Many consider them an abomination. Others thing they're just spidertanks on stilts. For many, this is the great question of our time.
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Quad Mechs?
- Thread starter Husky_Khan
- Start date
Uhh... no it's not? Sure Quads can carry less weapons than a comparable biped mech, but they actually have quite a few advantages that arguably make up for that drawback, plus they can carry more armor than a similar weight biped. There's quite a few environments where Quads are superior to Bipeds in BattleTech, if people actually remember to use the full Quadmech ruleset.
I'll grant, if they do ignore the special case rules for Quads, then yeah, they're probably worse, but Quads can be quite good designs for certain weight classes.
gral
Well-known member
I wasn't aware there were special rules for quads - whichever mech builder programs I've used apparently don't use them. Also, the part of carrying more armor IS a disadvantage - 75% armor for four legs weighs more than 75% armor for two legs and two arms, which means less tonnage for other things, not only weapons.
Bear Ribs
Well-known member
Quads have a few special rules. They get a small bonus to pilot rolls which is nice. The can mule kick an enemy directly in their rear and can "crabwalk" sideways into hexes so they're generally move mobile than bipeds, and the bonus to pilot means they can jump with more stability. They can stand up more easily when they've fallen than bipeds. They interact oddly with the cover rules, since hits to the legs are "misses" if you're behind partial cover, a quad behind partial cover has far more misses since all arm hits on it are actually leg hits so while partial cover protects a biped from maybe a quarter of hits, it soaks half the hits a quad would take. They also take less of a penalty to losing a leg, a biped is pretty much out of the fight barring a lucking roll if it has a leg blown off but a quad can keep going.
The problem with quads in BattleTech is twofold. Since they have no arms and no ability to torso twist, they have great huge swaths of area at their sides they can't fire into no matter what and that makes them extremely vulnerable to flanking. IF they don't have rear-facing legs they have to rotate around completely to attack an enemy that gets behind them and blow all their movement points on turning (unless said enemy is dumb enough to get into mule-kick position). They are also missing a lot of their criticals, a leg only has two empty slots while an arm has 8-10 so there's simply a lot less space to put stuff, they run out of criticals rather fast once out of level 1 tech, blowing 14 slots on endo-steel or ferro-fibrous is a no brainer for a lot of 'mechs but doing it when you're already 16 criticals down makes it more painful.
There's experimental rules allowing quads to mount a tank turret at the cost of a critical which mitigates the first problem but almost no canon units use it (the Araña does but it's an industrial 'mech from an incredibly niche faction that will almost never see play).
The problem with quads in BattleTech is twofold. Since they have no arms and no ability to torso twist, they have great huge swaths of area at their sides they can't fire into no matter what and that makes them extremely vulnerable to flanking. IF they don't have rear-facing legs they have to rotate around completely to attack an enemy that gets behind them and blow all their movement points on turning (unless said enemy is dumb enough to get into mule-kick position). They are also missing a lot of their criticals, a leg only has two empty slots while an arm has 8-10 so there's simply a lot less space to put stuff, they run out of criticals rather fast once out of level 1 tech, blowing 14 slots on endo-steel or ferro-fibrous is a no brainer for a lot of 'mechs but doing it when you're already 16 criticals down makes it more painful.
There's experimental rules allowing quads to mount a tank turret at the cost of a critical which mitigates the first problem but almost no canon units use it (the Araña does but it's an industrial 'mech from an incredibly niche faction that will almost never see play).
There is a game called Earthsiege 2 (or MetalTech Earthsiege, Earthsiege 2 and Starsiege) which has mechs (called Hercs).
The Cybrids had a Herc called a pitbull.
Cybrid Pitbull
That thing had powerful shields to defend itself with and the bigass turret on the back didn't help matters when fighting against a pack of them on a mission. The worst was when you had the Razor (aircraft) the turrets on the back of those things would track you and it could tank hits from a plasma cannon. Unless you had it on easy and used ELF weapons to bypass the shields.
The Cybrids had a Herc called a pitbull.
Cybrid Pitbull
That thing had powerful shields to defend itself with and the bigass turret on the back didn't help matters when fighting against a pack of them on a mission. The worst was when you had the Razor (aircraft) the turrets on the back of those things would track you and it could tank hits from a plasma cannon. Unless you had it on easy and used ELF weapons to bypass the shields.
I think it really depends on the mech specifically, not the number of legs. For example, mammoth mark 2?
Awesome.
The OG, GOL-1H Goliath:
Not so much.
