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What could centipedal mechs do that tracked & wheeled vehicles couldn't do?

It's been 6 years since the 2 legged mech question, it's been 3 years since the spider mech question. It's time for the centipede mech question.

A centipede mech is a mech with 10 or more (otherwise it'd just be a spider mech) legs. Made out of several segments with 1 or 2 pairs of legs each + maybe a head segment with no legs. They would have the advantage over bipedal mechs in lower profile & an advantage in maneuverability over a spider mech due to being able to articulate its torso.

What could a centipede mech do better than a tank? Also the mech don't have to replace tanks, it just needs to justify its own existence.

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    $\begingroup$ Can they have more than one head? $\endgroup$ Aug 4 at 8:19
  • $\begingroup$ @DescheleSchilder yes $\endgroup$
    – OT-64 SKOT
    Aug 4 at 8:20
  • $\begingroup$ Nice question! The reason I asked is because I saw an alien spider (no mech though) that had a circular array with eyes. $\endgroup$ Aug 4 at 8:23
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    $\begingroup$ Not precisely the same query, but this question about centipede mounts covers the same scope. $\endgroup$
    – elemtilas
    Aug 4 at 15:16
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    $\begingroup$ They could break down in so many new and interesting ways $\endgroup$
    – Separatrix
    Aug 5 at 9:40

11 Answers 11

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Swim

Wheel and tracks both suck for moving while buoyant in water. Lots of arms works.

Climb

A tank can climb a decent incline, but a cliff not so much. If you have lots of arms, you can climb the cliff

Rappel

Wheels and tracks suck for descending steep drops. Dozens of arms can lock into a rope allowing to control it's own rate of descent.

Right itself after a fall. Or repairs.

A tank can't replace it's own tracks without the crew getting out, but a mech with arms could remove a damaged leg and replace it with a spare from storage.

Maneuver in an enclosed zero gravity environment.

Think a massive open plan space station with zero gravity. You maneuver by grabbing onto rails and pushing off them. You need arms for this.

Bypass obstacles stealthily without destroying them.

Your mech can move tank traps out of the way, by pass them, and then reassemble the traps behind them, leaving the enemy no evidence they've been breached. It can also open gates and remove obstructions, say abandoned cars blocking the road, without leaving evidence in the form of flattened cars.

Dodge incoming projectiles.

Wheels and tanks aren't very good at side stepping when a projectile is inbound. A slow moving car or tank facing and travelling north can't move out of the way of a southbound missile with only a few seconds notice, whereas a human moving at walking speed could definitely jump sideways. So can your centipede.

Escape from being bogged.

If you have dozens or arms several meters apart, a swamp, slush, or mudpit that could trap a tank or car could be easily bypassed, you can adjust your weight distribution based on ground strength.

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    $\begingroup$ Your list is good, but you forgot "is immune to being stuck in the Russian spring mud", which neither tanks, nor horses, nor people were particularly good at. $\endgroup$
    – John O
    Aug 4 at 16:25
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    $\begingroup$ I am wondering if a female mech could still be boyant. $\endgroup$
    – Willk
    Aug 4 at 17:27
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    $\begingroup$ @Willk What would a female mech be? $\endgroup$
    – OT-64 SKOT
    Aug 5 at 6:37
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    $\begingroup$ Amphibious vehicles use propellers to move in water, even if they have wheels or tracks for moving on land. Even for a mech, that's probably a way better idea than paddling. For the others, I think you're assuming (without stating it) that the legs of the mech would be arm with full blown hands capable of relatively fine manipulation. Which isn't at all obvious for legs made for movement, compare e.g. human feet with human hands. $\endgroup$
    – ilkkachu
    Aug 5 at 7:50
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    $\begingroup$ @OT-64SKOT girlant, one would assume $\endgroup$
    – Onyz
    Aug 5 at 12:04
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They would probably make dragon's teeth less effective

enter image description here

Dragon's teeth (German: Drachenzähne) are square-pyramidal fortifications of reinforced concrete first used during the Second World War to impede the movement of tanks and mechanised infantry. The idea was to slow down and channel tanks into killing zones where they could easily be disposed of by anti-tank weapons.

This alone makes them better than tanks in moving into defended places, until the teeth are made taller to hinder the usage of the legs, to which the centipede can counter using the teeth themselve as support.

