Anyone with Mechanical Engineering knowledge/experience here who I can ask a question

The Dutch Ghost

The Dutch Ghost

Grouchy old man of NMA
Moderator
Hello all,

Is there anyone on this forum who has studied mechanical engineering here or has knowledge on the subject who I could ask a question?

A while back I was discussing the subject of robotics with someone else, in particular large bipedal ones (think Gundam and Macross).
There are of course various reasons why such a combat machine would be impractical but I also heard somewhere that such a machine would barely be able to move because of its own weight.

I don't know if that is right or wrong, that is why I would like to ask someone who knows the subject.
 
Think of the human body.

The human body is great for doing dexterous and small tasks, as well as being a social device.

However, it can't move very fast, can not carry much, and is quite fragile with a poor center of balance.



If you were going to create a gundam that was good at making tools to make other gundams then it is a good design. Other than that is doesn't have any advantages.


 
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Thanks for the responses.

I knew the Square-cube law was involved in why this would be very difficult but I just could not describe it well myself.
I could not even name the principle though I did know what it meant as it was several times mentioned in comics I had read.

Read about it the first time in a Manga when some crazy cultists had kidnapped a robot designer in order to have him make a giant robot.
He had to make clear to the cultists why such a thing would be technically almost impossible and asked them if any of them ever had learned anything about engineering.
 
If the mechanical engineering side of things isn't clear enough, just look at the military application:
  • Your profile is a lot bigger than a tank, as such, you're more exposed to enemy fire. There's a reason why so many tanks have a "squashed" design with a low turret.
  • Humanoid form means you have a lot of joints (think the knee joint). This is difficult to properly protect. This makes it a prime target for what is called a mobility kill. Hit the joint, take the target out of action. For a tank, a mobility kill tends to be shedding a track. This track is easy enough to reassemble, replacing the damaged section once the location has been secured by friendlies. I don't quite see you replacing a mecha's knee joint in the field.
  • Humanoid form means a lot of external surface for a given internal volume. This means a lot of heavy armor plating compared to a tank of the same internal volume. This weight in turn means that your 'feet' need to be very large or you'll just sink into the sand, mud, whatever. This weight (and size) also makes it ridiculously hard to transport.
  • Tracked or wheeled vehicles have fairly simple engines (or turbines in heavy tanks) & transmissions. A mech needs to transfer power to all kinds of pistons, while ensuring you can't lose power when one of them is rendered inoperable. Where does all this power come from to move such a heavy machine? Are we talking fantasyland nuclear power? If you're talking here & now, there's nothing we have that makes that kind of power demand combat effective.

From a military point of view, mechs/exosuits that are human sized or max 1.5x as large as humans, I could see having a significant impact on the battle field if fielded in moderate numbers. But huge mechs? Forget it. Too complex, too heavy, too much of a bullet sponge, too easy to kill.
 
The Dutch Ghost said:
Read about it the first time in a Manga when some crazy cultists had kidnapped a robot designer in order to have him make a giant robot.
He had to make clear to the cultists why such a thing would be technically almost impossible and asked them if any of them ever had learned anything about engineering.
Click to expand...

20th Century Boys High five!!!
 
SuAside said:
...
From a military point of view, mechs/exosuits that are human sized or max 1.5x as large as humans, I could see having a significant impact on the battle field if fielded in moderate numbers. But huge mechs? Forget it. Too complex, too heavy, too much of a bullet sponge, too easy to kill.
Click to expand...
I find it always funny when someone comes up with the idea that new technology, materials etc. would eventually make it possible in the future to see giant mechs in military service. Like some high tech-alloy that allows to build strong armored structures like mechs with almost no weight. And I always say, why not build also a tank with said materials? The tank, the kind of design we all know with tracks and a gun turret, simply has more advantages. Namely the one you listed. So the same advantage that a some mech would gain from new materials would obviously also translate to a tank design, you could give it more armor, more mobility, better guns etc. And it would be still superior to a giant mech.

Outside of all that I still love mechs and mech designs, even if they are unrealistic. It simply looks and feels cool. But if we are honest they are simply not realistic or practial in the real world compared to the designs that are in use now.
 
Walpknut said:
20th Century Boys High five!!!
Click to expand...

Yep, that's the one!
After reading it it always stuck with me since, and when I saw movies like Pacific Rim with their giant monsters and robots my first thoughts were 'Hey, isn't that biologically and technologically impossible?" (yes, I know its a movie)

SuAside, yep me and my conversation partner also had it about those drawbacks.
A fun concept in a comic book but impractical as hell.

Currently in the Hellboy BPRD comics the nations of the world are facing giant monsters. It was mentioned several times by in universe scientists that biologically these creatures should barely be able to move, let alone live.
 
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yeah, but with Hellboy many of the creatures are either demons or other magical monsters. I think it really depends on the setting in the end. I mean no ones complaining about the star ships in star wars either because we all know its a kind of fairy tale in space.
 
Crni Vuk said:
yeah, but with Hellboy many of the creatures are either demons or other magical monsters. I think it really depends on the setting in the end. I mean no ones complaining about the star ships in star wars either because we all know its a kind of fairy tale in space.
Click to expand...

I am not criticising it Crni Vuk, I just liked that the writers did remind us of that even in-universe the people understand that the laws of physics would normally prevent this from being possible (thus making clear that these creatures are unnatural).

But on the other hand the universe does have a massive heli platform or features a golem made of the fat of corpses that did not rely on anything supernatural like the other examples.
 
Well 20th Century Boys is a rather extensive deconstruction of Shonen Anime, specially 80's anime and it took delight in bringing reality into fantastical elements. But it wasn't malicious in intent, as later on the story used reconstructed the deconstructed tropes and made them all work in-universe too.

Pacific Rim from the very first second to the last one of the post credits scene made it rather obvious they were actively doing a for fun movie about giant robots fighting giant monsters, it was intentionally dumb and it was very smart at being dumb.
 
It is always nice to learn something like for example rules of mechanical engineering or physics through entertainment.
Science can be fun if you bring it to the people in a good way.
 
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