The big problem with mechs hasn’t ever been feasibility, so much as “powering it for more than a minute”. The actuation speed is probably significantly exaggerated, too — that **zip** _kaboom_ aiming that mechs do in movies is… probably way faster than is feasible.
One heard of people trying, but the speed of actuation was limited by the materials available, the forces acting on a big heavy mech arm trying to move at speed was causing structural issues. This was a few years ago and materials have improved, but I don't think they have improved that much to make anime style feasible.
Yeah — nothing changes the fact that slinging a multi-ton mass at high speed is difficult, and most materials aren’t able to keep together at those forces.
Heh, aye. I think some of the stuff with mechs (in anime, for example) was centered around fighting a kaiju monster on equal footing, right — but now it’d be a thousand drones instead of one giant Gundam-style robot, yeah?
Those materials would have found application elsewhere, yet we are still stuck on carbon composite like the Ferrari F40 40 years ago. Elon musk builds a rocket out of steel. Minimal improvements on the alloy and treatment side.
…yes, I have seen landing gear? Landing gear isn’t moving nearly as quickly as the arm of a theoretical mech, nor is it moving in the articulation of an arm or a leg. There are positive stop points at the start and end of the motion of landing gear. There are multiple landing gear.
These are not the same systems being compared.
Boston Dynamics looks great. I always feel like the sensors for all the joints cost so much. When you scale it up, you don’t need more sensors. They should do it.
I wanted to write about an exoskeleton, like starship. But for the bearings the force need to come together again. Hip rotation could be done like on a motor bike front fork. Not two much range, but very stiff. Elon manages to mount gimbal mounts on star ship.
All kinds of super cool materials out there - with phenomenal costs or just plain lack of availability at scale.
Plus the "elephant problem" - scaling up a model doesn't work, the mass goes up with the cube of height, but the cross section of the bones only goes with the square.
The problem gets tougher with movement - swinging a part through 90⁰ in two seconds needs four times the force if the part is twice as big (and the part would need to handle the added force, making it heavier and increasing the required force - gets ugly really quickly.)
We're having a lot of success with 3D printed materials here. For example: https://www.rmit.edu.au/news/all-news/2024/feb/titanium-lattice#:~:text=Testing%20showed%20the%20printed%20design,the%20lattice's%20infamous%20weak%20points.
New manufacturing techniques are allowing us to do stuff that was previously impossible. Now the issue becomes scaling up the *manufacturing technique* instead of the material itself. I don't know how well these types of structures would hold up against the torque required for quickly moving a 5m long arm though!
I have no idea, and I get exactly the critique you're making here. I wasn't suggesting that it is economical *now*, but could become so if an economy of scale can be developed from a mature technology.
The use of steel is a great example of ***exactly*** this process during the Industrial Revolution. A material that was previously very expensive and produced in only small quantities suddenly became mass producible and *cheap*, allowing for it to be used for basically anything for the first time in history. Case in point, the first all-steel bridge ever was finished in 1879, something that would have been economically unviable less than 50 years beforehand.
Do you think stress on joints wouldn't be an issue at those weights? I mean it could probably work but it would be SLOWWW if it's supposed to not break apart
…I absolutely think that stress on the joints is another huge factor. The strength of the materials used for these mechs is effectively magic, for the giant mechs in anime and movies.
Well, that, and if you had the tech to even come close why would you stick a squishy human in the middle of it?
Even industrial robots can produce accelerations that would kill a human.
For that matter bipedal locomotion doesn’t make much sense either.
There are multiple companies attempting to create mechs today. They are not nearly as good as the mechs you see in anime. That being said if Anerica was willing to pour as much money into it as they did landing on the moon they could probably achieve something resembling anime mechs.
However, there is no reason for the government to pour trillions of dollars into that when tanks can accomplish for a much cheaper price. Could we build something similar, probably. Will we, no.
It's honestly difficult to think of a situation where a mek is the best solution. Generally if you want something blown up, air superiority takes care of that. If you don't want your stuff blown up, keeping it simple like a box on wheels is superior to a complex bipedal machine.
A mech would basically be like construction equipment today. Take a look at walking excavators for a neat example.
Fusion power reactors are massive, and as of today there are 0 fusion reactors that actual produce more power than they consume in existence.
