Tracked Vehicles Instead of Walkers...

[Sikon]

You are aware that WRT the drive mechanism the track isn't the knee joint, ankle or anything, it's the Valendamned sneaker you're wearing, yes?

Sneakers and other shoes last for vastly more than 1000km, yet tank tracks are replaced about every 1000km, so clearly the comparison is imperfect.

Aside from suggesting GFFA materials might change the situation, the main argument I could see here would be one trying to argue that today's tank tracks wearing out after typically 1000km are poorly designed, arguing that tracks should be able to last much longer than 1000km. I am not sure about all of the details of why they don't last longer myself. Perhaps it is because tracks are relatively thin relative to area, stretched over a distance of a number of feet, made from flexible material, and harmed when going over the edges of rocks. I don't know. However, whatever the cause, making tracks last for long must not be particularly easy, considering that terrestrial militaries would surely prefer them to last longer.

[Sikon]

If the future can build practical walkers, then the future can build more durable tracks.

Possibly true. I have implied before that the situation with GFFA technology is uncertain. However, current tank tracks sure wear out fast, and it is possible that GFFA legged vehicles may get their legs broken even less often than GFFA tracked vehicles get their tracks broken or otherwise needing replacement.

[Batman]

You are aware that WRT the drive mechanism the track isn't the knee joint, ankle or anything, it's the Valendamned sneaker you're wearing, yes?

Sneakers and other shoes last for vastly more than 1000km, yet tank tracks are replaced about every 1000km, so clearly the comparison is imperfect.

People rarely weigh more than a couple hundred pounds while tracked vehicles routinely weigh double-figure tons so clearly the comparison is imperfect. See the connection?
You are using a part of the tracked vehicle design that is, to be bluntly, NOT a relevant part of it in context to comment on its reliability WRT walkers. Why don't you look at the drive train, transfer rollers, drive wheels etc and see how long THEY last instead. I notice you never bothered to run any of them numbers you say SHOULD support feasible walkers with modern-day materials.

Aside from suggesting GFFA materials might change the situation, the main argument I could see here would be one trying to argue that today's tank tracks wearing out after typically 1000km are poorly designed, arguing that tracks should be able to last much longer than 1000km.

That's funny, I can't see anybody arguing that. All I see is YOU arguing since tracks only last so short, a walker must last longer regardless of the fact that the mechanical stress on the drive train of a walker has very little to do with the stress on the treads of a modern tracked vehicle.

[GunDoctor]

Why did the Galactic Empire choose the concept of "tanks on legs" over the older concept of tanks with caterpillar treads? Why did the AT-TE, AT-ST, AT-RT and famous AT-AT have to be deseigned as "tanks on legs"? What practical military purpose do "walkers" really serve?

Who the fuck cares? They look cool!

[Connor MacLeod]

An AT-AT is a combination of troop transport and long range heavy artillery platform (It has very heavy, starfighter grade energy weapons with a long reach, but it has virtually no close in defenses.) Its not really a tank any more than the SPHA-T is.

Aside from terror and intimitation, the prime factor motivating the AT-AT being so freaking tall is to give it a long effective range. Remember that blasters and lasers are line of sight weapons and virtually incapable of ballistic arcing. Which means, of course, that in order to hit the target, the AT-ATs weapons have to see it (and if it can see them, they can see it.) Which no doubt neccesistated making the thing so heavily protected.

They probably could have gone with projectile weapons or missiles and a lower-profile, yes, but missiles and projectiles carry their own disadvantageS (they can be intercepted or jammed, they take up more space than energy weapons, they move slower, and they allow fewer shots.)

THe AT-TE I might point out is equipped with a projectile weapon, so it is probably designed for long-range sniping much the same wa the AT-AP is. The legs also probably could allow for a bit more change in height to either reduce profile or allow longer LOS targeting.

[Sikon]

You are aware that WRT the drive mechanism the track isn't the knee joint, ankle or anything, it's the Valendamned sneaker you're wearing, yes?

Sneakers and other shoes last for vastly more than 1000km, yet tank tracks are replaced about every 1000km, so clearly the comparison is imperfect.

People rarely weigh more than a couple hundred pounds while tracked vehicles routinely weigh double-figure tons so clearly the comparison is imperfect. See the connection?

