How easy can you modify a non-moveable frame MS to a moveable frame one?

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False Prophet
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How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by False Prophet » Wed Nov 06, 2019 8:43 am

You can certainly modify a pre-Gryps MS to accept moveable frame, as demonstrated by the Pale Rider being made into the Todesritter. What I want to ask how easy is this to do hypothetically? I presume not, since if it was the case, the EFF would had chosen to modify the GM III instead of making new Jegan units. With all the new reactor and backpack (I wonder whether the Jegan's backpack performs better than the GM III's MK-II's style backpack), it is probably easier to built an entirely new frame to accomodate these new components.

Do we have any real-world example about this situation? For example, how much can you modify the frame of a car? And how expensive is it?

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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by Seto Kaiba » Wed Nov 06, 2019 6:10 pm

False Prophet wrote:
Wed Nov 06, 2019 8:43 am
You can certainly modify a pre-Gryps MS to accept moveable frame, as demonstrated by the Pale Rider being made into the Todesritter. What I want to ask how easy is this to do hypothetically?
"Modify" might be the wrong word. The way it's described, it sounds a lot more like what Axis Zeon did was build an entirely new movable frame MS around the core components of the HADES system they salvaged from the Pale Rider wreckage that Zeon captured during the One Year War using mostly Neo Zeon technology.


False Prophet wrote:
Wed Nov 06, 2019 8:43 am
Do we have any real-world example about this situation? For example, how much can you modify the frame of a car? And how expensive is it?
Modifying the frame of a car usually means rebuilding the car from the ground up... if only because getting down to the frame means taking the entire car off the car. :lol:

One of the few major exceptions would be making "stretch" versions, which usually involves partially stripping that car down and then sawing it in freaking half. It's expensive and time consuming.
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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by MythSearcher » Wed Nov 06, 2019 10:19 pm

Seto Kaiba wrote:
Wed Nov 06, 2019 6:10 pm

"Modify" might be the wrong word. The way it's described, it sounds a lot more like what Axis Zeon did was build an entirely new movable frame MS around the core components of the HADES system they salvaged from the Pale Rider wreckage that Zeon captured during the One Year War using mostly Neo Zeon technology.
And most of the MSV-R EFF/AE/FSS Super Gelgoogs are newly built units, not modified ones.
One of the few major exceptions would be making "stretch" versions, which usually involves partially stripping that car down and then sawing it in freaking half. It's expensive and time consuming.
Sorry, extreme side question.
I have always wondered how do they do that without weakening the structure, they can surely cut it in half and weld it back together, but since they cannot quench and temper the finished product(at least not the whole thing), wouldn't that severely weaken the frame?

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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by False Prophet » Thu Nov 07, 2019 9:31 am

MythSearcher wrote:
Wed Nov 06, 2019 10:19 pm
And most of the MSV-R EFF/AE/FSS Super Gelgoogs are newly built units, not modified ones.
You mean suits like the Gelgoog Uma Lightning, or the ReGelgu? The later I suspect were built completely new, though they seemed to retain a level of part compatibility with the older Gelgood -- in the latest volume Johnny Ridden had a High Mobility Gelgoog equipped with the ReGelgu's binders.

Since you are here, Kaiba, can I ask how hard is it to install a rollcage to existing car?

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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by Seto Kaiba » Thu Nov 07, 2019 2:56 pm

MythSearcher wrote:
Wed Nov 06, 2019 10:19 pm
Sorry, extreme side question.
I have always wondered how do they do that without weakening the structure, they can surely cut it in half and weld it back together, but since they cannot quench and temper the finished product(at least not the whole thing), wouldn't that severely weaken the frame?
Most makers of stretch vehicles use overlapping frame rails to increase the strength of the resulting stretch vehicle.

By making the stretch frame rail slightly smaller than the manufacturer's frame, several inches of stretch frame are actually inside of the manufacturer's frame and the two frames are joined by welds at multiple locations along that overlapping section of frame. RWD stretch vehicles also sometimes further increase the structural rigidity with the installation of a reinforced driveshaft tunnel that acts as a fifth frame rail.



