Yes, I know this isn't strictly metalworking, but there are plenty of
gun people here.
A howitzer fires, with elevation 45 degs. So the shell exits, pointing
upward at 45 degs., spinning. When it hits the target, it is (to 1st
approximation) falling at 45 degs., but the spin should have kept it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?

On Thursday, March 9, 2017 at 9:52:34 PM UTC-5, David R Brooks wrote:
Yes, I know this isn't strictly metalworking, but there are plenty of
gun people here.
A howitzer fires, with elevation 45 degs. So the shell exits, pointing
upward at 45 degs., spinning. When it hits the target, it is (to 1st
approximation) falling at 45 degs., but the spin should have kept it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?

I don't know if this is a really accurate description of the dynamics, but this is the way it was explained to me, and it makes sense. It starts with the idea that aerodynamic force overcomes the gyroscopic effect, and the pitch of the shell is a response to greater aerodynamic force being applied *behind* the center of gravity:

http://www.4point2.org/ballistics.htm


Maybe someone will have a more precise explanation.

--
Ed Huntress

On 10-Mar-17 10:52 AM, David R Brooks wrote:
Yes, I know this isn't strictly metalworking, but there are plenty of
gun people here.
A howitzer fires, with elevation 45 degs. So the shell exits, pointing
upward at 45 degs., spinning. When it hits the target, it is (to 1st
approximation) falling at 45 degs., but the spin should have kept it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?

Aerodynamics does the steering / turning?

On Fri, 10 Mar 2017 10:52:30 +0800, David R Brooks
wrote:

Yes, I know this isn't strictly metalworking, but there are plenty of
gun people here.
A howitzer fires, with elevation 45 degs. So the shell exits, pointing
upward at 45 degs., spinning. When it hits the target, it is (to 1st
approximation) falling at 45 degs., but the spin should have kept it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?

The short answer is that the entire shell is effected by gravity. The
spin serves only to stabilize it just like a top. As the shell is
symmetrical there is effectively no lift developed by the spinning
shell, i.e., if one side is going up the other side with exactly the
same shape, size and velocity is going down :-)

The spin serves to stabilize the shell and is a complex subject. See
http://bisonballistics.com/articles/...y-robert-mccoy
for a review of a book giving a rather complete explanation of
exterior ballistics.

It might also be noted that a cross wind does effect the
bullet/shell's flight and a cross wind will generally move the
bullet/shell. A wind from the right tends to move the bullet in the
direction of 10 o'clock while from the left to toward the 4 o'clock.
Note that this movement depends on the direction of spin of the
bullet/shell as well as wind direction.

There has been rather extensive studies of exterior ballistics since
at least the 1800's. Siacci's theorem in dynamics is the resolution of
the acceleration vector of a particle into radial and tangential
components, which are generally not perpendicular to one another.
Siacci formulated this decomposition in two papers which were
published in 1879.
--
Cheers,

John B.

On Thursday, March 9, 2017 at 9:52:34 PM UTC-5, David R Brooks wrote:

A howitzer fires, with elevation 45 degs. So the shell exits, pointing
upward at 45 degs., spinning. When it hits the target, it is (to 1st
approximation) falling at 45 degs., but the spin should have kept it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?\\

The shell flies with its axis in line with the direction that the shell is moving.
So the shell starts out pointed up by 45 degrees , it flight path changes and its orientation also changes. Since the shell is spinning , changing the orientation causes it to precess. And the shell changes from not only the angle up but also changes sideways. So a shell with a clockwise rotation fired due west, will turn so it is going south west.

And it gets worse. A shell fired due North in the Northern hemisphere will go somewhat East because of the Coriolis effect.

Dan

"David R Brooks" wrote in message
...
Yes, I know this isn't strictly metalworking, but there are plenty
of gun people here.
A howitzer fires, with elevation 45 degs. So the shell exits,
pointing upward at 45 degs., spinning. When it hits the target, it
is (to 1st approximation) falling at 45 degs., but the spin should
have kept it pointing upward. This means it would be flying
sideways-on.
This sounds wrong to me, but where is the error?

General Hatcher was concerned about gun range safety back when troops
fired rifles up at towed aerial targets and investigated how bullets
fall by firing upward at a Florida lake where he could observe and
time their splashes.

https://books.google.com/books?id=Dt...down&f=fa lse

He wrote of coastal artillery mortar shells "At angles of elevation of
less than about 85 degrees, the action of the air keeps the shells
flying point forward, at higher elevations they are likely to fall
base first."

