Armoured Vehicles Discussion Thread

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Surya
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Re: Armoured Vehicles Discussion Thread

Post by Surya »

Sigh lets not even compare the armies

We are still essentially a "Lorry' army.

When we have a few thousand wheeled APCs (like 6 - 8K) - call me
aveek
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Re: Armoured Vehicles Discussion Thread

Post by aveek »

Guys I have a query for the experts on MBT Arjun. Looking at the turret of the tank, it gives an appearance of a virtual 'shell-trap'. It has an enormous silhouette, making it a really juicy target, large vertical faces on the turret in the frontal and side views. In comparison other MBTs of this class (M1Abrams, German Leopard, Israeli Merkava, British Chieftain, even our T-90!) have sloping turrets which would, to an extent, help deflect an incoming shell. Is there any reason for this sort of turret design for Arjun?
Vivek K
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Re: Armoured Vehicles Discussion Thread

Post by Vivek K »

First define what you mean by "enormous silhouette".

T-90 ht - 2.23 metres (7 ft 4 in)
Al-Khali ht - 2.40 metres (7 ft 9 in)
Arjun ht - 2.32 metres (7 ft 7 in)

Factor in the superior armor protection, the higher mobility of the Arjun and ability to fire on the move and then lets hear about the "enormous" part again!
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Re: Armoured Vehicles Discussion Thread

Post by Vivek K »

The only thing enormous about the Arjun is the size of the jhapad it gave to the T-90 in comparative trials.
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Re: Armoured Vehicles Discussion Thread

Post by Rahul M »

AFRCA wrote:Guys I have a query for the experts on MBT Arjun. Looking at the turret of the tank, it gives an appearance of a virtual 'shell-trap'. It has an enormous silhouette, making it a really juicy target, large vertical faces on the turret in the frontal and side views. In comparison other MBTs of this class (M1Abrams, German Leopard, Israeli Merkava, British Chieftain, even our T-90!) have sloping turrets which would, to an extent, help deflect an incoming shell. Is there any reason for this sort of turret design for Arjun?
username changed to aveek.
Rahul.

please do a search on BR with the keywords of your Q or post it in the newbie thread. every week someone asks the same question. :P
Drishyaman
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Re: Armoured Vehicles Discussion Thread

Post by Drishyaman »

rakall wrote: The maintainence issues can easily be sorted out if IA adopts a stakeholder & partnership attitude with CVRDE.. unfortunately that doesnot seem to come easily!!! In the early days it takes a bit of hardwork in partnership from both sides.. Take a typical example fo Dhruv -- IA was complaining incessantly on the maintainence issues with Dhruv & low availability (50-60% only) in the begining.. HAL embedded a small team at Leh with the Helo sqd to sort out the issues.. and in months all issues disappeared and availability imporved to 95+% or something.. there was a letter to HAL from the CO of the sqd praising the performance & availability of ALH..
I can confirm a similar kind of incident, a buddy of mine who till recent times had been tightening nuts and bolts on LCH ‘s tail rotor and hydraulic systems in b’luru has been moved to a small town ( won’t disclose the name of the place ;) ) in northeast where he tightens the nuts on 4 IAF Dhruvs which are stationed there. So, buying products from HAL and CVRDE can have this kind of advantage.
A man from HAL and CVRDE can always be there to tighten loose nuts.

BTW, where has "d_berwal" chacha gone, took a sabbatical to come back after another 6 month with more propaganda against Arjun ?
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Re: Armoured Vehicles Discussion Thread

Post by Viv S »

aveek wrote:Guys I have a query for the experts on MBT Arjun. Looking at the turret of the tank, it gives an appearance of a virtual 'shell-trap'. It has an enormous silhouette, making it a really juicy target, large vertical faces on the turret in the frontal and side views. In comparison other MBTs of this class (M1Abrams, German Leopard, Israeli Merkava, British Chieftain, even our T-90!) have sloping turrets which would, to an extent, help deflect an incoming shell. Is there any reason for this sort of turret design for Arjun?

The Leopard 2A4 is the most widely produced variant of the Leopard 2 family. And the most widely exported among its western peers as well.


Image


Also, while I haven't seen the pictures of the Arjun MkII, I'm fairly certain we'll see 'sloping' ERA on it.
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Re: Armoured Vehicles Discussion Thread

Post by D Roy »

Yes Yes,

the soviets were so concerned about casualties that they introduced the T-72 with an auto-loader to cut crew size to three from four. :mrgreen:

As per soviet philosophy ; three certain deaths better than four certain deaths onree.

The only tank in the post war (bow to the T-34) T-series worth its salt was the T-64 and that never saw enough development( i don't consider T-80 "enough development") because of cost. Also keep in mind I am talking about the setting at the time. In any case putting a gas turbine in place of a diesel is never a great idea.

In any case WARPAC knew that NATO would use tactical nukes out of Rammstein.


Arjun will smash Al-khalids literally by the dozens and the Pakis are shit scared that the IA may suddenly order 600-700 hundred of these. I just don't see Unkil giving the Pakis Abraams or the Pakis being able to afford the Leopard 2.