False Prophet wrote:
Thu Nov 07, 2019 9:31 am
You mean suits like the Gelgoog Uma Lightning, or the ReGelgu? The later I suspect were built completely new, though they seemed to retain a level of part compatibility with the older Gelgood -- in the latest volume Johnny Ridden had a High Mobility Gelgoog equipped with the ReGelgu's binders.
I'd say the Todesritter is more similar to what was done with the Mars Zeon mobile suits... which outwardly look like older Zeon mobile suits, but under the hood the technology is substantially newer.


False Prophet wrote:
Thu Nov 07, 2019 9:31 am
Since you are here, Kaiba, can I ask how hard is it to install a rollcage to existing car?
On an aftermarket installation, you'd have to remove the car's interior (seats, carpet, headliner, center console, etc.) first. Then the roll cage goes in in pieces and is either bolted or welded to the vehicle body and bolted or welded into a single contiguous piece. After that, the interior of the car can be reinstalled.
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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by MythSearcher » Thu Nov 07, 2019 11:33 pm

Seto Kaiba wrote:
Thu Nov 07, 2019 2:56 pm
Most makers of stretch vehicles use overlapping frame rails to increase the strength of the resulting stretch vehicle.

By making the stretch frame rail slightly smaller than the manufacturer's frame, several inches of stretch frame are actually inside of the manufacturer's frame and the two frames are joined by welds at multiple locations along that overlapping section of frame. RWD stretch vehicles also sometimes further increase the structural rigidity with the installation of a reinforced driveshaft tunnel that acts as a fifth frame rail.
I see, that makes sense. So basically they exchanged mass efficiency to reinforce the weakened parts.
False Prophet wrote:
Thu Nov 07, 2019 9:31 am
You mean suits like the Gelgoog Uma Lightning, or the ReGelgu? The later I suspect were built completely new, though they seemed to retain a level of part compatibility with the older Gelgood -- in the latest volume Johnny Ridden had a High Mobility Gelgoog equipped with the ReGelgu's binders.
Earlier in the story they specifically states that the should they picked up "looks like" a Gelgoog but is built with EFF's newest technology, so they are not modified but newly built.

Part compatibility isn't sticking an old units shoulders to a new suit's back pack, but directly using parts for the same purpose. Ok, it sort of is, but I can always make a universal hard point on a MS so that you can attach a head unit to the back of it an claim compatibility while it serves "additional" function but not its "original" function.

If they can install an old Gelgoog's arm to replace the newly built super Gelgoog (with some degree of lowering the performance, I assume), that is part compatibility.
A good example will be Zeta Zaku, that is part compatibility to its finest, but most impractical, moment.

Of course usually we get to replace a motor or a screw, not a whole MS limb.

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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by False Prophet » Sat Nov 23, 2019 5:26 am

On a related subject, do you think how easy is it to repair damaged moveable-frame armor? For example, how easy is it to remove the armor plates in this case, when compared to the Zeon's monocoque designs (the Zaku, etc.)

(On a related note, what is the difference between monocoque and unibody? They both have the frame on the outside, right? And is it true that unibody constructions are harder to fix, since any outward damage is damage to the frame?)

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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by Seto Kaiba » Sat Nov 23, 2019 4:18 pm

False Prophet wrote:
Sat Nov 23, 2019 5:26 am
On a related subject, do you think how easy is it to repair damaged moveable-frame armor? For example, how easy is it to remove the armor plates in this case, when compared to the Zeon's monocoque designs (the Zaku, etc.)
The more I read about the movable frame in Gundam, the more I'm convinced that this is a case of "you keep using that word, I do not think it means what you think it means". It doesn't even really make sense, looking at it.

If you look at the anime itself and the cutaways in artbooks, even the 1st Generation Mobile Suits very clearly have their armor hung on a load-bearing structural frame to which the powertrain is attached. That's not monocoque in any sense. The way it's described in Japanese, they say monocoque but what they're describing is actually unibody construction where the exterior structure (armor) and chassis (frame) share the structural load. The way that the movable frame is described in Japanese, it sounds more like they've gone backwards to old-school body-on-frame design... up-armoring the frame and reducing the defensive ability of the now-entirely-separate exterior armor.

