The CthulhuTech Broadsword mecha with Vehicles/Robots

[Eukie]

First time I post here, so I have no idea if I'm doing this right...

In spite of the whole rest of it, I am vaguely enamoured by the mecha design in CthulhuTech, and playing in a CthulhuTech-esque setting filled with giant robots, giant lobotomised eldritch horrors, and hovertanks flying around shooting at things with weapons that make pretty colours appeals to me. I've also recently fallen in love with GURPS 4E because of how flexible and supported social options are (like Allies, Patrons, Contacts, Wealth, Status, Rank, and everything to do with Social Engineering), and the construction-options from GURPS 3E Vehicles 2E and GURPS Robots appeal to the physicist in me. Among other things, the fact that Robots lets me know the volume of each individual component makes creating custom hit-location tables easy.

Because of this, I'm interested in using GURPS Robots, supported by GURPS Vehicles to build CthulhuTech(-esque) mecha. I figured I'd start with the most common giant walker of death in CTech, the Broadsword. However, I'm not really sure how to proceed with regards to armor thicknesses, armor slopes, and limb proportions, so I'd love it if a kind spirit could help me with this.

CthulhuTech mecha are powered by magical infinite energy black-boxes and have assistance from magical antigravity pods, but personally I would not be adverse to replacing these with non-superscience fuel cells, nuclear power units, or fusion reactors.

Physical Stats of the Broadsword:

• 26 feet tall
• can lift 10 short tons
• can move 30 miles per hour on land
• can move 15 miles per hour in water
• can float
• is submersible and reinforced against high pressures
• armed with an amphibious laser cannon (that, on average, cannot penetrate its own armour)
• armed with an amphibious "charge beam" (that, on average, can penetrate its own armour)
• armed with a pair of "hyperedged" blades (that, on average, cannot penetrate its own armour)
• has an escape pod with 16 hours of life support
• is airdropable
• it has two arms, a pair of legs, and a head

Based on the fact that it can lift 10 short tons, I know that it must have a Body ST of 667 and an Arm ST of at least that. Its walking speed tells me that it moves at roughly 15 yards per second, and consequently has a [motive power]/[weight]-quotient of ~13.45. Based on its water speed, I know that the [power factor]/[weight] quotient is somewhere between 6 and 10; linear interpolation suggests 6.67. Given that it can float, I know that its weight does not exceed its volume by more than a factor 62.5. Given its height and the fact that it has two legs, I know that the sum of its body area and head area is 200.

With this, if I knew the proportion between its head volume and body volume, I could calculate its body volume. With then, the proportions for leg volume and arm volume, I could also calculate the actual leg and arm volumes. This, together with good estimates for the armor slope of each component, could tell me the total surface area of the Broadsword. With this and knowledge of its material composition and armor thickness, I could calculate an estimate for its mass (power-plant and drivetrain not included). With this, I could solve the necessary differentials to calculate the mass of the power-plant and the drivetrain.

So, dear sisters and brothers of the SJG conspiracy, do any of you have suggestions for how to proceed? I'd like to know if anyone has suggestions for armor thickness, power plant type, material composition, armour slopes and volume proportions, or if you have any other suggestions for how to build the Broadsword with GURPS Robots?

[DangerousThing]

I wouldn't bother to stat it out as a full vehicle, but use what CthulhuTech gave you.

You really don't need to build the rest in detail.

There is a fairly abstract way to build mecha with GURPS Spaceships. I strongly recommend that you use 4e for doing this.

I like CthulhuTech also, and am trying to create templates for Taggers and their enemies. I'm definitely not using them like CthulhuTech does. For one thing the big C is dead again and it's many thousand years in the future.

[nick012000]

Yeah, vehicles are one of the few things that changed in a big way between GURPS 3e and 4e; as a result, GURPS 3e Vehicles isn't compatible with GURPS 4e. GURPS 4e Spaceships can do the job, though.

[Eukie]

Originally Posted by DangerousThing

I wouldn't bother to stat it out as a full vehicle, but use what CthulhuTech gave you.

You really don't need to build the rest in detail.

There is a fairly abstract way to build mecha with GURPS Spaceships. I strongly recommend that you use 4e for doing this.

I don't really need to if my goal is to build easily game-able mecha, but my goal is partly the joy and process of creation itself, and partly to have the extreme level of detail. I rather enjoy knowing the mass and volume of each components, it's location, and the exact fuel-consumption-rate for various activities. It lets me get an idea of what a (sur)realistic mecha should be able to do within a (sur)realistic framework. There are times when I want to know how much a severed mecha leg weighs, or how many mechanics are needed to lift an arm servo when replacing it. This is something I don't think I'll be able to use Spaceships 4E for.

However, I have come somewhat further in my quest. Since mecha have terrible power-to-weight ratios, I'll almost always want to fill all the available space in their Leg Subassemblies with Leg Drivetrains. Together with speed, this tells me the Motive Power and Maximum Weight of the mecha, and then I can design within those parameters.

(The Nazzadi mecha are more human-proportioned, so I might be able to design them a little easier though; the worked example in GURPS Robots tells me which propotions to use for a slim human being.)