They will most probably try to counter using T-99KMs and for H&D purposes fanboys will talk about some 155mm gun and 2100 hp engine. :((
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

Drishyaman wrote:
rakall wrote: The maintainence issues can easily be sorted out if IA adopts a stakeholder & partnership attitude with CVRDE.. unfortunately that doesnot seem to come easily!!! In the early days it takes a bit of hardwork in partnership from both sides.. Take a typical example fo Dhruv -- IA was complaining incessantly on the maintainence issues with Dhruv & low availability (50-60% only) in the begining.. HAL embedded a small team at Leh with the Helo sqd to sort out the issues.. and in months all issues disappeared and availability imporved to 95+% or something.. there was a letter to HAL from the CO of the sqd praising the performance & availability of ALH..
I can confirm a similar kind of incident, a buddy of mine who till recent times had been tightening nuts and bolts on LCH ‘s tail rotor and hydraulic systems in b’luru has been moved to a small town ( won’t disclose the name of the place ;) ) in northeast where he tightens the nuts on 4 IAF Dhruvs which are stationed there. So, buying products from HAL and CVRDE can have this kind of advantage.
A man from HAL and CVRDE can always be there to tighten loose nuts.

BTW, where has "d_berwal" chacha gone, took a sabbatical to come back after another 6 month with more propaganda against Arjun ?
No need to make comments personal here :), Its a forum and i have my rights to voice my opinions. If you read my post i haven't said Arjun is a BAD Tank. Since i dont condemn T-90 most of you, take it as i am against Arjun.

Your analogy of embedding CVRDE folks is wrong.
- HAL folks can be embedded to tighten the nuts and bolts and can even do the same from ALH in war time as the AIr bases are in Indian Territory and ALH will return to base after the flight.

- But CVRDE folks can only do this till there is peace. In war time MBT's operate differently as compared to air assets, and will only return to base after the war is over. So do you suggest we embed CVRDE folks with Tank crews in field. How do you plan to do this, at Tank Troop level, Squadron level , Regt level or Brigade Level ?

For the serious people here:

A List no of MBT acquisitions by Iraq from 1960-1991: Source SIPRI
Year 1960 - 91
Country Model Number
Czechoslovakia T-55 400
China T-59 1000
China T-69 1500
East Germany T-55 50
Egypt T-55 300
Poland T-55 400
Poland T-72M1 500 (250 assembled in CKD and rest assembled using parts from various communist states routed through poland)
Romania T-55 150
USSR PT-76 245
USSR T-54 300
USSR T-34/85 130
USSR T-55 700
USSR T-62 2850
USSR T-72B 50 (lost in Iran-iraq war)
TOTAL 8575 (does not include losses in Iran-iraq war)

The T-72 were only in republican guards.
T-72 profile in Republican Guards:
- No TI sights. (no night fighting capability) (some were rumored to have Belgium made gen 1 TI installed)
- No Laser Range Finders.
- Most had basis Armour (Their sides had just 60 mm protection, the turret side 300 mm standard and flat 45 mm at rear)
- Some did have additional reinforced armor plate present both at the turret and the front upper hull. (probably the ones with Belgian TI)

Iraqi Tank inventory as per Flight International March 6 1991
- Tanks Original Strength 4,280 Destroyed 3,008
(assuming +/- 20% deviation as no authoritative source is available)
Tanks surviving 1991 Gulf war: 1250 to 1750 approx

During the period between the send and the first gulf war:
- No Tank sale to Iraq.
- They did restore the damaged tanks.
- Iraq never had a Tank production facility. Only had repair facility.
- Taking GW 1 losses to T-72, in GW 2 it can be estimated to be around 300- 400.
Estimated Total Strength : 2000 - 2500 Aproxx (aproxx 300-500 T-72)
- After GW2 T-72 did survive and were repaired and server New Iraqi army (200-300 Numbers)


Looking at gulf war performance and equipment profile:
- The analogy that T-90 will suffer the same fate as its a T-xx series is wrong and illogical.
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Re: Armoured Vehicles Discussion Thread

Post by ParGha »

D Roy wrote:I just don't see Unkil giving the Pakis Abraams or the Pakis being able to afford the Leopard 2.
As a matter of fact, the Abrams were offered to the Paks in late 1980s in an export-downgraded variant (similar to the version used by Egyptian Army). The Paks did take evaluations (Gen Zia-ul-Haq was returning from an exhibitionary trial when he died), but rejected the offer. The Germans did give away Leo 1s for free and Leo 2 early variants for very modest prices during their downsizing (Turkey was the main beneficiary, but it was also offered to India and UAE AFAIK).
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Re: Armoured Vehicles Discussion Thread

Post by Drishyaman »

Applogies !! d_berwal Sahab, if you had taken that comment personally. I made that comment for your views on Arjun.
As of Iraq’s T – 72 tanks toasted, that was done by shear air power and not by tank to tank battle.
Do you mean to say that T – 90 would survive any such massive air attack (considering the tank bruster missiles available now)?
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

Viv S wrote:
aveek wrote:Guys I have a query for the experts on MBT Arjun. Looking at the turret of the tank, it gives an appearance of a virtual 'shell-trap'. It has an enormous silhouette, making it a really juicy target, large vertical faces on the turret in the frontal and side views. In comparison other MBTs of this class (M1Abrams, German Leopard, Israeli Merkava, British Chieftain, even our T-90!) have sloping turrets which would, to an extent, help deflect an incoming shell. Is there any reason for this sort of turret design for Arjun?

The Leopard 2A4 is the most widely produced variant of the Leopard 2 family. And the most widely exported among its western peers as well.