The comparison is imperfect. One shouldn't conclude tank tracks are like sneakers or last as long. My point is that tank tracks made with today's materials need to be replaced after around 1000km. The above isn't a problem for my argument. It would be a problem if I had argued tracks are like sneakers, but I didn't.

You are using a part of the tracked vehicle design that is, to be bluntly, NOT a relevant part of it in context to comment on its reliability WRT walkers. Why don't you look at the drive train, transfer rollers, drive wheels etc and see how long THEY last instead.

Whatever the rate of problems with other parts, the track replacement trouble is enough by itself to temporarily take modern tanks out of operation. I don't have to try to find data on every part, just find an upper limit on overall reliability, as determined by the weakest link.

I notice you never bothered to run any of them numbers you say SHOULD support feasible walkers with modern-day materials.

The bones of human and animal "walkers" are much weaker than suitable metals. Trying to do a real analysis would take too long, but one can give a very rough illustration of what is possible.

Darth Wong did here an evaluation of AT-AT legs using an elastic modulus of 200 GPa for modern-day structural steel. Let's assume that with a density of around 7800 kg/m^3.

Although the dimensions of the AT-AT legs do not seem structurally implausible, I am only trying here to show that walkers aren't impossible even with only modern-day materials. So let's modify the leg cross-section and quickly make up the characteristics of an imaginary legged vehicle roughly around the size of an AT-AT but without GFFA technology, without trying for precisely the same dimensions. Treat body volume as like that of a rectangular solid 8 meters wide, 10 meters high, and 20 meters long. Treat average density like that of a submarine (1000 kg/m^3), so body mass is 1600 metric tons.

Before considering more complicated loading, let's look at the situation when the legged vehicle is just standing still on all four legs. Body weight on each leg is 400 tons. Randomly decide the legs weigh half as much, so each leg masses 200 metric tons itself. For the example, arbitrarily consider a leg length of 15 meters and outer diameter of 2 meters. That gives an inner diameter around 1.35 meters.

To check for buckling, one needs the moment I, and for the circular leg cross-section it is (pi / 4) * [(r_o^4)-(r_i^4)], where r_o is the outer radius and r_i is the inner radius. For now, just considering the leg like a single column, one end fixed and one end free, the critical buckling load is F_crit = (pi^2 * E * I) / (4 * L^2) where E is Young's modulus of 200 GPa, I is 0.622 m^4, and L is 15 meters (not converting to effective length as the factor is already included in this formula). Thus, F_crit is 1.37E9 N, which is 139000 metric tons. Another potential method of failure is that a short column could fail by exceeding the compressive strength of the material even if loading is under the previously calculated buckling load. Checking, the stress at F_crit would be 800 MPa. This is above the yield stress for common structural steel. However, some types of steel have higher yield stress, and let's just assume the right type with a similar modulus is used so I can skip spending the time to recalculate. This isn't exact, rather just showing the order of magnitude involved.

Thus, during the ideal minimum loading condition of the vehicle standing still on all four legs, the above force before failure is up to the equivalent of 139000 metric tons per leg, up to more than 200 times the vehicle's weight.

Actual maximum loading with a real design and analysis would be vastly more complicated. There might be a safety factor of 2 or more; peak loading could be multiple times minimum loading; etc. As one random example, if the robotic control of a leg has its foot approach the ground at 5 m/s while deaccelerating over a distance of 0.5 meters, the average acceleration involved would be around two gravities. The working strength considering fatigue over many loading cycles might be as little as 50% or less of the standard yield strength value. Joints and bearings would be particular issues. One would have to consider stress concentrations depending upon subtleties like the effective radius of curvature at tapered joints, etc. Shock-absorbers and/or thickly padded feet might be used.

However, the above is still enough to give one a general idea of the situation. The legged vehicle with a 1600 metric-ton body weight and four large circular steel legs each 15 meters long massing 200 metric-tons each could easily be structurally sound.

This shouldn't be surprising. Admittedly animals are smaller with a lesser weight to leg dimensions ratio, but it is still a good intuitive observation to note how animals manage to stand up, walk, and move with bone that is not nearly as strong.

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Hopefully nobody reading the above is going to say the dimensions, mass, etc. are not those of the AT-AT. I know. I don't care. This is just an illustration.

