Move for Larger Creatures

[Kuu]

When designing larger monsters, does Move increase with size, a fraction of size, or as a square root of size?

Or should it be modeled as Enhanced Move, since a larger creature has more trouble turning around? If so, what is the ratio of Enhanced Move to size?


The reason I'm asking this is because I notice that, in many movies and fictional stories, larger creatures are much more clumsier and slower than smaller ones. This probably has to do with the square-cube law and encumberance, but I don't know the extent to which it affects a large creature.

For example, how fast would a 40-yard worm-like creature (with ST 200, BL 8000, and weight 500 tons, that, if 2 yards long, would have Move 1) be able to move?

EDIT: Looking through Space p151, it seems that a more accurate weight would be 800 tons, as well as a ST of 233 and a BL of 5.43 tons.
EDIT 2: Going by the square-cube law, it seems that something that big would be crushed under its weight. So much for that example.

[vierasmarius]

I think a general rule of thumb is to give Enhanced Move equivalent to the SM ratio. So SM +2 (x2 linear dimension) would be Enhanced Move 1, while the 40 yard, SM +8 critter would be Enhanced Move 4. Large creatures may also be clumsier, which would reduce their Basic Speed / Move and therefore their top speed with Enhanced Move.

[Lupo]

Originally Posted by Kuu

When designing larger monsters, does Move increase with size, a fraction of size, or as a square root of size?

Or should it be modeled as Enhanced Move, since a larger creature has more trouble turning around? If so, what is the ratio of Enhanced Move to size?

You seem to imply that there are some "biomechanical rules" in GURPS which "realistically" determine the relationship between move and size.

There aren't such rules, luckily...

Originally Posted by Kuu

The reason I'm asking this is because I notice that, in many movies and fictional stories, larger creatures are much more clumsier and slower than smaller ones. This probably has to do with the square-cube law and encumberance, but I don't know the extent to which it affects a large creature.

You are getting this backward. In fictional stories, larger creatures are slow because authors and audiences think it is appropriate for them to be slow.
In your fictional story (e.g., your campaign), you should feel free to make your "large creatures" as slow as you like...

For example, how fast would a 40-yard worm-like creature (with ST 200, BL 8000, and weight 500 tons, that, if 2 yards long, would have Move 1) be able to move?

Exactly 27,2 mph.
No, really, who knows? And, most of all, who really cares?
40-yard worms are quite clearly "fantastic" or "superscience" creatures... what is the point of exactly determining their weight in lbs / speed in y/s? Such creatures should move at the speed of plot :)

[Anubis]

true take the example of Godzilla when its being chased through Manhattan bye to apache choppers . it seams to move very quick and agile

[walkir]

Originally Posted by Kuu

EDIT: Looking through Space p151, it seems that a more accurate weight would be 800 tons, as well as a ST of 233 and a BL of 5.43 tons.

If you already use Space, you can look up p146 under "walking". There is a rule of thumb for this question.

[SuedodeuS]

Originally Posted by Kuu

For example, how fast would a 40-yard worm-like creature (with ST 200, BL 8000, and weight 500 tons, that, if 2 yards long, would have Move 1) be able to move?

Well, worms move by contracting and relaxing muscles - essentially, they pull themselves along using their skin. A larger worm should therefore be slower. I'd expect the energy they can spend on a "step" would scale with surface area. By the square-cube law, surface area would increase 400x, while mass would increase 8000x. The large worm would thus move at 1/20th the rate of the smaller worm at continuous movement. More likely it would move faster than this for short bursts, but take some time in setting up the next "step."

For a creature that walks, they have gravity (and thus their bulk) assisting them. Looking at the relationship from S146 (as recommended by walkir), quadratic scaling looks like it would work. So, if that were a 40-foot giant instead, it would move at about 4.5x the speed of a human (Move 22 or so). If you think large creatures should have turning issues, you can give them a level or so of Enhanced Move. In this case, the giant would have Move 11 and Enhanced Move 1.

Originally Posted by Lupo

Exactly 27,2 mph.
No, really, who knows? And, most of all, who really cares?
40-yard worms are quite clearly "fantastic" or "superscience" creatures... what is the point of exactly determining their weight in lbs / speed in y/s? Such creatures should move at the speed of plot :)

Plot pounds doesn't lend itself well to calculating Slam damage (or in determining if the superpowered hero can lift it), and plot yards per second doesn't tell you how rapidly it moves in tactical combat. Do keep in mind we are talking about a game system, rather than a story. GURPS requires actual numbers for certain effects.

[Kuu]

Thank you for the recommendation of Sp146.

You seem to imply that there are some "biomechanical rules" in GURPS which "realistically" determine the relationship between move and size.

There aren't such rules, luckily...

You don't need to follow the rules if you don't want to - though I can't find any "hard and fast" rules. A monster's speed can be anything you like it to be.

But even if I were to make an unrealistically large creature, I'd like a general assumption of how fast it should move, and place it somewhat close to that (read that as "semi-realistic statistics"). The problem is that I don't have a clue how fast it would move, because I've never seen something that large, and I want a general guideline.

[Flyndaran]

How big of a monster do you want?
The largest land animal weighed over 100 tons, and had a huge tail to contend with.

[sir_pudding]

Originally Posted by Flyndaran

How big of a monster do you want?
The largest land animal weighed over 100 tons, and had a huge tail to contend with.

Since all we know about Amphicoelias is from a single bone (and that subsequently lost) I don't think you can derive any meaningful estimate of it's top speed. Besides it most likely had legs and thus is a poor data point for giant worms anyway.

[Flyndaran]

Originally Posted by sir_pudding

Since all we know about Amphicoelias is from a single bone (and that subsequently lost) I don't think you can derive any meaningful estimate of it's top speed. Besides it most likely had legs and thus is a poor data point for giant worms anyway.

That has an estimate much greater. 100 tons is a conservative reasonable assertion for many of the giant sauropods.
But I give you the had legs point.

Slithering is just a horribly inefficient mode of locomotion no matter what your size. Even earthworms have numerous tiny moving hook-like structures to propel them through the dirt.