Also, while I haven't seen the pictures of the Arjun MkII, I'm fairly certain we'll see 'sloping' ERA on it.
Arjun MK II will see sloping ERA in the form of K-5

One can read about K-5 here
http://www.russianarmor.info/Tanks/EQP/era.html

If one wants to read about T-90 (or western MBTs) steven kotsch site is very informative (but its in german), this guy has done some massive research work and compiled data.
http://www.kotsch88.de/autolader.htm
Last edited by d_berwal on 19 Feb 2011 21:42, edited 1 time in total.
d_berwal
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

Drishyaman wrote:Applogies !! d_berwal Sahab, if you had taken that comment personally. I made that comment for your views on Arjun.
As of Iraq’s T – 72 tanks toasted, that was done by shear air power and not by tank to tank battle.
Do you mean to say that T – 90 would survive any such massive air attack (considering the tank bruster missiles available now)?
No MBT will survive massive Air attacks for tank buster missiles.
Nither Arjun nor T-90 (or M1A2)
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Re: Armoured Vehicles Discussion Thread

Post by D Roy »


As a matter of fact, the Abrams were offered to the Paks in late 1980s in an export-downgraded variant (similar to the version used by Egyptian Army). The Paks did take evaluations (Gen Zia-ul-Haq was returning from an exhibitionary trial when he died), but rejected the offer. The Germans did give away Leo 1s for free and Leo 2 early variants for very modest prices during their downsizing (Turkey was the main beneficiary, but it was also offered to India and UAE AFAIK).
I am well aware of this. thank you.

the early M1 or M1A1 is toast against the Arjun. we are talking about today. and the Pakis are simply not going to get M1A2 SEP or Leo 2A6 which is what they will need to take on Arjun Mk-2.

The best they can hope for is a Chicom product.
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

Marten wrote:4" taller than the T-90. Where do you get your data? What is your definition of enormous?
Are you sure ALL of the MBTs have sloped turrets or are you deliberately saying this? :)
From a Height perspective Arjun is 4inch taller.

But for a target engagement perspective, please take a normal binoculars take a 1 meter card board and another 1meter 4 inches and place them at 100-200m distance and observe. Not much difference.

So if some one is looking form a TI sight at T-90 or Arjun which is 1 km away not much noticeable difference in terms of size.

Sloped Armour:
Sloping an armour plate makes it harder to penetrate for antitank-weapons, such as armour-piercing shells (kinetic energy penetrators) and rockets, if they take a more or less horizontal path to their target, as is often the case.

Principal:
The cause for the increased protection of a certain point at a given normal thickness is the increased line-of-sight (LOS) thickness of the armour, which is the thickness along the horizontal plane, along a line describing the oncoming projectile's general direction of travel. For a given thickness of armour plate, a projectile must travel through a greater thickness of armour to penetrate into the vehicle when it is sloped.

The Cosine Rule:
Even though the increased protection to a point, provided by angling a certain armour plate with a given normal thickness causing an increased line-of-sight (LOS) thickness, is of no consideration in armour vehicle design, it is of great importance when determining the level of protection of a designed vehicle. The LOS-thickness for a vehicle in a horizontal position can be calculated by a simple formula, applying the cosine rule: it is equal to the armour's normal thickness divided by the cosine of the armour's inclination from perpendicularity to the projectile's travel (assumed to be in the horizontal plane)
Formula:
T(L) = T(N) / cos(θ)
* T(L): Line of sight thickness
* T(N): Normal thickness
* θ: Angle of the sloped armour plate from the vertical
For example, armour sloped sixty degrees back from the vertical presents to a projectile travelling horizontally a line-of-sight thickness twice the armour's normal thickness, as the cosine of 60° is ½. When armour thickness or rolled homogeneous armour equivalency (RHAe) values for AFVs are provided without the slope of the armour, the figure provided generally takes into account this effect of the slope, while when the value is in the format of "x units at y degrees", the effects of the slope are not taken into account.

SLOPING Also Helps in DEFLECTION:

Sloping armour can increase protection by a mechanism such as shattering of a brittle kinetic energy penetrator or a deflection of that penetrator away from the surface normal, even though the area density remains constant. These effects are strongest when the projectile has a low absolute weight and is short relative to its width.
(However, these effects are strongly dependent on the precise armour materials used and the qualities of the projectile hitting it: sloping might even lead to a better penetration. Shaped charge warheads may fail to penetrate and even detonate when striking armour at a highly oblique angle.)

Sloped armour can also cause projectiles to ricochet, but this phenomenon is much more complicated and as yet not fully predictable. High rod density, impact velocity, and length-to-diameter ratio are factors that contribute to a high critical ricochet angle (the angle at which ricochet is expected to onset) for a long rod projectile

The behaviour of a real world projectile, and the armour plate it hits, depends on many effects and mechanisms, involving their material structure and continuum mechanics which are very difficult to predict. Using only a few basic principles will therefore not result in a model that is a good description of the full range of possible outcomes. However, in many conditions most of these factors have only a negligible effect while a few of them dominate the equation. Therefore a very simplified model can be created providing a general idea and understanding of the basic physical principles behind these aspects of sloped armour design.

If the projectile travels very fast, and thus is in a state of hypervelocity, the strength of the armour material becomes negligible — as by the impact both projectile and armour will melt and behave like fluids — and only its area density is an important factor. In this limiting case the projectile after the hit continues to penetrate until it has stopped transferring its momentum to the target matter. In this ideal case only momentum, area cross section, density and LOS-thickness are relevant. The situation of the penetrating metal jet caused by the explosion of the shaped charge of HEAT ammunition, forms a good approximation of this ideal. Therefore, if the angle is not too extreme, and the projectile is very dense and fast, sloping has little effect and no relevant deflection takes place.

