IS-2: performance, variants, cost, units.

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Alejandro_
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Re: IS-2: performance, variants, cost, units.

Postby Alejandro_ » 24 Nov 2010 20:41

I found this report in M. Bariatinsky book on the IS-3. Can anyone improve/check my translation? it contains very interesting data on the IS-2 ballistic performance.

Image

In the second half of August the blueprints of the parts and systems of the modernized tank were sent to the GABTU. The report said the folllowing:

1. The armour

The front hull of the IS is flatter (compared to the previous one), made of high hardness steel . The upper armour -100mm/60° cannot be perforated with German 75mm and 88mm 1942 and 1943 models, with an initial velocity of 1000m/sec.

The lower part of the front hull can be pierced in case of a hit at 90° with piercing ammo:

a) 75mm model 1942 gun with an initial velocity of 1000 m/s from 900 meters.
b) 88mm model 1943 gun with an initial velocity of 1000 m/s from 2500 meters.
c) 88mm model 1936 gun with an initial velocity of 810 m/s from 100-300 meters.

The curved sections of the turret, with 130mm thick high hardness steel, cannot be pierced with the aforementioned guns.

The front part of the turret, made with high hardness steel and a thickness of 130mm can be pierced via a perpendicular hit with piercing rounds:

a) 75mm model 1942 gun with an initial velocity of 1000 m/s from 1100 meters.
b) 88mm model 1943 gun with an initial velocity of 1000 m/s from 3000 meters.

With this configuration, the armour of the IS in hull, torret and (front nose?) was significantly increased against impactos of rounds in these areas.

2. Setup of the gun

The installation of the gun in the modernized IS is through the roof of the hull, which can be dismantled. The installation is simple and easy, while the turret has a more has a more rational shape, which gives better protection against impacts.

3. Fighting compartment

The rotating system (teeth) in the turret of the modernized IS has new bearings, which leads to a more gentle rotation. The commander’s cupula has 2 MK-4 periscopes and is small. It is mounted in fixed locations at the movile hatch. This guarantees a reduction in the tank’s height and good all-around visibility for the commander.

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Re: IS-2: performance, variants, cost, units.

Postby Art » 21 Nov 2017 09:38

A "great tank scandal" in the summer of 1944.

A little known episode demonstrates that early IS-2 had their share of technical problems. On of the first units equipped with IS-2 tanks was 14 Guards Heavy Tank Regiment. In June 1944 the regiment with 28 IS was a part of the 5 Guards Tank Army in Belorussia. When operation "Bagration" was launched 29 Tank Corps to which the regiment was attached beginning from 25 June had to march on unpaved roads in a marshy and desolate region north of the Minsk-Orsha-Smolensk main road. As if that wasn't enough IS tanks distributed between brigades of the 29 TC were employed as tractors for towing T-34 tanks. The result was disastrous: already in the first days of the march so many IS were out of commission that the regiment had to say behind the main forces of the 29 TC to perform maintenance and tow unservicable vehicles. By 29 June the regiment had 11 IS operational at Oboltsy and the rest - 17 tanks stayed broken down in different places between Smolensk and Oboltsy. On that day the main forces of the 29 Tank Corps were already some 100 km to the west near Borisov. By 1 July the regiment marched further west to the town of Bobr on the Minsk-Smolensk main road. On that day only 6 tanks remained operational and 21 were out of commission, of them 3 at Bobr and the rest on the route from Smolensk to Bobr. A three days later on 4.7 the number of operational tanks dropped to just 3. The regiment stayed at Bobr until the second half of July performing evacuation and maintenance of its tanks for which purpose it was reinforced with Army's maintenance and tractor units. Only on 24 July after being transported by railroad it joined the main forces of the 5 GTA which were already in Lithuania hundreds of kilometers further west.

So basically the unit with two dozens tanks was rendered completely inoperative as a result of technical problems without even firing a single shot in battle.

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Re: IS-2: performance, variants, cost, units.

Postby Art » 21 Nov 2017 16:50

In a report submitted on 7 July 1944 technical officer of the 5 GTA noted that the army had to make marches on marshy and forested terrain, partly with sandy soil. "On those difficult roads heavy tanks and self-propelled guns of the 14 Guards Tank Regiment and 376 Guards Self-Propelled Regiment completely expended their maintenance resource and 70-80% of self-propelled guns and KV-2 (sic!) tanks are now in need of medium repair".
https://pamyat-naroda.ru/documents/view/?id=154006035
Some factory defects were discovered such as a flywheel having a faulty binding to a crankshaft or planetary steering mechanism's tendency to break down due to dust and sand. Special commissions from the Red Army's Tank Directorate and Commissariat for Tank Industry were called to investigate them.

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Re: IS-2: performance, variants, cost, units.

Postby Alejandro_ » 22 Nov 2017 12:23

Many thanks Art. In the link below you can find a report of 29th Independent Guards Heavy Tank Regiment, equipped with early IS-2.

http://tankarchives.blogspot.co.uk/2014 ... is-2s.html

There are quite a few reports in English in the link, definitely worth visiting.

