Armored giant?

[Tedronai]

Armour-generated friction would seem, to me, to be the product of a compel.

[Becq]

My comment was meant to be more of a cross between a reality check and a throwaway joke that a serious suggestion of mechanics.

That said, I think it's a bad idea to carry the "It is what it is" aspect (little 'a') of Items of Power to too much of an extreme.  The idea is to allow players to have 'for free' the bonuses that any Joe Schmoe could get by acquiring a non-supernatural, mundane item, then to allow them to pay refresh to layer a bit of something extra on top.  I tend to believe that the 'mundane items' need to be something that is within the realm of reason (given the context of the game).  I.e., it should be something that you might reasonably expect to find on an equipment list, assuming the game had one.

In this case, the 'mundane item' would need to be 'a suit of chainmail' (armor:2) or 'a suit of plate armor' (armor:3), with any benefits garnered from the fact that it is magically crafted from plates of tank hull and inscribed with runes and such being bought on top of that base.  The fact that it's large enough to fit on a giant is flavor text.  Realistic?  Maybe not.  But then again, if you want realism, then you need friction, too.  :p

[Kommisar]

Thirty tons on a biped with roughly human proportions.  As a Geotechnical Engineer, I can provide you with all of the actual, real life implications of him walking across a large number of terrains and pavements.  Heck, if anyone really wants me to, I can even post up .pdfs of my MathCAD design sheets showing the LRFD (Load Resistance Factored Design) design calculations for bearing pressure, punching shear effects and on and so forth.  Then I can even kick up the ASSHTO calculations for pavement deformation for extreme loading conditions.  We run those here when we permit extreme load transport over the state's highway and interstate system.  I also know enough structural engineering (though I do not wish to present myself as a structural engineer for purposes of professional ethics and licensure... and the displeasure of my wife who is a professional structural engineer) to lay out all the troubles he is going have in entering most buildings.

The problem is not the 30 tons.  It is the pressure generated by that 30 tons.  Very common mistake, actually.  There is a reason that tanks have treads and the really big heavy load trucks have lots of wheels.  They serve to spread the weight of the vehicle over a larger area and, therefore, reduce the over-all ground pressure they exert.

Take your giant.  I don't have his measurements, but let us say that he is three times the size of a human with the same basic proportions.  That would put him around 18-20 feet tall.  And, we shall be generous and give him large feet; say 3 feet long and 1 foot wide.  For the record, I'm 6 feet tall, have 10 inch long feet that are 3.75 inch wide.  Rounded of course.  And, yes, I keep a scale and ruler next to my computer.  LOL

Keep it simple and assume a rectangular shape of the foot.  That makes each foot 3 square feet.  He has two of them, 6 sq.ft. 

30tons / 6 sq.ft. = 5 tons/sq.ft. or 5 TSF.  Static; that is standing still.  That is a very hefty static load and one that most soils will deform under in dry conditions.  Under wet conditions, even more so.  For good clay soils here in Tennessee, I will often recommend an allowable soil bearing of around 2 TSF.  Now, that is allowable, meaning that it has a reduction factor (or Factor of Safety under the old ASD design methodology).  So, he would be okay standing on most soils.  Leave some good foot prints though that a five year old blind kid could track.  On good solid rock, he'll be fine.  I wouldn't get to close to any cliff faces though as they you have to start worrying about confining lateral pressures and loads.  And he will cause localized slope failures on anything steeper than a 5 to 1 slope most of the time.

Moving, things get more complicated.  Impact loading.  One one foot.  Unless he slides around everywhere somehow. 

Now we are looking at a starting value of 10 TSF.  That blows most soils right out and will fracture many softer shales and weathered regolith.  Now, standard ASSHTO impact loading is x1.2 (off the top of my head, my code is back at my office).  So at a casual walk, call it 12 TSF.  Running... call it around 20 TSF.  That is problematic in a big way and will require a great deal of caution on his part to maintain his own stability in moving about.  20 TSF and you could start to fracture weaker limestone.  You are not going to shatter it or cause punching shear failure; but you are cracking it as you move.

Most state DOTs have a maximum limit of weight on any one tire of a vehicle of around 10,000 lbs without special permitting.  It gets a LOT more complicated as you start to factor in axle lengths and loading combinations; but we'll keep it simple here.  For those that want to go all out:

http://www.dot.ca.gov/hq/traffops/trucks/trucksize/weight.htm

Have fun.

But that 10,000 lbs on one tire is going to be around 10,000 lbs / 1 sq.ft.  or 5 TSF.  That is not a failure point for most high end pavements; but a limit based on deformation of flexible pavements (asphalt). 

You'll be fine on commercial or air force pavements; though you will be causing damage unless you are careful.

Don't even bother going onto most structures.  I'll ask my wife about highway bridges; as that is her specialty.  But you would give a parking garage nightmares, crush an residential floors or foundations, decimate side walks and drive ways, and cause the local utilities company to have fits as you directly increase their budget for the year.  Watch for culverts as well; bad.  Climbing slopes is going to be challenging as the soils are likely to deform under your feet as you climb up.  Think walking up sand dunes; but with normal soils.  This is due to lacking that lateral capacity I mentioned above allowing for the soil to deform laterally more rapidly without compaction.

If anyone wants more, just ask.

OR, ignore it all and have fun with it.  I love giant robot/mecha stuff.   