Legs shaped like the AT-AT legs instead would be possible, but observe such would only be made in that manner if not much of a structural disadvantage. In fact, the AT-AT with relatively narrow legs hitting the ground hard suggests the Empire doesn't have to worry much about the structural strength of its walkers.

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What is being argued here is already getting confusing, so let's clarify. I am arguing that even modern-day materials would not prevent a suitable legged vehicle design from traveling a greater distance than 1000km on average without needing to undergo major maintenance during the journey. This is in contrast to modern-day tank tracks that have to be replaced approximately every 1000km.

As implied before, the situation with GFFA technology and materials instead is unclear, but there is a possibility that their legged vehicles may be able to go longer than tracked vehicles without the equivalent of track replacement.

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Aside from suggesting GFFA materials might change the situation, the main argument I could see here would be one trying to argue that today's tank tracks wearing out after typically 1000km are poorly designed, arguing that tracks should be able to last much longer than 1000km.

That's funny, I can't see anybody arguing that.

When I referred to a possible argument of one trying to argue so-and-so, I didn't mean to imply you were arguing such. That was why I said "would be one trying to argue" rather than saying "would be Batman trying to argue." Admittedly, I could have made my statement extra clear. Instead of having it just one blank line away from my reply to your post, I could have made a third separate post. Also, I could have inserted the word 'potential.' However, the point was to talk about a potential argument I anticipated one could make against me.

Keep in mind, from my perspective, arguing that no legged vehicle design made with modern-day materials could go further than 1000km without breakdown is implausible. Even the example of animals should make people be more cautious about such an assumption. Yet suggesting GFFA materials or different track design could change the relative performance of tracks beyond the present-day 1000km would be a better argument. I was addressing what I see as the best possible argument against my position.

All I see is YOU arguing since tracks only last so short, a walker must last longer regardless of the fact that the mechanical stress on the drive train of a walker has very little to do with the stress on the treads of a modern tracked vehicle.

Given that current tank tracks typically have to be replaced after the equivalent of at most several tens of hours of travel time at tens of kilometers per hour, I do believe an optimally designed legged vehicle made with modern materials could last longer before needing the equivalent of such troublesome maintenance.

[FTeik]

Can we even say for sure, that the AT-AT fills the role of MBT for the Empire? Because if not we're comparing apples with oranges. Aren't there things like the Juggernaut or AT-TE or AT-HE that fill that role? Curtis Saxton speculates, that the AT-ATs are actually patrol-vehicles, IIRC.

[Stark]

Er, I think you'll find AT-STs are patrol vehicles, AT-AT are (as the name suggests) assault transports. To be honest, I think it's likely they are *specifically designed* for assaults under theatre shields, where air support is difficult but long-range direct fire is required, as is advancing under heavy resistance. Star Wars battering rams.

[Elfdart]

Er, I think you'll find AT-STs are patrol vehicles, AT-AT are (as the name suggests) assault transports. To be honest, I think it's likely they are *specifically designed* for assaults under theatre shields, where air support is difficult but long-range direct fire is required, as is advancing under heavy resistance. Star Wars battering rams.

I was thinking Star Wars siege towers, only faster-moving and with longer-range weapons.

It's a foregone conclusion that AT-AT legs hit the ground hard because of the powerful audible groundshocks produced with each footfall. Having said that, it would probably be possible to design a shock-absorber system into the legs which greatly decreases the mechanical stresses, and the cross-sectional load-bearing area for legs can be made fairly generous if you don't mind wasting huge amounts of power.

Wouldn't the "knee", "hip" and "ankle" joints need to be packed with some kind of springy material for that to work?

I think the big problem for walkers is that if a wheeled or tracked vehicle loses a tire or tread or becomes entangled, the whole thing doesn't come tumbling down. An AT-AT that loses a leg or gets entangled is going to crash. With its high center of gravity, it's worse. Which is why AT-ATs shouldn't be thought of as tanks or APCs. They're siege towers.

[Darth Wong]

Wouldn't the "knee", "hip" and "ankle" joints need to be packed with some kind of springy material for that to work?