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Re: IS-2: performance, variants, cost, units.

Postby randwick » 23 Nov 2017 15:40

.
That's not much of an indictment of the Tank but demonstrate the rank stupidity of the command ,
the IS-2 was already pretty heavy for its gearbox , that was the weak point of the KV-1
it would have struggled on bad ground , towing T-34 would demonstrate the going was truly atrocious if this quite nibble machine could drag its sorry butt along
if other T-34 couldn't drag their brothers , the going must have been atrocious

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Re: IS-2: performance, variants, cost, units.

Postby Art » 23 Nov 2017 17:13

The area where operation "Bagration" developed wasn't exactly the best tank country in the world. 29 Tank Corps to which the regiment was attached also left quite a number of T-34 on the road due to malfunctions, lack of fuel, stuck in terrain etc. Still they apparently fared better than IS tanks.

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Re: IS-2: performance, variants, cost, units.

Postby randwick » 27 Nov 2017 06:50

.
Making tanks bigger make their problems bigger too ,
even as well made as the Tiger was it still was a maintenance pig
it's quite to be expected than the big boys would have a higher attrition rate than lighter machines ,
it should be pointed out that while soviet generals were totally unimpressed by the KV-1 and voiced their desire not to have anymore of them , they were rather satisfied by the IS-2

It was not perfect but on the whole performed as was required

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Re: IS-2: performance, variants, cost, units.

Postby Alejandro_ » 27 Nov 2017 23:46

That's not much of an indictment of the Tank but demonstrate the rank stupidity of the command ,
the IS-2 was already pretty heavy for its gearbox , that was the weak point of the KV-1


Gearbox was acceptable, it was the transmission. It was replaced by a planetary one in KV-1S/IS.

even as well made as the Tiger was it still was a maintenance pig


One of the reasons for placing them in heavy tank battalions was the higher maintenance when compared to other models.

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Re: IS-2: performance, variants, cost, units.

Postby randwick » 29 Nov 2017 06:50

.
Good point ,
I'm aware than after the failure of the original design , rejected by the inspectorate , the project was saved by adopting the new gearbox design in some haste
this was much more satisfying ,
still ,transmission is the very Achilles heel of large mechanical vehicle , it require a good touch by the driver

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Re: IS-2: performance, variants, cost, units.

Postby Art » 29 Nov 2017 20:51

A document on IS-2 technical performance. That is one of the documents pertaining to the battle experience of the 50 Guards Heavy Tank Regiment. In the summer 1944 the regiment was attached to the 11 Tank Corps and operated in Volynia/Poland.

Guards engineer-captain Gorobets.

Maximal strain on the heavy tank on a march.

Operations of our unit in the summer of 1944 demonstrated technical capabilities of the heavy tank, its pro and contras in a complex battle situation.
Battle operations in the period from 7 July to 31 August 1944 developed on a rugged terrain in ill-passable sands and marshes, with many rivers and fords crossed. A quite long distance was covered by tanks on highways. Marches were mostly made on deep sands with plenty of small dust penetrating in huge numbers tanks’ aggregates and mechanisms to which also the weather contributed.
Operations were mostly of maneuver character during pursuit of the enemy and tanks had to advance on rough terrain and winding roads. Great strain on vehicles, deep sands, winding roads, high temperature, the presence of huge amount of dust, long marching distances on roads, and irregular maintenance due to combat situation was the situation typical for operational conditions in the summer of 1944. Despite heavy operational conditions most of tanks passed 800-900 km and engines expended 200-250 motor-hours.

When the regiment crossed the Vistula River conditions of vehicles were as follows:
Tanks No. 77, 233, 122, and 22 broke down short of Kovel and No.66 and 199 – short of Lukow and Tsytsyn due to engine malfunction. Engines had spent 50-60 motor-hours and became completely unusable due to premature wear of the crank group (rings, pistons, pins, cylinders) as a result of a large amount of small dust which in combination with oil acted as an abrasive paste.
Dust was drawn in large amounts by air through the gaps in the air filter into engine cylinders due to a flawed objurgating and also owing to drivers and maintenance personnel lack of experience of operation on a dusty terrain. Also during forced marches dictated by military situation there was no possibility to make periodic stops for filters clearing and washing which required 1-1.5 hours after each 4-5 hours of engine operation. Those were the reasons for premature engine malfunction of the said tanks.

Save for 4 tanks destroyed at Siedlce the Trans-Vistula region was reached by 9 tanks which were at the end of their lifetime; each of them spent 200-250 motor-hours and had a 900 km mileage, their technical conditions were as follows:
Engines due to strong wear lost a lot of power, and oil expenditure was 10 kg per kilometer. Engine start was troublesome especially after long stops (3-4 days), in some cases oil started to leak out of the exhaust pipe which was an indicator of the terminal phase of the engine operation cycle.