Awesome.
The OG, GOL-1H Goliath:
Not so much.
This covers most of the special combat rules, but Bear Ribs doesn't actually explain just how much of a bonus Quads get for certain things.
For instance, where a Bipedal mechs needs to spend a movement point AND make a piloting skill check in order to stand after being knocked down, all a Quad has to do is spend the movement point. This means they just... get up, if knocked down. That piloting skill check bonus Quads get also means they are that much harder to knock prone to begin with. But they ALSO get a special maneuver concerning this fact, which is that Quads can go "hull down", which means they get all the bonuses of being prone with none of the drawbacks and don't need to make any special piloting checks to fire weapons mounted on their torso (unlike Biped Mechs, which are only allowed to fire the weapons from ONE ARM when prone).
As to how they interact with cover, it's not just the fact that Quads negate all leg hits taken while under cover, they ALSO get in cover more easily, as all Mechs are given a height statistic and despite the models and art, all Biped mechs are considered to be as high as level 2 terrain (or, that is, they sit two levels higher than the terrain they are on) for the purposes of line of sight and the like. Quads, on the other hand, are only are treated as having a height of level 1 terrain (or, sitting one level higher than the terrain they are on), the same as vehicles.
As to the lack of firing arcs, this is why they invented Jump Jets. Jumping Quads fix most of the firing arc problems.
But yeah, when you account for more potential armor, the interaction between cover and legs plus their easier ability to get cover from things like going hull down, etc. Quads are basically considerably much tankier than anything in their own weight category and can be an utter pain to hit. Plus they make very good ambushers. Throw on Jump jets and quads are some of the nastiest urban or rough terrain fighters in BattleTech.
Yinko
Well-known member
Quads seem like they have a lot of problems. Quadrupeds bounce a lot when they walk, so that kind of motion would not be ideal for a manned craft, and quadrupeds are actually white easy to trip, flip and disable (dog wrestling talking). I'd probably just go for a full spider-bot instead. There's a reason why carcinization is a thing, if a creature crawls then six to eight legs seems to be a pretty good number to ensure a good trade-off between agility, speed, balance and strength. Of course, on a mecha the issue is that more legs mean more mass which means worse fuel efficiency.
If you had to do quads, then I'd say to do it like the Tachikoma, where most of them time the legs are orientated as if they were spider bots and then use wheels to make them more effective.
If you had to do quads, then I'd say to do it like the Tachikoma, where most of them time the legs are orientated as if they were spider bots and then use wheels to make them more effective.
Hey, look. It's a giant quad mech that laughs at your feeble attempts to trip it.
On a side note, though, I think it's funny that the Covenant have multiple classes of quad mechs that are billed as 'excavation vehicles', yet they can all shrug off direct hits from tank guns. They're probably built that tough because some of the things that they dig up are likely to shoot back.
Yinko
Well-known member
Well, yes, that's why I referenced the Tachikoma as a good counter example.
In both this mech and the Convenant one you showed the center of gravity is lower than the knees, which makes them very stable. But if you contrast that with an AT-AT and they are so unbalanced that even most of the toys fall over. Statues of horses have a similar issue, as well, they have to be carefully balanced or the weight of the top will tend to destroy the statue.
I suppose there is a blurry line between virgin Quad Mechs and CHAD SPIDER TANKS!
Well, one has to look at the tradeoffs.
The most obvious of course is, well, more legs. But each leg still probably needs to be about as complicated with two as with 4.
So, if each leg needs to be about as complicated, that suggests each leg may be about as expensive. So, assuming the legs are a major share of the expense, a 4 legged mech is going to be about as expensive as 2 2 legged mech. And generally, two mechs seem like they would represent more firepower on the battlefield than 1 4 legged mech.
Now, as a firing platform 4 legged is more stable than 2, but a treaded vehicle would be even more stable at a similar size. So 4 legged seems like its sacrificing the mobility, compactness and relative simplicity of 2 legs and moving to body shapes that seem generally better suited to a tracked or wheeled vehicle.
Like, for the Boston dynamic robot mule. Yes, its cool.
But how much advantage does it actually give over using a little tracked vehicle?
The most obvious of course is, well, more legs. But each leg still probably needs to be about as complicated with two as with 4.
So, if each leg needs to be about as complicated, that suggests each leg may be about as expensive. So, assuming the legs are a major share of the expense, a 4 legged mech is going to be about as expensive as 2 2 legged mech. And generally, two mechs seem like they would represent more firepower on the battlefield than 1 4 legged mech.
