46 replies to this topic

[Alaric Wolf Kerensky]

Clearly, the number is just for convenience as stated before. Partly because we have no good methods of assessing the true weight of a BattleMech, and partly because it is easy to just say "100 tons", which while massive, is actually not much when it comes to military hardware. Even with made up "ultralight" materials, you can only go so light with matter before you critically compromise strength and resistance to shock and damage. It is simply unavoidable. Assault 'Mechs are HUGE. Their volume alone is several times more than modern main battle tanks, and the surface area of a BattleMech is very high. That means more area to structurally reinforce and armor, creating more weight use. Realistically, most 'Mechs, even some mediums, would weigh close to or well over 200 tons.

However, in the end it is just an arbitrary number that really changes nothing about the universe, but can be used to compare the relative weight of 'Mechs.

[Captain Hat]

Alaric's pretty much spot on. Don't let a misguided search for realism spoil your fun.

[Pht]

Captain Hat, on 29 February 2012 - 06:10 PM, said:

The conduction of heat is an aid to its ablative function, nothing more: I find it odd that anyone could mistake it for an additional function...

Ablation is not conduction. Ablation is not backstopping. Ablation is not flexing.

It is not a mistake to say that additional functions are, indeed, additional functions.

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...but even if it was, that doesn't make the armour non-ablative.

I did not post anywhere that the armor is non-ablative; I posted that it is not exclusively and only ablative.

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According to the game rules, in fact, the "ablative armour" concept correlates exactly with the way the armour on 'mechs behaves when shot at.

No. Even in the basic set of rules, a roll of 2 on the hit location table gives an armor penetrating shot; this does not represent finding a lucky gap only; it also represents blasting through the armor. If it represented only finding lucky gaps in the armor, than mechs would have to be walking around in pristine armor with heavy-gauss slugs sized gaps in their armor.

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Forgive me if I'm wrong, but none of those look relevant to the arguments regarding weight?

I missed that the discussion was regarding weight. I don't see what the problem is, though; all one has to do is get solaris skunk werks and turn on fractional accounting, stick in whatever equipment is wanted, and you know your weight.

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They provide some nice finagles to explain how BTech armour is tougher than, for example, chewing gum (which is what you get when you extrapolate directly from fall damage...

Falling damage is due to the armor panels ( which, while super hard, are *brittle*) bending. The titanium honeycomb layer that is supposed to stop the armor from bending cannot support the weight and lets the armor panel bend and shatter, just like a plate of tempered glass.

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...but there's nothing there that can get past the fact that a real vehicle the size of an Atlas would probably weigh a lot more than 100 tons regardless of the materials technology fiddles you put in the way

So if they have lighter materials than we do that allow for those size of structures ... that simply doesn't matter? Wow. Handy way to argue...

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...or the fact that a walking vehicle that weighed 100 tons would be unable to go pretty much anywhere: It would sink into the ground on metalled roads for goodness' sake.

We don't know the size of the feet.

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For me, personally, that doesn't matter: 'Mechs are cool because they're cool, and that has nothing to do with being realistic. In-universe justifications are fine for smudging the boundaries and aiding suspension of disbelief, but I am fully aware that my disbelief is merely suspended.

Which is fine, and I agree with this. What I don't care for is arguments that crop up due to ignorance of the in-universe tech, repeatedly, regardless of the fact that the in-universe information is out there.

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While BTech is at least semi-serious science fiction, 40K is more or less pure fantasy with a Wagnerian space opera tint. It isn't even trying to be realistic, ...

It isn't? Now the justification for this, I'd love to hear. They do a pretty good job of trying to explain their science in understandable terms.

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...and honestly neither should you be. If you want to write up technical explanations for the basic finagles of the universe, that's awesome, but please please please don't expect or need it to hold any water.

Um... lets see... no, I'm not going to do what you say simply because you say it and give no good reason for it.

I rather enjoy the technical end of the lore.

Edited by Pht, 29 February 2012 - 07:04 PM.

[Kartr]

Pht, on 29 February 2012 - 07:02 PM, said:

Ablation is not conduction. Ablation is not backstopping. Ablation is not flexing.

