IS-2

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中铁四局
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Re: IS-2

Postby 中铁四局 » Thu 13 Jun 2019 18:02

They buffed ISU-122 accuracy from 30% to 45%

This isn't all for nothing.
Dear Eugen, Please give T-72BU its iconic red-eye shtora system back! It looks mean and awesome!

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Re: IS-2

Postby Azaz3l » Fri 14 Jun 2019 00:07

中铁四局 wrote:They buffed ISU-122 accuracy from 30% to 45%

This isn't all for nothing.

Kinda disappointed IS-2 didn't get any accuracy buffs. It has literally no reason to have inferior accuracy to ISU-122 now.
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Re: IS-2

Postby vanDryten » Sat 15 Jun 2019 00:17

First you should remember that this is a game not a simulator. Balance is more important than perfect historical equality.


1) The accuracy

Currently, the IS-2 has 30% accuracy in game which is unreasonably low. In reality, D-25T gun had a pretty low dispersion which was comparable to the German 88 L/71 even, this is very well illustrated in this article https://tankarchives.blogspot.com/2013/02/accuracy.html. At the range of 1900 meters, D-25T only had a dispersion of 120cm.
To illustrate, here's a 2.5m x 2m target (typical tank target) put over the D-25T dispersion at that range.


But in this case I think 30% is pretty fine. Those 122mm and 152mm shells are to heavy for long range shotouts which was indeed a problem for the IS 2 facing the heavy german panzers. Those shells have lower velocity when fired and the ballistic trajectories have a higher angle which makes it even harder to hit on far distances, however when penetrated by those shells the damange is more devastating compared to 75&88mm. Thats just easy physics and everybody how says different has no idea.
I'm not exactly sure how the armor system works at the moment, but that armor increase is too low compared to what was historically done

MO, IS-2 '44 frontal armor should go up to 190-200mm.

If you have no clue how they calculate it, why you propose your wish to be value you anyway?

Additional "tank archives" is not a valid source of information. Some maybe true, some won't, some info lacks context, keep that in mind!

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Re: IS-2

Postby Azaz3l » Sat 15 Jun 2019 13:30

vanDryten wrote:First you should remember that this is a game not a simulator.

And this game isn't some arcade strategy with imaginary stats either. What I'm saying here is that the authenticity is broken in comparison to other vehicles.

vanDryten wrote:Those 122mm and 152mm shells are to heavy for long range shotouts which was indeed a problem for the IS 2 facing the heavy german panzers.

There's literally no correlation between projectile weight and its parabolic trajectory physically speaking. Moreover, projectile weight has a positive impact on the resistance to wind, the greater the weight the less deviation to wind the round will suffer during flight. 122mm and 152mm rounds are clearly winners here.
vanDryten wrote:Those shells have lower velocity when fired

795 m/s muzzle velocity for D-25T isn't exactly low and is in fact comparable to that of the 88mm KwK 36 gun firing AP round (810 m/s).
600 m/s for 152mm ML-20S is also comparable to the 76mm F-34 used by T-34. Note that I didn't mention anything about buffing the 152mm accuracy. I'm fine with tanks with long 75mm and 88mm having superior accuracy due to better muzzle vel. and sights, it's that the IS-2 having 30% accuracy in comparison to them is unreasonably low.

vanDryten wrote:and the ballistic trajectories have a higher angle

Not according to D-25T firing table https://digitalcommons.unl.edu/cgi/view ... myresearch
and these
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vanDryten wrote:Thats just easy physics and everybody how says different has no idea.

That's an interesting statement especially when you start claiming that weight has an impact parabolic trajectory.

vanDryten wrote:If you have no clue how they calculate it, why you propose your wish to be value you anyway?

As I said again, it's a too low armor increase considering how the protection improved historically speaking. We'll see how it performs in game with that value.

vanDryten wrote:Additional "tank archives" is not a valid source of information.