The yaw resistance of a projectile is a balance between the greater
air pressure on the nose and the gyroscopic stability from spin. The
rifling twist usually isn't much more than enough to keep the bullet
pointing forward.

https://en.wikipedia.org/wiki/Alfred_George_Greenhill

http://bulletin.accurateshooter.com/...pin-a-problem/

https://en.wikipedia.org/wiki/External_ballistics
"Mathematical models for calculating the effects of drag or air
resistance are quite complex and often unreliable beyond about 500
meters, so the most reliable method of establishing trajectories is
still by empirical measurement."

The empirical methods as calculated by radar-equipped WW2 US
mechanical fire control computers were good enough that for example
the battleship USS Washington straddled the Japanese battlecruiser
Kirishima with the first salvo at 8,400 yds at the Second Naval Battle
of Guadalcanal. Japanese damage control records show that 20 of the 56
shells were hits although at the time Washington claimed 8 or 9. The
others were simultaneous adjacent second hits or fell slightly short
and raised visible splashes before penetrating the hull underwater.
Other navies lacked our radar and computers and averaged less than 2%
hits.

I studied fire control and torpedo computers to learn to build
scientific instruments.
https://en.wikipedia.org/wiki/Ball-and-disk_integrator
Long range shooting is nearly impossible in densely forested New
England USA so I can't tell you more than the above about ballistics.

Now that the HMAS Sydney and Kormoran wrecks have been found, have you
heard any new details about their desperate battle?
-jsw

wrote in message
...
On Thursday, March 9, 2017 at 9:52:34 PM UTC-5, David R Brooks wrote:

A howitzer fires, with elevation 45 degs. So the shell exits,
pointing
upward at 45 degs., spinning. When it hits the target, it is (to 1st
approximation) falling at 45 degs., but the spin should have kept it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?\\

The shell flies with its axis in line with the direction that the
shell is moving.
So the shell starts out pointed up by 45 degrees , it flight path
changes and its orientation also changes. Since the shell is spinning
, changing the orientation causes it to precess. And the shell
changes from not only the angle up but also changes sideways. So a
shell with a clockwise rotation fired due west, will turn so it is
going south west.

And it gets worse. A shell fired due North in the Northern
hemisphere will go somewhat East because of the Coriolis effect.

Dan
==============

At the WW1 Battle of the Falkland Islands the Northern Hemisphere
Coriolis correction in the British firing tables didn't hurt their
shooting.
https://en.wikipedia.org/wiki/Battle...lkland_Islands

The link to Felix von Luckner in 'Outcome' is interesting.
English-language history omits a lot about our enemies, for instance
in German history Rome never fell, they rightfully inherited control.
https://en.wikipedia.org/wiki/Theoderic_the_Great
"Seeking to restore the glory of Ancient Rome, he ruled Italy in its
most peaceful and prosperous period since Valentinian.."

-jsw

"Jim Wilkins" wrote in message
news

At the WW1 Battle of the Falkland Islands the Northern Hemisphere
Coriolis correction in the British firing tables didn't hurt their
shooting.

This is the British Dreyer Fire Control Table, literally a 4-leg
table:
http://dreadnoughtproject.org/tfs/in..._Control_Table

The problem is to reconstruct the enemy's course relative to your own
and then calculate the gun angles to place shells on where he will be
after the shell's time of flight, assuming both ships hold straight
courses, which they must when firing at each other this way. A fast
ship too small to shoot back might confound the system by maneuvering.

By WW2 US radar fire control was automated enough to shoot back
accurately while dodging enemy shells.
https://en.wikipedia.org/wiki/USS_Johnston_(DD-557)
Large armor piercing naval shells tend to act like solid cannonballs
and just punch a hole their size when they strike thin-skinned targets
that don't slow the shells enough to detonate them.

Some of those torpedoes may have been the spread that chased the
monstrous battleship Yamato away from the action. The Japanese mistook
those incredibly bold little destroyers for larger cruisers.

