Hull Armor of the M1 Abrams

Ahhh so unfortunate. Didn’t know it was like that.

There goes your ticket for the steam awards LMFAO

Something to add for a new bug report:
Some Abrams Hull Armour reports on upgrades. (Source from where the pictures are in the comments from OP)
M1A2 Sep Armour Justification WITH DECLASSIFIED RECEIPTS (wtf am I doing with my life)

Regarding Nuclear Regulatory Commision:
What has been missed here is that Gaijin Source is the basis for Amendment No.9 which was shown:
Department of The Army, Request to Amed License SUB-1536. (nrc.gov)

Amendment No. 9 to Department of the Army to License No. SUB-1536. (nrc.gov)
Amendment number 9 extends Gaijins source til 2016.

Here is why the US army chose not to add DU armor to the Hull:
The Abrams is a relatively low vehicle being 10cm lower than the Leopard 2 while having a slightly taller turret, to achieve this they had to recline the driver which meant he would take up more space in the length of the vehicle. The positive was lower hull weight which meant more armor on the Abrams, same with the turbine, lower weight meant more weight for armor, the Abrams had armor all along the turret side compared to the Leopard which only had in the front 50degree of crew compartment otherwise only 23mm AP protection.
However the trade off is that after they had added decent protection to the front hull it is suspended in front of the suspension:

Impact of Loading Distribution of Abrams Suspension on Track Performance and Durability (dtic.mil)
When adding the DU armor to the front turret they already overloaded the front road wheels carrying 1.3 to ~2 times as much weight as the read road wheels.
Remember that a lever multiplies the force exerted on an object:
Simple Machines:Levers - YouTube
So adding a very dense material up front is not just increasing the total weight of the tank its multiplying the load the suspension has to deal with.
To maintain manuverability you have to make sure the weight is centered as best you can otherwise trench crosing etc. takes a sever hit. Not to mention wear and tear on drivetrain and suspension

To deal with the increased weight of the turret multiple suspension updates have been made but the turret is carrying by the road wheels the hulls armor is offset, which is why the US Army tested with extra weight but ultimately decided against adding alot of it, as we see in th NRC paper.
Here is an example of one of the test vehicles black in the 80ties :

See how much they added to the rear of the turret and hull to balance out the front.

but also changes it. “License number SUB-1536 is renewed in its entirety to read as follows:” meaning TO READ, as in will now instead be.
“maximum amount that licensee may possess at any one time under this license: A. as needed”
meaning limit of 5 hulls removed.
"A. and B. For use (excluding repair or maintenance) and storage of tank turrets and hulls as
Depleted Uranium armor components of Abrams M1 series tanks. "

and then we also have this:

suspension was upgraded to take heavier weight.

actual model name and specific upgrade.

Years of implementation

I dont know if this is reliable enough

DU Armor in turret sides // Gaijin.net // Issues

“nothing here”. Was it removed?

1. Go read Gaijin Source Document, it’s the documents submitted that resulted in Amendmed Number 9, numer 9 dosen’t change it.

2. I have not denied the suspension was updated; the first update was for the IPM1.

3. Okay let’s look at the sources cited: 1993 Alternatives for the U.S. Tank industrial Base; and Inetres.com. Before we look at the actual government source, we already see that this table is based on an enthusiast site rather than official sources. A thing I have come to find is that a lot of public papers are academic in nature and don’t rely on any real data but on public speculation, so it becomes a garbage in, garbage out data point. But lets go back to the 1993 paper and Inetres.com and see what they actually say:
   

   

   image804×1270 211 KB
   
   Alternatives for the U.S. Tank Industrial Base (cbo.gov)
   As we see here it calls DU for “Special Armor” and Chobham for “Standard” but no mention of where it’s placed. But we know from NRC that it was only in the Turret. Now lets look at Inetres:
   M1 Abrams Main Battle Tank (inetres.com)
   
   

   image2476×200 34.9 KB
   
   Interes is a decent source and repeats what we allready know DU was added to the Turret not the Hull. There is nothing about DU being added to the Hull.