Given the way movable frame armor is described as floating armor separate from the frame in the sources that I can find, replacing it would be pretty easy compared to the more unibody-like designs of the OYW.

False Prophet wrote:
Sat Nov 23, 2019 5:26 am
(On a related note, what is the difference between monocoque and unibody? They both have the frame on the outside, right? And is it true that unibody constructions are harder to fix, since any outward damage is damage to the frame?)
Old-school body-on-frame construction involves the rigid structural load-bearing frame of the vehicle (the chassis) be structurally separate from the body of the vehicle that holds the passenger(s) and support systems mounted to it. In the modern day, this construction method is used mostly for trucks (and SUVs, which are technically trucks anyway). If you wanted to think about this in organic terms, this is an endoskeleton like you and I have.

Unitized body - unibody - construction is a version of body-on-frame design in which the body and frame together are both load-bearing and combined form a single rigid structure that bears all the operating loads of the vehicle. This is the standard design architecture for most cars. This is kind of analogous to how turtle skeletons work.

Monocoque - lit. "single shell" - construction could be called a more extreme take on the unibody concept in which a vehicle has no internal load-bearing frame, and ALL the structural loads are handled by the rigid body structure. This is your invertebrates, in the real world, creatures with only an exoskeleton.
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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by MythSearcher » Sun Nov 24, 2019 11:25 pm

Seto Kaiba wrote:
Sat Nov 23, 2019 4:18 pm
The more I read about the movable frame in Gundam, the more I'm convinced that this is a case of "you keep using that word, I do not think it means what you think it means". It doesn't even really make sense, looking at it.

If you look at the anime itself and the cutaways in artbooks, even the 1st Generation Mobile Suits very clearly have their armor hung on a load-bearing structural frame to which the powertrain is attached. That's not monocoque in any sense. The way it's described in Japanese, they say monocoque but what they're describing is actually unibody construction where the exterior structure (armor) and chassis (frame) share the structural load. The way that the movable frame is described in Japanese, it sounds more like they've gone backwards to old-school body-on-frame design... up-armoring the frame and reducing the defensive ability of the now-entirely-separate exterior armor.

Given the way movable frame armor is described as floating armor separate from the frame in the sources that I can find, replacing it would be pretty easy compared to the more unibody-like designs of the OYW.
I guess that is because the description is not updated according to the redesigns, and the artists had no idea of the terms and just designed whatever they think worked.

I recall a discussion before about this, and the best I can come up with to get it to make sense is that the single modular parts are monocoque, say, the upper arm by itself is monocoque, and each part is than linked together by whatever they used to make them move, rendering the whole thing not quite monocoque.
This, however, is not the artists took in their designs and because they are more about designing working and cool looking plastic models, they are sticking more and more to a skeletal frame with attached armour.
I guess only the amphibian MSs are monocoque in the current art iteration. You can possibly design other MSs to be monocoque, but it would be very hard to show on a plastic model.
Old-school body-on-frame construction involves the rigid structural load-bearing frame of the vehicle (the chassis) be structurally separate from the body of the vehicle that holds the passenger(s) and support systems mounted to it. In the modern day, this construction method is used mostly for trucks (and SUVs, which are technically trucks anyway). If you wanted to think about this in organic terms, this is an endoskeleton like you and I have.

Unitized body - unibody - construction is a version of body-on-frame design in which the body and frame together are both load-bearing and combined form a single rigid structure that bears all the operating loads of the vehicle. This is the standard design architecture for most cars. This is kind of analogous to how turtle skeletons work.

Monocoque - lit. "single shell" - construction could be called a more extreme take on the unibody concept in which a vehicle has no internal load-bearing frame, and ALL the structural loads are handled by the rigid body structure. This is your invertebrates, in the real world, creatures with only an exoskeleton.
I always wondered what is the actual term for the Semi-monocoque OYW EFF MSs should be.