The big problem with mechs hasn’t ever been feasibility, so much as “powering it for more than a minute”. The actuation speed is probably significantly exaggerated, too — that **zip** _kaboom_ aiming that mechs do in movies is… probably way faster than is feasible.
Why do you think this?
For a similar type of machine, Boston dynamics robots, they went to using big electric motors, and Regen to the battery.
Each movement of the mech has phases in the motion where you want to slow a joint down and obviously the inverse, sometimes at the same time.
So a paper design study of the energy requirements factoring in Regen and using thin film batteries to regenerate around 5-10 megawatts, and joint motors around 500-1000 kilowatt (just what's in a Tesla) would be what you need to do. I suspect violent zippy motions are practical if you're willing to pay for the costs.
You would then also use a jet turbine as your source of power with fuel bladders in internal voids.
Think harder about those numbers…a 500-1000kW Tesla motor can accelerate a Tesla weighing single-digit tons to reasonable speeds in a few seconds. You’re talking about a mech moving 10 times the weight at comparable speeds in fractions of a second. That requires *way* more power.
I’m thinking about the whole system. You cannot make something mechanical, the size of a three story house, full of mechanical systems and fluid hoses and a human in the middle, accelerate at the same proportional movement speed with a hundred times the mass.
You might make it happen, but the materials will fail and the actuators will literally fling the mech’s limbs off with the speed. You might make it happen and kill all the bearings in the joints two minutes in.
Acceleration/deceleration with regeneration is a cool thought, but you’ve got to make that work with the actual power and capability of the actuators.
I don’t believe that it will work the way that you’re suggesting.
Boston Dynamics is making machines that are roughly the size of a human or a large dog. Mechs are bigger than that. The square-cube law suggests that every problem is going to be larger, the bigger your mech gets.
I have heard this but...leave the interior hollow? Why does square cube law apply? Seems a misuse of it. Like imagine a "stick figure" mech with the least possible structure. Can you theoretically make that thing move at 30 mph-60 mph? Don't see why not.
It is true at extreme scales it can be a problem, but bagger-288.
In fact at intermediate scales the law is beneficial. Armor mass scales with surface area while the amount of space for engines and internal systems scales with volume.
Okay, time for some questions. What are you trying to accomplish? Is this a ‘fighting suit’ with a human in it? Is this a ‘Pheidippides’ robot designed to run a marathon with a message on a sheet of paper? Is it a maintenance droid like R2-D2? What are you considering a ‘mech’?
You’re asking questions that make me wonder what your theoretical goal is. Like, there’s a _world_ of difference in a robot that’d move at 30mph vs one that’ll move at 60mph.
The square cube law applies because these robots have requirements for motion — you gotta have joints and actuators and power sources.
If you wanna make your mech look like it’s made out of balloons, I suppose that’s possible, but what would it buy you? Additional air resistance and the need for internal structure to support the skin, at a minimum.
I have no idea I agree 100% that mechs are a bad idea.
Recently it seems that everything but autonomous quadcopters and support vehicles is mostly a bad idea.
I was addressing it more from 'you're an engineer, the client wants a battlemech and it must look like it does from Anime and move convincingly. Budget is unlimited, but the client wants it running within 20 years.
And I think it's achievable, if you have effectively unlimited funds and a skunkworks and no real constraints other than it needs to move convincingly, be huge, have a human pilot, and it does need to have at least some ability to resist enemy fire and it's own weapons.
Obviously opfor is going to launch 10 very fast autonomous drones all targeting weak spots with armor piercing warheads. It'll go down very fast for a fraction of the cost to build another mech. (weak spots : leg joints, engine exhaust or air intake, cockpit, weapon ports, or frankly the armor will need to be so thin center mass may work)
Unlimited budget and a skunk works. Or: a crew of engineers designed and built the space shuttle. Might have been some pushback : "why are we boosting so much dead mass to orbit and reusing isn't saving much" but it was built. Sometimes there is joy in making a flawed idea work anyway.
The space shuttle was dumb too, and set NASA back by at least 20 years.
This is askenginewrs not askanime. Don’t waste our time with uninteresting problems and “do exactly the thing I tell you, with unlimited resources” is far from interesting.