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  • $\begingroup$ I don’t really see why Dragon’s Teeth (or Czech hedgehogs) would be less effective against a centipede. A wheeled vehicle with sufficiently tall wheels and/or the ability to adjust the suspension of individual wheels should be able to go over them as well. $\endgroup$
    – Michael
    Aug 5 at 5:49
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    $\begingroup$ @Michael, I have seen tall wheels vehicles in the countryside fighting against pests, not on a battlefield. Nevertheless the teeth can be arranged in such a way that there is no straight path going through them. In that case no matter how tall the wheel, a wheeled vehicle would be stopped $\endgroup$
    – L.Dutch
    Aug 5 at 6:02
  • $\begingroup$ How do legs help to get over the Dragon’s Teeth if they are too tall to drive over? A segmented/flexible body could help (because you can “snake” through or raise the front to climb over), but there is no reason you couldn’t make a segmented body with wheels. $\endgroup$
    – Michael
    Aug 5 at 7:00
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Stacking

Just like the human centipede, the tank centipede might be designed so as to allow for new subunits to be added to either the front of the back. This enables the tanks to form a linear megazord, or (unlike the human counterpart) get out of that formation as needed.

A longer centipede might be used, for example, as a bridge to allow for other units (both on foot or mechanized) to cross rivers or climb over walls or rough terrain. A really long centipede could encircle troops to serve as an improvised armored wall. If each unit has guns, then a centipede becomes a moving fortress - similar to the naval tactics that led to the development of the Battleship (which comes from "ship of the line of battle"), if you approach a centipede laterally you are going to take a broadside to your ***.

I can actually picture tanks in battle formation, then along comes a centipede racing very fast through them. As the tanks shoot the centipede loses a few unmanned units at the front, but once it is among the enemy tanks its continuous broadside shooting to both sides and every enemy tank is [bleep]ed.

Finally, a centipede could also be a train that does not need tracks. Excellent for cargo transport.

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  • $\begingroup$ You can chain wheeled (and to a lesser extend tracked) vehicles together just fine. Legs are not really an advantage in that regard. $\endgroup$
    – Michael
    Aug 5 at 13:48
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    $\begingroup$ @Michael can you control all chained vehicles from a single cockpit/bridge? Can chained vehicles raise the front section up from the ground? $\endgroup$ Aug 5 at 13:54
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Damage to a tank track will wreck the track, or at least render it less functional, whereas hits on centipede legs will break or damage a few legs but leave the vehicle capable of moving.

A centipede mech can climb over vertical obstacles that a tank might not be able to drive over/through.

Centipede mechs can "flow" around corners, whereas a tank needs to turn itself and slow down in the process.

If the centipede mech has reactors/engines and control systems at both ends, and enough redundant systems, it can survive being blown in half - each section goes off and does its own thing.

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Note: This is a copy-and-paste of this answer to the spider mech question. Where the bottom 2/3 of the answer were more relevant to the spider mech question (which just asked which was better), the first 1/3 is more relevant here (which is asking for advantages of one over the other).

Addition: Before anyone gets too wound up over my answer, please note the following excerpt from the Wikipedia article about walking vehicles: "Walking vehicles can provide greater ground clearance than wheeled or tracked vehicles, but the complexity of their leg mechanisms has limited their use." That complexity is 99.99% of the problem, and it always will be.


Legs are good for one thing: agility

Have you ever watched two boxers fight? I mean really watched what they were doing? Credit to everything on the human body, but it could be said that boxing is about your legs. They're used to:

  • Keep your balance
  • Shift your weight for leverage and strength
  • Move you deftly out of harm's way or into a superior position in almost any direction.

So your spider mech has an advantage over wheeled or (worse) tread tanks in that it can better keep its balance, hop out of harm's way, perhaps even right itself when knocked over (if they're designed well). Have you ever tried to tip an Abrams back on its treads? I haven't, but I bet it takes more than a couple of big Tongans to do it.

At literally everything else, legs stink

I'm assuming we're comparing apples to apples by talking about manned mechs. The arguments for drones are very, very different because you can make the mech (comparatively) very, very small. Wheels/treads are great when there's enough weight to keep them solidly in touch with the ground. They're less valuable when the object being moved is very light.

(1) Let's add some armor to that boxer. And a big ol' gun. Let's let him look a bit like the combat dudes from StarCraft.1 Suddenly you're having to add all kinds of mechanical enhancement to the armor — and you'd think you're doing that to enhance the combat abilities of the wearer, but you're spending most of the energy just moving the armor.

In the same way that most of your gasoline is being used to move the car... not you.

So, the more armor you add to the mech, the less valuable the legs become because adding enhancement to overcome the weight is seriously a losing battle. As armor increases, the mechanics to move the armor increases, the fuel needed to power the mechanics increases, all of which adds stress to complicated joints... and all you really wanted to do was kick the other guy's butt.2

Armor almost always succumbs to armament. You don't see plate mail anymore because rifles pack enough punch at enough distance that you might as well be standing there begging them to shoot you ... which is what you'd actually be doing.

