# Vehicle Size Considerations

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As vehicle size increases by each point, Length, Width, Height, and Volume increase.  Based on the Vehicle Size Table, the assumption is that the vehicle is roughly rectangular box-shaped.  Width and Height are half of the Length for calculation purposes.

What if I have an existing vehicle for which I am looking to generate characteristics, and the vehicle is an odd shape?  e.g. a pyramid-shaped vehicle.  If it has a 50m wide base and it is 100m high, a quick glance at the Table suggests that it would be SIZE 17, but is it really?  The Volume of a pyramid is significantly less than a box with the same dimensions, and therefore, less exposed surface area.

Edit: Just realized I could simply give it a +1 or +2 DCV for having less exposed surface area.

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I've usually gotten better results basing it on mass than on volume.  Do you have the mass of the pyramid?

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17 minutes ago, Chris Goodwin said:

I've usually gotten better results basing it on mass than on volume.  Do you have the mass of the pyramid?

I can figure it out.  Are you suggesting that Mass is a better metric than Volume for estimating vehicle Characteristics in Hero?

Edit: "The Ultimate Vehicle" page 8 backs you up:

"The dimensions (Length, Width, and Area) in the Expanded Vehicle Size Table are guidelines. Few vehicles fit the listed dimensions exactly. When you’re designing a vehicle that doesn’t fit all the dimensions of a Size category with reasonable precision, choose the Size category based either on the vehicle’s most prominent dimension (typically Length) or its mass."

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10 minutes ago, C-Note said:

I can figure it out.  Are you suggesting that Mass is a better metric than Volume for estimating vehicle Characteristics in Hero?

Yes!

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I've never cared for the Vehicle rules.  They seem to unbalance the game and make the characters seem useless.

I'm currently working on using the Density Increase/Growth rules to build vehicles as characters to use in Multiform.

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6 minutes ago, Cassandra said:

I'm currently working on using the Density Increase/Growth rules to build vehicles as characters to use in Multiform.

Dang straight!

You'll never go back; I promise!

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I actually built one for a slot in my ground based Weapons Master for characters like Batman, Moon Knight, and Nite Owl II.

Cost Powers

30 Armor +10 rPD +10 rED

15 EC [Vehicle]-15 Points

15 1) Density Increase: Mass 800kg, STR +15, KB -3", PD +3, ED +3, No END Persistent (+1)*

35 1) EB 10d6

15 2) Flight 10", 8x NCM or Running +5", 8x NCM, No END (+1/2)

15 2) Growth: Length 2", Width 1", Mass 800kg, BODY/STUN +3, DCV -2, PER +2, Reach +1", STR +15, KB -3", No END Persistent (+1)*

Total Powers Cost: 125 Points

*Density Increase/Growth Combined Mass 1600kg, KB -6"

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For really large vehicles, remember that a human body has a volume of roughly 0.7 cubic meters and one displacement ton (used for ships, starships, etc) is .99 cubic meters.

For smaller vehicles, figure a small motorcycle (to include most sport bikes up to about 700cc) are roughly the size of one person.

Consider Shrinking (only to reduce mass: -1)  as your model for reducing mass for high-tech vehicles or things that are just naturally really light.

Sure: for super vehicles and sci-fi vehicles, you don't have to really worry about realistic sizes and masses, but when (if) you do Heroic stuff, those are just three things that are nice to know.

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33 minutes ago, Duke Bushido said:

For really large vehicles, remember that a human body has a volume of roughly 0.7 cubic meters and one displacement ton (used for ships, starships, etc) is .99 cubic meters.

For smaller vehicles, figure a small motorcycle (to include most sport bikes up to about 700cc) are roughly the size of one person.

Consider Shrinking (only to reduce mass: -1)  as your model for reducing mass for high-tech vehicles or things that are just naturally really light.

Sure: for super vehicles and sci-fi vehicles, you don't have to really worry about realistic sizes and masses, but when (if) you do Heroic stuff, those are just three things that are nice to know.

I might have to use the Standard Effects Rule to protect the crew, which would be the Vehicle's DNPC.

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Okay, found the relevant section.  6E2 p186 states:

"The dimensions presented in the Vehicle Size Table are not absolute; you can alter them somewhat as long as the total volume remains the same. The interior size of a Vehicle equals half the external size; with a minimum of one cubic meter."

Going back to my pyramid-shaped vehicle example above, I should give it a SIZE value based upon its Volume, rather than its Height.

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14 hours ago, C-Note said:

Okay, found the relevant section.  6E2 p186 states:

"The dimensions presented in the Vehicle Size Table are not absolute; you can alter them somewhat as long as the total volume remains the same. The interior size of a Vehicle equals half the external size; with a minimum of one cubic meter."