In this very simple model the portion of the energy projected to the target depends on the angle of slope:

Ed / Ek = sin2(α)

where

* Ed: Energy transferred to the target
* Ek: Incident kinetic energy of projectile
* α: Angle of the sloped armour plate from the projectile's initial direction
However, in practice the AP-shells were powerful enough that the forces involved reach the plastic deformation limit and the elasticity of the plate could accumulate only a small part of the energy. In that case the armour plate would yield and much of the energy and force be spent by the deformation. As such this means that approximately half the deflection can be assumed (just α rather than 2α) and the projectile will groove into the plate before it slides along, rather than bounce off. Plasticity surface friction is also very low in comparison to the plastic deformation energy and can be neglected. This implies that the formula above is principally valid also for the plastic deformation case, but because of the gauge grooved into the plate a larger surface angle α should be taken into account.

Not only would this imply that the energy transferred to the target would thus be used to damage it; it would also mean that this energy would be higher because the effective angle α in the formula is now higher than the angle of the armour slope. The value of the appropriate real α' which should be substituted cannot be derived from this simple principle and can only be determined by a more sophisticated model or simulation.

On the other hand, that very same deformation will also cause, in combination with the armour plate slope, an effect that diminishes armour penetration. Though the deflection is under conditions of plastic deformation smaller, it will nevertheless change the course of the grooving projectile which again will result in an increase of the angle between the new armour surface and the projectile's initial direction. Thus the projectile has to work itself through more armour and, though in absolute terms thereby more energy could be absorbed by the target, it is more easily defeated, the process ideally ending in a complete ricochet.
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Re: Armoured Vehicles Discussion Thread

Post by Austin »

d_berwal wrote:Most had basis Armour (Their sides had just 60 mm protection, the turret side 300 mm standard and flat 45 mm at rear)
The Iraq T-72 belonged to Non-Warsaw ,Non-Soviet standards and its armour were sufficiently degraded , from what I have read the Iraqi T-72 was similar to what the Soviet T-72 used for training.

If opensource info is to be believe even the export Abrams are degraded and Armour lacks the DU layer.
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Re: Armoured Vehicles Discussion Thread

Post by Drishyaman »

Porkis can go in for M1A2 SEP anytime :) that will be best in India's interest.
Firstly, they will be half killed by the cost.
Secondly, it has gas turbine engine which will attract heat seeking missiles easily.
Thirdly, it will very noisy and at night it will be heard from 5 km distance.
Fourtly, Gas Turbines are Fuel guzzlers so in battle condition its has to have fuel supply lines.
Maintaining a V - 10/ V-12 engine and a Gas Turbine are different ball game. Will the porkis be able to maintain huge number of Gas Turbines engines in dusty desert environment ?
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Re: Armoured Vehicles Discussion Thread

Post by Arya Sumantra »

d_berwal wrote:Sloped Armour:
Sloping an armour plate makes it harder to penetrate for antitank-weapons, such as armour-piercing shells (kinetic energy penetrators) and rockets, if they take a more or less horizontal path to their target, as is often the case.

Why looking at only the vertical slopes for turrets? Even a horizontal slope gives you the same advantages of greater thickness and difficulty to pierce. Arjun's turret may be vertical but it is faceted at certain angles and not really a flat front. So there you get a horizontal slope.

Also during a battle a turret is constantly rotating firing at one enemy and then another and thus presenting its facets at different angles at different times. To assume that at all the times, the enemy is able to fire at it at angle perpendicular to its thickness is FALSE. IA is preparing for some serious coincidence here !!!
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

Arya Sumantra wrote:
d_berwal wrote:Sloped Armour:
Sloping an armour plate makes it harder to penetrate for antitank-weapons, such as armour-piercing shells (kinetic energy penetrators) and rockets, if they take a more or less horizontal path to their target, as is often the case.
1) Missiles don't seem to have a horizontal path at all.

2) Why looking at only the vertical slopes for turrets? Even a horizontal slope gives you the same advantages of greater thickness and difficulty to pierce. Arjun's turret may be vertical but it is faceted at certain angles and not really a flat front. So there you get a horizontal slope.

Also during a battle a turret is constantly rotating firing at one enemy and then another and thus presenting its facets at different angles at different times. To assume that at all the times, the enemy is able to fire at it at angle perpendicular to its thickness is FALSE. IA is preparing for some serious coincidence here !!!
The points presented were not specific to A particular MBT.

The general physics and the logic behind Armour sloping is what i presented.

Missiles don't have a horizontal path at all 95% of the times... (but missile will get through in any case looking at current level of armour on MBT's) thats why Armour blocks are put on the turret roof to provide some level of protection... roof is the weakest area ... top attack ammunition will easily get through.

- Can you point out where are the angled facets in case of Arjun MkI

- If attack were equally likely from all directions, the ideal form would be a sphere; because horizontal attack is in fact to be expected the ideal becomes an oblate spheroid. Angling flat plates or curving cast armour allows designers to approach these ideals. For practical reasons this mechanism is most often applied on the front of the vehicle, where there is sufficient room to slope and much of the armour is concentrated, on the assumption that unidirectional frontal attack is most likely. A simple wedge, such as can be seen in the hull design of the M1 Abrams, is already a good approximation that is often applied.