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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by Seto Kaiba » Mon Nov 25, 2019 1:38 am

MythSearcher wrote:
Sun Nov 24, 2019 11:25 pm
I guess that is because the description is not updated according to the redesigns, and the artists had no idea of the terms and just designed whatever they think worked.
Given how old some of the cutaways I'm looking at are, I suspect it's more a simple case of them not knowing what the term actually means.


MythSearcher wrote:
Sun Nov 24, 2019 11:25 pm
I recall a discussion before about this, and the best I can come up with to get it to make sense is that the single modular parts are monocoque, say, the upper arm by itself is monocoque, and each part is than linked together by whatever they used to make them move, rendering the whole thing not quite monocoque.
The problem with that line of reasoning is that you can't call the Mobile Suit a monocoque design if 90% of it is a unibody or body-on-frame design instead. The only instance of a true monocoque design I've found is in forearm design for the Zaku II and RX-78NT-1 Gundam ALEX. In both cases, the forearm is hollow and the wrist attached directly to the outside of the forearm instead of having any visible frame elements.


MythSearcher wrote:
Sun Nov 24, 2019 11:25 pm
I always wondered what is the actual term for the Semi-monocoque OYW EFF MSs should be.
If they were truly semi-monocoque, "semi-monocoque" is perfectly acceptable... though most of the designs that are described as "semi-monocoque" appear to truly be unibody.
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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by MythSearcher » Mon Nov 25, 2019 9:52 pm

Seto Kaiba wrote:
Mon Nov 25, 2019 1:38 am
Given how old some of the cutaways I'm looking at are, I suspect it's more a simple case of them not knowing what the term actually means.
I'd say the artist and whoever wrote the description are different, and obviously the artists have no idea what the term means.

Well, at least the early plastic models are monocoque.(Internal structures are only added since PG?)


The problem with that line of reasoning is that you can't call the Mobile Suit a monocoque design if 90% of it is a unibody or body-on-frame design instead. The only instance of a true monocoque design I've found is in forearm design for the Zaku II and RX-78NT-1 Gundam ALEX. In both cases, the forearm is hollow and the wrist attached directly to the outside of the forearm instead of having any visible frame elements.
There is no saving for almost anything they draw that resembles the newer MG models.
I don't recall when did they start using the skeleton design, but they are obviously forcing an image of all MS having an internal structure and even the Zakus are redesigned to be having a load bearing skeleton and none of the armour is load bearing.
If they were truly semi-monocoque, "semi-monocoque" is perfectly acceptable... though most of the designs that are described as "semi-monocoque" appear to truly be unibody.
So how would you design them to make them semi-monocoque?

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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by Seto Kaiba » Wed Nov 27, 2019 3:27 pm

MythSearcher wrote:
Mon Nov 25, 2019 9:52 pm
I'd say the artist and whoever wrote the description are different, and obviously the artists have no idea what the term means.
Given that the disparity between the claims of monocoque design and actual depiction extends into the animation itself and the sheer consistency with which these mobile suits are depicted as having internal load-bearing frames throughout their bodies over literal decades of material, it's vastly more likely that whoever originally attempted to describe these mobile suits as monocoque couldn't be arsed to look up what the term actually meant. :roll:


MythSearcher wrote:
Mon Nov 25, 2019 9:52 pm
Well, at least the early plastic models are monocoque.(Internal structures are only added since PG?)
That's a plamodel, it doesn't NEED an internal structural frame because it's small, made of plastic, and doesn't have to move under power.


MythSearcher wrote:
Mon Nov 25, 2019 9:52 pm
I don't recall when did they start using the skeleton design, but they are obviously forcing an image of all MS having an internal structure and even the Zakus are redesigned to be having a load bearing skeleton and none of the armour is load bearing.
While I cannot say with certainty when this disparity between description and official art emerged, I can say with confidence that it has been with us for over thirty years.

The oldest drawing of a non-monocoque Zaku II currently in my possession is from Bandai Entertainment Bible #1: Mobile Suit Gundam (Part 1), published 20 February 1989. (30 years, 9 months, and 7 days ago at time of writing.)