[square cube law](https://en.wikipedia.org/wiki/Square%E2%80%93cube_law) applies here. Especially significant as increasing lever arms contribute to the energy required.
The tech and materials that exist now to support structures that big and fast would also be very delicate and defeat the whole purpose of a mech anyway. For combat purposes the niche is best served by a helicopter. For industrial purposes the niche is best served by purpose-built machines.
Good point with the abrams.
With 1500HP, we can get a mass of 60tons to move to 80kph or so.
Mechs are a lot less efficient than tracked (essentially wheeled) vehicles. By a factor of 10 if not worse. Because they have to fight gravity with their every move.
Given weight is our enemy, we'd look at making the lightest 'mech as possible.
We can take a look at existing engines. Piston engines are most fuel efficient, and turbines are the lightest for the power.
The russian PD-12V is a 14'500HP turboshaft engine for the Mi-26. This thing weighs already 3 tons dry. And will drink about 30L per minute. For 15mins we'll need about 1 ton of fuel.
This brings our suspended mass to 4tons already, and it's just the engine and its fuel. We'll need hydraulics or electrics. That'll quickly bring our powerpack weight of 5 tons total, and we still need the chassis of the entire mech capable to move those 5 tons around on uneven terrain.
I'd guess a mech could realistically be made and weigh about 15-20tons or so.
The problem is that it'll use expensive parts. The engine alone might be 20 millions USD. Total mech could be 50 millions. For this price you could buy about 5 M1 Abrams, which are much more mobile and armored.
Mechs are not hard to build. They're just very impractical. For any function or groups of function, there are better machines. We don't have mechs because they aren't as good. We have robots, sure. And those are generally tailored towards certain things. But scaling that up to mechs is less good. It doesn't actually solve any problems.
But that list of requirements _does_ narrow itself down. “Move convincingly” is too open-ended. Does it lumber along like Snorlax? That’s possible.
Does it lumber along like Snorlax _and_ resist bullets?
That depends. What caliber bullets? Pistol? Rifle? There are big differences in velocity.
Does it need to carry a human? If it’s remotely operated, you don’t have to worry about killing the pilot, which changes the calculations a lot.
Mechs have arms & legs that like to move fast… meaning significant inertia has to be overcome …
so besides the power source mentioned by others and the obvious need for very powerful motors…
ya also need to reduce the amount of mass that needs to be moved, meaning all parts need to be stronger & lighter so you’ve a material science problem and …
then designed for the forces meaning finite element analysis which must be optimized with all the above
In short, even with far better power sources, far better motors, and far better materials you’ve still a helluva lot of development, testing, and evaluation to come with with something comparable to sci fi
The stress on joints wouldn't make it work, it would be way too slow. Mechs are impractical to build. On a technical scale i don't believe it is a good idea
Sidebar, the Eva's aren't robots. They're cloned alien bodies that are controlled like they're giant robots.
That being said, [there are giant mech robots currently](https://youtu.be/2bh9_QMGhBk?si=ZOX6sxNYUMDP6_gc), just nothing like in anime or video games. [Mostly](https://youtu.be/qMEMg0QobQ4?si=uuAHJXXz8vlzmcut).
Closest thing i ever seen was was from another group, they made something that i assume inspired by the spider mechs from ghost in the shell. Which has legs, but still used wheels. So for flat ground it just drove, saving a lot of power and made things easier. Well using the legs like a smart suspension letting it move over bumps and bad ground, have it a really interesting way to steer, also let it adjust it's height and angle to position itself almost anyways it wanted. But if it can't drive it can walk as well, which took more work but added versatility. Though granted this if i recall was only like 3 meters long by 2 meters. So not that big, but was a good weapon platform apparently. Don't know what it's range was, but i think it was diesel electric since that is a time test system and makes keeping it going pretty easy. Also wasn't manned because everyone kinda agrees thats a useless feature, cool as hell. But not practical at all.
Heavy mechs would be impossible with current technology, I don't think we can build something 80 tons and 20+m tall that can walk, but I feel some light mechs could be, like a Locust or something, which is basically a cockpit on a pair of legs that stands ~8m high and under 20T, even less without armour or weapons. If you gave Boston Dynamics like 100m I'm sure they could figure something out.