According to who? The only thing that this guy does is translate archived documents to English. If some people don't like what's written in those documents, it's whole another story.
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Re: IS-2

Postby vanDryten » Sat 15 Jun 2019 17:44

And this game isn't some arcade strategy with imaginary stats either. What I'm saying here is that the authenticity is broken in comparison to other vehicles.


If you want authentic stats then you might consider -10-20% of armour value to each soviet tank due to weak steal, weak welding and weak construction.

There's literally no correlation between projectile weight and its parabolic trajectory physically speaking.


Yes there is, and thats the velocity.

Not according to D-25T firing table https://digitalcommons.unl.edu/cgi/view ... myresearch
and these
795 m/s muzzle velocity for D-25T isn't exactly low and is in fact comparable to that of the 88mm KwK 36 gun firing AP round (810 m/s).


Less velocity higher angle, thats really easy to understand. Btw the PzGr40 (APBC) with the KWK36/L56 has a muzzle velocity of 930m/s.

Moreover, projectile weight has a positive impact on the resistance to wind, the greater the weight the less deviation to wind the round will suffer during flight.


You really think that the aerodynamic resistance is lower on a bigger shell because it is more heavy? Please educate yourself on some basical physic laws.

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Re: IS-2

Postby Azaz3l » Sat 15 Jun 2019 19:16

vanDryten wrote:If you want authentic stats then you might consider -10-20% of armour value to each soviet tank due to weak steal, weak welding and weak construction.

"Weak steel" isn't a very scientific term to describe steel properties. Did you mean steel quality? Steel hardness? Steel brittleness? Because any of those were pretty much on point in USSR tank building especially in 1944 since the manufacturing quality grew every year. Same goes for welding.
That's also a pretty ironic statement when comparing this to German tanks that had exactly the stated issues in 1944, ie: poor welding, armor cracking from the first hit, armor spalling even when not penetrated, etc.
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King Tiger's frontal armor cracked from the first hit from 122mm HE.
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Panther frontal armor absolutely cracked from ammo detonation.
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Panther's frontal armor cracked all over
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HE round to Panther's glacis cracked all over.
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100mm AP to KT UFP

-40% armor value for Germans then?
Panthers randomly suffering mechanical failures due to not very good engine/transmission engineering?

vanDryten wrote:Yes there is, and thats the velocity.

Now go find where's the question of weight (mass) in these equations: https://en.wikipedia.org/wiki/Projectile_motion
And an even better question: what does weight (mass) has to do with velocity which is in meters per second? I already gave the muzzle velocity for the D-25T gun (795 m/s) previously.
So
vanDryten wrote:Please educate yourself on some basical physic laws.


vanDryten wrote:Btw the PzGr40 (APBC) with the KWK36/L56 has a muzzle velocity of 930m/s.

1) PzGr40 is APCR and not APBC
2) PzGr40 was produced in very small numbers and saw its production stopped by the end of 1943
3) PzGr40 is not in game
4) Comparing full bore AP to APCR velocities isn't a good idea

vanDryten wrote:You really think that the aerodynamic resistance is lower on a bigger shell because it is more heavy? Please educate yourself on some basical physic laws.

I suggest you to read more on the matter, especially here http://dynref.engr.illinois.edu/afp.html (the correlation between drag and mass especially) and here https://sites.google.com/site/technical ... and-spears
before telling others to educate themselves.
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Re: IS-2

Postby vanDryten » Sat 15 Jun 2019 21:42

-40% armor value for Germans then?


fact is due to metal shortage in late 1944 the germans had to replace the usual composition of the metal. Which, and there I agree with you, resulted in a higher brittleness. But that is not the discussion here, in June 1944 the panzers had no such issue.

And an even better question: what does weight (mass) has to do with velocity which is in meters per second? I already gave the muzzle velocity for the D-25T gun (795 m/s) previously.


To get velocity you need acceleration and that my friend is common knowlege since Newton, is including the mass.
High mass -> less accerleration -> less velocity -> higher angle. Its really that simple.