Really, the idea of the early mobile suits being monocoque or semi-monocoque is a completely idiotic idea. 1st Generation Mobile Suits like the Zaku II had armor made out of steel plate. Their legs would've been crushed by the body's own weight like cheap soda cans if their weight was being supported on a dozen or so centimeters of steel armor, and they would've torn themselves to pieces the first time they tried to walk as the steel plates of their armor deformed under the torque of trying to walk, run, or god forbid JUMP. The only way you'd be able to make the armor thick enough to support all that weight would be by making it so thick there wouldn't be any room for internal mechanisms inside the armor anymore... at which point you've built a statue, not a robot.

Let's briefly put this in perspective:
  • Per official spec, a MS-06 Zaku II has an empty/unarmed base weight of 58,100kg. In real world terms, that's 29.6 full-size American minivans worth of weight, and a whopping 9,100kg more than the RX-0 Unicorn Gundam's statue in Odaiba - a difference of 4.6 minivans.
  • Fully loaded, a Zaku II has an operating weight of 73,700kg, equivalent to about 37.5 minivans. That's eight more minivans worth of weight, and 12 1/2 minivans more than the Gundam statue weighs.
The only thing stopping that Gundam statue from collapsing is a massive steel reinforcement frame holding the Gundam upright. There is no mortal way it could withstand the structural stresses of walking even with such a massive amount of structural reinforcement. The Zaku II weighs 50% more than the statue does, and all of the weight would be on maybe two dozen centimeters of steel skin IN ADDITION TO the torque stresses of all of its joint drive motors for walking, running, jumping, and so on? The square-cube law is a cruel mistress, and even if the Zaku's armor skin were twice as tough as the best cromoly steel we have today it would crumple like a beer can someone ran over with a car. The only way that Zaku's moving is if most of its weight is on an internal load bearing frame with proper shock absorption and reinforcement for all those moving parts.


MythSearcher wrote:
Mon Nov 25, 2019 9:52 pm
So how would you design them to make them semi-monocoque?
You bond a structural reinforcement frame to the inside of the load-bearing skin to reinforce it and prevent the skin from deforming under stress. (Similar to how an aircraft frame works, except with the skin being a load-bearing structure itself.)
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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by MythSearcher » Thu Nov 28, 2019 11:06 pm

Seto Kaiba wrote:
Wed Nov 27, 2019 3:27 pm
Given that the disparity between the claims of monocoque design and actual depiction extends into the animation itself and the sheer consistency with which these mobile suits are depicted as having internal load-bearing frames throughout their bodies over literal decades of material, it's vastly more likely that whoever originally attempted to describe these mobile suits as monocoque couldn't be arsed to look up what the term actually meant. :roll:
While I cannot say with certainty when this disparity between description and official art emerged, I can say with confidence that it has been with us for over thirty years.

The oldest drawing of a non-monocoque Zaku II currently in my possession is from Bandai Entertainment Bible #1: Mobile Suit Gundam (Part 1), published 20 February 1989. (30 years, 9 months, and 7 days ago at time of writing.)
I confirmed the first use of the term monocoque is from 1980 Gundam Century, where you cannot find any internal drawings of any MS. However, a bit later than that, Gundam SF World (also 1980) does give us TWO internal structures of RX-78, both are obviously either body-on-frame or unibody(Although I highly doubt this since the armour doesn't seem like in anyway load bearing), one of them is meant to be a joke(Spring powered MS? yes, it was specifically stated it is a joke)

The Gundam Century paragraph is about the development of MS and since they cannot meet the weight requirement, they switched to using a frameless monocoque structure for the MS-03. It did not specify if they still stick to this in the later MSs, but obviously the later books interpreted it to be a yes.
That's a plamodel, it doesn't NEED an internal structural frame because it's small, made of plastic, and doesn't have to move under power.
Yes, just making fun of the fact that maybe that's what they are getting the idea from.
Really, the idea of the early mobile suits being monocoque or semi-monocoque is a completely idiotic idea. 1st Generation Mobile Suits like the Zaku II had armor made out of steel plate. Their legs would've been crushed by the body's own weight like cheap soda cans if their weight was being supported on a dozen or so centimeters of steel armor, and they would've torn themselves to pieces the first time they tried to walk as the steel plates of their armor deformed under the torque of trying to walk, run, or god forbid JUMP. The only way you'd be able to make the armor thick enough to support all that weight would be by making it so thick there wouldn't be any room for internal mechanisms inside the armor anymore... at which point you've built a statue, not a robot.