I'm talking about hypothetically making a walker, not necessary making it look exactly like an AT-AT. Tank treads must be highly flexible, which limits their load-bearing capacity. Legs, on the other hand, could theoretically be made of arbitrary load-bearing cross-section as long as you don't mind wasting power. You could put the shock-absorbing mechanisms in the feet and the straight parts of the legs. In SW, you could do it with tensor fields.

I think the big problem for walkers is that if a wheeled or tracked vehicle loses a tire or tread or becomes entangled, the whole thing doesn't come tumbling down. An AT-AT that loses a leg or gets entangled is going to crash. With its high center of gravity, it's worse. Which is why AT-ATs shouldn't be thought of as tanks or APCs. They're siege towers.

I view them as self-propelled artillery. They have to be high off the ground because they use line-of-sight weapons and they have enough range to shoot over the horizon for a shorter vehicle. It also explains why they're so poorly designed for close-in combat.

[Anguirus]

The thing that bugs me about an AT-AT is that it's not even equipped to win a long-range artillery duel. Only against the poorly-armed Rebels could they be so virtually invulnerable...any high-impact or explosive weapons striking the walkers on the side has a good chance of toppling them, with their high-center of gravity. Much as I love the AT-AT design, it's hard to imagine them being used on most terrain when the RotS Juggernaut has more room for troops. While that vehicle also has an enormous target profile, it's also more heavily armed, almost certainly more heavily armored, and without nearly so much of a balance problem.

[Elfdart]

I view them as self-propelled artillery. They have to be high off the ground because they use line-of-sight weapons and they have enough range to shoot over the horizon for a shorter vehicle. It also explains why they're so poorly designed for close-in combat.

I was thinking of the siege towers used by Alexander with the ballistas mounted on top: a gun platform filled with troops.

[Winston Blake]

I think the big problem for walkers is that if a wheeled or tracked vehicle loses a tire or tread or becomes entangled, the whole thing doesn't come tumbling down. An AT-AT that loses a leg or gets entangled is going to crash. With its high center of gravity, it's worse. Which is why AT-ATs shouldn't be thought of as tanks or APCs. They're siege towers.

I view them as self-propelled artillery. They have to be high off the ground because they use line-of-sight weapons and they have enough range to shoot over the horizon for a shorter vehicle. It also explains why they're so poorly designed for close-in combat.

The last time this stuff came up I remember that they were classified as assault guns. Similar to artillery, but using direct fire and meant to support assaults on fixed positions. So rather than being intended to blanket a forward-observed area with indirect fire (artillery), or to roam around destroying enemy AFVs (tanks), the role of AT-ATs and real-world assault guns was more to defeat a defended position by destroying particular fortifications and groups of infantry. This is exactly what happened at Hoth.

AT-ATs are armoured well enough that they shrugged off all Rebel fire with ease. Given that, it's reasonable to put an assault gun as high as possible because of the advantages it gives to direct fire e.g. long range, clears obstacles, can feed 'bird's eye view' intelligence to other forces. Hence walking on legs, since making a very tall vehicle with tracks is obviously not a good idea. Real-life is different because the balance between modern firepower and armour means that a tall AFV could be easily destroyed by schmoes with RPGs.

Also, the fact that the AT-AT can protect a group of troops and dismount them directly into a compromised base makes them superior to real-world assault guns, where the infantry would have had to tag along separately.

Now, given that the Empire is geared towards counter-insurgency rather than full-scale war, it's possible that there's little need for the traditional roles of tanks. AFAIK, today with Iraq, American tanks that were intended to fight the Soviet tank horde are really only used as assault guns anyway. IFVs are much better suited to counter-insurgency, and the AT-AT neatly combines the assault gun and the IFV, with the twist that armour tech is good enough to make a very tall vehicle desirable, hence legs.

As for AT-STs and AT-TEs, um, I'm going mumble something about IED mine blasts and go to bed now. I know that I absolutely hate the SPHA-T's legs and whoever changed them from tracks to legs. Maybe we can pretend they're just anchors (recoil, pushing through theatre shields) for a main repulsor-based system.

[Stark]

The thing that bugs me about an AT-AT is that it's not even equipped to win a long-range artillery duel. Only against the poorly-armed Rebels could they be so virtually invulnerable...any high-impact or explosive weapons striking the walkers on the side has a good chance of toppling them, with their high-center of gravity. Much as I love the AT-AT design, it's hard to imagine them being used on most terrain when the RotS Juggernaut has more room for troops. While that vehicle also has an enormous target profile, it's also more heavily armed, almost certainly more heavily armored, and without nearly so much of a balance problem.