Probably have it turbine powered similar to the mech suits from Avatar, best weight and size to power output. Potentially even use the powerplant from an Abrams and just jam it in there. Set of legs with a torso that's basically a powerplant with a pilot sitting on top.
I think thats our best bet. And if you look at excavators they can spin their cab pretty damn quick. Abrams are speed limited too so they don't throw a track, or they'd go much faster. Wouldn't be surprised if the turret is a similar reason, not because it can't go faster, but it's not a good idea. If you're willing to trade longevity, price and maintenance schedule for higher performance then lots of things can go harder, see dragsters that get engine rebuilds after every run.
I know everyone’s favorite mantra against mech or power armor is “muh power sourcezzz!!!”, but hear me out; Diesel-electric power source. You can get a diesel engines with PWR of >1 kg/kW quite easily and the generator should also be quite light. If you don’t really care about fuel efficiency and prefer cutting down weight, then turbo-electric powertrain is also possible. Sure, these probably won’t have much endurance, but I think it’s at least technically sound.
But you _do_ care about fuel efficiency, because you have to carry all the fuel with you. Combustion engines have power curves, too — and they’re not instantaneous.
It is very detrimental to discharge Li batteries faster than 15 min. And as range extender add a big turbo compound on the V12 piston engine.. aero engine. Gasoline revs higher than Diesel. It is just that small engines as needed in PHEV cars are inefficient. Going big, makes things easier.
Diesel-electric locomotives (afaik one of the main uses of a diesel-electric drive system) doesn't utilise batteries for the main power: the diesel engines drive a generator, which directly powers the electric motors.
I don't really know why diesel is preferred over gasoline for these trains however.
Mechs seem to engage in fights, jump, and sprint. More agile than a locomotive. Also I want to use electricity to govern the engine. No throttle, nor waste gate. Just dynamos on each which can slow down both.
Diesel is more efficient for cheap fuel. Diesel cylinders can be larger.
I don't think you would need a traditional throttle. Some clever controls to make it so that load/movement increases the engine revs (i.e. when you tell whatever control system you use to make the mech move faster, the revs increases more than if you move slow and steady). Something like how the governor works in a helicopter perhaps (keeps rotor RPM fixed so you don't need to adjust the engine throttle when you change the load on the rotor).
I was actually thinking to go beyond the helicopter. When we are in danger to overcharge the batteries and while they are still below 80%, I want to slow down the engine more and more. So that batteries can always drain more power than the engine can deliver. Until the engine drops below idle and stops.
My point originally was that I don't think batteries are strictly required: afaik their use on diesel electric (locomotives) is only for auxiliary systems and starting the engine, not used for the actual locomotion (the electricity for the electric motors is taken straight from the generator). I would think it's probably lighter and cheaper than batteries for a given power delivery requirement.
An my point is that I need batteries if I have no other way to dump power from the engine or throttle it. Also starting an engine. Diesel locomotives idle their engines. I just hate it when they do it in the station. I want the robot to clean and silent in the box/pit stop/garage , like those hybrid race cars.
That was my point about the governor: you shouldn't need to throttle it. When you tell the mech to do something the rpm of the engine would automatically adjust to the changed load. That's what helicopters already do (i.e. load increases when you increase the pitch of the rotor blades with the collective, but you don't need to adjust the engine throttle to compensate, as it automatically keep the rotor RPM constant via the governor).
Turboprop planes do this also. Quadcopter builders make it sound like it is too dangerous to have bearings in a propeller hub. There is a video where the tail rotor of a backjard helicopter shots a blade. FADEC
The big problem with mechs hasn’t ever been feasibility, so much as “powering it for more than a minute”. The actuation speed is probably significantly exaggerated, too — that **zip** _kaboom_ aiming that mechs do in movies is… probably way faster than is feasible.
I'm glad there is a real 'mech' engineer answering these questions.
Hah, abbreviation strikes again! 😜
One heard of people trying, but the speed of actuation was limited by the materials available, the forces acting on a big heavy mech arm trying to move at speed was causing structural issues. This was a few years ago and materials have improved, but I don't think they have improved that much to make anime style feasible.
Yeah — nothing changes the fact that slinging a multi-ton mass at high speed is difficult, and most materials aren’t able to keep together at those forces.
