Author Topic: Rate of drop.  (Read 2371 times)

Offline Badboy

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Re: Rate of drop.
« Reply #30 on: July 14, 2012, 01:57:18 PM »
Doesn't everything drop at 32.2 ft/s/s?

Nope, that value is only correct if there were no resistance to cause deceleration. The actual value will depend on the drag and the mass of the ballistic object.

Badboy
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Offline Badboy

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Re: Rate of drop.
« Reply #31 on: July 14, 2012, 02:06:22 PM »

No, the weight of the projectile does not alter the drop rate. The drop rate is a constant as I explained above.

Not so, the weight does influence the deceleration and the drop rate. Generally speaking if you have two objects with the same shape and size and the same drag, the heavier one will be decelerated less than the lighter one which is partly why heavier projectiles have better ballistics than lighter ones.

Badboy
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Offline Badboy

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Re: Rate of drop.
« Reply #32 on: July 14, 2012, 02:42:40 PM »
The 647 grain round drops 32.2 feet after the second just like the 800 grain one, AS you stated...

Hi Ten60,

You have been led into some false assumptions there, the different weights do have an impact on the drop. Many people believe that things fall due to gravity at the constant rate of 32.2 ft/s/s because they assume that the acceleration will be constant because the force of gravity is constant but that is not true.

Let me explain with some simple math.

Let g = force of gravity
let m = mass of projectile
let a = acceleration of projectile

Now apply Newton's law F = ma

The force on any objectdue to gravity F = mg

So we get    mg = ma

where m cancels out and of course a=g

Thus the notion that that the acceleration is constant at g = 32.2ft/s/s

What is wrong with this is that it ignores other important forces. It isn't only gravity at work on a projectile, drag forces play an important part.

For example if we represent the force due to drag with the character d our equation for the force F becomes F = mg - d

Now when we put that into Newton's law we get      ma = mg - d

Now if we divide both sides by m to find the acceleration a we get    a = g - d/m

Now you see that the acceleration isn't just g, it is less than g by the amount d/m. So the mass, and thus the weight does play an important part in ballistics if drag is included in your thinking.

Hope that helps...

Badboy
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Offline JOACH1M

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Re: Rate of drop.
« Reply #33 on: July 14, 2012, 02:55:43 PM »
I just point and shoot where they are going to be and I kill them.
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Offline bustr

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Re: Rate of drop.
« Reply #34 on: July 14, 2012, 07:18:50 PM »
"I just point and shoot where they are going to be and I kill them."

Joachim,

Eventualy everyone figures that out. You are a "natural" air to air shooter like some are natural skeet shooters.

When you are trying to hit people at 400+ it usualy means you are having problems getting the red guys to fight you closer if they don't have freinds versus just you or a superior situational advantage. Then you go through a period of trying to become good at hitting them outside of 300 and fiddeling with convergence to maximise your rounds on target percentages. I've watched everyone in my squad go through this stage in the game over years of playing with them.

Convergence is nice, everyone finds theirs, and Ten60 looks like he's writing a great program that will augment auto level on full zoom shooting at the offline target. Past 300 it's knowing where your rounds are going to be relative to your gunsight picture, along with how much drop compensation at a given range, combined with your relative alt and atitiude, then how much lead to hold off related to G in your turn, or just shooting level at distance. Basic shooting "Dope" translated through your gunsight picture in "Mil" from a moving vehical. The K14 you set your wingspan at distance knob. Held the star on the target 1-2 seconds while the gyros moved the reticle against the G forces in your turn to compensate your hold off and atitiude. No mental calculations or lookup sheets to remember with a static reflector reticle.

Because of that ghost line in my gunsight I hit cons 600-800 becasue I have a known reference point relative to me in a 3D world and know what the dispersion blocks are at range from data collection testing. Dispersion is a bite and just gets worse at range, not your aiming. Past 300 dispersion becomes a major source of impediment to getting enough rounds on target to do the job unless they are running level away from you. You can see it in spades with the MK108 past 150 against the offline target. What is it..14ft dispersion at 200 yards for the Mk108. At least at that range the right hand spin drift is only 8 inches.

I hope Ten60 puts a sub calculation into his program for the amount of hold off of 100Mil rings at distance of a con moving left to right at different speeds for a round type's InitV. It would be a usefull tool for new players to understand why they miss so often on snap shots while just starting out in this game. They shoot way too late and either too low or too high from the atitiude they are in. I made a gunsight that corrected for alot of that. It just had too many static lines to keep track of in the heat of the moment even if I was pulling some fantasic point and click snap shots when I lined up the correct lines.

I came up with the lines after reading a K14 manual and tech description of the theory behind the function realted to zeroing the guns in the P51D for the K14 to achive a maximised shooting pattern at combat distance 200-350. Anything closer fills the screen and in theory you can't miss.