Let's briefly put this in perspective:
  • Per official spec, a MS-06 Zaku II has an empty/unarmed base weight of 58,100kg. In real world terms, that's 29.6 full-size American minivans worth of weight, and a whopping 9,100kg more than the RX-0 Unicorn Gundam's statue in Odaiba - a difference of 4.6 minivans.
  • Fully loaded, a Zaku II has an operating weight of 73,700kg, equivalent to about 37.5 minivans. That's eight more minivans worth of weight, and 12 1/2 minivans more than the Gundam statue weighs.
The only thing stopping that Gundam statue from collapsing is a massive steel reinforcement frame holding the Gundam upright. There is no mortal way it could withstand the structural stresses of walking even with such a massive amount of structural reinforcement. The Zaku II weighs 50% more than the statue does, and all of the weight would be on maybe two dozen centimeters of steel skin IN ADDITION TO the torque stresses of all of its joint drive motors for walking, running, jumping, and so on? The square-cube law is a cruel mistress, and even if the Zaku's armor skin were twice as tough as the best cromoly steel we have today it would crumple like a beer can someone ran over with a car. The only way that Zaku's moving is if most of its weight is on an internal load bearing frame with proper shock absorption and reinforcement for all those moving parts.
Walking gives your legs a loading about double your weight(Jumping gets you 5? Since they use thruster assisted jump, lets ignore that part for the moment) so lets give it a 150,000kgf baseline and a further 6 times maximum for a 100,000 cycle dynamic loading, so 900,000kgf, or 9,000,000N for ease of calculation.
(I guess 200,000 steps per sortie is reasonable? Though that is only about 28hrs of walking so it may not be enough for some cases)

Taking the yield strength of typical steel(A36) is about 250MPa, or 250,000,000N/m^2, so we need about 0.036m^2 cross-section of high tensile steel per leg. Estimating the radius of the knee part to be 1.5m, you require a thickness of about, err, 3.81mm? (I just plugged the numbers in google cal for area of ring)

Of course you still need more thickness for armour, if not, a small bullet hitting the leg causing a dent may be enough to crumble it.

Even if I multiply the area to 5 times, taking that while running, most of the force only focus on the front area, I get something like 20mm thickness, which is still rather thin and sounded quite absurd.
What am I doing wrong?

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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by Seto Kaiba » Sun Dec 01, 2019 4:10 pm

MythSearcher wrote:
Thu Nov 28, 2019 11:06 pm
Walking gives your legs a loading about double your weight(Jumping gets you 5? Since they use thruster assisted jump, lets ignore that part for the moment) so lets give it a 150,000kgf baseline and a further 6 times maximum for a 100,000 cycle dynamic loading, so 900,000kgf, or 9,000,000N for ease of calculation.
Just standing still, you're looking at a compressive load of 73,700kg at 1g. The yield strength of A36 steel is 25kN per square centimeter, or 25.5kg at 1g per square centimeter. To stand on one foot (which you need to be doing assuming you mean to walk) you need a footprint of approximately 30 square centimeters of steel to support the 73,700kg mass at 1g. That's a beam 5.48cm square. This is the absolute bare minimum just to stand up without immediately collapsing under its own weight in a perfect world scenario with no later stresses and assuming that the Zaku has perfectly regular dimensions (which it doesn't). That won't protect you from much, considering the modern PGU-14 can get through 5.5cm of RHA at 1.2km.

These plates are going to be deformed in all manner of different directions due to the range of motion of a Zaku's joints. It needs to be able to run, to jump, to rocket jump, to brawl, and resist armor-piercing munitions.