It is not a mistake to say that additional functions are, indeed, additional functions.

I did not post anywhere that the armor is non-ablative; I posted that it is not exclusively and only ablative.

I'd like to point out that no matter what kind of damage is done and no matter whether or not the round is shattered armor is lost, ablated. In fact if the round shattered on the armor then it wouldn't have done any real damage to it. For example, in WW2 they had to use tungsten penetrators in their tank rounds because the traditional steel rounds would literally shatter on impact doing no damage. The armor cannot be shattering rounds because if it was it wouldn't be taking damage.

Secondly that description of armor is completely wrong. If it were true then you would see armor behaving differently as it was damaged. The first layer has completely different properties than the second layer. A shot that might be stopped and ablated by the first layer could either be stopped cold by the second layer or meet almost no resistance from the second layer. For the armor to have the exact same properties no matter how much is left then it has to be a homogenous material.

Pht, on 29 February 2012 - 07:02 PM, said:

No. Even in the basic set of rules, a roll of 2 on the hit location table gives an armor penetrating shot; this does not represent finding a lucky gap only; it also represents blasting through the armor. If it represented only finding lucky gaps in the armor, than mechs would have to be walking around in pristine armor with heavy-gauss slugs sized gaps in their armor.

If a round were to blast through an extremely hard armor then it would have defeated the armor in that area and the entire section would no longer be protected, plus every time a round like that struck the armor it would defeat it. This is the type of armor modern tanks use, its all or nothing, either the round doesn't damage the tank or it blasts through the armor every time (barring a bad angle). The roll of 2 penetrating the armor works much better with a soft truly ablative armor, because under certain situations a round could find the weakest point and push through. In such a situation its possible (probably even likely) that the round would've lost enough force to only do damage to the first thing it hits behind the armor, rather than catastrophically destroying everything (especially since 'Mechs pack so much into those limbs).

Pht, on 29 February 2012 - 07:02 PM, said:

I missed that the discussion was regarding weight. I don't see what the problem is, though; all one has to do is get solaris skunk werks and turn on fractional accounting, stick in whatever equipment is wanted, and you know your weight.

The original discussion was whether or not the weight system (20-100tons by 5) had any basis in reality or if it was merely an arbitrary system created for the simplicity of designing and balancing a game. It has gotten sidetracked because people keep trying to use fluff to prove that it is "possible" that a 100 ton 'Mech is realistic. Now it seems we're arguing the validity of the fluff based on the rules and what happens in games and books.

Pht, on 29 February 2012 - 07:02 PM, said:

Falling damage is due to the armor panels ( which, while super hard, are *brittle*) bending. The titanium honeycomb layer that is supposed to stop the armor from bending cannot support the weight and lets the armor panel bend and shatter, just like a plate of tempered glass.

Brittle armor doesn't make sense period, if you harden it to the point of brittleness then the kinetic energy of a shell would simply shatter your armor and at best you'd be unprotected when the next shell hit. At worst the first shell would continue into your vehicle and destroy everything along with some of the razor sharp fragments of your shattered, brittle armor.

A softer more malleable armor makes more sense for an ablative armor, plus the armor has to be homogenous rather than having layers. Plus a layer of "flexible armor" wouldn't stop the brittle portion from shattering. The shockwaves traveling through the armor from the fall would shatter a brittle piece of armor not the weight of the 'Mech.

Pht, on 29 February 2012 - 07:02 PM, said:

So if they have lighter materials than we do that allow for those size of structures ... that simply doesn't matter? Wow. Handy way to argue...

An Atlas is less than half as dense than water.

Pht, on 29 February 2012 - 07:02 PM, said:

We don't know the size of the feet.

We can figure it out pretty easily, or at least get a close estimate. All you have to do is take the ratio of the width of the feet to the height of the 'Mech and the length of the feet to the height of the 'Mech and use the resulting numbers to find the area of each foot then multiply by 2.