4. “Front Armor Upgrade” we can be pretty sure dosen’t mean DU to the hull. Why? Because the AIM and the HA has similar weight distribution on its road wheels:
   

   

   image1234×1030 145 KB
   
   Impact of Loading Distribution of Abrams Suspension on Track Performance and Durability (dtic.mil)
   The AIM moved the weight balance slightly back while putting more weight under the turret, likely due to the additional turret side armor. Had DU been added to the front you would see more load on the front but it is almost the same.

You are actually wrong on so many levels. SEP is modification from late '90s early 2000. How document from 1993 can be a source in this matter? Gaijin says that some sources were too early released after modification, and are guess game, thus not accepted. And you are using sources from before modification (gaijin also) and somehow they are valid.
Great double standards my boy. And also the part about only 5 tanks modified was later removed from the document so XD

SEP did optimize a lot of weight, thus armor could be added without significant changes to COM and weight distribution in general. If the cassetes with NERA was removed, and in this place DU was mounted, this also gives us weight headroom.

How much do you think that this DU casette weighs?
Abrams track width is 63.5 cm, Abrams width is around 347 cm, sideskirts are 6.5 cm wide, then you have side hull armor which is 3cm thick (additional 3cm can be basically dropped due to it’s position). So it will be around 202cm wide. Abrams clearance is 483mm, but the hull height in needed place is not known. But when we compare the front view of the hull armor the the track itself, track is wider. Therefore we can say that the armor dimmension is 202cm wide and less than 63.5 high. Casette itself would contain 4-12 cm of uranium. This gives us overall Volume of the armor casette which is 0.154 cubical meters of depleted uranium in the 12 cm scenario and 0.0513 cubical meters in 4cm case. With density of 19grams per cubical centimeter it gives you 1 to 3 metric tons of armor, with the assumption that armor plate height is 63.5cm (Which is overestimation).

This calculation shows that adding depleted uranium to the armor won’t show that much of a difference in the COM and weight distribution. We can see that Between M1A1DU and M1A2SEP V2 there is 1.6 tons of additional weight. Taking into account that they would take non du casette and put one with DU in it, it can easily have 8 cm of DU inside and weight would match with gaijin sources.

You can’t say this “we already see that this table is based on an enthusiast site rather than official sources.” and then use the same website in question to try and disprove DU in the Hull.

“Interes is a decent source and repeats what we allready know DU was added to the Turret not the Hull. There is nothing about DU being added to the Hull.” these two can’t go hand in hand 😂

I will even add to that. Someone in this topic wrote that DU is 2.5 heavier than Steel. This means that adding 2 tons of uranium removes 0.8 ton of steel. Therefore the mass delta is only 1.2 ton despite having 2 tons of DU armor.

Did you not read what I was replying too? I found the sources of of the table, to show that they don’t actually support the claim in the table.

What is your source for SEP optimizing a lot of weight. Great so “IF” they removed the HEAT protection they might be able to put in DU. Why would they only disclose the Turret DU if they mounted it all over the tank?

I appreciate your calculation; you realize 1-3 tons is a large discrepancy right, do you have a source or is it pure fantasy? and mounting 3 tons offset multiplies its strain on the suspension.

And yet explain how giving an abrams a faster reload and a more modern shell fixes its non historically accurate getting one shot by everything? It’s like giving a leopard its modern round and getting rid of its composite armor. Which by the way has equal amounts of open sources as the abrams.

I think you need to go touch som grass, I used it to say the table is wrong about the claim of hull DU, not as a proof that DU hull armor dosen’t exist.
I see why you could misunderstand, I should have phrased it differently, what I meant was that Inetres doesn’t make wild speculations but just report what was published.

Well that’s how it worked in abrams tank, to insert DU inserts they had to remove hull insert with steel (well, not exactly steel, there were multiple alloys inside, copper, aluminum, titanium). Just like they did in the turret. Even gaijin wrote about it in their devblog. In hull, where there is even less space the case would be the same.

