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IS-7 "Autoloader"

IS-7 autoloader

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Malleted11 #81 Posted 21 December 2013 - 12:13 AM

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View PostVlevs, on 20 December 2013 - 02:33 AM, said:

 

Can't disagree on the internet urban legend. Imagination (and national pride) tends to fill any gaps in knowledge. Still, some quite knowledgeable people are convinced of IS-7's excellency as a machine, and I really can't say I know any better. But some things I do disagree with.

 

First, armor protection. I really can't say how faithful WG has been in this regard, but frontal protection should be very good. So good, that I can't think of any weapon prior to 105 mm L7 APDS (1959) going through it at range. Early HEAT munitions were quite sensitive to angle, and IS-7's front has plenty of that. IS-7 is immune to Bazooka and PIAT at any horizontal angle.

 

Second, anti-armor performance is strong for the era, and doesn't seem to fall short of 120 mm L1, thus easily defeating any western tank until Chieftain (1966). This gives the design 10 years of immunity against rivals. Also, IS-7 was in theory possible to up-gun to 130 mm M-65 gun that could fire APDS, thus making it relevant up to 1980s.

 

Third, it's been mentioned that IS-7 prorotypes were more reliable than contemporary T-54 protos. The one that caught fire had supposedly reached the end of its engine's service life. Yes, a tank that spontaneously combusts when its 'warranty' runs out is a bit troublesome.

 

Fourth, the tank's power-to-weight ratio is close to T-54's and its height is similar. Both of these are better than contemporary western tanks, so saying it's a sluggish large target is wrong. Also it would've fit within Soviet railway loading gauge, and thus was rail-transportable. None of the Cold War tanks was transportable in western European rails. I can't see IS-7 exhibiting Maus-levels of logistical planning fail.

The British were mounting 183mm guns onto TD's (FV 4005 etc) in anticipation of threat, these were dropped when the Soviets abandoned there heavy armour.

 

We took the threat seriously enough, however don't fall for the propaganda.



TheKroo #82 Posted 23 December 2013 - 12:30 PM

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View PostT___A, on 20 December 2013 - 07:16 PM, said:

It had mostly to do with the size, the red army was skeptical of a 68 ton heavy tank after the failure of the IS-4.

 

Yep, the weight of it was most definitely one of the key factors in its demise.



BaZkeT #83 Posted 09 January 2014 - 09:01 PM

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There is lot's of nice info here. It's not only for the gun related things. I will copy a part for the gun:
-Armament-

The first prototype was armed with a 130-mm S-26 gun. It used separate-case ammunition, the mass of the projectile was 33 kg. To increase the rate and ease the work of the crew a pneumatic loading mechanism was installed, developed in conjunction with the Institute of artillery.

The next version of the IS-7, was armed with a new 130-mm naval gun S-70 (7020mm long) a 54 caliber barrel and it's weight was 4225kg. The shell had a mass of 33.4 kg and an initial velocity of 900 m/s with the ability to punch through 163-mm armor, mounted at an angle of 30 °, at a distance of 1000m and 143 mm - 2,000m. Rare of fire was from 6 to 8 shots per minute thanks to the naval style "rammer" (Unconfirmed)

-S-70 Penеtration values-

Shell \ Distance--------------------------------->500---1000---1500----2000---3000 (m)
БР-482 (Angle of impact 30°)----------------->205-----195-----185----175------145 (mm)
БР-482 (Angle of impact 90°)----------------->250-----240-----225----210------180 (mm)

Keep in mind that at different times and in different countries, different methods for determining armor penetration were used. As a consequence, a direct comparison with similar data from other sources is often impossible or incorrect

-Details about the IS-7s guns-

Ammunition for the S-70 consisted of 30 shells. Rather then the bulky pneumatic loading mechanism that was used on the first machine, a smaller chain mechanism with the electric drive was developed. The characteristic difference between guns was the muzzle brake design: The C-70 used small holes, and a C-26 has a slot design.