Going back to my pyramid-shaped vehicle example above, I should give it a SIZE value based upon its Volume, rather than its Height.

I did the math (for anyone who's interested). To determine the Length of a rectangular prism where the Width and Height are each 1/2 the length, you can use the following formula:

Length = ∛(4v)

(the cube root of 4 times the volume)

That should give you, for any volume, the equivalent Length (and thus the Width and Height) of a rectangular prism with the same volume. It might help if you have a size table based on Length but have an unusually shaped volume. Calculate the length and find the nearest entry in the table.

Lee

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19 hours ago, C-Note said:

I can figure it out.  Are you suggesting that Mass is a better metric than Volume for estimating vehicle Characteristics in Hero?

18 hours ago, Chris Goodwin said:

Yes!

Really? Remember the old joke (paraphrased here for the given context):

"Which has more mass, one kilogram of lead or one kilogram of feathers?"

Of course the answer is they have the same mass (one kilogram). But, they will have radically different volumes. So, for determining the "size" of something, I think that volume would be a better measure. The "size" of one kilogram of feathers would be much larger than one kilogram of lead.

Having said that, I think mass would be better for determining things like STR, CON, BODY, etc. as that would seem to have more to do with mass (or density which is mass/volume). But strictly for the "size" of something, I like volume better.

That's just my opinion, I could be wrong.

Lee

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14 minutes ago, Lee said:

I did the math (for anyone who's interested). To determine the Length of a rectangular prism where the Width and Height are each 1/2 the length, you can use the following formula:

Length = ∛(4v)

(the cube root of 4 times the volume)

That should give you, for any volume, the equivalent Length (and thus the Width and Height) of a rectangular prism with the same volume. It might help if you have a size table based on Length but have an unusually shaped volume. Calculate the length and find the nearest entry in the table.

Lee

Thanks!  Based on your equation, solving for Volume is: V = (L^3)/4.

I also found many online calculators for the volume of a rectangular pyramid with any size Length, Width, Height.  Here's one:

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Just now, C-Note said:

Thanks!  Based on your equation, solving for Volume is: V = (L^3)/4.

I also found many online calculators for the volume of a rectangular pyramid with any size Length, Width, Height.  Here's one:

You are absolutely correct. That's the volume of a rectangular prism (box) where the width and height are 1/2 the length. I was assuming that you had the volume of the pyramid and were trying to determine the length of a rectangular prism for lookup in a table. If I'd known you wanted the volume of that rectangular prism, I'd have posted the formula you determined instead (or both).

Lee

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34 minutes ago, Lee said:

You are absolutely correct. That's the volume of a rectangular prism (box) where the width and height are 1/2 the length. I was assuming that you had the volume of the pyramid and were trying to determine the length of a rectangular prism for lookup in a table. If I'd known you wanted the volume of that rectangular prism, I'd have posted the formula you determined instead (or both).

Lee

Got it, thanks.  Just for context:  I'm "reverse-engineering" several Traveller starships for HERO.  Traveller's metric is "displacement tonnage" for starships.  I'm not using that, but rather, volume to calculate its primary HERO Characteristics.  Some streamlined starships in Traveller are wedge-shaped and terminate at a point, so I think the volume calculation for a rectangular pyramid is the best approximation.

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You lost me.  Displacement tonnage _is_ volume.  Roughly. 9 cubic meters in a displacement ton.

I found that to be extremely helpful when doing the same thing a few years back.

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1 hour ago, Duke Bushido said:

You lost me.  Displacement tonnage _is_ volume.  Roughly. 9 cubic meters in a displacement ton.

I found that to be extremely helpful when doing the same thing a few years back.

I should have been more clear. Traveller "displacement tonnage" never seems to match the ship's actual measured volume.  Also, I think it's 1 cubic meter per displacement ton (a "block" of water 1m x 1m x 1m).

Edit: I think you typed ".9".  I saw it as "9".  My bad.

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43 minutes ago, C-Note said:

Traveller "displacement tonnage" never seems to match the ship's actual measured volume.

Agreed.  Often to the point that I wondered if they were measuring the volume of space inside the structure without regard for the volume of the materials from which the structure was made.

Or perhaps even the other way around: the volume of the materials making up the structure, regardless of how thinly they were spread.

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6 hours ago, Duke Bushido said:

Agreed.  Often to the point that I wondered if they were measuring the volume of space inside the structure without regard for the volume of the materials from which the structure was made.

Or perhaps even the other way around: the volume of the materials making up the structure, regardless of how thinly they were spread.

It is the volume of one ton of Liquid hydrogen, for the jump drives I think

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Well yes.

I simply meant that comparing the listed sizes of the ship to the amount of area that would actually be-- well, that results in some interesting discrepancies with the old published deck plans.

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