Er, didn't someone determine that you'd need to explode nuclear bombs against AT-ATs to knock them over? Nuclear landmines are more likely. But by the time your into the 'assault under the shield' phase, there are pretty tight restrictions on what kind of weapons your enemy can use, particularly in 'only LOS guns' SW.

The Juggernaut is even less agile than an AT-AT, and I'm not convinced wheels would actually provide more reliable traction than the AT-AT giant feet idea. Aren't wheels a really bad idea for snow? Juggernauts appear to have more ground area, but they're described as even heavier. Sure, they can't be tripped, but being instantly bogged probably isn't helping.

EDIT: Juggernauts are also shorter, and have significantly *less* armamant. They are incapable of the powerful, 17.6km shots that AT-ATs can dish out.

[Howedar]

Joints and bearings would be particular issues.

This is the crux of the matter, obviously, but you do not address it in any detail. If you ignore bearings and joints, congratulations. You've just designed a building. A fairly menacing building, but a building nonetheless.

What is being argued here is already getting confusing, so let's clarify. I am arguing that even modern-day materials would not prevent a suitable legged vehicle design from traveling a greater distance than 1000km on average without needing to undergo major maintenance during the journey. This is in contrast to modern-day tank tracks that have to be replaced approximately every 1000km.

I believe that you're also ignoring the severity of the maintenance required for both the treaded vehicle and the walker. If I remember correctly, a tank's treads (which I note are more in the 2000mi lifetime range) can be replaced in single-digit man-hours with no real specialized equipment. This is certainly not the case with any bearing/joint/whatever leg maintenance you care to name.

As implied before, the situation with GFFA technology and materials instead is unclear, but there is a possibility that their legged vehicles may be able to go longer than tracked vehicles without the equivalent of track replacement.

That could well be, but other maintenance would probably make the entire scheme a no-go.

[VT-16]

I know that I absolutely hate the SPHA-T's legs and whoever changed them from tracks to legs.

That would be George Lucas, who changed the design from tracked to legged. :P

Maybe we can pretend they're just anchors (recoil, pushing through theatre shields) for a main repulsor-based system.

Their approach to Harnaidan in the CW cartoon appeared to hint at this, since their motion seemed too smooth to be fully done by legs.

[Anguirus]

Er, didn't someone determine that you'd need to explode nuclear bombs against AT-ATs to knock them over? Nuclear landmines are more likely. But by the time your into the 'assault under the shield' phase, there are pretty tight restrictions on what kind of weapons your enemy can use, particularly in 'only LOS guns' SW.

I find it hard to believe that you'd need a nuke to topple an AT-AT with a direct hit, but even if you did, proton torpedoes anyone? They're small enough to be used in portable weapon systems, if one can afford them. AT-ATs have, of course, proven to be horrendously vulnerable to starfighters in the literature.

The Juggernaut is even less agile than an AT-AT, and I'm not convinced wheels would actually provide more reliable traction than the AT-AT giant feet idea. Aren't wheels a really bad idea for snow? Juggernauts appear to have more ground area, but they're described as even heavier. Sure, they can't be tripped, but being instantly bogged probably isn't helping.

They are certainly more massive, but they have a LOT more ground area. I doubt that they'd be bogged down more quickly than an AT-AT under almost any circumstances, but even if they were, that would only explain why the Imperials failed to use MBTs on Hoth in the first place, and not why a significant number of AT-ATs--personnel carriers that don't carry any more personnel, and artillery carriers with smaller weaponry--were even built.

Plus, they performed well on the beach in RotS, and that's hardly ideal conditions for a massive "rolling slab."

EDIT: Juggernauts are also shorter, and have significantly *less* armamant. They are incapable of the powerful, 17.6km shots that AT-ATs can dish out.

The A6 Juggernaut seen in RotS is twice the size of the old EU A5 Juggernaut, at a full 30 meters tall. In addition, while the AT-AT has two light and two heavy cannons, the Juggernaut has a heavy laser cannon turret with line-of-sight to everything around it, five other laser weapons of various sizes, and two front-mounted rocket launchers that are certainly capable of carrying nukes, concussion missiles, or anything else that would fit in them.