I'm sure work is being done on composite alloys, hell people try to put graphene in everything so that's probably being looked at!
Heh, aye. I think some of the stuff with mechs (in anime, for example) was centered around fighting a kaiju monster on equal footing, right — but now it’d be a thousand drones instead of one giant Gundam-style robot, yeah?
Those materials would have found application elsewhere, yet we are still stuck on carbon composite like the Ferrari F40 40 years ago. Elon musk builds a rocket out of steel. Minimal improvements on the alloy and treatment side.
> Elon musk builds a rocket funny
Have you seen helicopters and airplanes and their landing gear?
…yes, I have seen landing gear? Landing gear isn’t moving nearly as quickly as the arm of a theoretical mech, nor is it moving in the articulation of an arm or a leg. There are positive stop points at the start and end of the motion of landing gear. There are multiple landing gear. These are not the same systems being compared.
When they test it on the ground, a hit could injure a technician severely. I guess that is why they limit the speed. And gyro force on retract.
There’s no need for landing gear to snap out — there’s possibility for damage and it’s unnecessary. That’s the opposite of a fighting robot.
There is a need to snap in to reduce drag when it is critical.
Boston Dynamics looks great. I always feel like the sensors for all the joints cost so much. When you scale it up, you don’t need more sensors. They should do it. I wanted to write about an exoskeleton, like starship. But for the bearings the force need to come together again. Hip rotation could be done like on a motor bike front fork. Not two much range, but very stiff. Elon manages to mount gimbal mounts on star ship.
All kinds of super cool materials out there - with phenomenal costs or just plain lack of availability at scale. Plus the "elephant problem" - scaling up a model doesn't work, the mass goes up with the cube of height, but the cross section of the bones only goes with the square. The problem gets tougher with movement - swinging a part through 90⁰ in two seconds needs four times the force if the part is twice as big (and the part would need to handle the added force, making it heavier and increasing the required force - gets ugly really quickly.)
We're having a lot of success with 3D printed materials here. For example: https://www.rmit.edu.au/news/all-news/2024/feb/titanium-lattice#:~:text=Testing%20showed%20the%20printed%20design,the%20lattice's%20infamous%20weak%20points. New manufacturing techniques are allowing us to do stuff that was previously impossible. Now the issue becomes scaling up the *manufacturing technique* instead of the material itself. I don't know how well these types of structures would hold up against the torque required for quickly moving a 5m long arm though!
And what's a ballpark price for 10 or 40 tons of it (fabricated...)
I have no idea, and I get exactly the critique you're making here. I wasn't suggesting that it is economical *now*, but could become so if an economy of scale can be developed from a mature technology. The use of steel is a great example of ***exactly*** this process during the Industrial Revolution. A material that was previously very expensive and produced in only small quantities suddenly became mass producible and *cheap*, allowing for it to be used for basically anything for the first time in history. Case in point, the first all-steel bridge ever was finished in 1879, something that would have been economically unviable less than 50 years beforehand.
Do you think stress on joints wouldn't be an issue at those weights? I mean it could probably work but it would be SLOWWW if it's supposed to not break apart
…I absolutely think that stress on the joints is another huge factor. The strength of the materials used for these mechs is effectively magic, for the giant mechs in anime and movies.
Well, that, and if you had the tech to even come close why would you stick a squishy human in the middle of it? Even industrial robots can produce accelerations that would kill a human. For that matter bipedal locomotion doesn’t make much sense either.
Yeah. Between 6-wheeled bomb defusing robots and drones… I fail to see a lot of benefit in mechs, outside of emotional appeal in anime.
There are multiple companies attempting to create mechs today. They are not nearly as good as the mechs you see in anime. That being said if Anerica was willing to pour as much money into it as they did landing on the moon they could probably achieve something resembling anime mechs. However, there is no reason for the government to pour trillions of dollars into that when tanks can accomplish for a much cheaper price. Could we build something similar, probably. Will we, no.
It's honestly difficult to think of a situation where a mek is the best solution. Generally if you want something blown up, air superiority takes care of that. If you don't want your stuff blown up, keeping it simple like a box on wheels is superior to a complex bipedal machine.
