290 replies to this topic

[Major Bill Curtis]

They weigh 'mechs on a low-gravity planet

More likely, it's an equivalency system based on an arbitrary metric, and everyone who drives a 90-ton (or whatever) 'mech knows that it doesn't actually weigh 90 tons. This doesn't matter; what matters is that it's twice the mass of a 45-ton 'mech.

A .38 caliber bullet isn't .38 inches in diameter either, by the way (it's .356), yet there has been no hue and cry for this to be changed, even though a .357 is, in fact, .357 inches across.

Finally are all you guys talking about long tons or short tons? If you can't answer this, you've probably not considered everything there is about analyzing this fictional universe.

Edited by Major Bill Curtis, 13 June 2012 - 08:01 PM.

[Major Bill Curtis]

Thomas Hogarth, on 13 June 2012 - 06:15 PM, said:

It's been speculated by people that write for Catalyst that are smarter than I am that 'Mechs have similar densities to foam. That's right, by all rationale, 'Mechs should float quite easily and be blown over in a light wind.

Well, the total volume of this is less dense than water, but it probably won't be raining down from the sky any time soon.

[Tincan Nightmare]

OMG you people love math way too much to be figuring out the formulas to explain why mechs are impossible. I hate math so I gotta give you all kudos.

[Full Metal Monte]

Approximations:
Atlas volume = 15m x 4m x3m (height, width, depth) = 180 meters**3
Atlas mass = 100 tons = 100000 kg

Atlas box density = 100000kg/180m3 = 555 kg/m3
density of water = ~1000kg/m3

Is it too much of a stretch to think that 1/2 of this box of mech parts is empty air so that it won't float in water? Given that only 10% of the weight is chassis, I don't think so.

The devs of Battletech way back when might have used some createve realism license, but I don't think they were totally physics anti-geniuses. I'd give them at least a little credit for not creating a very tech intensive Sci-Fi game without doing some very basic homework.

[Kartr]

Praetorians, on 13 June 2012 - 07:37 PM, said:

...and mass is still mass 100 tons is 20,000 lbs wich equals 640,000 newtons if i remeber correctly and mass is weight in zero g so no mater what its still 640,000 newtons...

O.o

Where to start...

2000lbs=1ton so 100 tons=200,000lbs and that's in pounds force (lbf) not pounds mass (lbm). Pounds force are based on pounds mass times the acceleration of earths gravity (32ft/s^2). This means that 200,000lbf is equal to 6,250lbm [200,000lbf/(32ft^2)].

Newtons are a measure of force and 1 newton = 1kg*(1m/s^2), so to convert it into the english measure you're using: 1kg=~2.2046lbm so 1 newton = 2.2046lbm*(32ft/s^2) = 70.5lbf. So 200,000lbf would equal 2,837 newtons, roughly.

On earth 200,000lbs would be 6,400,000 newtons, in orbit or on a planet with different gravity it wouldn't be 200,000lbs or 6,400,000 newtons because the weight would be different. In orbit that 200,000lbs would have no weight because there's no acceleration, on a different planet those 200,000lbs would weigh something completely different since you'd have to multiply 6,250lbm times the local gravity.

Deathjester, on 13 June 2012 - 07:59 PM, said:

I think you might have gone the wrong way with the unit conversion.
If 1cm^3 of water is 1g and 1cm^3 of steel is 15g, then if a 1m^3 of water is a ton then 1m^3 of steel is 15 tons.
Therefore density = 15g/cm^3 = 15t/m^3
As mass divided by density equals volume:
100t/15t/m^3 = 6.67m^3

Yeah its late here and I had a calculus final this morning so my maths are a little fried.

Major Bill Curtis, on 13 June 2012 - 08:00 PM, said:

Finally are all you guys talking about long tons or short tons? If you can't answer this, you've probably not considered everything there is about analyzing this fictional universe.

Neither, we're talking about tonnes which is mass as opposed to weight. Since weight is dependent on acceleration and acceleration is different on different planets and DropShips weight will be different so only mass makes sense.