Now, as a firing platform 4 legged is more stable than 2, but a treaded vehicle would be even more stable at a similar size. So 4 legged seems like its sacrificing the mobility, compactness and relative simplicity of 2 legs and moving to body shapes that seem generally better suited to a tracked or wheeled vehicle.
Like, for the Boston dynamic robot mule. Yes, its cool.
But how much advantage does it actually give over using a little tracked vehicle?
I see two assumptions that don't hold up. I don't think that a quad-mech's legs will be as complicated as a biped's for the simple fact that they don't have to do the fine balancing act of a bipod. A quadruped is inherently stable, even when walking. That's why we build tables with three or four legs. But a biped needs broad, articulated feet to do constant balance corrections, and the relative size of those feet is only going to increase as the weight increases.
Second, the idea that you can field two biped's for the price of one, because biped's have half of the legs. This assumes that the bipeds won't have arms, and it assumes that the mechs won't have expensive radar, ECM, or other systems that are comparatively expensive.
Yinko
Well-known member
The legs on a person are only about 1/3rd of the mass of the individuals, a lot of that is because they have to carry more weight on their limited frames though. Since the weight of the torso would be the same, each leg on a quad (or more) mech could be considerably thinner across the board. So while quad mechs would still be a bit more expensive in terms of materials costs, it's no where near 200%, probably closer to 125%.
Bipedalism is rare for a reason, it is horrifically difficult to do consistently. Every moment you are standing and walking your whole body has to go through dozens of rebalancing micro-corrections. As an example, try standing perfectly still and see how you start to sway after a bit without your body's normal corrective actions taking place. This would be the real reason why most mech designs are unrealistic.
If your setting has mechs, that question will either be studiously ignored, or they will invent reasons for mechs to have that edge. Even if those reasons are "mechs can mount dual heat sinks and combat vehicles can't, even if the mech and vehicle are using the exact same engine that comes with built in DHS if you put on a mech, because reasons*".
It'll also need two pilots, and from what I can tell pilots are among the most expensive elements of a military force. From what I've seen, it's about the same cost to train an F-35 pilot as it is to buy an F-35 engine.
And that's a best case scenario, loads of settings have some arbitrary limit that makes mech pilots even more rare than they would be normally.
*Those reasons being "because if we don't arbitrarily nerf tanks they'll easily outperform mechs".
Definitely doing two legs consistantly would be more advanced than doing 4 legs. That's part of why I'm sure many of the testing walkers are 4 legged.
As to the more expensive, my assumption there is that the cost of the legs is not in structural support, but in the servos. For example, take the simplest leg structure:
By this simplest walking system, your going to need at least 2 powered joints. In that model above, I would not be surprised if 80-90% of the manufacturing cost of those legs were in the servos in the legs, with the supporting plastic being comparatively minor.
So, if most of the cost is in servos, then having a system where you need 8 servos instead of 4 servos is going to be more or less twice as exensive.
Now, admittedly this assumes servo size doesn't scale up linearly with servo power: as you were suggesting, for the same power to weight ratio the mech with 4 legs might be able to get away with half the power per servo as the two legged one. However, if much of the cost is building any sort of servo, and you get returns to scale with servo power, then a twice as powerful servo is going to be much cheaper to buy and maintain than two servos of half the power.
This sense is based upon my experience with the price of engines and generators, where a wide variation in power output does not seem to result in wide variation in cost.
So, basically I'm assuming most of the cost of a leg will be in things that don't vary all that much with anything else, like how many legs: each leg needs approximately the same number of servos, the same amount of power wiring, the same number of sensors on the legs.
That could of course be a faulty assumption.
Tryglaw
Well-known member
The OG, GOL-1H Goliath:
Not so much.
LOL, if you look close enough, that's a T-34 tank hull on legs.
On the left side of forward glacis you've got the hull-mounted MG, to the right is the driver's hatch, on the sides you've got fuel tanks turned into missile pods, heck even the towing attachment points are there, just moved to lover glacis...
Bear Ribs
Well-known member
What's really sad is that's not original art, that particular Goliath is the unseen version, borrowed from Dougram. So they literally paid to use art somebody else had already traced, then got in legal trouble from Harmony Gold for it.
The Reseen version is a dramatic improvement IMO, and looks a bit less like a giraffe somebody tried to drive through a railway tunnel.
The Reseen version is a dramatic improvement IMO, and looks a bit less like a giraffe somebody tried to drive through a railway tunnel.