Question: Tank Gun Thermal Sleeves?
PaPa Peng
guns? I would have thought that the sleeves will retain heat. After
firing a number of rounds won't that cause the gun barrel to overheat
and cause serious problems?
Rob Gronovius
Couple of different reasons; one is that it keeps the gun at a more
constant temperature and minimizing inaccuracy due to gun tube droop.
Secondly it retains the heat signature that can distort thermal
sights.
willshak
http://en.wikipedia.org/wiki/Thermal_sleeve
--
Bill
In Hamptonburgh, NY
In the original Orange County. Est. 1683
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PaPa Peng
Thanks for the answer. There is still the question of overheating.
It won't take too many rounds for the gun barrel to become red hot.
The tube metal expands, The tube diameter shrinks and that seizes the
round (as per overheated machine gun barrel.) What then?
willshak
Cool water circulating around the barrel, like from the tank's AC unit.
AMP...@aol.com
The shroud helps the gun heat at a constant rate (for example, sun on
the topside of the barrel will make it expand faster than the bottom,
thus inducing curve and droop). Most modern systems (including the
Russians now) have a muzzle reference system which tells the gunsight
and fire control computer how far the barrel has warped out of its
boresight.
Cookie Sewell
Bruce Burden
:
: Thanks for the answer. There is still the question of overheating.
: It won't take too many rounds for the gun barrel to become red hot.
: The tube metal expands, The tube diameter shrinks and that seizes the
: round (as per overheated machine gun barrel.) What then?
I understand modern gun tubes are made with a process
called "hydro swaging". Two telescoping tubes are used,
the tube is filled with a fluid, the ends sealed, and the
fluid is expanded.
The inner tube expands past its' plastic limit, and
remains forever expanded to its current size. The larger
outer tube does not expand past its' plastic limit, so it
is constantly attempting to squeeze the smaller tube back
to its original diameter.
Also, I doubt the tube diameter shrinks. At Waterloo,
IIRC, the Kings German Regiment was frantically looking
for oversize balls for their muskets at the farmhouse(?)
they were attempting to hold. Same story at Rorke's Drift
during the Zulu wars. (Actually, I believe the KGR were
simply looking for ammo, period).
And, finally, I wonder how much heat a modern smooth
bore gun tube absorbes? Without the friction of the rifling,
it is probably not as much as a rifled barrel would generate/
absorb.
Bruce
--
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"I like bad!" Bruce Burden Austin, TX.
- Thuganlitha
The Power and the Prophet
Robert Don Hughes
Rufus
...why would you think a modern gun bore isn't rifled?
--
- Rufus
Rob Gronovius
>
> - Show quoted text -
Because some are not. The 120mm smooth bore gun is used on the Abrams,
Leopard 2, Type 90, etc.
Don Stauffer
If the tube metal expands, then the diameter cannot shrink, it must also
expand. That is, if the circumference of a circle increases, the
diameter must also.
The only reason a car engine seizes when it overheats too much is that
the piston is hotter than the cylinder walls because it does not get
cooled as well.
Don Stauffer
depends on the gun.
PaPa Peng
> PaPa Peng wrote:
> If the tube metal expands, then the diameter cannot shrink, it must also
> expand. That is, if the circumference of a circle increases, the
> diameter must also.
This agrees with a long ago high school physics test question. What
is the diameter of a hole in a metal plate given the coefficient of
expansion and the temperature change? The answer at the back of the
book was too simple. Treat the hole as if it is a disc of the metal.
It also agrees with observation that one can heat a tube, slip it over
the axle and then cool it to form a tight sleeve over that axle.
>
> The only reason a car engine seizes when it overheats too much is that
> the piston is hotter than the cylinder walls because it does not get
> cooled as well.
This explanation doesn't quite agree with the observation that the red
hot barrel of a gun causes the bullet or shell to jam in the barrel
(?). Remember those stories about peeing on the mortar barrel to cool
it? Then the pictures of the gun crew hosing water on overheated 40
mm Bofors both in WWII USN ships and one of a schellboot Bofors crew
doing the same. Then of course you can't use a machine gun with a red
hot barrel. There are reports of peeing on the barrel in a desperate
attempt to get it working again.
Rufus
...ok, "some" I'll buy. All of the medium to large bore guns I've
personally encountered have been/are rifled. Up to and including artie
bores...I'm not up on the tank world.
--
- Rufus
Rufus
That I'll buy...our local Marine Detachment has a heavy aritie shell
that has been pierced in-flight by a Phalanx round sitting outside the
CO's door...that shell has rifle marks on it. I guess I need to go hang
out around some tanks.
--
- Rufus
AMP...@aol.com
Today nearly all 120mm and 125mm tank guns are smoothbores -- the
British are the only ones who stand by the rifled gun in that caliber.
105mm are mostly rifled but the French had smoothbores.
Smoothbores work better with APFSDS and HEAT rounds as they do not
impart spin, and the fins on the projectiles provide stability. HE-
FRAG and normal APDS work better from a rfiled gun.
Cookie Sewell
WmB
>
>This explanation doesn't quite agree with the observation that the red
>hot barrel of a gun causes the bullet or shell to jam in the barrel
>(?). Remember those stories about peeing on the mortar barrel to cool
>it? Then the pictures of the gun crew hosing water on overheated 40
>mm Bofors both in WWII USN ships and one of a schellboot Bofors crew
>doing the same. Then of course you can't use a machine gun with a red
>hot barrel. There are reports of peeing on the barrel in a desperate
>attempt to get it working again.
The issue with putting rounds in a hot tube (e.g., mortars, closed bolt MGs)
is the round cooking off prematurely due to the heat. Thus the desire to
cool it by any means available in the... ahem... heat of battle.
WmB
Bruce Burden
:
: This explanation doesn't quite agree with the observation that the red
: hot barrel of a gun causes the bullet or shell to jam in the barrel
: (?).
I read a comment about US 105mm crews using replacement
barrels faster than was expected. When a team showed up to
find out what was going on, they found the 105 crews could
fire the gun faster than the 5 rpm "offical" factory max,
and as a result, were wearing out the rifling. Apparently,
up to 30% of the lands was gone.
It is also possible that, in the case of the Bofors,
the crew was attempting to change the barrel. I expect if the
tube expands, you will have a hell of a time getting the
barrel to rotate to unlock the threads. Not to mention, it
can't be pleasant to handle. :-)
Rufus
Yeah...different weapon(s). The only large guns I have any sort of
brush with are ship-board or mobile artillery. Of those, I've
always/only seen rifling marks on the rounds. Far lower rates of fire
too, I'd expect.
--
- Rufus
Rufus
...or sitting on a hot tarmac. We had some Harriers cook off some 25mm
sitting still way back, as I recall.
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- Rufus