Author Topic: Sweet pic of a destroyed t34 from the bk37 of a stuka  (Read 2437 times)

Offline Charge

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Re: Sweet pic of a destroyed t34 from the bk37 of a stuka
« Reply #15 on: December 04, 2014, 07:39:51 PM »
"Sure you can increase the muzzle velocity without necessarily increasing the peak chamber pressure for a given rd."

AFAIK you can't. Any increase in burn speed will burst the breech open (it can even happen with a too small load!) and the increase of driving substance will do you no good if the barrel length is not enough to contain the projectile for duration of that extra acceleration. Of course if the initial load was small to begin with there is room for increase but why would they do that?

The breech is designed to correlate with the load and the load correlates with the barrel length. The brake does not lighten the explosive load expressed on the breech but to the carrier aircraft in this case. A lighter projectile will have higher MV but it will also decelerate faster. Thus the heavier standard AP will retain its performance on longer ranges, where as the lighter projectile will have to be fired closer to regain its advantage in added MV.

Bk37 AP energy 13486J
Bk37 APCR energy 16837J
Mk103 APCR energy 8513J

To me the breech looks quite slim.



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Offline Cthulhu

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Re: Sweet pic of a destroyed t34 from the bk37 of a stuka
« Reply #16 on: December 04, 2014, 11:47:09 PM »
"Sure you can increase the muzzle velocity without necessarily increasing the peak chamber pressure for a given rd."

AFAIK you can't. Any increase in burn speed will burst the breech open (it can even happen with a too small load!) and the increase of driving substance will do you no good if the barrel length is not enough to contain the projectile for duration of that extra acceleration. Of course if the initial load was small to begin with there is room for increase but why would they do that?

The breech is designed to correlate with the load and the load correlates with the barrel length. The brake does not lighten the explosive load expressed on the breech but to the carrier aircraft in this case. A lighter projectile will have higher MV but it will also decelerate faster. Thus the heavier standard AP will retain its performance on longer ranges, where as the lighter projectile will have to be fired closer to regain its advantage in added MV.

Bk37 AP energy 13486J
Bk37 APCR energy 16837J
Mk103 APCR energy 8513J

To me the breech looks quite slim.

(Image removed from quote.)

-C+
Yes you can. But unless the current powder charge is low and can be increased without over pressuring the chamber (which I doubt it was on the BK37), then it would necessitate a change in powder and/or ignition source. What blows the breech apart is PEAK chamber pressure. This peak pressure correlates directly with the hoop tension in the walls of the chamber. Provided you stay below the tensile yield point in the elastic range you're ok (your barrel fatigue life is gonna suck though).

The total impulse applied to the round is the AREA under the Pressure vs Time curve, NOT the pressure itself. The trick is to stay BELOW the limiting max pressure, but to INCREASE the area under the P vs T curve. This can actually be done by varying the powder type (maybe a SLOWER burning powder) and varying the amount of powder. A blend of powders (yeah, I know  :eek: ) can also help. Changing the energy of the ignition source (primer) lets you fine tune it even more if needed. Refinements in powders over the years have actually allowed this. The improvements have been small, but significant. (~5%)

Once again, the muzzle brake has absolutely nothing to do with the primary recoil at the bolt or breech block. The purpose of the muzzle brake is to reduce the secondary recoil effects due to muzzle blast impingement on the face of the muzzle. The total recoil is primary & secondary recoil combined. And yes, the gun attachment structure has to be designed for this cyclic transient load.

You're correct that lighter rounds decelerate more quickly, but armor penetration is affected more by kinetic energy than momentum. At higher velocities the armor fails in a totally different manner (think brittle shear fracture) because at very high loading rates the stresses in the armor material don't have time to redistribute, and subsequently the armor fails at a lower load than if loaded more slowly. There's a reason why modern anti-tank rds are small sub-caliber projectiles moving at ungodly velocities.


And yeah, the whole chamber and breech look VERY slim.  :uhoh  I don't think I'd feel too comfortable standing next to this thing when it was being fired.  :)

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Offline DaveBB

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Re: Sweet pic of a destroyed t34 from the bk37 of a stuka
« Reply #17 on: December 05, 2014, 04:48:33 PM »
At what point does extending barrel length stop increasing velocity?  The Germans just mounted a longer version of the Rhinemetal 120mm cannon on their Leopard tanks.  It's the same as the cannon they supplied us with to put on our Abrams, except longer.  Velocity and armor penetration increased.