The tank fire control unit  provided guidance, regardless of the position of the gun and fired automaticly as soon as there was a target lock. The number of machine guns on the IS-7 reached eight: Two - large caliber, and the rest - 7.62 mm RP-46. A second CPV-44 was aded on the roof of the turret for firing at air and ground targets. Aditionally two 7.62 mm machine guns and a 14.5mm were mounted in the gun mantlet. All of them had a remote control. Ammunition for the machine guns consisted of: 400 rounds of ammunition for the CPV and 2500 for the ER.
Source: FTR wot blogspot (I cant post link for some reason)

 

T___A #84 Posted 10 January 2014 - 04:13 AM

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View PostBaZkeT, on 09 January 2014 - 01:01 PM, said:


-S-70 Penеtration values
Shell \ Distance--------------------------------->500---1000---1500----2000---3000 (m)
БР-482 (Angle of impact 30°)----------------->205-----195-----185----175------145 (mm)
БР-482 (Angle of impact 90°)----------------->250-----240-----225----210------180 (mm)
 

Going to have to call BS on those stats.

Block Quote

In order to perform factory trials of the S-70 gun and the loading mechanism, LKZ was scheduled to provide NIIAV MV with a production IS-2, equipped with an IS-7 turret, with the 130 mm gun and loading mechanism.

 

prem?



Vlevs #85 Posted 10 January 2014 - 09:16 AM

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View PostT___A, on 19 December 2013 - 04:49 AM, said:

The book that has that picture says

Quote

Ammunition to the gun was 30 rounds with 6 were in mechanical loader. RoF was up to 8 shots per minute.

 

Doesn't dispute it is burst RoF. I'm staying with my claim.

 

 

View PostBaZkeT, on 09 January 2014 - 10:01 PM, said:

[...]
Source: FTR wot blogspot (I cant post link for some reason)

 

Thanks for the transcript. WoT Forums do not permit linking directly to that site (Ha!).

 

 

View PostT___A, on 10 January 2014 - 05:13 AM, said:

Going to have to call BS on those stats.

[Table]

 

Quote

In order to perform factory trials of the S-70 gun and the loading mechanism, LKZ was scheduled to provide NIIAV MV with a production IS-2, equipped with an IS-7 turret, with the 130 mm gun and loading mechanism.

 

prem?

 

That table doesn't really dispute it. Figures might be for 30° impact angle, for which those match very well (205 mm vs 207 mm - insignificant difference). But then, we're dealing with WG-endorsed Soviet AccuracyTM, so there is no mention of impact angle, plate quality or penetration criteria. Also this document alone leaves dubious whether those were real-world tests or mathematical extrapolations. However, we do have the blog keeper's word every figure is utterly reliable.

 

As for IS-2 with IS-7 turret. IS-2 has turret ring diameter of 185 cm and IS-7 has 240 cm. Thus it isn't possible to fit IS-7 turret on IS-2 hull without drastically modifying the hull. And seeing that it is a cast hull, the hull and its expensive casting equipment would have to be essentially redone. Related to that, I've never heard of such tank being made. An open test mount for the gun might be possible, but a workable turreted tank not without excessive expenditure. But hardly a hindrance for WG's gifted metallurgists.



T___A #86 Posted 10 January 2014 - 10:20 AM

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View PostVlevs, on 10 January 2014 - 01:16 AM, said:

Doesn't dispute it is burst RoF. I'm staying with my claim.

 

That table doesn't really dispute it. Figures might be for 30° impact angle, for which those match very well (205 mm vs 207 mm - insignificant difference). But then, we're dealing with WG-endorsed Soviet AccuracyTM, so there is no mention of impact angle, plate quality or penetration criteria. Also this document alone leaves dubious whether those were real-world tests or mathematical extrapolations. However, we do have the blog keeper's word every figure is utterly reliable.

 

As for IS-2 with IS-7 turret. IS-2 has turret ring diameter of 185 cm and IS-7 has 240 cm. Thus it isn't possible to fit IS-7 turret on IS-2 hull without drastically modifying the hull. And seeing that it is a cast hull, the hull and its expensive casting equipment would have to be essentially redone. Related to that, I've never heard of such tank being made. An open test mount for the gun might be possible, but a workable turreted tank not without excessive expenditure. But hardly a hindrance for WG's gifted metallurgists.

I think it does, it would state if it was burst.

 

cost of IS-7 turret, 125,000 rubles

cost of an IS-7 turret on IS-2, priceless.

 

If you look at these numbers they align with 90 degrees.


Edited by T___A, 10 January 2014 - 10:29 AM.


Vlevs #87 Posted 10 January 2014 - 02:41 PM

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View PostT___A, on 10 January 2014 - 11:20 AM, said:

I think it does, it would state if it was burst.

[...]

If you look at these numbers they align with 90 degrees.

 

It does state "up to", so RoF doesn't go higher than that.

