angle for mortor,

[dominick]

I know, may have said this before, that with rifled modern artillery rounds the angle is near 43 degrees - for what ever the reason is - don't remember all the physics behind it.

According to Artillerist/Historian Ian Hogg, The 45 degree rule for maximum range was only good until the "twentieth century produced weapons capable of pitching their projectiles into the stratosphere."  [History of Artillery p.30]  Dom

[MikeR C]

It appears that from multiple sources 45 deg is the angle for maximum range, IF you are shooting on a flat plane of infinite size (no curvature of the earth) and no wind resistance. If you add wind resistance the range changes according to the resistance which seems to change according to altitude, ballistic coefficient of projectile, and velocity. I found this simple and intuitive explanation:

The "terminal range" problem is one I've looked at in some detail. In a
nutshell, here's the underlying physics.

45° is the optimum angle for maximum range only when air drag isn't a factor
-- e.g., in a vacuum. As air drag increases, the optimum angle decreases.
For artillery shells, it's typically ~40°. For rifle bullets (as you say)
~30°. For airgun pellets, it's ~20° and even less.

The reason for this effect is evident when you consider the respective roles
of the two components (i.e., horizontal and vertical) in contributing to
range. It's the horizontal component that actually covers "ground." The
contribution of the vertical component is only in determining the time that
the projectile is in the air. When free-fall is the only factor determining
the time of flight, then the optimum partition of kinetic energy between
horiz. and vertical components is 50:50 -- i.e. a 45° elevation angle.

But as air drag becomes more and more important, then a larger fraction of
the time of flight is contributed by the slowing of the projectiles fall by
drag -- and is therefore independent of the initial vertical velocity
component.

This works out to mean that as air drag increases, more range is to be had
by allocating a bigger and bigger fraction of MV to the horizontal component
and less and less to the vertical -- which is equivalent to sayiing that the
optimum elevation angle gets lower and lower.

Here's a handy table parameterized in terms of ballistic coefficient -- a
measure of the ratio of mass to drag:

BC = infinity : OA = 45°
--------- 2.0 ------ 42°
--------- 1.0 ------ 40°
---------- .75 ----- 39°
---------- .5 ------ 37°
---------- .25 ----- 34°
---------- .1 ------ 29°
---------- .05 ----- 25°
---------- .025 ---- 22°
---------- .02 ----- 20°
---------- .015 ---- 19°
---------- .01 ----- 17°
---------- .005 ---- 14°

Here:

http://www.luchtbuks.net/index.php?s=1494aeee8715d26e4e682fb3848b7bcd&showtopic=482&st=0&p=3530&#entry3530

It's not in english.
 So it looks like MAXIMUM range will always be 45 deg or less, how much less is too much trouble to figure out!

Thx
MikeR C

[Cat Whisperer]

dominick -

This is ABSOLUTELY fascinating - re the history.

My step-mother (now retired) was the head of the Classics Department at GSU for many years and with my father (now deceased) spent many years (still does several month stints) doing research in - VENICE!  I'll quote your comments and ask her if she's come across any mention of his name.  It is very likely that we could get some microfilm of the original documents - but translating them could be a real issue.

Venice was the center of civilization - with great connections because of being a key link in shipping in many directions.  Not surprising that something in print about trajectories would surface from there.

So, how did you come by this info?  There has to be a story behind it!

[Cat Whisperer]

Mike -

This is the first I'd heard of it being related to BC - but that makes perfect sense!  As you mentioned the theory is on a level plane with no wind resistance.  I can remember in running the calculations for elevation and azimuth (of the gun) we had to input the elevations of gun and target, wind direction and rotation of the earth - all affected the trajectory.

THANKS!

phalanx -  this is all your fault for asking the original question!     THANKS!

[Cat Whisperer]

...

http://www.luchtbuks.net/index.php?s=1494aeee8715d26e4e682fb3848b7bcd&showtopic=482&st=0&p=3530&#entry3530

It's not in english.
 ...

Mike -

I plugged that URL into bablefish ( http://babelfish.altavista.com/babelfish/tr ) translating from Dutch to English.  Most of the words come through, but due to some folks writing style the translations are a little crude.  It might be a derivitive of Dutch - like Africaner (spoken in South Africa).

Interesting thread - 2003?

[MikeR C]

This:

http://books.google.com/books?id=6TN800M3sY8C&pg=PA382&dq=projectile+%22history+of+ballistics%22&as_brr=1

Has history of ballistics, written in 1867 so a little more in keeping with what we are doing, and has a formula for estimating muzzle velocity from powder and projectile weight. Also covers flight in vacuum and air.
this is actually fun.
MikeR C

[Cat Whisperer]

About 2 hours down load (dial up).