So that means that not every machine gun or cannon is at it's full potential, as many can gain an increase in performance just from extra barrel length.
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Offline Oldman731

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Re: Sweet pic of a destroyed t34 from the bk37 of a stuka
« Reply #18 on: December 05, 2014, 06:48:46 PM »
So that means that not every machine gun or cannon is at it's full potential, as many can gain an increase in performance just from extra barrel length.


True, until you reach the point where all the powder has burned before the round exits the barrel.  Then the extra length slows things down.

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Offline Charge

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Re: Sweet pic of a destroyed t34 from the bk37 of a stuka
« Reply #19 on: December 05, 2014, 07:17:35 PM »
Extra barrel length will give you better MV but it does not give you better absolute accuracy. You can shoot the same hit grouping on a static target with a short barrel as with a long barrel. Longer barrel is more suspect to vibrations of the platform and it may become cumbersome when applied to a tank cannon.

-C+
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Offline Karnak

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Re: Sweet pic of a destroyed t34 from the bk37 of a stuka
« Reply #20 on: December 05, 2014, 07:51:25 PM »
From an aircraft point of view a longer barrel also adds significantly to the weight.  A Hispano Mk V is essentially a Hispano Mk II with a number of inches removed from the barrel and the manual cocking mechanism removed.
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Offline MK-84

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Re: Sweet pic of a destroyed t34 from the bk37 of a stuka
« Reply #21 on: December 05, 2014, 09:43:49 PM »
did anybody try mounting a recoiless rifle to an aircraft?


They did:
http://en.wikipedia.org/wiki/Jagdfaust

The had an experimental recoiless weapon installed. The Wikipedia link I added explains it better than I ever could.

Offline Karnak

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Re: Sweet pic of a destroyed t34 from the bk37 of a stuka
« Reply #22 on: December 06, 2014, 01:53:34 AM »
They did:
http://en.wikipedia.org/wiki/Jagdfaust

The had an experimental recoiless weapon installed. The Wikipedia link I added explains it better than I ever could.
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Offline Rich46yo

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Re: Sweet pic of a destroyed t34 from the bk37 of a stuka
« Reply #23 on: December 08, 2014, 01:17:15 PM »
Taking a look at the original T34 and it kinda looks to me that it was used as practice with the cannon, or aircraft, mounted on the ground. I dont think this tank was destroyed by a Stuka in battle. It looks more like one used in test target practice.
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Offline bangsbox

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Re: Sweet pic of a destroyed t34 from the bk37 of a stuka
« Reply #24 on: December 09, 2014, 03:08:37 PM »
Taking a look at the original T34 and it kinda looks to me that it was used as practice with the cannon, or aircraft, mounted on the ground. I dont think this tank was destroyed by a Stuka in battle. It looks more like one used in test target practice.

the trajectory of the penetration holes look like they came down from the sky into the tank...not straight into it from the ground.

Offline bustr

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Re: Sweet pic of a destroyed t34 from the bk37 of a stuka
« Reply #25 on: December 09, 2014, 06:08:46 PM »
The BK 3.7 could penetrate from 100m-200m fired at an angle at Russian tanks or level. The MK101\103 in the Hs 129 couldn't penetrate until sub 100m. The BK 7.5 was a 1000m weapon but, used more often closer for accuracy. The round reloader allowed firing 4 rounds starting at 1000m into 200m. In testing, and after action results, the 75mm round ruptured a very large hole in the T34 as it penetrated the armor.

Hs 129 pilots were so used to flying in the grass, one flew down a street in a town with the buildings just feet away from his wing tips to shoot a Russian tank that was hiding in the town.
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Offline Rich46yo

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Re: Sweet pic of a destroyed t34 from the bk37 of a stuka
« Reply #26 on: December 10, 2014, 01:51:25 PM »
the trajectory of the penetration holes look like they came down from the sky into the tank...not straight into it from the ground.

The ones on the Hull do. They also look like a larger caliber. Its the turret ones that look different.

Either way I found the same picture in a search as well. With no documentation theres no way to know tho the rear hull ones look like the classic bk37 Stuka attack profile.
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