Depending on how quickly you're walking, you can see loads of anywhere from 4-25 times your weight on one leg at a time.

For the lower bound, now that solid steel beam needs to be bare minimum 11cm square to avoid crushing like an egg under load. Under less than ideal conditions like rough terrain, a heavy step, a stumble, etc. now you're at a solid beam that's 27.4cm square (10 3/4 inches thick). At 7.9g per cubic centimeter, this 750 square centimeter footprint frame that's about 16m tall (1.2 million cubic centimeters) weighs 9,480kg, approximately 1/8th of the Zaku's weight (loaded) or 1/6th (unloaded).

That is JUST to walk assuming a perfectly uniform structure and no lateral loading whatsoever. The Zaku's limbs aren't uniform, and they're subjected to all kinds of lateral stresses, and you've already got a leg that needs to be perfectly circular and 5 1/2 inches thick. Since it's NOT uniform, the thinnest areas need to be barely minimum 27.4cm thick and the rest needs to be even thicker to counter the asymmetric loading.

To have any hope of repelling fire from armor-piercing munitions at calibers of over 100mm, you're looking at more 1-2m thick. Modern M829 series tank shells can easily slice through a meter of RHA and they'll have had almost a century to improve on that sh*t by the OYW.

Of course, this is considering modern A36 steel. Presumably whatever UC-modern steel alloy is being used is more dense and therefore can be thinner while providing the same structural support.
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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by MythSearcher » Tue Dec 03, 2019 11:03 pm

Seto Kaiba wrote:
Sun Dec 01, 2019 4:10 pm
Just standing still, you're looking at a compressive load of 73,700kg at 1g. The yield strength of A36 steel is 25kN per square centimeter, or 25.5kg at 1g per square centimeter. To stand on one foot (which you need to be doing assuming you mean to walk) you need a footprint of approximately 30 square centimeters of steel to support the 73,700kg mass at 1g. That's a beam 5.48cm square. This is the absolute bare minimum just to stand up without immediately collapsing under its own weight in a perfect world scenario with no later stresses and assuming that the Zaku has perfectly regular dimensions (which it doesn't). That won't protect you from much, considering the modern PGU-14 can get through 5.5cm of RHA at 1.2km.

These plates are going to be deformed in all manner of different directions due to the range of motion of a Zaku's joints. It needs to be able to run, to jump, to rocket jump, to brawl, and resist armor-piercing munitions.

Depending on how quickly you're walking, you can see loads of anywhere from 4-25 times your weight on one leg at a time.

For the lower bound, now that solid steel beam needs to be bare minimum 11cm square to avoid crushing like an egg under load. Under less than ideal conditions like rough terrain, a heavy step, a stumble, etc. now you're at a solid beam that's 27.4cm square (10 3/4 inches thick). At 7.9g per cubic centimeter, this 750 square centimeter footprint frame that's about 16m tall (1.2 million cubic centimeters) weighs 9,480kg, approximately 1/8th of the Zaku's weight (loaded) or 1/6th (unloaded).

That is JUST to walk assuming a perfectly uniform structure and no lateral loading whatsoever. The Zaku's limbs aren't uniform, and they're subjected to all kinds of lateral stresses, and you've already got a leg that needs to be perfectly circular and 5 1/2 inches thick. Since it's NOT uniform, the thinnest areas need to be barely minimum 27.4cm thick and the rest needs to be even thicker to counter the asymmetric loading.

To have any hope of repelling fire from armor-piercing munitions at calibers of over 100mm, you're looking at more 1-2m thick. Modern M829 series tank shells can easily slice through a meter of RHA and they'll have had almost a century to improve on that sh*t by the OYW.

Of course, this is considering modern A36 steel. Presumably whatever UC-modern steel alloy is being used is more dense and therefore can be thinner while providing the same structural support.
That's pretty much the same as my calculations. (I do admit I accidentally inputed diameter as radius)
750cm^2 on a 75cm inner radius ring gives you an outer radius of 76.58cm. (I estimated it as a ring because the load will be on the vertical section, not the bottom of the foot, and also should be focused on the joint)
So you only need a 1.58cm thickness, which sounded really absurd if you are thinking of supporting a 73t unit.
My calculations(with much more torlerance), gave me a 2cm thickness, still absurd.