[FaustianQ]

Kiriko, on 13 June 2012 - 07:56 PM, said:

15g/cm3 means that 1m3 of that material is 15t, so 15t/m3. (http://www.smartconv...calculator.aspx)
So a 100t cube of material, would be 6.67m3
(edit, got my math wrong)

According to this (http://hypertextbook...utherland.shtml) delicious steel is more like 8g/cm3 (or 8t/m3).
So it would be 12.5m3 of steel in 100t.

Like tanks, I highly doubt mechs are made completely of steel, so it makes no sense to use steels absolute number. Mechs will be composed of a lot more mass efficient material and empty space, so a fairer number is likely 15-20. What really doesn't fit about Battlemechs is size, not weight persee. I bet you could get something plausible if it's only 7m high and 100t, not 13m.

[rilianv]

Its science fiction.
90% of the stuff in science fiction is supposedly impossible in real life

[LordDeathStrike]

Frostiken, on 13 June 2012 - 02:42 PM, said:

What I don't understand is how mechs function on worlds with more than 1g. Is there anything in the lore that ever describes a high-gravity world that basically causes heavier mechs to crumple under their own weight?

Also, jumpjets. Jumpjets put mechs under a lot of acceleration - I honestly can't picture a heavyweight mech activating the jumpjets and dealing with the high G-forces from acceleration and landing without breaking things.

Under a mere 2g, which you'd experience after simply falling 20 meters, your Archer weighs 140 tons o_O

Naturally there'd be some wiggle-room in the 'maximum weight' of a frame just to prevent this, but realistically why are mechs limited to x tons of weapons then? Even aircraft can overload themselves but it means they can't pull as many Gs, so wouldn't a mech on a high-gravity world have to go out missing a lot of weapons, and shouldn't they be able to overload the frame on a low-gravity world?

The mind boggles.

people dont settle high G worlds, why? because you cant live on them. think about it, you can settle lower G areas like mars or the moon, but after a few years you couldnt go back to even a 1G world because the strain would be too much for your body.

on the surface of a 5G world a 200 pound man would weigh 1000 pounds and would be completely unable to move, and his organs would be under incredible strain. hence no mech pilot would be there either. mechs fight between 0G and 2G at most gravity would be a sain and solid theory. and yes at full 2 G an atlas would struggle to move, missiles and guns ranges would be cut in half, the pilot wouldnt be comfortable, but theres likely not much to fight over on a world where it would be hard to just live on the surface of let alone work and play.

[Steel Raven]

Is just a game guys, chalk it up to BT Magic.

Besides, makes more sense than some other giant robot stats. The Gundam only weighs in at 63 metric tons and has roughly the same size as a assault mech.

[Full Metal Monte]

Physics and math aren't "magic". The devs and authors for the MW universe have obviously made up a lot of shiznit. The basic tenet of Sci-Fi. But they didn't attempt to defy any known laws of physics due to laziness. (I'm sure they have, but prove it). For instance, you can't argue FTL travel won't be figured out in the next 1000 years. You can make up polymers and metals that are not currently possible. You can say that no machine guns that in the future can penetrate the outer layer of Mech armor past 90 meters. I guess.

The the OP asked a question that has not been been justified. I refute it.

[Nitrome04]

An Atlas alone wouldnt weigh more than 100 tons. they arent solid, thats how they have the cargo bays. but I do understand that even hollow it would look like more than 100 tons.

[Dataman]

[Killashnikov]

Battlemechs are not really all that massive, just maneuverable. The skeletons are foamed aluminium, armor coverage is thin by current standards only made of superior alloys. Musculature is plastic myomers etc. none of this is necessarily dense or massive.

In reference to an underweight mech being faster, if you redesign an atlas with less or no armor or weapons but leave a 300 engine in it, it could go faster... but only because it would be a 60 or so ton mech... Get a Dragon, it is cheaper and easier.

[Full Metal Monte]

Frostiken, on 13 June 2012 - 02:42 PM, said:

What I don't understand is how mechs function on worlds with more than 1g. Is there anything in the lore that ever describes a high-gravity world that basically causes heavier mechs to crumple under their own weight?

