WesWorld

How do you calculate the antiaircraft ceiling of a gun you have simulated in BigGun?

You have got the V/O, D/max and angel of the barrel.

We'll do it step by step. You will have noted that you can't get it in your report, but it is there when you create it.
1) Enter caliber.
2) Enter weight.
3) Enter caliber or muzzle velocity (whichever you use).
4) Enter shell factor.
5) Design acceptable y/n
6) Enter elevation => enter the maximun elevation of your AA gun.
After you have entered your elevation and hit enter, you'll see a list scroll by with:

time, gees, velocity, flight angle, altitude and range.
Write it down and add it to your AA gun report.
Not entirely accurate but gives you an idea.

Walter

ok, thanks I'll try that, isn't there any formula you can use when you have the numbers on paper?

Well, both physics and mathematics have vanished into the nether regions of my brain, but you need (as I was taught more than 10 years ago):

A) <delta> s = v(0)*t + 1/2*a*t^2
'<delta> s' is distance (your gun's ceiling; the <delta> should be the Greek letter)
'v(0)' is the speed at t=o and is your upward speed (which is, if I'm correct, the muzzle velovity multipled by the sinus of the angle of the gun)
't' is time
a is acceleration (which when firing a shell upward becomes decelleration equal to the gravity 'g' which is 9.81 meters per second per second)

and

B) v(t) = v(0) + a*t

v(t) is your speed at time t


First you need to know the velocity of your shell as well as the angle of your gun.
Taking my Wesworld 25mm Model 1918 gun, it has a muzzle velocity of 715 m/s and a maximum elevation of 80 degrees.

The upward speed is muzzle velocity multipied by the sinus of 80 which gives us:
v(up) = 715 * 0.985 = 704 meters per second.

Next you have to calculate to see when the shell speed comes to 0 meters per second.

With the shell having an upward speed of 704 meters per second, you will get the next with formula B:
0 = 704 + - 9.8*t
moving the -9.8*t in fron of the '=' gives us:
9.8*t = 704
To get 't', you have to divid both sides by 9.8 which gives you:
t = 704/9.8 = 71.8 seconds
... so after 71.8 seconds, your shell has slowed down to 0 meters per second.

Now that you know 't', you can use it in formula 'A' which gives you
<delta> s = 704*71.8 + 1/2*-9.8*71.8^2 = 50,547 - 25,261 = 25,286 meters (= 82,959 feet).

One problem: I haven't taken drag into account (not sure how to incorporate that into the problem; I would have to look that stuff up somewhere) so the ceiling of the gun is much higher than it should be. So in a vacuum, with only gravity slowing the shell down, you will get this shell to 82,959 feet.
But when adding drag... I would have to look it up.
... but I think the best way to get the ceiling of your AA gun is by using Big Gun as I mentioned above cause I get the impression the drag formula is already incorporated into that program.

Walter
*_*

Very nice post, Walter. Indeed... ;o)

Keep em coming!

Thanks, very nice, I just have to find my calculator(and play around some with excel)

If do all th guns in drag =, you will have them comparabel, and thats whats intrestinf, doesn't BigGun, calculate with some drag (shellform factor)?

I think this might give the answer to the drag issue... at least if you understand it, cause I don't (need to look at it more closely and much, much longer before I get it).
:-)
The only thing I understand of that formula is that once the F(d) is known, you can use the formula F=m*a to calculate the deceleration of the shell.
Big Gun does seem to take drag into account since the maximum altitude it gives for my 25mm gun is 20,400 feet. Looking at the historical 25mm AA gun of the Japanese (as given in the Warship1 database), the maximum altitude for that gun is 18,040 feet at 85 degrees, which is not that far off what Big Gun gives me for my gun.