I see no reason why the heavy laser cannon on this, a dedicated MBT, cannot match the range and power of what the AT-AT is packing under its chin. The missiles also give it long-range and non-LOS capability.

Better yet, the Juggernaut may not be able to turn quickly (though it asbly avoided an AT-AP during the Kashyyyk battle) but it can instantly change direction with its secondary cockpit. It also has weapon coverage in all directions, and it cannot possibly be taken out of commission by a line of cable. Nor does it appear to have weak spots like the AT-AT's neck.

[Vympel]

EDIT: Juggernauts are also shorter, and have significantly *less* armamant. They are incapable of the powerful, 17.6km shots that AT-ATs can dish out.

Actually, they have way more armament. And the multi-missile launchers, which are awesome.

As for firepower- the RotS:ICS says the cannons can blast the heat of a nuclear bomb into a small area.

[Stark]

Angurius, the Jug can't turn slowly - it can BARELY TURN AT ALL. You turn it around by DRIVING FROM THE OTHER END. Hence, almost-zero agility. This cannot be avoided. The AT-AT is *more agile*.

Also, even the gaylord EU says it sucks at non-urban environments, so clearly things like SNOW WASTES would challenge it. The AT-AT has *better terrain handling*.

Get this: the ATAT chin guns are BIGGER and HIGHER, hence BETTER. Are you going to counter any of these points, or just say 'nah it must be better'? The AT-AT is *similar or better armed*.

Also, there is a thread specifically about toppling AT-ATs, go read it. It's very amusing... and you simply saying 'nah it's easy' doesn't convince anyone, champ. Maybe firing nuclear weapons might be A BIT DANGEROUS to the defenders? How would the fireball interact with the shield?

PS, the only 'hideously vulnerable to starfighters I remember is getting killed by the Falcon with a supergun. Also, you're just being a troll and ignoring that it's likely these vehicles are used for ASSAULTS UNDER SHIELDS where full fighters are difficult or impossible to use. You know, with the legs instead of repulsors? The deliberately high stature?

[Stark]

[Actually, they have way more armament. And the multi-missile launchers, which are awesome.

As for firepower- the RotS:ICS says the cannons can blast the heat of a nuclear bomb into a small area.

What, two tiny lasers, two grenade launchers, and two proper guns is 'way more'? The RotS version is the 'really big' version, it's several times the bulk of an AT-AT - I don't feel direct comparisons are valid, particularly given the problems with the Juggernaut design (which are clearly simply weak retcons as to why they abandoned the design, but blame the EU not me).

And nuclear bomb references don't impress me in the world of 7kt fighterguns.

[Fingolfin_Noldor]

Angurius, the Jug can't turn slowly - it can BARELY TURN AT ALL. You turn it around by DRIVING FROM THE OTHER END. Hence, almost-zero agility. This cannot be avoided. The AT-AT is *more agile*.

I was under the impression they could try running the wheels on both sides in opposite direction to maneuver. That's how tanks move anyway.

[Stark]

Oh you'd think, but you're not as stupid as EU writers. That's their explanation for the back drivers seat: they can't turn worth shit.

Also, they're described as being very fast in 'urban' environments (I'm thinking roads) but dealing with rough terrian poorly. I'm not sure how that squares with RotS, but the only one I remember seeing in that was on flat grass in a forest.

[Sikon]

Joints and bearings would be particular issues.

This is the crux of the matter, obviously, but you do not address it in any detail. If you ignore bearings and joints, congratulations. You've just designed a building. A fairly menacing building, but a building nonetheless.

What is being argued here is already getting confusing, so let's clarify. I am arguing that even modern-day materials would not prevent a suitable legged vehicle design from traveling a greater distance than 1000km on average without needing to undergo major maintenance during the journey. This is in contrast to modern-day tank tracks that have to be replaced approximately every 1000km.

I believe that you're also ignoring the severity of the maintenance required for both the treaded vehicle and the walker. If I remember correctly, a tank's treads (which I note are more in the 2000mi lifetime range) can be replaced in single-digit man-hours with no real specialized equipment. This is certainly not the case with any bearing/joint/whatever leg maintenance you care to name.