- When the turret is rotating in a fight its most of the time in its own a frontal arc(relative to the vehicle), and not doing 180 turns. If a situation arises where one is doing 180 turns , that means you are out flanked and about to be overwhelmed.

- when ever a turret turns towards the target it is engaging it is providing its angled facet which is better protected.

- if you read the full post you may see i am not assuming anything. Its just an attempt to explain the principal and working of sloped Armour.

- where did you get the idea its IA approach. Its the general scientific principal applied by MBT/ AFV designers.

this video explains the sloping in simple terms:
http://www.youtube.com/watch?v=_zglZRDhNQc

Video on reactive armour:
http://www.youtube.com/watch?v=t459NbF5Vek

Very good and comprehensive read on Armours. and Protection levels
http://sudden-strike.ru/forum/attachmen ... entid=6811
Last edited by d_berwal on 20 Feb 2011 02:52, edited 1 time in total.
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Re: Armoured Vehicles Discussion Thread

Post by Surya »

The Iraq T-72 belonged to Non-Warsaw ,Non-Soviet standards and its armour were sufficiently degraded , from what I have read the Iraqi T-72 was similar to what the Soviet T-72 used for training.

By other reports most soviet stuff exported including India were degraded.

So makes it all the worse!!!

Not that I believe the Soviet\Russian non degraded Tin crap will fare any better based on Checnya and Georgia -
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Re: Armoured Vehicles Discussion Thread

Post by Tanaji »

Ah, so after not being able to find anything to nitpick on the Arjun, its obviously the lack of "angled facet" that makes it inferior to the T90.
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Re: Armoured Vehicles Discussion Thread

Post by Rahul M »

of course the T-90's armour isn't angled either, just the ERA bricks on top.
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

Tanaji wrote:Ah, so after not being able to find anything to nitpick on the Arjun, its obviously the lack of "angled facet" that makes it inferior to the T90.
now did i say that... please read the posted reply in the correct context.
The reply was posted, when some one claimed that Arjun has angled facets. I was not aware of this fact so i have posted the reply, if some one can point out the angled facet on Arjun then i can correct my present understanding.
Am i nitpicking or you are NITPICKING!!!!
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

Rahul M wrote:of course the T-90's armour isn't angled either, just the ERA bricks on top.
Would you define ERA(Explosive Reactive Armour) as not a category of Armour.

Or my understanding of Armour is wrong?
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Re: Armoured Vehicles Discussion Thread

Post by Rahul M »

T-90's ERA bricks are separately added (bolted on ?) over the underlying composite armour. ERA bricks are usually considered separately from the main armour because of inherent weaknesses in add-on armour. ERA bricks are primarily for protection from shaped charge projectiles and their performance against modern APFSDS rounds remain questionable. so how does it matter if ERA is angled or not ?
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

Rahul M wrote:T-90's ERA bricks are separately added (bolted on ?) over the underlying composite armour. ERA bricks are usually considered separately from the main armour because of inherent weaknesses in add-on armour. ERA bricks are primarily for protection from shaped charge projectiles and their performance against modern APFSDS rounds remain questionable. so how does it matter if ERA is angled or not ?
It does matter as its the first part which will come into contact with the incoming round.

and it plays the part of sloped Armour also or my understanding is incorrect?
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Re: Armoured Vehicles Discussion Thread

Post by Viv S »

Drishyaman wrote:Thirdly, it will very noisy and at night it will be heard from 5 km distance.
Actually gas turbines are far quieter than regular diesel powerplants, and the Abrams is probably the quietest MBT out there despite having a 1500hp engine.
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Re: Armoured Vehicles Discussion Thread

Post by sudeepj »

d_berwal wrote:
Rahul M wrote:T-90's ERA bricks are separately added (bolted on ?) over the underlying composite armour. ERA bricks are usually considered separately from the main armour because of inherent weaknesses in add-on armour. ERA bricks are primarily for protection from shaped charge projectiles and their performance against modern APFSDS rounds remain questionable. so how does it matter if ERA is angled or not ?
It does matter as its the first part which will come into contact with the incoming round.

and it plays the part of sloped Armour also or my understanding is incorrect?
1. The ERA bricks provide protection by way of the E(xplosion) and the R(eaction), not their slope. Hence, IMO, its incorrect to categorize them as sloped armor.
2. The Arjun Turret is faceted, but doesnt have the slope one sees in the Merkava IV etc. Having said that, one needs to understand the composition of the armor package and what material properties it relies on on defeat APFSDS darts and shaped charge jets.

As per my limited understanding of the subject, it is advantageous to place Ceramic armor (the kind Kanchan is) in a flat profile to defeat APFSDS, while perforated armor (the applique sloping blocks on Leo2A6) is best placed in a highly sloped profile.

All this has been repeatedly rehashed in this forum since the days of 'JCage' etc., so I am not really adding anything new here.

The point I would like to make, berwal babu is, did you notice the qualifiers I put in the two statements about armor packages? The reason I put those qualifiers in, is because I am not an expert in the field.

What gives you the confidence to make bold confident statements about the relative efficiencies of armor packages, without being at least a dabbler in the field? Whatever conclusions you have reached using your skillset should have been as obvious to the DRDO designers, who are doers in the field. What makes you think they did not take an informed decision? Material properties is quite an arcane field, even people with pretty good technical backgrounds are circumspect about making definitive statements in this area.
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Re: Armoured Vehicles Discussion Thread

Post by Arya Sumantra »

d berwal wrote:- Can you point out where are the angled facets in case of Arjun MkI
Image
d berwal wrote: - if you read the full post you may see i am not assuming anything. Its just an attempt to explain the principal and working of sloped Armour.