Spoiler

If the Atlas is 18m tall then: from the knee down is roughly a third of the height or 6m and the width of the foot is a third of that or 2m and the foot seems to be twice as long so 4m. That means each foot has a rough surface area of 8m^2. Total estimated surface area for the Atlas's feet is 16m^2 to support 100,000kg of 'Mech. That's roughly 6,250kg/m^2 of ground pressure, ground pressure is measured in Pascals (N/m^2) and a newton is weight so we have to multiply 6,250kg times the acceleration of gravity 9.81m/s^2: (6,250kg*9.81m)/s^2=61,312.5 kg*m/s^2. Divide that by m^2 and you get 61,312.5kg/m*s^2 or 61.31kPa standing still. Walking doubles that (using the fact that a human walking exerts double the ground pressure) to 122kPa. Keep in mind that this is for a 'Mech which is less than half as dense as water.

Pht, on 29 February 2012 - 07:02 PM, said:

Which is fine, and I agree with this. What I don't care for is arguments that crop up due to ignorance of the in-universe tech, repeatedly, regardless of the fact that the in-universe information is out there.

My problem is when people treat the in universe fluff as if it's infallible. Things like layered armor which doesn't reflect the way armor works in the game and novels, or "brittle" armor which is absurd to begin with and gets even worse when you look into it and realize it would act as an ablative armor at all, probably wouldn't even work as armor. The game isn't based on realistic numbers or ideas and we shouldn't expect it to have them. However if you're going to try and figure out how things work, don't just take the word of some author who doesn't have a clue, work it out for yourself and see what makes sense.

Pht, on 29 February 2012 - 07:02 PM, said:

It isn't? Now the justification for this, I'd love to hear. They do a pretty good job of trying to explain their science in understandable terms.

Well like the man said don't expect it to hold water, after all the Atlas is less dense than water!
They do a pretty good job of making up stuff that sounds believable at first. If you take the time to compare the things they say to how things actually work in the game and in the books you'll find a lot of discrepancies.

Pht, on 29 February 2012 - 07:02 PM, said:

Um... lets see... no, I'm not going to do what you say simply because you say it and give no good reason for it.

I rather enjoy the technical end of the lore.

I too like the technical side of the lore, which is why I'm not willing to accept it at face value. Figure out which parts make sense and which parts don't. For the stuff that doesn't make sense come up with a logical way for them to work the way they do.

[Octavian]

Just wanna point out that you guys are arguing about the realism of the weights of giant robots controlled by neural interfaces and powered by self contained fusion engines that have no no mention of a fuel source.

[guardiandashi]

Kartr, on 29 February 2012 - 08:31 PM, said:

I'd like to point out that no matter what kind of damage is done and no matter whether or not the round is shattered armor is lost, ablated. In fact if the round shattered on the armor then it wouldn't have done any real damage to it. For example, in WW2 they had to use tungsten penetrators in their tank rounds because the traditional steel rounds would literally shatter on impact doing no damage. The armor cannot be shattering rounds because if it was it wouldn't be taking damage.

Secondly that description of armor is completely wrong. If it were true then you would see armor behaving differently as it was damaged. The first layer has completely different properties than the second layer. A shot that might be stopped and ablated by the first layer could either be stopped cold by the second layer or meet almost no resistance from the second layer. For the armor to have the exact same properties no matter how much is left then it has to be a homogenous material.




If a round were to blast through an extremely hard armor then it would have defeated the armor in that area and the entire section would no longer be protected, plus every time a round like that struck the armor it would defeat it. This is the type of armor modern tanks use, its all or nothing, either the round doesn't damage the tank or it blasts through the armor every time (barring a bad angle). The roll of 2 penetrating the armor works much better with a soft truly ablative armor, because under certain situations a round could find the weakest point and push through. In such a situation its possible (probably even likely) that the round would've lost enough force to only do damage to the first thing it hits behind the armor, rather than catastrophically destroying everything (especially since 'Mechs pack so much into those limbs).



The original discussion was whether or not the weight system (20-100tons by 5) had any basis in reality or if it was merely an arbitrary system created for the simplicity of designing and balancing a game. It has gotten sidetracked because people keep trying to use fluff to prove that it is "possible" that a 100 ton 'Mech is realistic. Now it seems we're arguing the validity of the fluff based on the rules and what happens in games and books.