While one can see the 1000km figure came from a reference linked in an earlier post, your reference does look more specific. One can conclude that at least the M1A1 can go 2000 miles between track replacements, which is better, though still no more than around a hundred hours of cumulative driving at moderate speed. If a much more massive vehicle like the hypothetical 1600 metric-ton legged vehicle in my earlier post was made with tracks, a lot more weight than the M1A1 would be put on the stretched flexible material rolling over the edges of rocks and debris. However, admittedly, I can't rule out the possibility of such more heavily loaded tracks still lasting for 2000 miles, although it seems questionable.

Writing a post trying to design joints and bearings for a legged vehicle in detail isn't a practical option here. I can observe that the minimum loading condition on the legs of my random example gave on the order of 3.5 MPa average stress, and the legs could actually taper to be much larger at massive joints. Combine with the robotic control of the feet deaccelerating them before contacting the ground to "walk softly," thickly padded feet further decreasing peak stress, and shock-absorbers. Even the maximum transient peak stress shouldn't have to be many MPa, not that extraordinary for a bearing; some present-day commercial bearings handle at least up to many tens of MPa, smaller but still handling greater stress, more force per unit area.

As another analogy, consider how car axles last much longer than 100-hours between maintenance; if anything, the optimal legged vehicle design might give a smoother ride with less vibration than a car going fast down a rough road. I am not suggesting that major bearing maintenance would be faster than replacing tracks but rather that the former could be needed much less often than the latter.

I don't dispute that a sub-optimal legged vehicle design could require excessive maintenance or even more maintenance than current tanks, but this has been instead about the optimum possible with modern-day materials. After full use of foot contact velocity control, thickly padded feet, and shock-absorbers, surely good engineers could make bearings operating at a few MPa last much more than ~100-hours between maintenance, if that is made an important design goal. There is also the analogy of machines ranging from car engines to animals lasting much longer than even the ~100-hour M1A1 tracks. However, there is not going to be any practical absolute proof I can give of the preceding.

The AT-AT instead has narrow legs and hits the ground hard, but that just implies the Imperial designers accept such because their legged vehicles can still be reliable regardless.

As implied before, the situation with GFFA technology and materials instead is unclear, but there is a possibility that their legged vehicles may be able to go longer than tracked vehicles without the equivalent of track replacement.

That could well be, but other maintenance would probably make the entire scheme a no-go.

I wouldn't argue against "could well be"; as said before, the situation with the GFFA is unknown. I just see their legged vehicles lasting longer without stopping long for maintenance as a possibility. In the context of the other possibilities suggested in my original post like Imperial vehicle production cost not simply proportional to mass and direct-fire weapons dominating, my original overall point in this thread was that the Empire may benefit from having some large, legged vehicles as opposed to only having small, tracked vehicles.

[montypython]

Hybrid electric drive AFVs with band tracks can get double the performance for the same cost level.

http://www.g2mil.com/hybrid.htm

[Howedar]

As another analogy, consider how car axles last much longer than 100-hours between maintenance; if anything, the optimal legged vehicle design might give a smoother ride with less vibration than a car going fast down a rough road. I am not suggesting that major bearing maintenance would be faster than replacing tracks but rather that the former could be needed much less often than the latter.

You just proved my point! Yes, car drivelines can last a long damned time because they are loaded in a uniform and controlled way.

You can not in any way consider a car driveline analogous to joints in massive legs.

I don't dispute that a sub-optimal legged vehicle design could require excessive maintenance or even more maintenance than current tanks, but this has been instead about the optimum possible with modern-day materials. After full use of foot contact velocity control, thickly padded feet, and shock-absorbers, surely good engineers could make bearings operating at a few MPa last much more than ~100-hours between maintenance, if that is made an important design goal.

Read: handwaving. I can't think of a similar loading condition and application anywhere in the field of mechanical engineering. Feel free to correct me, my knowledge isn't exactly encyclopedic, but I don't think you can come up with one either.

There is also the analogy of machines ranging from car engines to animals lasting much longer than even the ~100-hour M1A1 tracks. However, there is not going to be any practical absolute proof I can give of the preceding.

Both tremendously less massive, and so poor examples.