- where did you get the idea its IA approach. Its the general scientific principal applied by MBT/ AFV designers.
I am not questioning the validity of the sloped armour principle. I am question IA’s application of that logic in Arjun’s context. On what basis did you come to conclusion that from whichever angle the enemy hits Arjun, he will get a hit perpendicular to its armour thickness ?

On the vast plains of battlefield the tanks of both sides are spread all over and not one in straight line of another. Given that Arjun shoots while on the move and with its turret swinging between left and right aiming at enemies spread all over, it would take a fortuitous coincidence of suitable (1) timing (2) relative position and angle (3) precise aim for an enemy to get a hit perpendicular to armour thickness of Arjun.

Now find the probability of doing that on a vehicle constantly on the move. And how many such lucky coincidences is the enemy going to get to knock down several Arjuns? It is in this light that IA’s logic is like clutching at the straws.

Image
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

sudeepj wrote:
d_berwal wrote:
It does matter as its the first part which will come into contact with the incoming round.

and it plays the part of sloped Armour also or my understanding is incorrect?
1. The ERA bricks provide protection by way of the E(xplosion) and the R(eaction), not their slope. Hence, IMO, its incorrect to categorize them as sloped armor.
2. The Arjun Turret is faceted, but doesnt have the slope one sees in the Merkava IV etc. Having said that, one needs to understand the composition of the armor package and what material properties it relies on on defeat APFSDS darts and shaped charge jets.

As per my limited understanding of the subject, it is advantageous to place Ceramic armor (the kind Kanchan is) in a flat profile to defeat APFSDS, while perforated armor (the applique sloping blocks on Leo2A6) is best placed in a highly sloped profile.

All this has been repeatedly rehashed in this forum since the days of 'JCage' etc., so I am not really adding anything new here.

The point I would like to make, berwal babu is, did you notice the qualifiers I put in the two statements about armor packages? The reason I put those qualifiers in, is because I am not an expert in the field.

What gives you the confidence to make bold confident statements about the relative efficiencies of armor packages, without being at least a dabbler in the field? Whatever conclusions you have reached using your skillset should have been as obvious to the DRDO designers, who are doers in the field. What makes you think they did not take an informed decision? Material properties is quite an arcane field, even people with pretty good technical backgrounds are circumspect about making definitive statements in this area.

what disadvantage will kanchan give if its sloped:
- will the LOS thickness not actually increase ?

- Isnt Chobham ( its more of a ceramic composite) , but why do we see challenger series MBT having sloped Armour?

- I know a pure ceramic is not useful for sloped Armour, but Kanchan is a composite Armour (Kanchan composite had a composition of ceramic, alumina, fiber glass and some other such materials mixed)
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

Arya Sumantra wrote:
d berwal wrote: - if you read the full post you may see i am not assuming anything. Its just an attempt to explain the principal and working of sloped Armour.

- where did you get the idea its IA approach. Its the general scientific principal applied by MBT/ AFV designers.
I am not questioning the validity of the sloped armour principle. I am question IA’s application of that logic in Arjun’s context. On what basis did you come to conclusion that from whichever angle the enemy hits Arjun, he will get a hit perpendicular to its armour thickness ?

On the vast plains of battlefield the tanks of both sides are spread all over and not one in straight line of another. Given that Arjun shoots while on the move and with its turret swinging between left and right aiming at enemies spread all over, it would take a fortuitous coincidence of suitable (1) timing (2) relative position and angle (3) precise aim for an enemy to get a hit perpendicular to armour thickness of Arjun.

Now find the probability of doing that on a vehicle constantly on the move. And how many such lucky coincidences is the enemy going to get to knock down several Arjuns? It is in this light that IA’s logic is like clutching at the straws.

Image
SLOPED ARMOUR
Sloped armour is armour that is neither vertical nor horizontal and is typically mounted on tanks and other armoured fighting vehicles (AFVs). For a given normal to the surface of the armour, its plate thickness, increasing armour slope improves the armour's level of protection of a certain point by increasing the thickness measured in the horizontal plane.

The effect of increasing the armor resistance by slope can also be achieved by curving the armor. The slope then is a combination of both the ‘tangent’ of the horizontal and the vertical planes.

Based on your diagram most of the MBT by nature have slope in horizontal plane because of movement of vehicle and the probability of impact not hitting perpendicular to armour thickness. (this is inherent in every AFV).

On the face of it, slope should not impact on armor design at all since the more you incline a plate to armor a volume or profile, the more material you need to cover that profile. (This is where you are coming form based on you diagrams)

Where slope becomes a factor is in the effect it has on the attacking projectile. This means that whatever effects it has, it’s
tied to the projectile nose design as much as the armor slope.

Firstly, all projectiles will ricochet. The real question is at what angle and velocity do they ricochet.

Ricochet occurs when a attacking projectile glances off the sloped armor of an AFV without digging in far enough to penetrate the plate. If it has no time to dig in before it ricochets, it can’t penetrate even modest amounts of armor. A complex model has been developed to predict the angle at which a projectile is expected to ricochet, this is called the ‘critical ricochet angle’.