-jsw

On Fri, 10 Mar 2017 05:17:54 -0800 (PST), "
wrote:

On Thursday, March 9, 2017 at 9:52:34 PM UTC-5, David R Brooks wrote:

A howitzer fires, with elevation 45 degs. So the shell exits, pointing
upward at 45 degs., spinning. When it hits the target, it is (to 1st
approximation) falling at 45 degs., but the spin should have kept it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?\\

The shell flies with its axis in line with the direction that the shell is moving.
So the shell starts out pointed up by 45 degrees , it flight path changes and its orientation also changes. Since the shell is spinning , changing the orientation causes it to precess. And the shell changes from not only the angle up but also changes sideways. So a shell with a clockwise rotation fired due west, will turn so it is going south west.

And it gets worse. A shell fired due North in the Northern hemisphere will go somewhat East because of the Coriolis effect.

Dan

Correct.

And it should be noted that the shell travels in an arc. There are no
square corners


---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

wrote:
On Thursday, March 9, 2017 at 9:52:34 PM UTC-5, David R Brooks wrote:

A howitzer fires, with elevation 45 degs. So the shell exits, pointing
upward at 45 degs., spinning. When it hits the target, it is (to 1st
approximation) falling at 45 degs., but the spin should have kept it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?\\

The shell flies with its axis in line with the direction that the shell is moving.
So the shell starts out pointed up by 45 degrees , it flight path changes and its orientation also changes. Since the shell is spinning , changing the orientation causes it to precess. And the shell changes from not only the angle up but also changes sideways. So a shell with a clockwise rotation fired due west, will turn so it is going south west.

And it gets worse. A shell fired due North in the Northern hemisphere will go somewhat East because of the Coriolis effect.

Well, it seems the people who designed the Rheinmetall Rh120 knew
what they were doing.

--

"I'm a doctor, not a mechanic." Dr Leonard McCoy
"I'm a mechanic, not a doctor." Volker Borchert

"Volker Borchert" wrote in message
news
wrote:
On Thursday, March 9, 2017 at 9:52:34 PM UTC-5, David R Brooks
wrote:

A howitzer fires, with elevation 45 degs. So the shell exits,
pointing
upward at 45 degs., spinning. When it hits the target, it is (to
1st
approximation) falling at 45 degs., but the spin should have kept
it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?\\

The shell flies with its axis in line with the direction that the
shell is moving.
So the shell starts out pointed up by 45 degrees , it flight path
changes and its orientation also changes. Since the shell is
spinning , changing the orientation causes it to precess. And the
shell changes from not only the angle up but also changes sideways.
So a shell with a clockwise rotation fired due west, will turn so
it is going south west.

And it gets worse. A shell fired due North in the Northern
hemisphere will go somewhat East because of the Coriolis effect.

Well, it seems the people who designed the Rheinmetall Rh120 knew
what they were doing.

Joseph Whitworth knew what he was doing in 1860.
http://civilwarwiki.net/wiki/12_pdr....hloading_Rifle
"At 1600 yards the Whitworth gun fired 10 shots with a lateral
deviation of only 5 inches."

But the Confederacy had only a few pieces of superior British
artillery, and Lee's Chief of Artillery was incompetent.
https://en.wikipedia.org/wiki/William_N._Pendleton
At Gettysburg Lee chose a talented but inexperienced junior officer to
command the artillery and Pendleton mainly interfered with him. The
Union artillery commander tricked him by pulling guns out of action
randomly as though they had been destroyed. Gunpowder smoke obscured
what was really happening. Expecting a disaster he'd been unable to
prevent, General Longstreet delegated the decision on when the
infantry should charge to the junior artillery officer who didn't
realize he hadn't really crushed the opposition that then massacred
Picket's Charge.

-jsw

On Sun, 12 Mar 2017 11:18:28 -0400, "Jim Wilkins"
wrote:

"Volker Borchert" wrote in message
news
wrote:
On Thursday, March 9, 2017 at 9:52:34 PM UTC-5, David R Brooks
wrote:

A howitzer fires, with elevation 45 degs. So the shell exits,
pointing
upward at 45 degs., spinning. When it hits the target, it is (to
1st
approximation) falling at 45 degs., but the spin should have kept
it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?\\

The shell flies with its axis in line with the direction that the
shell is moving.
So the shell starts out pointed up by 45 degrees , it flight path
changes and its orientation also changes. Since the shell is
spinning , changing the orientation causes it to precess. And the
shell changes from not only the angle up but also changes sideways.
So a shell with a clockwise rotation fired due west, will turn so
it is going south west.

And it gets worse. A shell fired due North in the Northern
hemisphere will go somewhat East because of the Coriolis effect.

Well, it seems the people who designed the Rheinmetall Rh120 knew
what they were doing.