I eventualy went back to using the "Bag the Hun" book's method and a 100Mil ring with most of my conv 300ish becasue it was alot of bother remembering how to use the lines in place of the K14 gyro doing it for me.
bustr - POTW 1st Wing


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Offline nrshida

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Re: Rate of drop.
« Reply #35 on: July 15, 2012, 02:57:20 AM »
You have been led into some false assumptions there,


It was a simplification to illustrate a point. Respectfully Badboy, your model is also a simplification and does not contribute anything practically useful to learning the flight paths of our virtual bullets.


I also tried the calculation approach once, practically however I agree with Joachim and Bustr: people have the potential to develop special 'equipment' to work these things out instinctively (with careful practice).

If you really want to get a feel for shooting take up archery. I apply that experience a lot when shooting 30-mm.

Bag the Hun will help a lot with learning to lead correctly.


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Offline Ten60

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Re: Rate of drop.
« Reply #36 on: July 15, 2012, 06:38:47 AM »

It was a simplification to illustrate a point. Respectfully Badboy, your model is also a simplification and does not contribute anything practically useful to learning the flight paths of our virtual bullets.


I also tried the calculation approach once, practically however I agree with Joachim and Bustr: people have the potential to develop special 'equipment' to work these things out instinctively (with careful practice).

If you really want to get a feel for shooting take up archery. I apply that experience a lot when shooting 30-mm.

Bag the Hun will help a lot with learning to lead correctly.



I guess I'm just gonna give up.

THIS ISN'T A POST ABOUT AIMING!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I guess trying to be nice about it just hasn't worked.  I'll no longer be posting on this thread, thanks to those who helped.
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Offline RTHolmes

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Re: Rate of drop.
« Reply #37 on: July 15, 2012, 06:44:02 AM »
Now do you guys understand what I'm doing?

I do, and its why I set my jug guns staggered so I get a tunnel of bullets a few feet wide (ie. the size of the damage box for most of the crucial parts of the aircraft) which extends 150-200yd either side of the average convergence. works great, which is presumably why they set up 8-gun jugs this way during WWII :aok


edit: btw are you staggering them parallel or crossing streams? I have them parallel (ie. outer guns set furthest out.)
« Last Edit: July 15, 2012, 06:46:02 AM by RTHolmes »
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Offline Alky

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Re: Rate of drop.
« Reply #38 on: July 15, 2012, 11:33:13 AM »
  considering the 50 cal round has been made from ~650 grains up to ~800 grains.  This alters the drop rate, which was my initial question.

Hmm... how do you convert that to pixels??   :rolleyes:
George "AlkyŽ" Fisher

Offline Badboy

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Re: Rate of drop.
« Reply #39 on: July 15, 2012, 12:30:27 PM »
I guess I'm just gonna give up.

That would be a shame, because I think I can help. Just hang in there a little longer. There was a thread posted some time ago in which hitech posted enough information to reverse engineer the ballistics for at least one of the AH .50 calibre weapons. 

You originally posted:

I'm looking to see if anyone out there has the information on the specific round drop rate's that Ah uses.

What happens in AH is that the trajectory of the rounds are determined by a physics model based on the properties of each round and weapon. The model runs everytime you fire your guns and just like the flight model it calculates the position of the round in real time. It may be that at some point drop rates were used to calibrate the model, but if you want to discover the drop rates being used in AH, you don't need the drop rates that AH used to fine tune their model, all you need is ingame data. hitech was kind enough to provide sufficient information in this thread:

http://bbs.hitechcreations.com/smf/index.php/topic,309540.0.html

In that thread the following data was provided:

With the assumption that the bullet does not destabilize , I would think it would given the numbers below.

Alt                                 25k            45k
Launch Speed                 450mph     528mph
Secs to impact                65             97
Horizontal Distance          30858       55107
Plane Dist Traveled          42880       75082
Speed at impact.             444FPS     446FPS


HiTech

Using that information it is possible to calibrate a ballistics model, just like the one used in the game, in order to produce your own drop rates either graphically or in tables.

As it happens I've already done that and graph below shows the trajectory based on my model of a .50 calibre round that matches AH almost exactly, same range, time of flight and speed on impact etc.



That graph isn't helpful by itself, what would be more helpful would be a graph based on the same model, that showed the trajectory, and thus the drop over the sort of ranges we use in the game. The image below uses the same data as the previous one for a convergence at 300yds. The actual trajectory is really very flat, but it looks more curved on the graph because the axis are drawn to different scales.   



Is that the kind of information you were looking for?

If you were serious about not posting again, feel free to PM me.

Regards

Badboy



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