The longer the rod, the higher the ricochet angle and the faster the rod, the higher the critical ricochet angle. In addition, heavy metal rods of WHA or dU2 ricochet at higher angles that steel. The critical ricochet angle is measured from the vertical plane [i.e. 90° is horizontal].

A rod of 10:1 L/d [Length to rod Diameter ratio] @ 1.7km/s should ricochet at ~78° when made of steel, while its WHA /dU counterpart will ricochet @ 81°. Stretching the penetrator to 15:1 L/d increases the ricochet angle to 82—83°, and it’s likely that 30:1 rods will ricochet at >84—85°. Tate’s ricochet formula predicts a ±5° variation around these values, so 50% of the 10:1 steel rods should ricochet @ ~78°, while ricochet will occur as high as 83°and as low as 73°. The above cases apply to thin plate targets, but if the plate is over 4:1 T/d [plate Thickness / rod diameter ratio] the ricochet angles should go down a few degrees.

Since the time it takes a projectile to ‘turn’ is around 40—60 micro seconds, and since the entire penetration event takes 300—400 microseconds [large warhead], even shaped charge warheads [HEAT] will ricochet when the right combination of striking velocity and angle are reached. Modern HEAT rounds will ricochet as well, the only question is whether this is before or after jet penetration.

The second aspect of slope is the asymmetrical force acting on the penetrator. When a projectile strikes a sloped plate, the side of the penetrator closest to the plate will suffer more force, erosion, and damage than the opposing side. This puts an unbalanced force on the rod, turning it in towards the plate – and then into the opposite direction. The penetrator takes a longer overall route through the armor, resulting in less penetration of sloped armor.

If you can get the above then. You assumption that the angled facet will give the same level of Armour protection as a sloped Armour is flawed.

Key here is:
- Sloped armor weighs more or less the same as vertical of the same LOS thickness
- It is specifically designed use of slopes as a way of increasing both the effective length of the armour and the angle of incidence.
Last edited by d_berwal on 20 Feb 2011 06:19, edited 1 time in total.
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Re: Armoured Vehicles Discussion Thread

Post by negi »

d_berwal wrote: what disadvantage will kanchan give if its sloped:
- will the LOS thickness not actually increase ?

- Isnt Chobham ( its more of a ceramic composite) , but why do we see challenger series MBT having sloped Armour?

- I know a pure ceramic is not useful for sloped Armour, but Kanchan is a composite Armour (Kanchan composite had a composition of ceramic, alumina, fiber glass and some other such materials mixed)
Should go to Arjun MBT FAQ 101.

The boxy turret or even the frontal glacis plates are only the exoskeleton the actual layers of Armour are beneath the structure itself so how do you know if 'Kanchan' is sloped/curved or normal to the LoS ?

Having said that coming to the point about wedge shaped turret increasing the protection level I would say may be yes, however that is a moot point what is important is does the present turret provide the protection levels as desired by the IA (i.e. meeting GSQR specs) ?

Why compare with Chobham ? Rahul_M and CJ have already posted reports about the successful tests of the Arjun armour against both the RU and Israeli APFSDS , and then of-course we have Mr. Fofonov's website which has a different story to tell about the T-90's armour.
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

negi wrote:
d_berwal wrote: what disadvantage will kanchan give if its sloped:
- will the LOS thickness not actually increase ?

- Isnt Chobham ( its more of a ceramic composite) , but why do we see challenger series MBT having sloped Armour?

- I know a pure ceramic is not useful for sloped Armour, but Kanchan is a composite Armour (Kanchan composite had a composition of ceramic, alumina, fiber glass and some other such materials mixed)
Should go to Arjun MBT FAQ 101.

The boxy turret or even the frontal glacis plates are only the exoskeleton the actual layers of Armour are beneath the structure itself so how do you know if 'Kanchan' is sloped/curved or normal to the LoS ?

Having said that coming to the point about wedge shaped turret increasing the protection level I would say may be yes, however that is a moot point what is important is does the present turret provide the protection levels as desired by the IA (i.e. meeting GSQR specs) ?

Why compare with Chobham ? Rahul_M and CJ have already posted reports about the successful tests of the Arjun armour against both the RU and Israeli APFSDS , and then of-course we have Mr. Fofonov's website which has a different story to tell about the T-90's armour.
Mr. Fofonov's website is quite informative plus his research on Armour design.
Can you explain what different story does his website portray for the T-90 Armour. In fact it portrays the effectiveness of K-5 and the strength of base T-90 Armour.

Coming to GSQR specs: My assumption would be it does not meet the current requirement that's why K-5 on Arjun MkII . (otherwise why would you do that, it carries a 2.5 ton weight penalty approx)
{It might have met the 1995 specs not present}

Non of the reports mention the origin of rounds used for test, its a mere speculation. (let me know if i need to correct my self here, i might be wrong)
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Re: Armoured Vehicles Discussion Thread

Post by Viv S »

d_berwal wrote:Coming to GSQR specs: My assumption would be it does not meet the current requirement that's why K-5 on Arjun MkII . (otherwise why would you do that, it carries a 2.5 ton weight penalty approx)
{It might have met the 1995 specs not present}
That's a rather big assumption. How do you know its not just a regular upgrade - incremental improvement in firepower(LAHAT), protection(APS and armor) and mobility(1500hp engine). I would make the assertion that it was ideal for 2010 and its being upgraded for 2015-20 requirements.
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

Viv S wrote:
d_berwal wrote:Coming to GSQR specs: My assumption would be it does not meet the current requirement that's why K-5 on Arjun MkII . (otherwise why would you do that, it carries a 2.5 ton weight penalty approx)
{It might have met the 1995 specs not present}
That's a rather big assumption. How do you know its not just a regular upgrade - incremental improvement in firepower(LAHAT), protection(APS and armor) and mobility(1500hp engine). I would make the assertion that it was ideal for 2010 and its being upgraded for 2015-20 requirements.
My assumption may be way off, I agree and it look like an upgrade. A genuine upgrade after the induction experience.