Joseph Whitworth knew what he was doing in 1860.
http://civilwarwiki.net/wiki/12_pdr....hloading_Rifle
"At 1600 yards the Whitworth gun fired 10 shots with a lateral
deviation of only 5 inches."

I think I would take that figure with a grain of salt. After all, at
1,000 yards with a muzzle velocity of 1,300 fps ( probably similar to
the Whitworth ) with a .45-90 rifle, wind drift is approximately 15"
per mph of wind speed, at 90 degrees to the line of sight. Even air
temperature and humidity has a measurable effect at these kind of
ranges.

But the Confederacy had only a few pieces of superior British
artillery, and Lee's Chief of Artillery was incompetent.
https://en.wikipedia.org/wiki/William_N._Pendleton
At Gettysburg Lee chose a talented but inexperienced junior officer to
command the artillery and Pendleton mainly interfered with him. The
Union artillery commander tricked him by pulling guns out of action
randomly as though they had been destroyed. Gunpowder smoke obscured
what was really happening. Expecting a disaster he'd been unable to
prevent, General Longstreet delegated the decision on when the
infantry should charge to the junior artillery officer who didn't
realize he hadn't really crushed the opposition that then massacred
Picket's Charge.

-jsw

--
Cheers,

John B.

On Mon, 13 Mar 2017 08:33:42 +0700, John B.
wrote:

On Sun, 12 Mar 2017 11:18:28 -0400, "Jim Wilkins"
wrote:

"Volker Borchert" wrote in message
news
wrote:
On Thursday, March 9, 2017 at 9:52:34 PM UTC-5, David R Brooks
wrote:

A howitzer fires, with elevation 45 degs. So the shell exits,
pointing
upward at 45 degs., spinning. When it hits the target, it is (to
1st
approximation) falling at 45 degs., but the spin should have kept
it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?\\

The shell flies with its axis in line with the direction that the
shell is moving.
So the shell starts out pointed up by 45 degrees , it flight path
changes and its orientation also changes. Since the shell is
spinning , changing the orientation causes it to precess. And the
shell changes from not only the angle up but also changes sideways.
So a shell with a clockwise rotation fired due west, will turn so
it is going south west.

And it gets worse. A shell fired due North in the Northern
hemisphere will go somewhat East because of the Coriolis effect.

Well, it seems the people who designed the Rheinmetall Rh120 knew
what they were doing.

Joseph Whitworth knew what he was doing in 1860.
http://civilwarwiki.net/wiki/12_pdr....hloading_Rifle
"At 1600 yards the Whitworth gun fired 10 shots with a lateral
deviation of only 5 inches."

I think I would take that figure with a grain of salt. After all, at
1,000 yards with a muzzle velocity of 1,300 fps ( probably similar to
the Whitworth ) with a .45-90 rifle, wind drift is approximately 15"
per mph of wind speed, at 90 degrees to the line of sight. Even air
temperature and humidity has a measurable effect at these kind of
ranges.

snip

I think he was referring to the Whitworth rifled cannon, 2.75" bore,
hexagonal rifling with a matching twisted "long bolt" projectile.
Don't know the velocity, but it probably had a very high ballistic
coefficient due to mass as much as shape.

Pete

On Mon, 13 Mar 2017 07:30:37 -0500, Pete Keillor
wrote:

On Mon, 13 Mar 2017 08:33:42 +0700, John B.
wrote:

On Sun, 12 Mar 2017 11:18:28 -0400, "Jim Wilkins"
wrote:

"Volker Borchert" wrote in message
news wrote:
On Thursday, March 9, 2017 at 9:52:34 PM UTC-5, David R Brooks
wrote:

A howitzer fires, with elevation 45 degs. So the shell exits,
pointing
upward at 45 degs., spinning. When it hits the target, it is (to
1st
approximation) falling at 45 degs., but the spin should have kept
it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?\\

The shell flies with its axis in line with the direction that the
shell is moving.
So the shell starts out pointed up by 45 degrees , it flight path
changes and its orientation also changes. Since the shell is
spinning , changing the orientation causes it to precess. And the
shell changes from not only the angle up but also changes sideways.
So a shell with a clockwise rotation fired due west, will turn so
it is going south west.

And it gets worse. A shell fired due North in the Northern
hemisphere will go somewhat East because of the Coriolis effect.

Well, it seems the people who designed the Rheinmetall Rh120 knew
what they were doing.

