface it is hitting.

  The above ball breakage data would appear to conflict with a comment in another study - the "Lapco Barrel Challenge" by Richard Allen on barrels. This study was concerned with trying to answer what is the best barrel. In the document, it was mentioned that some balls were bouncing off a plywood target at 150'. I calculated the speed that the balls should have at this distance and found it to be around 110 ft/s. This is quite a bit different than the ~24 ft/s found in the previous results. The difference between hitting a plywood surface and a concrete floor should be only slight, so it is not clear why the large difference. One possibility is that in this study the balls were hitting the target at a glancing angle rather than perpendicular to the surface as in the drop tests."

• Now for the controversial part.  I concluded that paintballs from a flatline hit harder than those fired from a regular barrel because they do actually lose speed slower than the shots from the regular barrel.  I base this on the following:
• Drag slows down objects that are moving on inertia only.  This is a given.
• The data above shows that at a critical Reynolds number, drag on a smooth object is reduced by nearly a factor of five.
• The data above also indicates that paintballs do not move fast enough to achieve the critical Reynolds number.
• However, the data also describes perfectly what happens when an object slows below that number; it appears to "slow down very rapidly", which is exactly what happens with paintballs fired from a flatline barrel.
• I can only conclude that a part of the equation is missing (as I pointed out, the Reynolds equation does not take spin into account) and that if the missing part was included, the Reynolds number would change to match the observed behavior of the shots.
  

Edited by Mack

KillerOne wrote: KillerOne is back again I had to go work for awhile -  at any rate I've been catching up on what�s been going on and I'm glad to see that HALO finally read the NASA page - I'm sure glad that it helped you out there buddy boy - So far we got back spin = reduced drag, and lift.   Thus farther shots right - So have we agreed that because its goes Farther it also Hits harder or are we still working on that one?    This is taking along time to figure it out � but wouldn�t it stand to reason that if I have two barrels a Flatline like mine and a wonderful POS like UV HALO uses  ï¿½ and if both of these barrels were shooting at the same PSI/FPS � wouldn�t it stand up in court that because of the Back Spin the Flatline would go Farther and Hit harder? Understanding of course that Backspin = lift, reduced drag. What say you ?

KillerOne-  Get a clue, or are you too dumb to follow links?  I responded to your NASA bit back in the Marker Gallery section, and I even mentioned it again in the beginning of this thread.  The picture I posted above was on the NASA website (just in case you weren't paying attention again).   I always have maintained that a backspinning paintball flies farther because of the lift it generates so, don't even try to come on this board and try to act like you helped me out.

You're the one who draws the illogical conclusion that if it flies farther, it must hit harder.  Nobody else here is subscribing to that crap.

  Neither in your alleged 'email', or in any NASA pages does it say that a smooth spinning projectile gains the benefit of reduced drag.  In fact, the only reference I have seen to this is in the one Monk provided.  If anyone bothers to read the Physics calculator pages, the author references the speeds a smooth spinnning ball needs to be traveling to gain the benefit of reduced drag, and a paintball, at 280-300fps, clearly does not. 

No, just because a paintball goes farther doesn't mean it hits harder.  Why can't you seem to grasp the concept that the paintball goes farther horizontally because the backspin generated lift gives it more time to move horizontally before it hits the ground?

 For crying out loud, you said you have a bachelors in physics.  Yet most of the people here with Jr. High, High School, and even 100 level physics can grasp this concept.

Additionally, how can you even place yourself on the same playing field as myself in this discussion?  When all you have done is gave us a link to a NASA center homepage (which I used to provide further proof of the backspin generating lift for you, and the pic I included above), and give us a supposed quote that you obviously misconstrued.  All this after how many references I have provided from .edu, .gov, the internet in general, and further, an interview from the inventor of the flatline?

I for one, do not believe you have a B.S. and I find it highly unlikely that you are a marine, because a marine would not lie about having a degree, and a marine would have paid a higher attention to detail.  Further, you continue to demonstrate your probability of being an immature brat, when you can't even restrain from mud-slinging.  To even go so far as to call my gun a POS, When you've never seen it perform.  I would even go to say that it would outperform your gun, in terms of consistancy and fire rate, as I'm double regged (a Dye fixed output tank, and a palmer fatty stab), I have an E-bolt, and a Qloader.

And this test isn't being done because people have too much to do.  It's a matter of having the right equipment.  Which unless you happen to have it lying around it's very expensive (at least one, actual, old-school shooting chrony, not your radar ones).


Edited by UV Halo

KillerOne wrote: So far we got back spin = reduced drag, and lift.

No.

So far we have lift, and reduced drag UNDER SOME CIRCUMSTANCES, and INCREASED drag under other circumstances.

What we DON'T have is a precise calculation to determine which of these circumstances apply, or an empirical study to determine the actual result.

LordJovian wrote: Nobody read my post? Killerone- you're right and wrong at the same time. At closer range- yes it "hits harder" (you need to use a term that isn't so elementary). At long range- no, it doesn't hit harder. It has slowed down too much, and the lift is causing a ball that shouldn't be in the air anymore to stay in the air.

Ladies and Gentlemen we use elementary terms so that all can understand -

Bruce A Frank - I often get the same attention because of my flatline.

 

Range

Lift

Drag

All of these are relevant to the initial velocity (FPS/PSI) – so far all we have is speculation biased on formulas and theories – but none of this is relevant to a flatline or a POS because they will present their own set of variables, to say nothing of paintballs used – so what we really need is for some one to walk there happy self out-side and try this out.

Get a Chronometer – a cardboard box – a Tippmann a-5 , a flatline and then an assortment of other barrels. Fire a few rounds through each barrel at the cardboard box at different ranges. Record the results. Ie. what effect did each round have on the box, we are looking for Penetration, Denting ect... 

Then come back and let everyone see the results – I can’t be the one to test this and neither can UV HALO since we started this mess and would likely be accused of some sort of impropriety.

So someone who has nothing else to do and who will do it right get out and run some tests –  

 

Edited by KillerOne

Nobody read my post?

Killerone- you're right and wrong at the same time.

At closer range- yes it "hits harder" (you need to use a term that isn't so elementary).

At long range- no, it doesn't hit harder. It has slowed down too much, and the lift is causing a ball that shouldn't be in the air anymore to stay in the air.

oh, ok. the way i viewed was him calling him immature...which is an insult. but yes, insulting is really uncalled for, and isnt neccessary.  put down eachother with facts on the subject and by proving your point...not insults.

but in a way didnt you just insult him? im not trying to start anything or point fingers...