Brittle armor doesn't make sense period, if you harden it to the point of brittleness then the kinetic energy of a shell would simply shatter your armor and at best you'd be unprotected when the next shell hit. At worst the first shell would continue into your vehicle and destroy everything along with some of the razor sharp fragments of your shattered, brittle armor.

A softer more malleable armor makes more sense for an ablative armor, plus the armor has to be homogenous rather than having layers. Plus a layer of "flexible armor" wouldn't stop the brittle portion from shattering. The shockwaves traveling through the armor from the fall would shatter a brittle piece of armor not the weight of the 'Mech.


An Atlas is less than half as dense than water.




We can figure it out pretty easily, or at least get a close estimate. All you have to do is take the ratio of the width of the feet to the height of the 'Mech and the length of the feet to the height of the 'Mech and use the resulting numbers to find the area of each foot then multiply by 2.

Spoiler

If the Atlas is 18m tall then: from the knee down is roughly a third of the height or 6m and the width of the foot is a third of that or 2m and the foot seems to be twice as long so 4m. That means each foot has a rough surface area of 8m^2. Total estimated surface area for the Atlas's feet is 16m^2 to support 100,000kg of 'Mech. That's roughly 6,250kg/m^2 of ground pressure, ground pressure is measured in Pascals (N/m^2) and a newton is weight so we have to multiply 6,250kg times the acceleration of gravity 9.81m/s^2: (6,250kg*9.81m)/s^2=61,312.5 kg*m/s^2. Divide that by m^2 and you get 61,312.5kg/m*s^2 or 61.31kPa standing still. Walking doubles that (using the fact that a human walking exerts double the ground pressure) to 122kPa. Keep in mind that this is for a 'Mech which is less than half as dense as water.


My problem is when people treat the in universe fluff as if it's infallible. Things like layered armor which doesn't reflect the way armor works in the game and novels, or "brittle" armor which is absurd to begin with and gets even worse when you look into it and realize it would act as an ablative armor at all, probably wouldn't even work as armor. The game isn't based on realistic numbers or ideas and we shouldn't expect it to have them. However if you're going to try and figure out how things work, don't just take the word of some author who doesn't have a clue, work it out for yourself and see what makes sense.




Well like the man said don't expect it to hold water, after all the Atlas is less dense than water!
They do a pretty good job of making up stuff that sounds believable at first. If you take the time to compare the things they say to how things actually work in the game and in the books you'll find a lot of discrepancies.

actually I am going to nitpick and toss out a theory for armor that you ignored in your haste to badmouth battletech armor theory.

each point of armor is a plate, scale, or layer (depending on your point of view) that constitutes an INDIVIDUAL unit of armor this means that the 16 "points" of armor you get for 1 ton of standard is actually 16 seperate sets of steel, ceramic, and titanium layers this also resolves the "arguement" that a round that shatters the steel layer and doesn't penetrate fully will "ruin" the armor and the next round will go right through the ceramic and "backing" layer. the actual answer is it does, but there are additional layers (sets of layers) of each of the materials until the armor for the location is fully depleted.

in some ways the battletech armor works like whipple shields in others it works like scale mail, and in yet another way it sort of works like a wooden hulled ship, or an iron clad, of the type where the iron plating was bolted (or nailed) to the wooden hull.

I would have to say that I believe you are actually under estimating the actual size of mech feet, as well. in the NEW artwork by FD you may have a point, but especially if you look at the older artwork most mechs have significantly bigger feet.

additionally historically mechs are between ~8 and 12 meters tall, there are a few exceptions the thor is a little bigger and is specifically noted as one of the tallest mechs at closer to 14-15 meters.