Joseph Whitworth knew what he was doing in 1860.
http://civilwarwiki.net/wiki/12_pdr....hloading_Rifle
"At 1600 yards the Whitworth gun fired 10 shots with a lateral
deviation of only 5 inches."

I think I would take that figure with a grain of salt. After all, at
1,000 yards with a muzzle velocity of 1,300 fps ( probably similar to
the Whitworth ) with a .45-90 rifle, wind drift is approximately 15"
per mph of wind speed, at 90 degrees to the line of sight. Even air
temperature and humidity has a measurable effect at these kind of
ranges.

snip

I think he was referring to the Whitworth rifled cannon, 2.75" bore,
hexagonal rifling with a matching twisted "long bolt" projectile.
Don't know the velocity, but it probably had a very high ballistic
coefficient due to mass as much as shape.

Pete

Yes, I was aware of that. But one of the determining factors in wind
drift is the amount of time the projectile is exposed to the wind,
i.e., distance and muzzle velocity. From all I could find on the net
the Whitworth 12 pound had a muzzle velocity of 1,500 fps thus wind
drift might have been in the neighborhood of 1300/1500 of the .45 cal
rifle I mentioned. Perhaps 13"/mph.

My point was that the figure given (the Whitworth gun fired 10 shots
with a lateral deviation of only 5 inches.), which seems to a
quotation from one magazine article, is very highly unlikely.

--
Cheers,

John B.

"John B." wrote in message
...
On Mon, 13 Mar 2017 07:30:37 -0500, Pete Keillor
wrote:

On Mon, 13 Mar 2017 08:33:42 +0700, John B.
wrote:

On Sun, 12 Mar 2017 11:18:28 -0400, "Jim Wilkins"
wrote:

"Volker Borchert" wrote in message
news wrote:
On Thursday, March 9, 2017 at 9:52:34 PM UTC-5, David R Brooks
wrote:

A howitzer fires, with elevation 45 degs. So the shell exits,
pointing
upward at 45 degs., spinning. When it hits the target, it is
(to
1st
approximation) falling at 45 degs., but the spin should have
kept
it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?\\

The shell flies with its axis in line with the direction that
the
shell is moving.
So the shell starts out pointed up by 45 degrees , it flight
path
changes and its orientation also changes. Since the shell is
spinning , changing the orientation causes it to precess. And
the
shell changes from not only the angle up but also changes
sideways.
So a shell with a clockwise rotation fired due west, will turn
so
it is going south west.

And it gets worse. A shell fired due North in the Northern
hemisphere will go somewhat East because of the Coriolis
effect.

Well, it seems the people who designed the Rheinmetall Rh120
knew
what they were doing.

Joseph Whitworth knew what he was doing in 1860.
http://civilwarwiki.net/wiki/12_pdr....hloading_Rifle
"At 1600 yards the Whitworth gun fired 10 shots with a lateral
deviation of only 5 inches."

I think I would take that figure with a grain of salt. After all,
at
1,000 yards with a muzzle velocity of 1,300 fps ( probably similar
to
the Whitworth ) with a .45-90 rifle, wind drift is approximately
15"
per mph of wind speed, at 90 degrees to the line of sight. Even air
temperature and humidity has a measurable effect at these kind of
ranges.

snip

I think he was referring to the Whitworth rifled cannon, 2.75" bore,
hexagonal rifling with a matching twisted "long bolt" projectile.
Don't know the velocity, but it probably had a very high ballistic
coefficient due to mass as much as shape.

Pete

Yes, I was aware of that. But one of the determining factors in wind
drift is the amount of time the projectile is exposed to the wind,
i.e., distance and muzzle velocity. From all I could find on the net
the Whitworth 12 pound had a muzzle velocity of 1,500 fps thus wind
drift might have been in the neighborhood of 1300/1500 of the .45
cal
rifle I mentioned. Perhaps 13"/mph.

My point was that the figure given (the Whitworth gun fired 10 shots
with a lateral deviation of only 5 inches.), which seems to a
quotation from one magazine article, is very highly unlikely.

--
Cheers,

John B.