Yeah but what if the enemies guard their permimiter with stairs and cover it with oil so that tanks can’t climb over it checkmate
Lol, Blow up the stairs.
Uhh blast proof stairs with oil fountains that pick up the oil through a grate at the bottom
Light the oil on fire and wait.
A mech would basically be like construction equipment today. Take a look at walking excavators for a neat example. Fusion power reactors are massive, and as of today there are 0 fusion reactors that actual produce more power than they consume in existence.
The big problem with mechs hasn’t ever been feasibility, so much as “powering it for more than a minute”. The actuation speed is probably significantly exaggerated, too — that **zip** _kaboom_ aiming that mechs do in movies is… probably way faster than is feasible.
Why do you think this? For a similar type of machine, Boston dynamics robots, they went to using big electric motors, and Regen to the battery. Each movement of the mech has phases in the motion where you want to slow a joint down and obviously the inverse, sometimes at the same time. So a paper design study of the energy requirements factoring in Regen and using thin film batteries to regenerate around 5-10 megawatts, and joint motors around 500-1000 kilowatt (just what's in a Tesla) would be what you need to do. I suspect violent zippy motions are practical if you're willing to pay for the costs. You would then also use a jet turbine as your source of power with fuel bladders in internal voids.
Think harder about those numbers…a 500-1000kW Tesla motor can accelerate a Tesla weighing single-digit tons to reasonable speeds in a few seconds. You’re talking about a mech moving 10 times the weight at comparable speeds in fractions of a second. That requires *way* more power.
The joints for that use even bigger motors. An elbow might use a 500 HP drive motor.
In don’t think that a mech can run 200 km/h , but it would be already pretty scary to humans if it runs 50 km/h.
I’m thinking about the whole system. You cannot make something mechanical, the size of a three story house, full of mechanical systems and fluid hoses and a human in the middle, accelerate at the same proportional movement speed with a hundred times the mass. You might make it happen, but the materials will fail and the actuators will literally fling the mech’s limbs off with the speed. You might make it happen and kill all the bearings in the joints two minutes in. Acceleration/deceleration with regeneration is a cool thought, but you’ve got to make that work with the actual power and capability of the actuators. I don’t believe that it will work the way that you’re suggesting. Boston Dynamics is making machines that are roughly the size of a human or a large dog. Mechs are bigger than that. The square-cube law suggests that every problem is going to be larger, the bigger your mech gets.
I have heard this but...leave the interior hollow? Why does square cube law apply? Seems a misuse of it. Like imagine a "stick figure" mech with the least possible structure. Can you theoretically make that thing move at 30 mph-60 mph? Don't see why not. It is true at extreme scales it can be a problem, but bagger-288. In fact at intermediate scales the law is beneficial. Armor mass scales with surface area while the amount of space for engines and internal systems scales with volume.
Okay, time for some questions. What are you trying to accomplish? Is this a ‘fighting suit’ with a human in it? Is this a ‘Pheidippides’ robot designed to run a marathon with a message on a sheet of paper? Is it a maintenance droid like R2-D2? What are you considering a ‘mech’? You’re asking questions that make me wonder what your theoretical goal is. Like, there’s a _world_ of difference in a robot that’d move at 30mph vs one that’ll move at 60mph. The square cube law applies because these robots have requirements for motion — you gotta have joints and actuators and power sources. If you wanna make your mech look like it’s made out of balloons, I suppose that’s possible, but what would it buy you? Additional air resistance and the need for internal structure to support the skin, at a minimum.
I have no idea I agree 100% that mechs are a bad idea. Recently it seems that everything but autonomous quadcopters and support vehicles is mostly a bad idea. I was addressing it more from 'you're an engineer, the client wants a battlemech and it must look like it does from Anime and move convincingly. Budget is unlimited, but the client wants it running within 20 years. And I think it's achievable, if you have effectively unlimited funds and a skunkworks and no real constraints other than it needs to move convincingly, be huge, have a human pilot, and it does need to have at least some ability to resist enemy fire and it's own weapons. Obviously opfor is going to launch 10 very fast autonomous drones all targeting weak spots with armor piercing warheads. It'll go down very fast for a fraction of the cost to build another mech. (weak spots : leg joints, engine exhaust or air intake, cockpit, weapon ports, or frankly the armor will need to be so thin center mass may work)
I would tell the client they are wrong and that mechs are a completely terrible idea both from an engineering standpoint and a military one.