[Kartr]

guardiandashi, on 29 February 2012 - 09:52 PM, said:

actually I am going to nitpick and toss out a theory for armor that you ignored in your haste to badmouth battletech armor theory.

each point of armor is a plate, scale, or layer (depending on your point of view) that constitutes an INDIVIDUAL unit of armor this means that the 16 "points" of armor you get for 1 ton of standard is actually 16 seperate sets of steel, ceramic, and titanium layers this also resolves the "arguement" that a round that shatters the steel layer and doesn't penetrate fully will "ruin" the armor and the next round will go right through the ceramic and "backing" layer. the actual answer is it does, but there are additional layers (sets of layers) of each of the materials until the armor for the location is fully depleted.

Yet your explanation doesn't fit the established fluff either since that just has a simple two layer armor with a flexible backing over the entire surface of the 'Mech. So now you are breaking with the established fluff yourself, just like I am, in order to come up with a better theory for how the armor works.

My objection to the original theory put forward was layered armor would react differently depending on which layer was getting struck. Once the surface layer was destroyed the second layer would react to the damage differently. Now it might be weaker or stronger than the surface layer depending on the type of attack striking. This is still a problem with your scale theory, since if the upper layer of a scale got vaporized by a laser strike, the second (ceramic) layer could still be intact and might prove more resistant to the next laser shot, or it might not.

With multiple scales overlapping each other you'd see this problem compounded as some scales were partially destroyed yet still contributed to the defense of the scale underneath. Also you run into the problem that each scale/point would have to be huge as you need multiple sets to cover the entire region. To me it makes more sense that it is a homogenous material (it can and probably is reinforced by some sort of mesh the way rebar reinforces concrete) and that the point system is simply an abstraction of the overall thickness. Enough strikes and you've hammered away the thickness to the point where you can start penetrating the armor to strike what lies beneath.

Another problem with the scales idea is that you have to have mounting points for all of them. While a simple homogenous armor can be cast in the proper shape and secured at a handful of points, a scale system would have to have each scale secured individually. If the scales are stacked over each other you have to have a framework to secure each scale over the scales beneath it. A system that increases weight, bulk and work.

Also I'm not trying to badmouth BattleTech armor technology, I'm saying that the established fluff doesn't make sense with what we see represented in the game rules and in the novels and video games.

Pht, on 29 February 2012 - 07:02 PM, said:

in some ways the battletech armor works like whipple shields in others it works like scale mail, and in yet another way it sort of works like a wooden hulled ship, or an iron clad, of the type where the iron plating was bolted (or nailed) to the wooden hull.

The analogy of an iron clad ship where the iron plating was bolted/nailed to a wooden hull is more akin to the established fluff. The hard outer layer of armor backed by a softer more flexible layer.

Scale mail is extremely elaborate, difficult to repair, adds weight and bulk and doesn't solve the problem of different behavior depending on how much armor has been destroyed.

The whipple shields are interesting, but ultimately the same concept as offset armor paneling used today on vehicles to defeat HEAT rounds. The thin layer of armor set a short distance from the main armor causes the HEAT round to detonate to soon and the lethal jet is focused at the wrong distance to penetrate the main armor belt. Also it's not supported by the novels or the rules.

Pht, on 29 February 2012 - 07:02 PM, said:

I would have to say that I believe you are actually under estimating the actual size of mech feet, as well. in the NEW artwork by FD you may have a point, but especially if you look at the older artwork most mechs have significantly bigger feet.

And this is where I point out that at rest the Atlas has less ground pressure than an M1 Abrams and only ~17kPa more ground pressure when walking. The main point of that was to show that we can figure out the the ground pressure fairly easily. Also the main problem with the Atlas's weight is that it is less than half as dense as water.

Pht, on 29 February 2012 - 07:02 PM, said:

additionally historically mechs are between ~8 and 12 meters tall, there are a few exceptions the thor is a little bigger and is specifically noted as one of the tallest mechs at closer to 14-15 meters.

It's Summoner, and the actual size of 'Mechs is debatable, the stated sizes don't always match the artwork, nor do they always make sense when you consider the amount of ammunition and equipment that has to be crammed inside of them. FD's Atlas is one of the first that actually looks like it has room for everything inside. Remember that the Atlas's AC/20 has to carry a significant number of AC/20 rounds since each shot actually fires multiple rounds. If anything I think the 18m tall estimate might be on the conservative side.