2G gravity would be a design concern for a mech, but dealing with pressure and vacuum is much more difficult. We have spacecraft in space and subs in the marianna trench, so operating in 2G isn't a stretch for the mech. Humans are squishy so a grav suit and bleeding eyeballs would suit my needs for suspension of disbelief.

[Scrawny Cowboy]

It's science fiction, stop poking at it.

[Deathjester]

Full Metal Monte, on 13 June 2012 - 10:46 PM, said:

2G gravity would be a design concern for a mech, but dealing with pressure and vacuum is much more difficult. We have spacecraft in space and subs in the marianna trench, so operating in 2G isn't a stretch for the mech. Humans are squishy so a grav suit and bleeding eyeballs would suit my needs for suspension of disbelief.

You're getting gravity and pressure mixed up. Subs in the Mariana trench still experience gravity the same as at sea level, they're just under an extreme ammount of pressure. So under higher gravity where it feels like you weigh twice as much, a compression suit, similar to what fighter pilots wear I believe, would stop the mech jockeys blood from pooling in their legs and feet. Under higher or lower pressure, a sealed cockpit would be fine unless it sprang a leak, say from a large laser (if that's the case you've probably got worse problems to deal with), in this case you'd want to be wearing a pressure suit, so depending on the environment something similar to what divers or astronauts wear.

[Full Metal Monte]

True dat. My brain was clear but my keyboard failed. I was trying to say that gravity is more of a problem for the pilot than than the mech. And that pressure/vacuum (and temperature) is more of a problem for the mech as the pilot is in a pressurized, temp controlled cockpit.

[Killhunger]

Heh, I love the people who are trying so hard to explain this stuff. The reality is that the whole idea is complete unrealistic nonsense.

But... huge walking tank like robots blowing things up is awesome! Technical accurate explanation = unnecessary.

Here is where Battletech fits in the scale of realism in comparison to awesome.

Realistic............................................................................Battletech.....Awesome

Kind of irrelevant when you think about it.

Why are the gun ranges so damn terrible so far in the future? Why? Because close up destruction is awesome. Shooting at ants (Targets at extreme range) = Not awesome.

I think I covered it. No math needed.

- Kill

[Justin Wolf]

Kartr, on 13 June 2012 - 04:19 PM, said:

Why would they be? Considering how dense modern armor has to be to defeat modern weapons, future armor would be much more dense and correspondingly heavier. No that's not something that can be changed using "future tech' to make it less dense/heavy as armor effectiveness is related to density.

Also if this were the case then every time a 'Mech used the intakes to fill the 'Mech with water and increase its density it would also be increasing it's mass/weight at the same time. Also you have to ensure that every 'Mech has enough open internal space in order to fill it with sufficient water to increase the density to the required amount. Occam's razor suggests that the 'Mechs are simply much heavier than the official "weight" rather than some complex system that allows them to function properly.


Yes I'm quite familiar with the differences between tons, tonnes, etc., your point?


Tech Manual is wrong, the math (volume/mass) shows that it is physically impossible for BattleMech "tonnage" to be based on the metric system.



'Mechs are cooled by heatsinks, which are by their nature connected to the outside of the 'Mech. Heatsinks that are not connected to the exterior would simply heat up the interior of the 'Mech and do no good. Water merely needs to run across the heat exchangers on the exterior of the 'Mech.

Also you would not simply want to let water run into the interior of the 'Mech because that would allow material deposits in the water to enter the 'Mech and clog it with gunk. It would also likely lead to corrosion on critical components and possibly shorts if it comes into contact with any uncovered wiring.


Care to explain how armor with the same density or less density, which is also much much thinner than current armors is better capable of stopping enemy weapons fire?

Well there are different kinds of armor in reference to the density statements. For instance ancient Samurai wore silk arrow shields on their backs that looked like lil silk sissy capes, proved to be very effective at dispersing the energy imparted by the arrows, obv a mechs not worried bout arrows, but like you must know as a tank killer, Composite armors are more effective then "denser" armours, they are capable of dispersing more energy for generally less weight. Thats an axiom even the Romans knew all their shieds were basiscally ply wood with something reinforcing the sides. hell our interceptor armour is a composite, Super Kevlar, