Main Battle Tanks and Armour Technology

[methos]

@methos, I have doubts, I mean M1 was definetely not better protected than Leopard 2 at a time when both were inducted in to service, IMHO protection was comparable, in fact M1 had better protected hull, and turrets had similiar protection.

There is no reason why the M1 should have similar protection. It weighed slightly less, is much larger and had thinner armour.

Also remember that difference in turrets internal volume came from the fact that M1's turret have more sloped armor, and the fact that contrary to Leopard 2, M1 have frontal turret armor sloped in, I don't know if this will be correct, sloped in 2 dimensions, while Leo2 have it sloped only in one dimension., so actually at the turret roof, internal volume is probably comparable and in M1 due to sloped armor it increases at the bottom, on the race ring level.

That's not the case for the turret, you can see that by looking at scale drawings. The hull is also much larger, that cannot be explained with "slope". The internal volume is bigger, the frontal profile is bigger, the side profile is bigger and more armour volume is used for the sides.

What is important to note is that British designers were provided with informations about FRG armor developments and in their opinion, none were as good as Burlington. Przeździecki assumed that Germans then adopted Burlington instead of domestic designs, however I know that you supports theory that Leopard 2 received armor developed in Germany not Burlington, if this would be truth, then according to British scientists, these armor were not at the same level of offered protection compared to Burlington. In such case American and later British claims might be true. But only if such scenario is truth, I do not say it is, simply I don't know.

I know that you and militarysta consider Przezdzieblo's articles as very good, but a lot of the sources mentioned aren't very scientific. When he says that German armour was worse based on British accounts there is always a lot of possible bias; read a British book and they will tell you that rifled guns are better.
I also don't have scientific sources saying how the exact German armour looked and if it was better than Burlington. But the general non-scientific description of the armour does not say that it is Burlington armour. Spielberger says that it is based on the same working mechanism, while Frank Lobitz calls it "Beulblechpanzerung" (bulging plates NERA).

The point is however: NERA in the sense of metal plates with an elastic interlayer material (like rubber) was patented in Germany 1973 by Dr. Manfred Held, even prior they received any information about Burlington according to the Polish articles.

Regardless wether the Leopard 2 carries original Burlington ("Chobham") or not (what is IMO more likely since the Germans did have different requirements for armour protection) - it will likely not be worse than Burlington given that the Brittons shared Burlington technology with the Germans.

PS. M1 turret is not unique, Leclerc turret also have composite armor protection over turret bustle side surfaces.

No, take a look:

And about weight, you also should first consider if we weight "dry" or combat weight, the latter is allways bigger.

Yes, but the M1 Abrams got more stuff put inside. Both weight values by STGN seem to be the combat weght.

BTW there are also issues with Leopard 2 weight, for all variants from A1 to A4, have provided weight data of 55 metric tons, then we should assume that tank didn't had improved armor all that time?

What are you trying to do?
Armour technology did improve for no weight gain. But not so much that the M1 with the weight limit to survive 115 mm APFSDS could survive 125 mm APFSDS from the same range - that's depending on the ammunition more than 70% more protection required. 115 mm APFSDS was always simulated by NATO with a 105 mm APDS from a little smaller range (e.g. 105 mm APDS from 500 m) - penetration was slightly above 300 mm. If NATO did simulate 125 mm APFSDS ammunition during the 1970s, then they would probably use the German 120 mm gun - which penetrated 450 mm RHA at 1,000 m.
Unless the armour got magically nearly twice as efficient than the earlier version, the M1 Abrams could not be protected against 125 mm APFSDS with it's low combat weight. We also don't assume that the Leopard 2A4 is capable to survive 140 mm APFSDS, do we?

 

[Damian]

There is no reason why the M1 should have similar protection. It weighed slightly less, is much larger and had thinner armour.

And you have data for Leopard 2A0/A1 when it comes to weight? It seems that provided data is for Leopard 2A4, and I am more certain that weight for earlier Leopard 2 variants that are provided are just copy paste from Leopard 2A4 data.

As for thinner armor, I really would want @STGN to present his 3d models and estimations. This might put a fresh look on to this subject.

That's not the case for the turret, you can see that by looking at scale drawings. The hull is also much larger, that cannot be explained with "slope". The internal volume is bigger, the frontal profile is bigger, the side profile is bigger and more armour volume is used for the sides.

Yes turret itself is bigger but it is because of the side armor slope, if side armor would be vertical then internal volume would be roughly the same.

As for turret sides, remember that their thickness does not mean that they are especially heavy, internal structure, density and weight my differ.

It was mentioned that Burlington can be "tuned" for specific threats, so side armor configuration might tuned in such way that frontal armor can offer better protection.

I know that you and militarysta consider Przezdzieblo's articles as very good, but a lot of the sources mentioned aren't very scientific.

Most of materials that Przeździecki use are official, declassified Burlington program documents, it is difficult to not call them scientific, rest also seems to be very reliable sources.

The point is however: NERA in the sense of metal plates with an elastic interlayer material (like rubber) was patented in Germany 1973 by Dr. Manfred Held, even prior they received any information about Burlington according to the Polish articles.

Seems it is error in translation, in article it is only mentioned that patented ERA designed by Mr. Held had similiar working mechanism to Burlington besides the lack of explosive material in British design, these were observations of British scientists working on Burlington.

No, take a look:

Nope, armor modules were just deattached, search for photos of complete turret, armor modules can be clearly visible from behind.

You can see the actuall turret bustle bulkhead, armor module and storage box mounted to the module.

Yes, but the M1 Abrams got more stuff put inside. Both weight values by STGN seem to be the combat weght.

More stuff, at that time? Besides ammunition I can hardly see more stuff there.

What are you trying to do?
Armour technology did improve for no weight gain. But not so much that the M1 with the weight limit to survive 115 mm APFSDS could survive 125 mm APFSDS from the same range - that's depending on the ammunition more than 70% more protection required. 115 mm APFSDS was always simulated by NATO with a 105 mm APDS from a little smaller range (e.g. 105 mm APDS from 500 m) - penetration was slightly above 300 mm. If NATO did simulate 125 mm APFSDS ammunition during the 1970s, then they would probably use the German 120 mm gun - which penetrated 450 mm RHA at 1,000 m.
Unless the armour got magically nearly twice as efficient than the earlier version, the M1 Abrams could not be protected against 125 mm APFSDS with it's low combat weight. We also don't assume that the Leopard 2A4 is capable to survive 140 mm APFSDS, do we?

Sorry, I just do not agree with such oversimplification. Mainly because we really know very little about Burlington and it's performance. You should consider that most of more proffesional armor estimations are based on the simplified models that do not include due to many reasons, more data.

This is why I would not put too much faith in to estimations avaiable in the internet or various publications. Especially that many of them are based on armor model that was not Burlington but rather a disinformation to put in to confusion foreing intelligence services from countries not friendly to NATO. Przeździecki in his article notice this by presenting older, very popular model of how Burlington/Chobham might look like and that it does not look anything like what we could seen on more recent photos.

 

[methos]

And you have data for Leopard 2A0/A1 when it comes to weight?

Yes, I have.

As for thinner armor, I really would want @STGN to present his 3d models and estimations. This might put a fresh look on to this subject.

It is a point were scale measurements done by me, done by Russians, done by someone who posted it on wikipedia and U.S. claims match. I doubt that STGN's 3-D model is easily enough to proof several independant sources wrong.

Yes turret itself is bigger but it is because of the side armor slope, if side armor would be vertical then internal volume would be roughly the same.

Depends on wether the sides would be vertical at the top or bottom line of the current slope. But this "what if" stuff doesn't help anyone here, the M1 Abrams has more internal volume and this generates more weight.

As for turret sides, remember that their thickness does not mean that they are especially heavy, internal structure, density and weight my differ.

Yes, but then the armour protection provided would be lower, unless the U.S. did use better composite armour. Since both U.S. and FRG did have access to Burlington armour there is no logical reason to assume that.

Most of materials that Przeździecki use are official, declassified Burlington program documents, it is difficult to not call them scientific, rest also seems to be very reliable sources.

Most, but not all. I don't speak polish and cannot easily identify the passage where he says that the Brittons found German armour to be inferior, but I have seen that his sources also include Hunnicutt, Ogorkiewicz and Hilmes.

Seems it is error in translation, in article it is only mentioned that patented ERA designed by Mr. Held had similiar working mechanism to Burlington besides the lack of explosive material in British design, these were observations of British scientists working on Burlington.

ERA was patented in 1970. NERA in 1973. According to an article written by Dr. Held himself. I didn't refer to the article.

Nope, armor modules were just deattached, search for photos of complete turret, armor modules can be clearly visible from behind.

There are no armour modules at this location. There is a big storage box and a mount for the GALIX protection system. Look at the previously posted image, how small the screws normally connecting the deattached boxes with the turrets are... do you think such small screws can hold a composite armour module?

More stuff, at that time? Besides ammunition I can hardly see more stuff there.

More ammunition and more fuel. But this doesn't matter as STGN provided values for the combat weight.

Sorry, I just do not agree with such oversimplification. Mainly because we really know very little about Burlington and it's performance. You should consider that most of more proffesional armor estimations are based on the simplified models that do not include due to many reasons, more data.

Yes, the estimations are based on oversimplified models, but the protection requirements show us that there wasn't any more protection required. We also know by Hunnicutt that Burlington was the only type of armour to meet these without exceeding the weight limit.
You noticed that I didn't argue using the estimated values? I argued using actual penetration data and the requirements for armour protection.

 

[Damian]

Yes, I have.

So?

It is a point were scale measurements done by me, done by Russians, done by someone who posted it on wikipedia and U.S. claims match. I doubt that STGN's 3-D model is easily enough to proof several independant sources wrong.

You should give his model a chance, IMHO it is better.

Most, but not all. I don't speak polish and cannot easily identify the passage where he says that the Brittons found German armour to be inferior, but I have seen that his sources also include Hunnicutt, Ogorkiewicz and Hilmes.

When he speaks directly about armor performance he use official documents, Hunnicutt, Ogorkiewicz and Hilmes are used mostly as a source for historical events etc.

There are no armour modules at this location. There is a big storage box and a mount for the GALIX protection system. Look at the previously posted image, how small the screws normally connecting the deattached boxes with the turrets are... do you think such small screws can hold a composite armour module?

It is armor module, you should as some French guys that have better knowledge about Leclerc.

Yes, the estimations are based on oversimplified models, but the protection requirements show us that there wasn't any more protection required. We also know by Hunnicutt that Burlington was the only type of armour to meet these without exceeding the weight limit.
You noticed that I didn't argue using the estimated values? I argued using actual penetration data and the requirements for armour protection.

Well IMHO armor back then was about 450-500mm RHAe vs KE, both for M1 and Leopard 2, I think Militarysta had something about this issue. Later the improvements gave them 500-600mm, Americans in 1988 with fielding of heavy armor package exceeded that level, it was then known that to have proper protection armor must have around 700-800mm or more vs KE.

 

[methos]

So?

"55 t" according to Waffen-Arsenal Band 69 from 1981
"55.15 t" according to Waffen-Arsenal Band 98 from 1986 (at this time the newest tank is the Leopard 2A3 which only differs by the use of the newer SEM 80/90 radio set from older models)
"55.15 t" according to Kampfpanzer Entwicklungen der Nachkriegszeit from Rolf Hilmes (1984)

It is armor module, you should as some French guys that have better knowledge about Leclerc.

What you call "armor module" covers only two thirds of the height of the ammunition compartment, because the smoke grenade dischargers cover the upper third. I doubt that this would make sense.

Well IMHO armor back then was about 450-500mm RHAe vs KE, both for M1 and Leopard 2, I think Militarysta had something about this issue. Later the improvements gave them 500-600mm, Americans in 1988 with fielding of heavy armor package exceeded that level, it was then known that to have proper protection armor must have around 700-800mm or more vs KE.

This is a way too simple approach to protection levels. With 500 mm RHAe vs KE a tank would be immune to then existing large caliber ammunition point blanc - is there any case known to you where a vehicle was required to be immune against existing ammunition from point blanc?
The requirements for the M1 Abrams we know - even though they theoretically could have changed later - required armour protection against 115 mm APFSDS from 800 m.
The Chieftain was expected to resist then existing 115 mm APFSDS from 800 to 1,000 m.
The Marder IFV was expected to resist 25 mm APDS from 500 m.
Chieftain Mk 5/2 with Burlington was required to resist 115 mm APFSDS from 700 m.
The Soviet T-72 was required to survive 105 mm APDS from 500 m.
MBT-70 should resist 105 mm APDS from 800 m.
Even current STANAG 4569 requires armour protection for a given range and not point blanc.

Considering that everybody in the past required armour protection from a range and not point blanc, your values are too large. Then again the M1 cannot have as much armour as the Leopard 2, the later M1A1 versions may have.

 

[Damian]

"55 t" according to Waffen-Arsenal Band 69 from 1981
"55.15 t" according to Waffen-Arsenal Band 98 from 1986 (at this time the newest tank is the Leopard 2A3 which only differs by the use of the newer SEM 80/90 radio set from older models)
"55.15 t" according to Kampfpanzer Entwicklungen der Nachkriegszeit from Rolf Hilmes (1984)

So then any armor upgrade would be minimal in the A4.

What you call "armor module" covers only two thirds of the height of the ammunition compartment, because the smoke grenade dischargers cover the upper third. I doubt that this would make sense.

It is armor module, believe me.

This is a way too simple approach to protection levels. With 500 mm RHAe vs KE a tank would be immune to then existing large caliber ammunition point blanc - is there any case known to you where a vehicle was required to be immune against existing ammunition from point blanc?
The requirements for the M1 Abrams we know - even though they theoretically could have changed later - required armour protection against 115 mm APFSDS from 800 m.
The Chieftain was expected to resist then existing 115 mm APFSDS from 800 to 1,000 m.
The Marder IFV was expected to resist 25 mm APDS from 500 m.
Chieftain Mk 5/2 with Burlington was required to resist 115 mm APFSDS from 700 m.
The Soviet T-72 was required to survive 105 mm APDS from 500 m.
MBT-70 should resist 105 mm APDS from
Even current STANAG 4569 requires armour protection for a given range and not point blanc.

Considering that everybody in the past required armour protection from a range and not point blanc, your values are too large. Then again the M1 cannot have as much armour as the Leopard 2, the later M1A1 versions may have.

It depends what you consider as point blanc, STANAG's are not considered as MBT's protection, as for the rest, maybe yes, maybe not, without detailed data that is classified we can only speculate.

Or we can consider that due to cost reduction and to please congress, designers and army decided to manufacture initial variant as protected as per requirements published, and as quick as possible it was followed by M1IP that was protected against 125mm ammunition, and was as interim variant was as quickly as possible replaced in production by M1A1 with all the goodies army wanted and could afford back then.

 

[methos]

So then any armor upgrade would be minimal in the A4.

The Leopard 2A4 has been made in four different batches. During the second batch (a total of 150 vehicles) after the production of the 96th tank a new "generation" of armour was adopted making use of more advanced technology. The last two batches consisted of 100 and 75 tanks. This means that only 229 Leopard 2A4s with the improved armour were made, while a total of 466 Leopard 2A4s with older armour were produced. To this come more than 1,000 converted Leopard 2s which were also designated "Leopard 2A4". So if someone writes down "the Leopard 2A4 weighs 55.15 tonnes" it depends on of which Leopard 2 exactly he is talking about.
According to what I was told the 229 Leopard 2 tanks with improved armour weigh more than the previously made, but not very much; somewhere above 56 tonnes. These tanks however were split up; 225 hulls were used to create the first Leopard 2A5 tanks - the turrets were mounted on older tanks. Militarysta once said that the Polish Leopard 2s have turrets of different weight - so some of them might mount the "late" Leopard 2A4 turret, others the "early" Leopard 2A4 turret.

It is armor module, believe me.

Why should I? There is no reason to believe you here, you don't have access to any sources about the Leclerc which should be better than mine.
If there was armour, answer me the following three questions:

1. Why does the armour cover only two thirds of the height of the ammunition comparment?
2. Why is this the only place where the armour is used modular, when the rest of the turret has integral composite armour?
3. Why is there a handle at the "armour module" if it should be too heavy to be carried by hand (considering that the thinner and smaller side skirts elemnt of Leopard 2 and Merkava cannot be carried by single men).

 

[Damian]

Why should I? There is no reason to believe you here, you don't have access to any sources about the Leclerc which should be better than mine.
If there was armour, answer me the following three questions:

1. Why does the armour cover only two thirds of the height of the ammunition comparment?
2. Why is this the only place where the armour is used modular, when the rest of the turret has integral composite armour?
3. Why is there a handle at the "armour module" if it should be too heavy to be carried by hand (considering that the thinner and smaller side skirts elemnt of Leopard 2 and Merkava cannot be carried by single men).

1) Might be a tradeoff for lower weight or for more plausible granade dischargers placement.
2) Well the whole armor is modular, although at the crew compartment changing modules is a bit more dofficult, you need to cut sort of material to get to the modules.
3) Perhaps the hande is there to slide out armor module that can be attached to sort of rails.

I think that some French guys can say more about it.

 

[STGN]

That the original M1 is less protected than the Leopard 2 is a very simply logical conclusion. It is simply the result of the comletely different conception of the tanks.
If you compare the hulls of both tanks, you will notice that both have about the same height, but the Leopard 2 has more ground clearance. If you look at the hulls without the side skirts, the Leopard 2's hull is 3,420 mm wide and 7,570 mm long, while the M1's is 3,480 mm wide and 7,916 mm long.
When it comes to the turret it is very similiar: The M1's turret is wider and longer, while the height from turret ring to turret roof is nearly the same. The M1 simply has a greater volume and a much greater surface than the Leopard 2, so it has to have more armour weight for reaching the same level of armour protection.
But there is also something to consider: the M1 has a kind of unique turret design. While all other NATO tanks have thick composite armour at the turret sides over the crew compartment, but the turret bustle is only protected by thin homogenous or spaced armour, the M1 Abrams has thick composite armour at the sides of the crew compartment and the turret bustle (which means about twice (!) as much side turret armour as the Leopard 2 without any gain in crew protection). The reason for this is the huge amount of ammunition stored in the bustle - while other tanks like the Challenger 1 & 2, the Leopard 2 and Leclerc store a considerable amount of ammunition in the hull, the M1A1 and M1A2 store only six 120 mm rounds in the hull - once the turret bustle is penetrated the M1 tank is a mission kill!

The original M1 produced from 1980 to 1984 also featured the "short turret" with thinner armour (according to Zaloga the armour was thickened from M1 to M1IP/M1A1 by about 9 inches). Russian estimates put the original armour thickness at about 600 mm, while an U.S. book claim that it is two feet thick and wikipedia says it is ~650 mm thick.

As far as the component weight is concerenced: Not all parts of the Leopard 2 are heavier and it is not as simple as shown by you.
For example look at the weight difference of the Leopard 2's powerpack and the M1's powerpack (figures by Rolf Hilmes):
If you compare only the MB 873 to the AGT-1500C the M1's powerpack is 71% lighter.
If you compare the complete powerpack (including transmission etc.) of the Leopard 2 with the complete powerpack of the M1, the later is 51% lighter.
If you compare the complete powerpack and the nominal fuel load of the Leopard 2 with the complete powerpack and nominal fuel load of the M1, the later is only 11% lighter.

What Rolf Hilmes does not provide is the weight of the fuel tanks; 1,200 l are much easier to store than 1,900 l - how much did that affect weight? I have seen different values for military class fuel tanks but unluckily none for thrid generation tanks: it is possible and very probable that the weight difference is smaller than 5% in the end.
Then several components of the Leopard 2 are lighter - for example the 42 rounds 120 mm ammunition (1/3 HEAT-Frag-FS (23 kg) and 2/3 APFSDS (19 kg)) will weigh less than 55 rounds 105 mm ammunition (18-19 kg APFSDS, 22 kg HEAT-FS). The PERI R17 weighs less than the M1's commander cuppola and the coaxial armament (and the ammunition for this) also weighs less. There are many different values, without knowing most of them speaking about the internal systems is not very helpful.

As Damian said - even though he speaks of "fairy tales" (because he is a big fan of the Abrams) - the original requirement for the M1's armour protection was to resist 115 mm APFSDS from 800 m distance and to resist shaped charges with a diameter of 127 mm. He is correct when saying that we don't know if the requirements for armour protection were changed, but this is no proper reason to say that the M1 is better protected than that. Let me show you why I think that the armour protection requirements weren't increased:
According to Hunnicutt the weight requirements were made at the same time as the previously mentioned protection requirement. However the weight requirement wasn't changed a single time (because the values given there are the same as used on production M1) - so where should the increased protection come? According to Hunnicutt the reason why the M1 ended up with Burlington armour is that it was the only type of armour fulfilling the protection requirement without exceeding the weight limit. The M1 also was superseded by the M1IP and the M1A1 - both having thicker and heavier armour. Why would they increase the amount of armour, if the previously armour was enough to resist current and future threats?

The "short" turret is not that short it gives same LOS protection as a LEO2 turret. Its true that the armor array is only 2 feet thick(660mm from my calculations, right side) but only if you take a shot perpendicular to it. Because of the slope the frontal LOS is much thicker:

This is a simplified top view.
Its the same with the sides.
We also has to remember that the side armor is not uniform and that the armor plates used on the turret bustle is only about .25" compared to the side over the crew compartment which is about 1" thick so the bustle is probably not as well protected as the crew compartment. and probably lighter.
Zaloga's 9" I don't know where he got that one from the long turret is only about 15.5 cm longer on the x axis. About 120mm was added to the armor array on both sides of the turret on the long turret. Some M1A1s had extra ~1.5" plate welded on the front during ODS.
I think the reason the armor was increased was to stay ahead of the game and let the turret be able to be updated in the future unlike the Leo2, Abrams still uses same length turret while the Germans have had to mount a huge beak on theres to keep up.
Another thing that is considerably heavier on the Leo2 is the tracks are 3000(1360Kg) pounds more than T156(installed on an M1) according to Hunnicut. Comparing the PERI R17 to the cupola is not fair you would have to include the commander hatch on the Leo too, but I agree Mg's and ammo are heavier, though it doesn't seem off set the heavier parts of the Leo2.
STGN

 

[methos]

The "short" turret is not that short it gives same LOS protection as a LEO2 turret. Its true that the armor array is only 2 feet thick(660mm from my calculations, right side) but only if you take a shot perpendicular to it. Because of the slope the frontal LOS is much thicker:

This is a simplified top view.

From my PoV a typical case of overestimaton/inaccurate measuring. The armour ends at the corner in front of the gunner's primary sight, at about the same height of the sight's cover:

Also note that the side armour at the GPS is not reduced. May I ask you what source you use for your 3-D model? It doesn't match with the drawings from Hunnicutt's book and also not with the values by Paul L. for SteelBeast, nor with any scale measurement I have seen.
The relation between hatches and armour thickness is also very odd, considering the values from official reports.

We also has to remember that the side armor is not uniform and that the armor plates used on the turret bustle is only about .25" compared to the side over the crew compartment which is about 1" thick so the bustle is probably not as well protected as the crew compartment. and probably lighter.

You know the thickness of the outer layer (?) of the armour because of what? The armour cavity has the same size.

 

[darklabor]

I think that some French guys can say more about it.

I'm coming!

1) The thing that you don't figure out is that the autoloader is only 22 rounds just because it is flat. The two-third armor is just two-third compaired to the crew compartment height. It is 100% the height of the autoloader. Above the autoloader, you got ammunitions for coax, roof-mounted armament, GALIX ammo as well, plus air-conditionning (depending on the serie).
2) It is NOT the only place where you can change the modules. The picture only shows two modules removed for unknown reasons. My guess is that the two modules where removed to be torn apart and recycled. At any case to be used as a spare, that's definitely sure (this armor is waaaaay too old now).
Keep in mind that everywhere you got figer glass, there is modular armor (plus the armored block for the GPS aka VTI).
3)It's not because there is a handle that it means it can be carried. The front turret sides got a handles as well...
The easy explaination is : because you need to grab something to climb a tank (especially for field maintenance). Tankers tend to always get on board by the very forward access path (no need to have handles there is the skirt armor for this). But there is actually three way to access the tank per side.

 

[Damian]

@methos, Hunnicutt drawings are not 100% accurate as well, there is sort of disinformation included there as well with weld lines for example.

Still armor should be around 800mm thick at front at 0 degrees.

As for side turret armor, yeah on photos of damaged M1's you can see that bustle had thinner outer plates and inner plates (structure) is same thickness over the bustle and crew compartment.

@darklabor thanks!

 

[STGN]

From my PoV a typical case of overestimaton/inaccurate measuring. The armour ends at the corner in front of the gunner's primary sight, at about the same height of the sight's cover:

Also note that the side armour at the GPS is not reduced. May I ask you what source you use for your 3-D model? It doesn't match with the drawings from Hunnicutt's book and also not with the values by Paul L. for SteelBeast, nor with any scale measurement I have seen.
The relation between hatches and armour thickness is also very odd, considering the values from official reports.



You know the thickness of the outer layer (?) of the armour because of what? The armour cavity has the same size.

You are not taking into account that the GPS chimney is quit deep that is why you are underestimating armor depth. There is armor around the levers for the GPS doors.
What do you mean the armor at the GPS is not reduced, the GPS chimney cuts right up through it?
My source is late XM1 dimensional characteristic. Hunnicutts drawings are inaccurate just look at the M1A1 mantle its way too short because somebody was lazy and just reused the M1 drawing showing the mantel of the M1 forward(the crew placement blueprint is pretty good though). Not sure I am familiar with Paul L.s work. Anyway all blueprints I have found on the web are inaccurate in some way or other(the ones from the 3 color NATO drawing manual are also okay) until i found the exterior dimensions of the XM1 these produces a 3d model which actually looks like the Abrams you see on photos. CATTB document then revealed the size of the cupola hole and GPS hole and using those numbers together fits like a glove on a 3d model. I think you are misreading those reports.
I know the thickness of outer layer because I use my eyes and look at pictures of the Abrams, the pictures of blown up Abrams tanks makes it even easier too see. The armor cavity size might be the same but the armor in them are different as pictures from Iraq has shown. Crew compartment side has spring loaded NERA array. Bustle has very different rack mounted NERA array plus it makes sense that you would make the bustle weaker to make sure energy released is not going into the crew compartment.
STGN

 

[Damian]

Crew compartment side has spring loaded NERA array.

This issue is still not solved, I have a theory that spring loader NERA array is just a part of the bigger array, this is because these bolts mounted to the spring are to fragile to hold the array on their own + the inner bulkhead surface is smooth, no attachements, no welding marks, neither welding marks or attachements on this bolts, so there must be some sort of more armor there.

Not to mention that armor array on XXI century variants might and probably is (per informations from some docs) than 1980-1990's variants.

 

[STGN]

This issue is still not solved, I have a theory that spring loader NERA array is just a part of the bigger array, this is because these bolts mounted to the spring are to fragile to hold the array on their own + the inner bulkhead surface is smooth, no attachements, no welding marks, neither welding marks or attachements on this bolts, so there must be some sort of more armor there.

Not to mention that armor array on XXI century variants might and probably is (per informations from some docs) than 1980-1990's variants.

Well my hypothesis is that the springs does one thing and that is too keep the array in place, they would be almost completely compressed, the array weight is supported by the bottom of the armor cavity. Whether or not there is something behind it is off cause unknown. But it seems strange to me that there would be springs and something behind it to support it, why not just remove the springs then.
STGN

 

[Damian]

Well the whole array known to us looks like this - NERA + springs + bolts (or that look like a bolts), however Militarysta made some closeups on these bolts and he noticed that bolts are broken, made from thin material, just too fragile to keep that in one place, for example if armor would be hit and whole array would start to move (compress backwards) these bolts would just crush. So my hypothesis is that these bolts are placed in openings inside more solid, non spring mounted array, so the outer array have bigger movement capabilities while there is behind in some distance a backup array and then there is backplate.

Something like this:

Look, the bulkhead is smooth, nowhere to attache these bolts, neither weld marks are visible, any of them, so IMHO there needs to be something more inside.

PS. I know, I know, drawing is not perfect, it is not meant to be, it is only general idea how it might looks like.

 

[methos]

@methos, Hunnicutt drawings are not 100% accurate as well, there is sort of disinformation included there as well with weld lines for example.

I know. I showed the inaccuracy of his drawings the last time we were discussing the armour thickness of the M1A1/2, which was about ~70-100 pages earlier in this thread, when you wanted to proof that the M1A2 has 960 mm thick armour.

Still armor should be around 800mm thick at front at 0 degrees.

No, that is not the case. If we take a look at the images above showing we can see that the armour directly ends (without any cut-out part) at about 15% of the total size of the gunner's primary sight from the side armour away. Measuring this distance in the image from STGN and using his 84.5 cm as scale, I end up with an armour thickness of 67.5 to 71.5 cm. That is enough to say that it should not be "around 800 mm".

As for side turret armor, yeah on photos of damaged M1's you can see that bustle had thinner outer plates and inner plates (structure) is same thickness over the bustle and crew compartment.

That the outer layer is thinner does not mean that armour array is lighter. It is still taking up the same space and is definetly heavier than the armour the Leopard 2 or the Challenger 1 and 2 have at their turret bustles.

You are not taking into account that the GPS chimney is quit deep that is why you are underestimating armor depth. There is armor around the levers for the GPS doors.

I am taking that into account. That's why I also posted an image from the GPS. The armour however ends in front of the main sight, while the steel cover of the main sight does only slightly increase the external appearance vs the actual location.

What do you mean the armor at the GPS is not reduced, the GPS chimney cuts right up through it?

Look at the image I posted above! It can easily be seen at photos from the turret rebuild that the chimney only cuts through the right corner of the turret frontal armour.

My source is late XM1 dimensional characteristic. Hunnicutts drawings are inaccurate just look at the M1A1 mantle its way too short because somebody was lazy and just reused the M1 drawing showing the mantel of the M1 forward(the crew placement blueprint is pretty good though). Not sure I am familiar with Paul L.s work. Anyway all blueprints I have found on the web are inaccurate in some way or other(the ones from the 3 color NATO drawing manual are also okay) until i found the exterior dimensions of the XM1 these produces a 3d model which actually looks like the Abrams you see on photos.

In other words, it is just an more or less "educated guess". With your work you can easily see that Zaloga, who earns his money with writing about tanks is wrong with the 9 inches size difference and it is in reality 15.5 cm? With your work you can easily say that the Micheal Green, who took all the images in his book by himself (including images from the interior and from the turret roof) is wrong when he says that the turret armour of the M1 is about two feet thick?
Hunnicutt's drawings are inaccurate, we have seen that already ages ago. But neither I nor other people on the internet are completely morons and rely blindly on a single drawing. However all drawings I could find with the google image search show that the frontal armour is less than claimed by you. And guess what: I am not the only one. Militarysta posted other values in the thread some time ago, the Russian come up with other values, the Americans come up with different values, but you - using a 3-D model based on the exterior dimensions of the XM1 - are the only one who found the exact values?

CATTB document then revealed the size of the cupola hole and GPS hole and using those numbers together fits like a glove on a 3d model. I think you are misreading those reports

You do realize that the CATTB used a completely different and new turret? You could have used also the values for the M60's cuppola and hatches instead...

This is one of the sources about the hatches, the other one is not easily to copy & paste:
"The crew compartment of a "married" tank has an air volume of 69.7 cubic feet and poor ventilation. It has a diameter of approximately 90 inches and is approximately 5'6" deep. The area is enclosed, the only openings being a hole in the side leading to the driver's compartment and two hatch openings. One of the hatches is 17 inches and the other is 22 inches in width. Egress from the compartment is accomplished by grabbing the top of the tank and pulling oneself out of the tank, by use of a portable ladder, or by climbing through the opening to the driver's compartment."

I know the thickness of outer layer because I use my eyes and look at pictures of the Abrams, the pictures of blown up Abrams tanks makes it even easier too see.

So, it's an estimation. Like the rest of your values seem to be.

The armor cavity size might be the same but the armor in them are different as pictures from Iraq has shown. Crew compartment side has spring loaded NERA array. Bustle has very different rack mounted NERA array plus it makes sense that you would make the bustle weaker to make sure energy released is not going into the crew compartment.

You are refering to this image. Notice how the exterior plate is bend away from the rest of the turret side armour? Do you know for sure that this wasn't done by a spring armour array like the one lying on the vehicle rear?

 

[Damian]

IMHO if we would have a detailed 3d model made with original dimensions, with well modeled interior, the estimation could be very accurate, maybe not 100% but still better than drawings.

 

[STGN]

You are refering to this image. Notice how the exterior plate is bend away from the rest of the turret side armour? Do you know for sure that this wasn't done by a spring armour array like the one lying on the vehicle rear?

Well that is one of them. And the question you are asking is can you ever be sure of anything? which is a philosophical question you have to answer for yourself but do you really think there is room there for both? and how did it get out with the springs still attached?

I am taking that into account. That's why I also posted an image from the GPS. The armour however ends in front of the main sight, while the steel cover of the main sight does only slightly increase the external appearance vs the actual location.

Look at the image I posted above! It can easily be seen at photos from the turret rebuild that the chimney only cuts through the right corner of the turret frontal armour.

Look I realize you haven't spent too much time trying to model the Abrams but what you think you are seeing is not the whole picture, look hard at page 195 in Hunnicutt you will hopefully see what you are missing.

In other words, it is just an more or less "educated guess". With your work you can easily see that Zaloga, who earns his money with writing about tanks is wrong with the 9 inches size difference and it is in reality 15.5 cm? With your work you can easily say that the Micheal Green, who took all the images in his book by himself (including images from the interior and from the turret roof) is wrong when he says that the turret armour of the M1 is about two feet thick?
Hunnicutt's drawings are inaccurate, we have seen that already ages ago. But neither I nor other people on the internet are completely morons and rely blindly on a single drawing. However all drawings I could find with the google image search show that the frontal armour is less than claimed by you. And guess what: I am not the only one. Militarysta posted other values in the thread some time ago, the Russian come up with other values, the Americans come up with different values, but you - using a 3-D model based on the exterior dimensions of the XM1 - are the only one who found the exact values?

Have you ever tried to take a photo of a M1 Abrams and extend the turret by 9"? Try it some day, then compare to real M1A1 Abrams photo. Maybe Zaloga measured from the weld line on top of the IPM1 and made the mistake of assuming that is where the turret of the M1 would have ended?(I used a long time trying to fit 9" in there somewhere and I had to admit to myself that it could not fit)I think I actually confirmed Micheal Green, the whole array is 2 feet thick, its just sloped. I am a late on the hole estimating scene but that has its advantages, lots of photos of the interior of the Abrams, tanks blow apart revealing the insides. And using a 3d model instead of 2d quickly shows you when you are wrong. I can't really help that others are not dedicated to making accurate models and have not used the time I have collecting information, watching pictures and pondering how different views fit together.

You do realize that the CATTB used a completely different and new turret? You could have used also the values for the M60's cuppola and hatches instead...

What kind BS is this, M60 copula, you could not insult me more. So I gather that you have never really looked properly at the CATTB turret, try again and you will realize that it uses a M1 copula with the MG removed. And it used similar GPS house.

This is one of the sources about the hatches, the other one is not easily to copy & paste:
"The crew compartment of a "married" tank has an air volume of 69.7 cubic feet and poor ventilation. It has a diameter of approximately 90 inches and is approximately 5'6" deep. The area is enclosed, the only openings being a hole in the side leading to the driver's compartment and two hatch openings. One of the hatches is 17 inches and the other is 22 inches in width. Egress from the compartment is accomplished by grabbing the top of the tank and pulling oneself out of the tank, by use of a portable ladder, or by climbing through the opening to the driver's compartment."

Interesting, the hole for the loader is 22" wide and the commanders is ~20" wide and ~14" long which is an average of 17".

So, it's an estimation. Like the rest of your values seem to be.

I guess you meant to say guesstimate? But yes it is an estimation of photos. Every thing I do, if I don't have hard facts is estimations of photos based on known distances.

So what do you think, is it way off?:

STGN

 

[Damian]

This might solve a problem with Zaloga's claim.