 

Your newer table is confirmed to be a mathemathical extrapolation, and doesn't have criteria attached, so I don't consider it very informative. For one, that table is probably a wartime (1944?) table, and IS-7 project was completed by 1949. During that time Soviet AP performance improved substantially. Besides, since BaZkeT's table doesn't give any criteria either, so it might be that all tables are somewhat accurate, just by different standards. And since there are no known 3rd party tests on S-70... Tough luck.



T___A #88 Posted 10 January 2014 - 07:10 PM

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 The first IS-7 with the S-70 was made in 1947 and the table is from testing.

Vlevs #89 Posted 11 January 2014 - 01:09 AM

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View PostT___A, on 10 January 2014 - 08:10 PM, said:

 The first IS-7 with the S-70 was made in 1947 and the table is from testing.

 

Going a bit off-topic, but this interest me.

 

How do you know that? And any idea of test criteria? I compared that table to results produced by DeMarre equation, and they matched a bit too well - particularly suspicious for German guns that use different shell designs - different from Soviet guns and from each other. I've been trying to find penetration data on Soviet guns for some time, but search has been quite frustrating. No source has been substantially better than another. If you can rectify that, I'm grateful indeed.

 

To elaborate why I'm dissatisfied with that table, let me compare it to some other articles from the same site.

http://tankarchives.blogspot.fi/2013/06/soviet-very-high-power-guns-bl-9.html

http://tankarchives.blogspot.ca/2013/03/bl-8-high-power-152-mm-gun.html

To summarize, those are practical test results for BL-9 and BL-8 guns, or the OBM-50 and OBM-53 guns on the table. First, there are test results for BL-9 against 203 mm plate @ 1000 m @ 0°. BL-9 fails to penetrate said plate according to Soviet criteria (75% of projectile mass through 80% of the time), and fails even against 180 mm plate. Second, BL-8 against 203 mm plate @ unknown range @ 0°. BL-8 fails to penetrate said plate according to Soviet criteria. And your table says both very narrowly pass said tests (204 and 205 mm @ 1000 m @ 0° respectively). Clearly there is something amiss here or I'm reading everything very wrong. Yes, I'm aware that the table gives higher figures than real-life tests, and BaZkeT's table gives higher figures than this one. No, I have no idea.

 

There's no word when and how tests that made it to wiki (which BaZkeT quotes) were made. As hazy as they are, I haven't seen a reason to believe tables you provided are much better. I don't read Russian, but if you do, given source is this book: http://www.panrus.com/books/details.php?bookID=189

 

Beyond that, there might been many tests with different ammo batches up to 1949 when IS-7 was cancelled.



rush0620 #90 Posted 11 January 2014 - 09:24 AM

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IS-7 historical pictures

 

http://imgur.com/a/Xd4mD

 

We will cover one more of Grabin's guns, the 130 mm S-70. This was the first domestic gun with an automatic loading mechanism. The mechanized ammo rack held both shells and propellant. The gun was loaded with mobile carriages and a mechanical rammer. The S-70 reached a rate of fire of 5.5 RPM with the automatic loader and 1.1 RPM without. A small batch of guns was produced in 1948.

 

S70


Edited by rush0620, 11 January 2014 - 10:21 AM.


T___A #91 Posted 11 January 2014 - 10:11 AM

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View Postrush0620, on 11 January 2014 - 01:24 AM, said:

I was the one who made that and posted that to reddit.

 

For some reason the IS-7 is firing M-65 shells.



T___A #92 Posted 11 January 2014 - 10:22 AM

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The sources I've seen put the BL-8 shell at 43kg vs the 49kg of the BL-10 which just adds to the mystery.

Vlevs #93 Posted 11 January 2014 - 10:40 AM

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View PostT___A, on 11 January 2014 - 11:22 AM, said:

The sources I've seen put the BL-8 shell at 43kg vs the 49kg of the BL-10 which just adds to the mystery.

 

152 mm ML-20's AP shell weighs ~49 kg and HE shell weighs ~43 kg. This might explain at least some of it, as I don't think BL-8 would have lighter AP shell than its shorter parent. But then, I really don't know much about Soviet shells and a separate, lighter AP shell might actually exist. In my experience, general reference books sometimes get these details wrong, as all figures aren't double-checked very well, and our topic is a bit obscure. Doesn't make this hobby any easier, for sure.

 

Edit: M-65 rocks.


Edited by Vlevs, 11 January 2014 - 10:41 AM.


AlbanianCommando #94 Posted 31 January 2014 - 05:42 PM

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