I've read historical accounts on military matters that show reporters
weren't any better educated in technology then than they are now. The
report could be interpreted as a 5" radius of the pattern and doesn't
tell how far it was from the point of aim. Presumably the team trying
to sell the gun would choose a calm morning in Foggy Bottom.
-jsw

On Mon, 13 Mar 2017 21:20:14 -0400, "Jim Wilkins"
wrote:

"John B." wrote in message
.. .
On Mon, 13 Mar 2017 07:30:37 -0500, Pete Keillor
wrote:

On Mon, 13 Mar 2017 08:33:42 +0700, John B.
wrote:

On Sun, 12 Mar 2017 11:18:28 -0400, "Jim Wilkins"
wrote:

"Volker Borchert" wrote in message
news wrote:
On Thursday, March 9, 2017 at 9:52:34 PM UTC-5, David R Brooks
wrote:

A howitzer fires, with elevation 45 degs. So the shell exits,
pointing
upward at 45 degs., spinning. When it hits the target, it is
(to
1st
approximation) falling at 45 degs., but the spin should have
kept
it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?\\

The shell flies with its axis in line with the direction that
the
shell is moving.
So the shell starts out pointed up by 45 degrees , it flight
path
changes and its orientation also changes. Since the shell is
spinning , changing the orientation causes it to precess. And
the
shell changes from not only the angle up but also changes
sideways.
So a shell with a clockwise rotation fired due west, will turn
so
it is going south west.

And it gets worse. A shell fired due North in the Northern
hemisphere will go somewhat East because of the Coriolis
effect.

Well, it seems the people who designed the Rheinmetall Rh120
knew
what they were doing.

Joseph Whitworth knew what he was doing in 1860.
http://civilwarwiki.net/wiki/12_pdr....hloading_Rifle
"At 1600 yards the Whitworth gun fired 10 shots with a lateral
deviation of only 5 inches."

I think I would take that figure with a grain of salt. After all,
at
1,000 yards with a muzzle velocity of 1,300 fps ( probably similar
to
the Whitworth ) with a .45-90 rifle, wind drift is approximately
15"
per mph of wind speed, at 90 degrees to the line of sight. Even air
temperature and humidity has a measurable effect at these kind of
ranges.

snip

I think he was referring to the Whitworth rifled cannon, 2.75" bore,
hexagonal rifling with a matching twisted "long bolt" projectile.
Don't know the velocity, but it probably had a very high ballistic
coefficient due to mass as much as shape.

Pete

Yes, I was aware of that. But one of the determining factors in wind
drift is the amount of time the projectile is exposed to the wind,
i.e., distance and muzzle velocity. From all I could find on the net
the Whitworth 12 pound had a muzzle velocity of 1,500 fps thus wind
drift might have been in the neighborhood of 1300/1500 of the .45
cal
rifle I mentioned. Perhaps 13"/mph.

My point was that the figure given (the Whitworth gun fired 10 shots
with a lateral deviation of only 5 inches.), which seems to a
quotation from one magazine article, is very highly unlikely.

--
Cheers,

John B.

I've read historical accounts on military matters that show reporters
weren't any better educated in technology then than they are now. The
report could be interpreted as a 5" radius of the pattern and doesn't
tell how far it was from the point of aim. Presumably the team trying
to sell the gun would choose a calm morning in Foggy Bottom.
-jsw

True, but even today's artillery, which one assumes are more accurate
than a weapon built in the mid 1800's doesn't have the accuracy
claimed for the Whitworth. In fact at the end of WW II the standard of
accuracy for light artillery which approximates the 12 pound horse
drawn artillery used the field in 1860 was "1 in 500" so for 1600
yards the standard, in 1945, would be 2.3 yards.
(which is a bit different than 5 inches :-)

--
Cheers,

John B.

"John B." wrote in message
...
On Mon, 13 Mar 2017 21:20:14 -0400, "Jim Wilkins"
wrote:

"John B." wrote in message
. ..
On Mon, 13 Mar 2017 07:30:37 -0500, Pete Keillor
wrote:

On Mon, 13 Mar 2017 08:33:42 +0700, John B.
wrote:

On Sun, 12 Mar 2017 11:18:28 -0400, "Jim Wilkins"
wrote:

"Volker Borchert" wrote in message
news wrote:
On Thursday, March 9, 2017 at 9:52:34 PM UTC-5, David R
Brooks
wrote:

A howitzer fires, with elevation 45 degs. So the shell
exits,
pointing
upward at 45 degs., spinning. When it hits the target, it
is
(to
1st
approximation) falling at 45 degs., but the spin should
have
kept
it
pointing upward. This means it would be flying sideways-on.
This sounds wrong to me, but where is the error?\\

The shell flies with its axis in line with the direction that
the
shell is moving.
So the shell starts out pointed up by 45 degrees , it flight
path
changes and its orientation also changes. Since the shell is
spinning , changing the orientation causes it to precess.
And
the
shell changes from not only the angle up but also changes
sideways.
So a shell with a clockwise rotation fired due west, will
turn
so
it is going south west.