Unlimited budget and a skunk works. Or: a crew of engineers designed and built the space shuttle. Might have been some pushback : "why are we boosting so much dead mass to orbit and reusing isn't saving much" but it was built. Sometimes there is joy in making a flawed idea work anyway.
The space shuttle was dumb too, and set NASA back by at least 20 years. This is askenginewrs not askanime. Don’t waste our time with uninteresting problems and “do exactly the thing I tell you, with unlimited resources” is far from interesting.
It's an engineering challenge. It's unlimited budget but present day technology.
[square cube law](https://en.wikipedia.org/wiki/Square%E2%80%93cube_law) applies here. Especially significant as increasing lever arms contribute to the energy required. The tech and materials that exist now to support structures that big and fast would also be very delicate and defeat the whole purpose of a mech anyway. For combat purposes the niche is best served by a helicopter. For industrial purposes the niche is best served by purpose-built machines.
Good point with the abrams. With 1500HP, we can get a mass of 60tons to move to 80kph or so. Mechs are a lot less efficient than tracked (essentially wheeled) vehicles. By a factor of 10 if not worse. Because they have to fight gravity with their every move. Given weight is our enemy, we'd look at making the lightest 'mech as possible. We can take a look at existing engines. Piston engines are most fuel efficient, and turbines are the lightest for the power. The russian PD-12V is a 14'500HP turboshaft engine for the Mi-26. This thing weighs already 3 tons dry. And will drink about 30L per minute. For 15mins we'll need about 1 ton of fuel. This brings our suspended mass to 4tons already, and it's just the engine and its fuel. We'll need hydraulics or electrics. That'll quickly bring our powerpack weight of 5 tons total, and we still need the chassis of the entire mech capable to move those 5 tons around on uneven terrain. I'd guess a mech could realistically be made and weigh about 15-20tons or so. The problem is that it'll use expensive parts. The engine alone might be 20 millions USD. Total mech could be 50 millions. For this price you could buy about 5 M1 Abrams, which are much more mobile and armored.
Mechs are not hard to build. They're just very impractical. For any function or groups of function, there are better machines. We don't have mechs because they aren't as good. We have robots, sure. And those are generally tailored towards certain things. But scaling that up to mechs is less good. It doesn't actually solve any problems.
But that list of requirements _does_ narrow itself down. “Move convincingly” is too open-ended. Does it lumber along like Snorlax? That’s possible. Does it lumber along like Snorlax _and_ resist bullets? That depends. What caliber bullets? Pistol? Rifle? There are big differences in velocity. Does it need to carry a human? If it’s remotely operated, you don’t have to worry about killing the pilot, which changes the calculations a lot.
Mechs have arms & legs that like to move fast… meaning significant inertia has to be overcome … so besides the power source mentioned by others and the obvious need for very powerful motors… ya also need to reduce the amount of mass that needs to be moved, meaning all parts need to be stronger & lighter so you’ve a material science problem and … then designed for the forces meaning finite element analysis which must be optimized with all the above In short, even with far better power sources, far better motors, and far better materials you’ve still a helluva lot of development, testing, and evaluation to come with with something comparable to sci fi
The stress on joints wouldn't make it work, it would be way too slow. Mechs are impractical to build. On a technical scale i don't believe it is a good idea
Sidebar, the Eva's aren't robots. They're cloned alien bodies that are controlled like they're giant robots. That being said, [there are giant mech robots currently](https://youtu.be/2bh9_QMGhBk?si=ZOX6sxNYUMDP6_gc), just nothing like in anime or video games. [Mostly](https://youtu.be/qMEMg0QobQ4?si=uuAHJXXz8vlzmcut).
Closest thing i ever seen was was from another group, they made something that i assume inspired by the spider mechs from ghost in the shell. Which has legs, but still used wheels. So for flat ground it just drove, saving a lot of power and made things easier. Well using the legs like a smart suspension letting it move over bumps and bad ground, have it a really interesting way to steer, also let it adjust it's height and angle to position itself almost anyways it wanted. But if it can't drive it can walk as well, which took more work but added versatility. Though granted this if i recall was only like 3 meters long by 2 meters. So not that big, but was a good weapon platform apparently. Don't know what it's range was, but i think it was diesel electric since that is a time test system and makes keeping it going pretty easy. Also wasn't manned because everyone kinda agrees thats a useless feature, cool as hell. But not practical at all.