(2) Now let's add tree roots, bushes, things that are easily squashed and driven over with wheels and treads but are an amazing hang-up for legs. The issue isn't tripping, the issue is the inability to move a hung-up leg forward, which means you're a sitting duck.3

(3) And your center of gravity, which is high for anything with legs but low for (almost anything) with wheels or treads (monster trucks violate this rule... but that's outside the scope of your question). A high center of gravity means it's easier to make the unit unbalanced, tip it over, or control it with trip wires (see my last point). It also raises the unit unecessarily high off the ground, making it an easier target.

(4) Then think about speed. This is where legs really, really stink. It doesn't matter how much you enhance joints, wheels and treads can always out run legs.

(5) Finally, add to this the increased complexity of affecting knees, ankles, hips, rotor cuffs, tendons, muscles, and a whole lot more. There's an engineering axiom that, frankly, should be considered a Universal Law.

KISS: Keep it simple, stupid!

Those cool mechs, gundam, and all other things robotic used to fight Godzilla and who knows what else from the 8th Dimension and Beyond are just that... cool... and absolutely useless. Complicated design and automation that can only be driven by an operator with a PhD in physics costing bazillions of dollars and it's all wasted by a single shot from some crazy dude with a big ol' gun that cost pennies on the dollar to build compared to your mech and that can be aimed and fired by a 10-year-old hiding behind a rock.

So, looks cool in anime, but in real life the cost-to-value ratio is way, way, way in favor of wheels and treads. If you really want mechs in your story, you need to do what all previous authors have done... you need to declare it to be so and move on with the story, because you'll never be able to justify the tech.


1Which, if you think about it, is so unbelievably unrealistic that it makes angels weep. Think about how far you'd have to dislocate your sholders to get them into the arms, etc. But, it's a heckuva game to play, so no complaints. Nosireebob.

2An astute observer might claim that the same is true for wheeled vehicles and tanks. That's true, but not to the degree of moving joints. It's relatively easy to increase engine size to turn a more heavily loaded axel compared to all that needs to be done to move 2–3 joints. If the problem increases geometrically for tanks, it increases exponentially for mecha.

3If you don't believe me, the next time you get your foot stuck in some brambles stop and really think about what your brain can do with your foot pretty much unconsiously — you twist them, rotate them, tip and tilt them... and still you occasionally get your feet stuck. What the human brain can do with a foot is almost as breathtaking as the enormous effort it takes us to simulate it artificially — and we still can't build a robot that does it as well. EDIT: This is changing. This is why my argument is that drones are a different discussion.

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  • $\begingroup$ You say this came from a spider mech question but seem to focus on bipedal? People have spend a lot of effort trying to armor wheels and tracks as well with the exact same "downside" of having to move that with the tank, but they can't ever be fully armored as the track/wheels need to lose any rocks, dirt and mud that get stuck and the armor skirts can't be touching the ground when the track suspension kicks in. This means that legs would have the advantage of full armor. Considering size and redundancy you would likely put HMG/shrapnel armor on there and not 120mm armor. $\endgroup$
    – Demigan
    Aug 4 at 18:48
  • $\begingroup$ @Demigan My answer is applicable to anything with legs. Legs are a whole lot more complicated than wheels or tracks. Legs require a sense of balance, lots of articulated joints, and have a ton less leverage than tracks and wheels ever will. Your point about armor is moot, as legs have that problem in spades (see any joint on plate mail, always weak). On the "what can go wrong?" scale, legs are an 8-9 where tracks and wheels are a 2-3. There can be specific instances where legs are better than tracks (agility...), but over all, that benefit is no where near enough to justify legs over tracks. $\endgroup$ Aug 4 at 19:03
  • $\begingroup$ tracks are already a lot more complicated than wheels, as for armor the fact that you CAN armor them is a step up. As for complicated, when it comes to the high-end of military equipment it becomes meaningless. An MBT is a complicated mess all by itself, and modern fighter aircraft make legs look like simplicity itself once we have the means to let them adapt to uneven ground on the fly. Also this question is not "what problems do legs have" but "what could a centipedal mech be useful for", which assumes many current technical problems solved. $\endgroup$
    – Demigan
    Aug 4 at 20:16
  • $\begingroup$ @Demigan As I said in my first note at the top, the bottom two thirds apply particular to the other question where the top third applies more to this one. However, the conclusion is the same - there are only a couple of reasons to choose legs over anything else. (And to make the comparison to airplanes more relevant, it's like asking when making wings that can flap would have advantages over fixed wings.) Keep in mind, if you don't like my answer you can downvote it - but if your goal is to get me to change my opinion, that isn't going to happen. $\endgroup$ Aug 4 at 20:23
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Climb stuff.

Steep hills and mountainous terrain is anathema to tanks. They can't spread out much when attacked, ambushes are easy, destruction of the roads, bridges and tunnels can completely cut them off from reinforcements and supplies, mines are easily placed and artillery has an easy time getting a bead on them. Many mountains that form borders between countries are considered unassailable except with infantry, which will be exposed once they reach the other side.