1/6 of you mass as frame isn't that much of a problem given the M1 has about 55% weight as armour. Although given the surface area of a MS, 55% of its empty weight as armour will only give you a really thin armour.

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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by Seto Kaiba » Wed Dec 04, 2019 2:09 pm

MythSearcher wrote:
Tue Dec 03, 2019 11:03 pm
That's pretty much the same as my calculations. (I do admit I accidentally inputed diameter as radius)
750cm^2 on a 75cm inner radius ring gives you an outer radius of 76.58cm. (I estimated it as a ring because the load will be on the vertical section, not the bottom of the foot, and also should be focused on the joint)
So you only need a 1.58cm thickness, which sounded really absurd if you are thinking of supporting a 73t unit.
My calculations(with much more torlerance), gave me a 2cm thickness, still absurd.
The problem with trying to compute this as a monocoque design is that you end up with some unusual stressors in a variety of weird places, especially where the sole of the foot corners to meet the armored skin going up the side of the foot. I'm not even sure how to begin computing THAT one. If it were a reinforced skin I'd be looking at math to compute punching shear stresses for the reinforcement to just go clean through the skin under load.

I'd love to have the time to model a Zaku in proper structural engineering CAD, and see just how many places that design won't work as monocoque. I have a feeling it's a LOT, especially high-stress areas like the ankles, knees, backpack mount, and neck. EDIT: Actually, the pelvis should probably be the worst of it...


MythSearcher wrote:
Tue Dec 03, 2019 11:03 pm
1/6 of you mass as frame isn't that much of a problem given the M1 has about 55% weight as armour. Although given the surface area of a MS, 55% of its empty weight as armour will only give you a really thin armour.
Granted, but the M1's so compact that it can actually get away with a semi-monocoque structure that uses the rigid armor as a load-bearing material due to its high rigidity and the distributed load across the tank's traction surface.
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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by MythSearcher » Fri Dec 06, 2019 5:54 am

Seto Kaiba wrote:
Wed Dec 04, 2019 2:09 pm
The problem with trying to compute this as a monocoque design is that you end up with some unusual stressors in a variety of weird places, especially where the sole of the foot corners to meet the armored skin going up the side of the foot. I'm not even sure how to begin computing THAT one. If it were a reinforced skin I'd be looking at math to compute punching shear stresses for the reinforcement to just go clean through the skin under load.

I'd love to have the time to model a Zaku in proper structural engineering CAD, and see just how many places that design won't work as monocoque. I have a feeling it's a LOT, especially high-stress areas like the ankles, knees, backpack mount, and neck. EDIT: Actually, the pelvis should probably be the worst of it...
That is why I tried to focus the force on the front 1/5 of it and multiplied the required area by 5.
I guess it is still not good enough.

I am sure the Zaku isn't going to live up to any engineering claims it makes.

While we are on topic, Turn A's original design by Syd Mead seems to be a more monocoque worthy design. Maybe other than the foot part(curving down like that is going to be focusing the stress on the top part)
Granted, but the M1's so compact that it can actually get away with a semi-monocoque structure that uses the rigid armor as a load-bearing material due to its high rigidity and the distributed load across the tank's traction surface.
Of course. Its shape is also much less strange in terms of taking stress.
Every step a MS takes is changing the force distribution by a lot.

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Re: How easy can you modify a non-moveable frame MS to a moveable frame one?

Post by Seto Kaiba » Fri Dec 06, 2019 1:29 pm

MythSearcher wrote:
Fri Dec 06, 2019 5:54 am
While we are on topic, Turn A's original design by Syd Mead seems to be a more monocoque worthy design. Maybe other than the foot part(curving down like that is going to be focusing the stress on the top part)
I'd quite forgotten about the Turn-A... that might have a legitimate claim to being monocoque.
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