[dominick]

Cat Whisperer wrote:
dominick -

This is ABSOLUTELY fascinating - re the history.

My step-mother (now retired) was the head of the Classics Department at GSU for many years and with my father (now deceased) spent many years (still does several month stints) doing research in - VENICE!  I'll quote your comments and ask her if she's come across any mention of his name.  It is very likely that we could get some microfilm of the original documents - but translating them could be a real issue.

Venice was the center of civilization - with great connections because of being a key link in shipping in many directions.  Not surprising that something in print about trajectories would surface from there.

So, how did you come by this info?  There has to be a story behind it!

__________________________________________________________________________________________________________________________


Most of info is from old 'out of print' artillery books, a few which are very old and rare, and some newer that I have collected over the years.  Dom

[Victor3]

 CW said:

 "Venice was the center of civilization"

******

 I couldn't agree more. I lived there until I was 20.

 We are talking about Venice, California, aren't we?

 Ahem... Meanwhile, I wonder if spin on the ball was ever taken into account by the early mortar users. Backspin on a sphere creates lift (Magnus Effect) and increases range.

[Cat Whisperer]

...
 We are talking about Venice, California, aren't we?
...
 Ahem... Meanwhile, I wonder if spin on the ball was ever taken into account by the early mortar users. Backspin on a sphere creates lift (Magnus Effect) and increases range.

Of course they were aware of it - notably the Scottish ones.  But they never applied it to spheres over 1.75" in diameter.

[GGaskill]

I wonder if spin on the ball was ever taken into account by the early mortar users.

This was actually discussed here sometime back in the context of golf ball artillery but we couldn't come up with a practical means of imparting uniform spin.  Paintballers have started intentionally bending their barrels and it seems to work well but their barrels are aluminum. 

While the old guys probably observed the effects of spinning shot, since it likely varied from shot to shot and it would have been difficult to determine the spin orientation, they probably didn't reach any conclusions about it.

One would think that the shot more or less rolled down the bottom of the bore which would give it a forward spin, but the windage allows the powder gas to escape around the shot which would have a tendency to prevent contact with the bore.  Interested parties should conduct some experiments.

[phalanx]

OK :another question ,i am trying to learn about Mortars.
Would a Gunners Quadrant be of any use on a Mortar ?
I have one from WW1 , It was a Vet bring back passed down then given to me.
It was in a wooden case ,with calipers ,a breech level,some old charts ,and some other stuff.
I didn't know what it was ,or was even used for until I sent photos to a member here and he Knew what it was ,but couldn't really tell me how to use it.
I have tried to sell it before but i got no offers ,so i am going to keep it and hang it on the wall unless someone knows about them.

[Cat Whisperer]

There were two types - one for howitzers one for machine guns (maybe more that I'm not aware of).

Note the two sets of pads, one on one edge the other on an adjacent edge.

One set would be placed on the tube on a machined-flat surface (parallel to the axis of the bore) and the swing arm in the middle adjusted to the point where the bubble level is centered.  One then can read the elevation at the point where the swing arm is pointing to.  (One set of pads reads for tube elevations at high angle (above 45 degrees) the other low angle.)

I have the one for machine guns.  I think yours is for the cannons.

The charts/tables would give  charges for specific cannon/projectile combinations and the ranges for elevations.

You'll see gunner's quadrants for sale from time-to-time on ebay.

It certainly can be used with mortars or cannons, as long as there is a place on the tube that offers a repeatable location for placing it.

[phalanx]

It was for cannon , The best i can tell ,we are trying to sell it now through my Aunt ,but i don't want to break up the set.
I thought about using it on my 1919A4 ,but it has a T&E and it works fine.
Thanks Cat Whisperer.

[Cat Whisperer]

Phalanx -

(off topic, but related)

Looking at mine, it is marked 'Clinometer machine gun  M 1917'.  Would likely work for many types.

It goes up to 800 + mils (6400 mils in a 360 degree circle).

It would be used for raising up the elevation on the mg for looong range shooting at troop concentrations or other H&I fires.

Mine has a leather case.

[phalanx]

Cat Whisperer :
Mine also says M1917.
The left hand side has graduations on it from 0 to 800.
The right is from 800 to 1600.
Is that called Mills ? i didn't know what it meant.
This one is brass and has a metal box ,or the wooden box if it is stored with the other tools.
They are fun to mess with.Can i show you some of the charts ?
Or if i need to i can PM them to you , the dates on them say U S Government printing office.
U S Army Artillery 1905 ed . Cat .number  S1905-193211.

[Cat Whisperer]

Let me start a new thread, as this will have some broader interest.