I think K-5 inclusion if for giving Arjun a decisive advantage in future battlefield.
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Re: Armoured Vehicles Discussion Thread

Post by Anujan »

d_berwal wrote:Coming to GSQR specs: My assumption would be it does not meet the current requirement that's why K-5 on Arjun MkII . (otherwise why would you do that, it carries a 2.5 ton weight penalty approx)
{It might have met the 1995 specs not present}

Non of the reports mention the origin of rounds used for test, its a mere speculation. (let me know if i need to correct my self here, i might be wrong)
When was it EVER stated that Arjun failed in firepower, mobility or protection? All whines were about "unreliability" or "lack of enough indigenous components". We seem to go round and round in this forum.

1. People said a lot about "heavier weight", completely ignoring that Arjun has lower ground pressure, can climb steeper gradient, can run faster, ford deeper and cross longer trenches. Finally that shut the mobilitiy whines up.

2. People whine about rifled barrel, completely ignoring the fact that Arjun's GSQR called for it. People say it cant fire APFSDS which is a lie. Original whine about lack of accuracy turned out to be malfunctioning electronics, and in the ensuing trials and advertisements (where even politicians scored bulls eye) shut up the Firepower wallahs.

3. Then come the protection wallahs. In all the hatchet jobs about Arjun (which even included torsion bar breaking) there is not one NOT ONE report of lack of protection. People talk about sloping armors and such without even basic knowledge of ballistics or material physics. (Pray tell me what angle does a ballistically fired projectile hit a tank? Assume 2km distance and if you knew high school physics you can probably compute the angle of impact. Now tell me, will an armor sloped up present a perpendicular or sloped facet to the projectile?). On top of that how do we know what the shape of the composite armor is inside the Arjun and its protection profile along various angles. Whether it was optimized for HEAT or APFSDS ? What was considered the main threat? Other tanks, Tandem missiles, RPGs or Helicopters? Before "all of the above" whines start, let me point out that *every* tank is optimized for some threat profile or other. Else all tanks will be carrying 20 ton armor on the roof and the top and there would be no top-attack missiles and the LCH project would have been shelved.

Arjun might very well feature ERA. Probably in the skirts and the rear. Even if it features ERA in the turret and glacis, how would we know it was not a weight reduction exercise (to trade the thickness of basic armor for ERA)?

Is there any evidence whatsoever of Arjun not meeting GSQR for protection? A single article or hearsay or hatchet job or any mention in whatever vision the army has for Mk 2 or any speech any interview? Nada. None.

And somehow it is reasonable to suspect that Arjun failed GSQR for protection. When the most quotable quote is "It is unfair to compare a BMW (Arjun) with a Maruti (T90)" Had it been the other way round, with Arjun as maruti and T90 as BMW, people would have gone to town about SDRE technology, soldiers lives in stake etc.
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Re: Armoured Vehicles Discussion Thread

Post by d_berwal »

You could have read my comment above instead of pouring your emotions...
Last edited by d_berwal on 20 Feb 2011 07:44, edited 1 time in total.
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Re: Armoured Vehicles Discussion Thread

Post by NRao »

d_berwal,

Could you please avoid quoting entire posts?

Thx.
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Re: Armoured Vehicles Discussion Thread

Post by Anujan »

d_berwal wrote:You could have read my comment above instead of pouring your emotions...
I did read your comments d_berwal-saar. Very carefully. I assume that you have the best of intentions for the IA, but I know how things go on in the forum here.

It starts out with:
1. Complete speculation onlee, but Arjun might have a propensity to catch fire because it carries more fuel (I REPEAT complete speculation)
a few days later it becomes
2. Did anyone analyze the threat of Arjun catching fire because of too much fuel?
and then
3. Arjun MK2 should increase Arjun's range to reduce fuel to reduce chances of catching fire
and then
4. The propensity to catch fire should be rectified in MK2
and then
5. The rampant fire problem should be rectified immediately in Arjun.
and then
6. Even in the presence of rampant fire problem, Arjun was thrust down the throats of the Armed forces who didnt complain at all. I met a junior who said that Arjun crew always carry a portable fire extinguisher with them
So sorry if I came down hard on your speculation.
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Re: Armoured Vehicles Discussion Thread

Post by Prasad »

Err a couple of posts from the past (ca 2007 by JCage)

http://forums.bharat-rakshak.com/viewto ... 23#p405923

http://forums.bharat-rakshak.com/viewto ... 47#p405947

Do we really need to rehash stuff from 2007 again on this thread about Arjuns armour? jmt.

Edit: Article by Chacko (again 2007) on Kanchan armour and a bit on the trials - http://frontierindia.net/the-kanchan-armor

And here is Kersi saab's post from DefExpo 2006 on the Arjun armour trials -
http://forums.bharat-rakshak.com/viewto ... 56#p187056
Last edited by Prasad on 20 Feb 2011 08:16, edited 1 time in total.
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