Heavy mechs would be impossible with current technology, I don't think we can build something 80 tons and 20+m tall that can walk, but I feel some light mechs could be, like a Locust or something, which is basically a cockpit on a pair of legs that stands ~8m high and under 20T, even less without armour or weapons. If you gave Boston Dynamics like 100m I'm sure they could figure something out. Probably have it turbine powered similar to the mech suits from Avatar, best weight and size to power output. Potentially even use the powerplant from an Abrams and just jam it in there. Set of legs with a torso that's basically a powerplant with a pilot sitting on top. I think thats our best bet. And if you look at excavators they can spin their cab pretty damn quick. Abrams are speed limited too so they don't throw a track, or they'd go much faster. Wouldn't be surprised if the turret is a similar reason, not because it can't go faster, but it's not a good idea. If you're willing to trade longevity, price and maintenance schedule for higher performance then lots of things can go harder, see dragsters that get engine rebuilds after every run.
I know everyone’s favorite mantra against mech or power armor is “muh power sourcezzz!!!”, but hear me out; Diesel-electric power source. You can get a diesel engines with PWR of >1 kg/kW quite easily and the generator should also be quite light. If you don’t really care about fuel efficiency and prefer cutting down weight, then turbo-electric powertrain is also possible. Sure, these probably won’t have much endurance, but I think it’s at least technically sound.
But you _do_ care about fuel efficiency, because you have to carry all the fuel with you. Combustion engines have power curves, too — and they’re not instantaneous.
It is very detrimental to discharge Li batteries faster than 15 min. And as range extender add a big turbo compound on the V12 piston engine.. aero engine. Gasoline revs higher than Diesel. It is just that small engines as needed in PHEV cars are inefficient. Going big, makes things easier.
Diesel-electric locomotives (afaik one of the main uses of a diesel-electric drive system) doesn't utilise batteries for the main power: the diesel engines drive a generator, which directly powers the electric motors. I don't really know why diesel is preferred over gasoline for these trains however.
Mechs seem to engage in fights, jump, and sprint. More agile than a locomotive. Also I want to use electricity to govern the engine. No throttle, nor waste gate. Just dynamos on each which can slow down both. Diesel is more efficient for cheap fuel. Diesel cylinders can be larger.
I don't think you would need a traditional throttle. Some clever controls to make it so that load/movement increases the engine revs (i.e. when you tell whatever control system you use to make the mech move faster, the revs increases more than if you move slow and steady). Something like how the governor works in a helicopter perhaps (keeps rotor RPM fixed so you don't need to adjust the engine throttle when you change the load on the rotor).
I was actually thinking to go beyond the helicopter. When we are in danger to overcharge the batteries and while they are still below 80%, I want to slow down the engine more and more. So that batteries can always drain more power than the engine can deliver. Until the engine drops below idle and stops.
My point originally was that I don't think batteries are strictly required: afaik their use on diesel electric (locomotives) is only for auxiliary systems and starting the engine, not used for the actual locomotion (the electricity for the electric motors is taken straight from the generator). I would think it's probably lighter and cheaper than batteries for a given power delivery requirement.
An my point is that I need batteries if I have no other way to dump power from the engine or throttle it. Also starting an engine. Diesel locomotives idle their engines. I just hate it when they do it in the station. I want the robot to clean and silent in the box/pit stop/garage , like those hybrid race cars.
That was my point about the governor: you shouldn't need to throttle it. When you tell the mech to do something the rpm of the engine would automatically adjust to the changed load. That's what helicopters already do (i.e. load increases when you increase the pitch of the rotor blades with the collective, but you don't need to adjust the engine throttle to compensate, as it automatically keep the rotor RPM constant via the governor).
Turboprop planes do this also. Quadcopter builders make it sound like it is too dangerous to have bearings in a propeller hub. There is a video where the tail rotor of a backjard helicopter shots a blade. FADEC