1) PzGr40 is APCR and not APBC
2) PzGr40 was produced in very small numbers and saw its production stopped by the end of 1943
3) PzGr40 is not in game


1)My fault it is actually APCBC in todays terms
2)wrong production ended 1943/44 with tungsten core(see US/UK pressure on Portugal due to tradings with germany), they continued building it with steal resulting in less penetration capabilities
3)yes, Panther G has it


I suggest you to read more on the matter, especially here http://dynref.engr.illinois.edu/afp.html (the correlation between drag and mass especially) and here https://sites.google.com/site/technical ... and-spears
before telling others to educate themselves.


Thanks for the link, with this I can show you without mathematical explaination that I was indeed correct.

Attached you can see that the diameter of a projectil has more influence on the range than its mass. Note that the mass has the same proportion as the 88mm to the 122mm diameter.
Attachments
88mm.JPG
88mm.JPG (42.27 KiB) Viewed 294 times
122mm.JPG
122mm.JPG (41.91 KiB) Viewed 294 times

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Re: IS-2

Postby Azaz3l » Sat 15 Jun 2019 23:40

vanDryten wrote:in June 1944 the panzers had no such issue.

And in August 1944, 2 months later, as seen in the KT armor report, they suddenly started to have them. Magic.

vanDryten wrote:To get velocity you need acceleration and that my friend is common knowlege since Newton, is including the mass.
High mass -> less accerleration -> less velocity -> higher angle. Its really that simple.

You mistake the initial acceleration to get the initial speed and the velocity of the projectile while in flight. You should absolutely learn the difference between those two. High mass only has an impact when the round is initially accelerated through the gun barrel, in this case more force is needed to accelerate the 122mm projectile which is three times heavier than the 88mm one.
You still fail to answer my question how does mass impact on the parabolic trajectory of a round while in flight.
PS: in the trajectory formula of projectile, there's no correlation between mass and (X, Y, time) coordinates. In vacuum, two projectiles fired at the same velocity and angle would always land at the same point, no matter their initial mass.
Moreover, the firing tables show pretty much comparable descent angles of 122mm and 88mm fired from L/56.

vanDryten wrote:1)My fault it is actually APCBC in todays terms

No, you started talking about
vanDryten wrote:Btw the PzGr40 (APBC) with the KWK36/L56

which is an APCR round for the KwK 36 gun.
vanDryten wrote:2)wrong production ended 1943/44 with tungsten core(see US/UK pressure on Portugal due to tradings with germany), they continued building it with steal resulting in less penetration capabilities

The production of the PzGr40 for KwK36 ended in late 43 and only a small number was made.
vanDryten wrote:3)yes, Panther G has it

Panther can fire 88mm APCR rounds with its main gun now?

vanDryten wrote:Thanks for the link, with this I can show you without mathematical explaination that I was indeed correct.

You claimed that mass has no effect on aerodynamic resistance of a projectile. Those sites prove you are wrong.

vanDryten wrote:Attached you can see that the diameter of a projectil has more influence on the range than its mass. Note that the mass has the same proportion as the 88mm to the 122mm diameter.

And this comparison is totally wrong, because:
1) This graphic is made to compare ball shaped projectiles which obviously have different ballistic coefficients from tank fired projectiles.
2) You are using proportions in a non linear equation
3) You use realistic values for diameter but not the mass
Little data:
122mm BR-471 AP: 25,0 kg
88mm PzGr39 APCBC: 10.2kg
That's 2.45 times the difference in weight.
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Re: IS-2

Postby vanDryten » Sun 16 Jun 2019 15:46

You told me mass has no influence on the angle of a shot but then you say it has because more mass gets less influenced by air drag.

You know the muzzle velocity of those projectils, you know 122mm has more mass. Why you think that the velocity is slower?

I hope you can see your contradictory.

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Re: IS-2

Postby varis » Mon 17 Jun 2019 10:13

Thread cleaned.

Please keep it civil and on topic.
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