Sources regarding my own calculations done on the run? Bro, what? Open for example book called “Pancerze Budowa projektowanie i badanie” by Wiśniewski. To contradict my own calculations i’ve overestimated density of depleted uranium, treated the casette as if it was made just out of it, and overestimated the size of the plate, and my argument STILL PHISICALLY MAKES SENSE, DISPROVING GAIJIN CLAIM ABOUT COM AND DISTRIBUTION (which was the point of my post).

Taking all of this into consideration now i need only 2 sources to confirm if the armor was applied.
At least one tank which had it (and we have even 5 of those in tank school)
And Fiscal Year statement which says that us government spend money on this armor.
Oh an by pure COINCIDENCE we have this source to, stating that between year 2000 and 2007 Us spend 870 milion US dollars on uparmoring the FRONTAL armor.
Funny how they specified that there is only turret side, but whole frontal armor uparmored.

Therefore the final conclusion of any engineer discussing this problem should be that US actually used around 1 to 2 tones of DU inside the hull of the abrams, because there is too much evidence point that it is possible, physics won’t be violated and most important thing: MONEY WAS SPENT ON THIS STUFF.

Curious how to get to the truth you only need to follow MONEY.

Discrepancy between 1 and 3 tones is present because i’ve calculated it for edge cases, there is no ballistic reason to use less than 4 cm of uranium inside the armor, and there is no reason to go higher than 12 cm. 12cm seems kinda unrealistic (mostly because the backplate behind is 10cm thick).
As a material engineer i’d use around 6cm of uranium in 3 layers 2 cm thick each. Inbetween of those layers i’d use something softer, copper and steel, aluminium maybe, with steel casing to prevent the radiation exposure of the crew despite the NBC and Spall liners. (yeah it would be present, in Mrads but still, better safe than sorry). This casette would be 12-16cm thick, would be inserted right before the main armor and plating inside would be angled 90 degrees to the existing NERA filler. I don’t have ansys to check it but should give around 540-600mm of KE protection.

Weight reduction, savings, and trade has always been a part of Abrams development.

“While every vehicle is designed to have a space, weight and power (SWaP) margin for incremental improvements, recent up- grades made to the Abrams M1A2 SEPv2 have left little margin for future improve- ments. To alleviate these SWaP constraints, the Army launched the Abrams engineer- ing change proposal (ECP) 1 program, which is designed to buy back SWaP by re- designing and modernizing many elements of the tank.”

Older examples.:
https://www.tms.org/pubs/journals/jom/9705/montgomery-9705.html

https://man.fas.org/dod-101/sys/land/m1.htm

" Changes to the M1A2 Abrams Tank contained in the System Enhancement Program (SEP) and “M1A2 Tank FY 2000” configuration are intended to improve lethality, survivability, mobility, sustainability and provide increased situational awareness and command & control enhancements necessary to provide information superiority to the dominant maneuver force. The Abrams Tank and the Bradley Fighting Vehicle are two central components of the dominant maneuver digital force.System Enhancement Program upgrades are intended to:

• improve target detection, recognition and identification with the addition of two 2nd generation FLIRs.
• incorporate an under armor auxiliary power unit to power the tank and sensor suites.
• incorporate a thermal management system to provide crew and electronics cooling.
• increase memory and processor speeds and provide full color map capability.
• provide compatibility with the Army Command and Control Architecture to ensure the ability to share command & control and situational awareness with all components of the combined arms team.

Additional weight reduction, embedded battle command, survivability enhancement, signature management, safety improvement, and product upgrade modifications to the M1A2 will comprise the “M1A2 Tank FY 2000” configuration fielded to units of the digital division beginning in FY 2000."

Notice “Titanium Components*.”

Doesn’t take much to piss of American mains. Just show them that life is not like a Hollywood movie and you can’t win all the time. That should do the trick.

I think Call of Duty has more influence on the kids these days.