Vehicle chassis were also extremely worn-out. Track pins looked like crankshafts and were oval in section, most of track ears had cracks. It was also impossible to remove a pin at normal track strain, teeth of the driving sprockets had their operational surface strongly worn-out (up to … mm) and engaged ears of the tracks that were changed [?]. Arms of the idling sprockets were bent which made tanks to lose track when turning, and it was difficult to apply strain to tracks. Torsion bars of suspension wheels due to a constant strain and long-term exposure to alternating load lost an ability to resist torsion force and were partly deformed and some of them were in need of replacement. Axes of the suspensions wheels were bent. Such a condition of chassis made their renovation necessary, and tank engines had to be replaced. As concerns transmission oil started to leak through grease-retainers of the final drive, adjustment of the final drive was necessary as a makeshift solution and replacement of grease-retainers as an ultimate solution of the problem.
The main reason of the extraordinary wear of the chassis were the forced marches on dusty highways and difficult sandy dirt roads at high speeds and heavy strain on vehicles.

As a conclusion one should note that 6 tanks mentioned above required a premature replacement of engines due to rather difficult road conditions, constructional defects of air filters, inexperience of drivers and maintenance technicians, since it was the first time when operations were conducted in such a difficult situation. Later on those problems in tanks operation were solved and tanks started to conform to a normal operating lifetime. Air filters connections were additionally sealed, thanks to that engines served a long time which was 1.5-2 times longer than the lifetime guaranteed by the manufacturer.
As concerns planetary steering drive, main gearbox and the main clutch in the process of operation in the summer of 1944 they proved themselves reliable and fail-safe.

CONCLUSIONS:

In conditions of the maneuver warfare heavy tanks operated on forced marches and difficult road conditions – dust, dirt, sands, rivers, marshes, and at high speeds and heavy loads on mechanisms. In case of proper operation and regular maintenance tanks and provided that defects of the air filtration are fixed the maximal lifetime of the B-2K engine of KV-2-122 [sic!] is 250-300 motor-hours, and lifetime of the chassis – 900-1000 km.

… September 1944.

Link to the folder:
https://pamyat-naroda.ru/documents/view/?id=134586388

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Re: IS-2: performance, variants, cost, units.

Postby Art » 29 Nov 2017 21:19

It should be added that 50 Guards Regiment had 17 IS-122 and 1 IS-85 in mid July 1944. From 18 to 31 July the regiment lost 4 IS-122 as irreparable combat losses, 4 were damaged in combat, 2 had technical malfunctions (water pump failure) and 6 were lost to wear (those 6 tanks with engine failure mentioned in the document). On 1 August 1944 the regiment had 9 IS-122 operational and 4 in need of repair, total 13.

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Re: IS-2: performance, variants, cost, units.

Postby Alejandro_ » 03 Dec 2017 02:24

I'm aware than after the failure of the original design , rejected by the inspectorate , the project was saved by adopting the new gearbox design in some haste
this was much more satisfying ,
still ,transmission is the very Achilles heel of large mechanical vehicle , it require a good touch by the driver


IS series were much improved compared to KV. The cooling unit was more efficient; this was an issue in the KV series. There several evaluations and the IS series always came first. Some designers even proposed KV-122 with a 122mm gun.

and 6 were lost to wear (those 6 tanks with engine failure mentioned in the document)


Interesting Art, do you know what would happen to these vehicles? Broken up for pieces? Scrapped? Send back to the factory?

Thank you for the translation.

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Re: IS-2: performance, variants, cost, units.

Postby Art » 03 Dec 2017 19:31

Alejandro_ wrote:Interesting Art, do you know what would happen to these vehicles? Broken up for pieces? Scrapped? Send back to the factory?

Here available documents are ambiguous somewhat. Looks like 3 tanks were shipped to front-level repair, the other 3 had their engines replaced at some point after 1.08.44.

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Re: IS-2: performance, variants, cost, units.

Postby Alejandro_ » 07 Dec 2017 13:12

Here available documents are ambiguous somewhat. Looks like 3 tanks were shipped to front-level repair, the other 3 had their engines replaced at some point after 1.08.44.


Thanks, the reason why I asked is because as I understand, vehicles written off due to wear/tear, obsolescence and even lack of spares were also counted as losses in the analysis of Grigori F. Krivosheev. It is hard to find (in English sources) data on vehicles written off due to wear in specific units.

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Re: IS-2: performance, variants, cost, units.

Postby Art » 11 Dec 2017 17:23

Well, the regiment had 13 IS-2 on strength on 1.8.44. Additional 8 Is were received in November 44. On 14 January 1945 there were 21 IS available - all in running condition. From report on technical operation and maintenance of 11 Tank Corps' armor in the Vistula-Oder operation:
https://pamyat-naroda.ru/documents/view/?id=134586373
A basic match suggests that no tanks were written off after 1 August 1944 and all broken tanks were repaired.
From the same source regiment's tanks losses in the VO operation (14.1-4.2.45) were:
1 IS destroyed (write-off)
1 damaged by gunfire
2 drowned in a river
3 stuck in a marsh
1 stuck in a hole
2 had technical malfunctions due to a faulty operations
7 had malfunctions due to wear.
total 17 tanks.
On 4 February only 3 IS remained operational out of original 21. For comparison on the same day the number of operational T-34 in the 11 Tank Corps was 83 out of original 204.


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