Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: bangsbox on December 03, 2014, 10:38:42 AM
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(http://i.imgur.com/9mHnEEv.jpg)
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Nonsense they would bounce off from that angle!!! :devil
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Offline put a T34 in the drone circuit so it sits on the runway. Fly the Ju87-G2 at it. Fire at sub 100yd. Tungsten carbide core round will pass through the armor. The pilots of the Hs 129 discovered this with their 30mm tungsten carbide core rounds after failures in battle shooting at 200m. When they fired sub 100m, the 30mm rounds passed through the T34 armor like butter. Slapping your plane's tail against the turret and angering was a very real danger. The inventor of the tactic died giving a demonstration against a captured T34. He slapped the tail of his Hs 129 against the turret.
In the game, commander mode will make you dead trying it on most competent GVers.
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Offline put a T34 in the drone circuit so it sits on the runway. Fly the Ju87-G2 at it. Fire at sub 100yd. Tungsten carbide core round will pass through the armor. The pilots of the Hs 129 discovered this with their 30mm tungsten carbide core rounds after failures in battle shooting at 200m. When they fired sub 100m, the 30mm rounds passed through the T34 armor like butter. Slapping your plane's tail against the turret and angering was a very real danger. The inventor of the tactic died giving a demonstration against a captured T34. He slapped the tail of his Hs 129 against the turret.
In the game, commander mode will make you dead trying it on most competent GVers.
The tungsten APCR rd is very lightweight compared to the HE and AT rds. Even so, it's surprising that a rd of that size would lose sufficient energy over just 100 yds to fail to penetrate. I'm surprised the Germans didn't experiment with different powders (to raise the muzzle velocity) or possibly a lighter, but longer rd (higher muzzle velocity/greater sectional density for penetration).
Then again, maybe the rd/gun was already optimized within the limits of their technology.
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The biggest problem was recoil destroying the aircraft when it came to mounting guns like the Mk101\103 and larger. The more pizzazz you put in the powder or the design of the round to build more initial barrel pressure. The more weight you have to add to the aircraft to over come the reaction. Yes they put a BK 7.5 under the Hs 129. Firing it almost stopped the forward momentum of the aircraft. The recoil mount made an already dog plane into a bigger dog plane. The destructive power of a single round out weighed the problems , dangers, and short lifespan of the platform. By that time the MK103 was the pinnacle of aviation mounted automatic cannon tech for Germany.
Think of the 75mm in the B-25H. Firing it even once, required inspecting the whole aircraft for sheared rivets and other damage. It was the best of the technology at that time especially when the final lightened version was mounted.
The Hs 129 pilots thought the factory specs would work as advertised. They shot British tanks in North Africa at 200m with great success. In Russia the T34 was a different beast. The whole program for Hs 129 almost failed because the 30mm rounds didn't penetrate. Until the sub 100m shooting was discovered. One tiny core inside the tank killed the crew and chewed up other things or, inside the engine compartment killed the engine. Or, setting off one of the tanks own rounds.
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(http://www.aef.se/Flygvapnet/Bilder/T18%2057mm%20akan%201000p.jpg)
Saab put a 57mm Bofors gun in the bomb bay of the B-18B, that with 2x20mm cannons and 8 rockets and a top speed of 360 mph made it to a pretty decent gorund attack plane. (bomber version took 3300lbs of bombs)
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Firing it almost stopped the forward momentum of the aircraft.
Not possible. Think Newton.
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Think of the 75mm in the B-25H. Firing it even once, required inspecting the whole aircraft for sheared rivets and other damage. It was the best of the technology at that time especially when the final lightened version was mounted.
The Mollins 57mm was better. Even per US tests it was better.
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I thought we were talking about the Bk37. Sure you can increase the muzzle velocity without necessarily increasing the peak chamber pressure for a given rd. It's just a matter of optimizing burn rate and powder selection. Barring that, reducing the weight of the carrier material in the rd (usually aluminum for an APCR rd and totally useless from a terminal ballistics standpoint) would also allow for a higher muzzle velocity without appreciably reducing the lethality of the rd.
As far as recoil goes, there probably would be little to no net increase in primary recoil force due to firing a lighter projectile at a slightly higher velocity (Conservation of Momentum). There might be a slight increase in secondary recoil due to blast impingement on the muzzle, but that can be mediated by a well designed muzzle brake.
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Yes both the MK101\103 had a well designed brake along with the BK 7.5 when mounted in the Hs 129. Otherwise the program was going to be canceled due to recoil issues. Why are you questioning what men did with their best abilities 70 years ago in a war with limited resources? At that moment the engineers in Germany working with that technology were it in the world. The core of those rounds was considered revolutionary at that time.
You are 70 years later second guessing them while they were in a war with limited resources. What is the point of this?? We both have access to google and you appear to be playing devils advocate with this like many engineers I've known. They did the best with what they had, or are you bent on showing they didn't. How about we hold a séance and ask them........
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did anybody try mounting a recoiless rifle to an aircraft?
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Yes both the MK101\103 had a well designed brake along with the BK 7.5 when mounted in the Hs 129. Otherwise the program was going to be canceled due to recoil issues. Why are you questioning what men did with their best abilities 70 years ago in a war with limited resources? At that moment the engineers in Germany working with that technology were it in the world. The core of those rounds was considered revolutionary at that time.
You are 70 years later second guessing them while they were in a war with limited resources. What is the point of this?? We both have access to google and you appear to be playing devils advocate with this like many engineers I've known. They did the best with what they had, or are you bent on showing they didn't. How about we hold a séance and ask them........
I never said they didn't do their best. In fact I pretty much assumed that in my initial post. My comments were regarding how the energy loss over a mere 100 yds was sufficient to defeat the rd, and how it wasn't resolved. It's surprising given that the Germans were experts at solving problems of this very sort.
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I never said they didn't do their best. In fact I pretty much assumed that in my initial post. My comments were regarding how the energy loss over a mere 100 yds was sufficient to defeat the rd, and how it wasn't resolved. It's surprising given that the Germans were experts at solving problems of this very sort.
I think we have something in common maybe - reloading centerfire and the study of exterior ballistics?
To address your earlier comment... Optimizing loads for AC armament is too expensive in a war. The Nation has to balance economics and therefore squeezing out a few FPS for a given round/weapon is out of the question. Too expensive
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did anybody try mounting a recoiless rifle to an aircraft?
Apparently there was some thought to putting one with an autoloader on the OV-10's early on. Wouldn't that be cool. :D
Recoiless guns tend to have low velocities, so if you're looking to kill a tank, you'll need a HEAT or squash-head rd. Most recoiless guns have HEAT rds for that.
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I think we have something in common maybe - reloading centerfire and the study of exterior ballistics?
To address your earlier comment... Optimizing loads for AC armament is too expensive in a war. The Nation has to balance economics and therefore squeezing out a few FPS for a given round/weapon is out of the question. Too expensive
Absolutely. It's a fascinating subject, though lately I've found terminal ballistics and lethality effects to be extremely interesting.
I agree wholeheartedly with your assessment of the wartime economic burden, though I tend to modify my thinking a bit for wartime Germany. Remember that these are the guys who made countless production line changes (usually to their detriment). That practice couldn't have been very cost effective.
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"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.
(http://wwiimodeller.co.nz/wp-content/uploads/Bordkanone-BK-37-30.jpg)
-C+
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"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.
(http://wwiimodeller.co.nz/wp-content/uploads/Bordkanone-BK-37-30.jpg)
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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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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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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.
- oldman
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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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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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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.
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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.
Ki-44 as well.
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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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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.
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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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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.