[Kommisar]

Talked with the wife over lunch at the pub.  Yea, you armored giant needs to avoid bridges.  Even interstate bridges.  If he walked (WALKED) and made sure that he kept his feet directly over the bridge beams themselves, he might make it across.  But it would cause enough damage to the structure that it would most likely have to be replaced.  If he went off the beams, he would punch right through the pavement structure and bridge decking.  Think about walking through the attic and stepping off the wood joists... save you weight 400lbs.  If he ran or moved to carelessly... he's not making it.  And smaller municipal bridges are toast.

Additionally, walking through an urban area is going to be "interesting".  He will be rupturing any underground utility lines he steps to near.  Sewer, water, gas... are all going to rupture depending on how deep they are buried.

Also, if you want to get more technical, you can take into account the actual mechanics of walking and the fact that when you walk/run, your foot rolls and, therefore, you are not getting the full area of the foot in contact with the ground as you move.  So, up on the ball of a foot as you walk with the 1.2 impact loading... 36 TSF.  CRAP!!!  Running, 60 TSF!!!  You are in danger failing anything below solid igneous bed rock at this point.  You would be leaving dented craters in Limestone bed rock.  Beware karst terrain.


To give some comparison for you non-engineering folks.  The M1A2 Abrams Main Battle Tank has a stated ground pressure of 15.4 PSI (Pounds per square inch).  Converted, that is around 1.1 TSF.  As per ASSHTO, DOD, Federal Highways and all the State DOTs, an Abrams tank (or the HETs that can transport them:  http://en.wikipedia.org/wiki/Heavy_Equipment_Transport_System#M1070.2FM1000) can only cross a bridge if it is the only vehicle on the bridge.  One at a time, no other traffic.  You're boy is exceeding the ground pressure of the M1 tank series by a significant amount.

[tymire]

Lol, and that Kommisar is why I rarely if ever go in to details about engineering (structural here) since it gets way too long and you always lose people.  Maybe not from the math, which is generally fairly simple, but when you start explaining 90% of the time the eyes always glaze over.

But really 30 tons is way off.  Elephants weight 10,000-12,000lbs and am sure that giants are typically much less.  Also need to remember regardless on how strong you are mass makes a difference.  It would be infeasible for a biped that only weighs 10,000lbs to use much more than 5,000lbs of armor just from a balance standpoint.  Sure they could carry more, but move even semi-efficiently?  Not so much.

Actually questions like this is why I really don't like gaming with most science/physics masters and phd students any more .  No doubt that they are extremely intelligent, but they typically have no experiance and very little common sense yet they know EVERYTHING.  Ofcourse forgive me for generalizing. 

Fyi, your 1.2 impact factor is correct (it's also used on bridge cranes and others), however those are for tire loads over flat surfaces.  It should be MUCH higher for instances when someone is running or even walking due to the motion.  But by the same token you can just throw out the safety factors as which range from 1.5-3 depending on the failure conditions.

[Kommisar]

Well, the 30 tons wasn't my number.  I just went with what the OP came up with.     I really didn't feel like specing out the weight of a giant and the armor he could reasonable wear/use.  For a 18ft giant... I would probably stick with something in the 10 to 12 thousand pound realm, like you.  So, 15,000 lbs with armor sounds reasonable; which is 7.5 tons.

He's still going to have fun moving around civilized areas with his approximate 9 TSF walking ground pressure.  A main battle tank is 1.1 TSF for those that didn't read above.  And elephant exerts (standing on all 4 feet) approximately 5.5 lbs/sq.in. or about 0.34 TSF.  They have 4 big feet.

Mind you all of this could be rendered moot by the physiological limits of the human body's shape.  But I don't think that should stop us.   

[tymire]

Yep, elephants have 4 big round flat feet. 

Imo only the Rule of Consistancy is > than the Rule of Cool for rpgs, as you cannot have a believable world where things don't operate according to "mostly unchanging" guidelines.  Besides the fact the character defined as a giant which means the player wants to have (or deal with) collateral damage.  Main thing is soak it for all it's worth, lol.

[Belial666]

An 18 ft giant weighs 27 times as a 6ft man of the same build, IF giants are about as dense as humans. Since giants are kinda bulky, let's go for a 200 pound base. That's 5400 pounds. If giants are really bulky and/or denser than humans, we could go with twice that much. As for the armor, we are talking a 55 pound plate (as in 16th century platemail) for a human, or around 1500 pounds. Now, the armor would be made of tungsten and would be twice as thick as normal giant-sized platemail, so we're looking at 9000 pounds. So we are looking at 14400 pounds for a heavily armored giant. The plate would be no more than an inch thick and would be the equivalent of 3 inches of steel in both toughness and weight.


That's for realistic numbers though, not a giant wearing actual tank armor.


PS: substantially heavy armor evenly distributed could even help the giant apply his supernatural/mythic strength by helping his balance when lifting really big things.

[fantazero]

you know what defeats tanks? Molotov Cocktails. Just saying

[Belial666]

Probably 1920s tanks. Maybe, if you're lucky, 1940s tanks. Modern main battle tanks have armor equivalents from 400mm to 1100mm of RHA steel, nearly 10 times as much as that of their WWI-WWII equivalents. Unless you throw the Molotov Cocktail down an open hatch, you aren't burning one.

[Tedronai]

The most effective use of a molotov cocktail against a modern main battle tank is not to pit it against the armour at all, but to target it for the tank's primary air intake.  That does, of course, assume that the tank ISN'T being driven around with open hatches.

[Belial666]

Isn't this why clever designers would put the air intake underneath the tank? Extra filtering needed against the dust but it avoids shenanigans.

[fantazero]

yeah, but the air intake on this giant is his head 

[Sanctaphrax]

Why do you people know so much about tanks, anyway?

[Tedronai]

Well, technically, my familiarity is with LAVs, but for this, I figured it was close enough...