But a centipede with its moveable body? It can climb alongside the infantry. It does not have to be fast, although it probably could, as long as it can avoid roads and deal with adverse conditions. Like with spider mechs you would design the feet differently than we see in games and movies, which would allow a centipede to carry more weight than a tracked vehicle by utilizing the space beneath it with feet that point inwards rather than forwards. Extendable spiky-bits (r) on the soles of the feetwould help it climb steeper surfaces by augmenting its ground friction with anchoring the feet in the surface below with each step. On icy and snowy surfaces like glaciers or above the eternal snow line this would be a lifesaver for such centipedes. Once they have cleared the mountains and steep hills of enemies the tanks and supply lines can pass through and take over when centipedes become inefficient or incapable of fighting off the maneuverability of MBT's.

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Urban environments

rubble and scattered holes makes contested urban areas difficult for tanks and wheeled vehicles alike. But a low long flexible legged vehicle will handle those much better. It should also corner better.

A centipede mech can literally lift a few front sections up walls or over gaps then walk over it with a hanging section. perfect for a bombed out urban battlefield. They may even handle forest, glacier, and jungle in a similar fashion, by weaving around obstacles and bridging gaps.

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This idea sounds very similar to an existing concept: whegs!

Whegs are mechanisms for robot locomotion. Whegs use a strategy of locomotion that combines the simplicity of the wheel with the obstacle-clearing advantages of the foot.

What are the tradeoffs between whegs and wheels/treads?

  • Whegs are great at traversing obstacles and rough terrain
  • Whegs are worse at carrying heavy loads

So for small agile vehicles, whegs work great. For heavy tanks, probably not so much.

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If the mech can move sideways too, it can achieve a higher velocity as moving in the length direction. All leg movements can then be coordinated for making speed only. Sideways will then be the new straight ahead. High speed is an important advantage.

If there are multiple heads also, say one on each side and evenly distributed in the middle (above the legs) this will have the advantage ofthe mech being aware of almost its entire surroundings. There has to be communication between all of these heads obviously. One willing to go to the back, some to the front, and others sideways, will result in chaos.

You can question if this is still one mech but I think it can be seen as a functioning unit. When one head detects danger or something to eat they can cooperate to engange in a coordinated parallel action.

What is there more to gain from having a lot of legs? You can make the weirdest movements while being low to the ground. A bird trying to catch you can maybe be distracted. You can enter deep holes while using all power of your legs.

If the legs are strong enough he could even stand on his front legs (or back legs in the case of multiple heads) to threaten an enemy or take a look around.

For sure there are other possibilities I haven't touched upon.

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    $\begingroup$ You seem to confuse video game running physics with real world physics. In a video game they often dont subtract the forwards speed from the sideways speed, and if you could go faster "sideways" then you would design your feet to be angled and make "sideways" be "forwards", with 50% of the legs angled left and the other 50% angled right to maintain symetry and mobility. $\endgroup$
    – Demigan
    Aug 4 at 10:42
  • $\begingroup$ @Demigan Cant you make the legs turnable? So the forward walk can adjust? $\endgroup$ Aug 4 at 11:03
  • $\begingroup$ You can make it turnable, although you might sacrifice power and speed per leg for it as you need to stabilize more. But there would be no additional speed for going sideways, unless I misunderstood your answer $\endgroup$
    – Demigan
    Aug 4 at 11:13
  • $\begingroup$ @Demigan. In the case of sideway (considered forward) motion you can think as if a lot of runners run in tandem. Forward motion is different. $\endgroup$ Aug 4 at 11:19
  • $\begingroup$ Wheels or legs in tandem or series doesn't really matter. That is why there isn't a massive difference in crab versus spider walk, both are functional for the environments they are used in. Adding both spider and crab walking styles would mean sacrificing stability, which you need to compensate by using more power. $\endgroup$
    – Demigan
    Aug 4 at 13:05
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One Missing Advantage: More Armament

Thr other answers don't address one advantage: more segments allows more places to put guns, rocket launchers, lasers, etc., and more options to work those independently to target all around the mech. While this is not specifically an advantage based off "more legs" (vs. wheels or tracks), it would be the advantage of segments (which is another unique feature of a "centipedal" mech).

Of course, the disadvantage is it makes for a bigger target. To counter this, ideally, if a middle segment gets destroyed, the "ends" could go on independently (i.e. each segment might function independently as needed, but "better" merged together).

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There is one thing a walker can do that a wheeled vehicle cannot: Be completely connected. While this might seem silly or trivial, it allows one other feature: It can Grow!

A living biomech walker is viable. A biomech wheeled or tracked vehicle, not so much. This also accounts for why you see so many walking creatures, and so few wheeled ones. (Zabriskan Fontema?)

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