And it gets worse. A shell fired due North in the Northern
hemisphere will go somewhat East because of the Coriolis
effect.

Well, it seems the people who designed the Rheinmetall Rh120
knew
what they were doing.

Joseph Whitworth knew what he was doing in 1860.
http://civilwarwiki.net/wiki/12_pdr....hloading_Rifle
"At 1600 yards the Whitworth gun fired 10 shots with a lateral
deviation of only 5 inches."

I think I would take that figure with a grain of salt. After all,
at
1,000 yards with a muzzle velocity of 1,300 fps ( probably
similar
to
the Whitworth ) with a .45-90 rifle, wind drift is approximately
15"
per mph of wind speed, at 90 degrees to the line of sight. Even
air
temperature and humidity has a measurable effect at these kind of
ranges.

snip

I think he was referring to the Whitworth rifled cannon, 2.75"
bore,
hexagonal rifling with a matching twisted "long bolt" projectile.
Don't know the velocity, but it probably had a very high ballistic
coefficient due to mass as much as shape.

Pete

Yes, I was aware of that. But one of the determining factors in
wind
drift is the amount of time the projectile is exposed to the wind,
i.e., distance and muzzle velocity. From all I could find on the
net
the Whitworth 12 pound had a muzzle velocity of 1,500 fps thus
wind
drift might have been in the neighborhood of 1300/1500 of the .45
cal
rifle I mentioned. Perhaps 13"/mph.

My point was that the figure given (the Whitworth gun fired 10
shots
with a lateral deviation of only 5 inches.), which seems to a
quotation from one magazine article, is very highly unlikely.

--
Cheers,

John B.

I've read historical accounts on military matters that show
reporters
weren't any better educated in technology then than they are now.
The
report could be interpreted as a 5" radius of the pattern and
doesn't
tell how far it was from the point of aim. Presumably the team
trying
to sell the gun would choose a calm morning in Foggy Bottom.
-jsw

True, but even today's artillery, which one assumes are more
accurate
than a weapon built in the mid 1800's doesn't have the accuracy
claimed for the Whitworth. In fact at the end of WW II the standard
of
accuracy for light artillery which approximates the 12 pound horse
drawn artillery used the field in 1860 was "1 in 500" so for 1600
yards the standard, in 1945, would be 2.3 yards.
(which is a bit different than 5 inches :-)

--
Cheers,

John B.

You can't compare a new barrel to one worn to the relining standard.

A Whitworth in action:
https://www.youtube.com/watch?v=er1dgRH23XU

http://www.accurateshooter.com/compe...nchrest-guide/
"When conditions are right, a good shooter can put ten shots into a
pattern you can cover with the palm of your hand."

http://riflebarrels.com/winners-worl...ds/1000-yards/

https://en.wikipedia.org/wiki/Billy_Dixon

"John B." wrote in message
...
On Mon, 13 Mar 2017 21:20:14 -0400, "Jim Wilkins"
wrote:


True, but even today's artillery, which one assumes are more
accurate
than a weapon built in the mid 1800's doesn't have the accuracy
claimed for the Whitworth. In fact at the end of WW II the standard
of
accuracy for light artillery which approximates the 12 pound horse
drawn artillery used the field in 1860 was "1 in 500" so for 1600
yards the standard, in 1945, would be 2.3 yards.
(which is a bit different than 5 inches :-)

--
Cheers,

John B.


I've seen evidence that the allowance was 1 in 400 for battleship guns
which had the added problems of the rolling of the ship and
interfering with each other through their toilet-shattering vibration
and the leading shell's shock wave. The middle barrel was delayed by
50 milliseconds to help.

They determined barrel life from the numbers of shots fired at various
charge weights. It was a fairly small multiple of the number of shells
they carried.

This shows how closely pairs of shells from new barrels hit:
http://www.navweaps.com/index_lundgr...e_Analysis.pdf

The barrel of the WW1 Paris Gun wore so quickly that the shells had to
be fired in numerical order of increasing diameter.
http://www.firstworldwar.com/atoz/parisgun.htm

-jsw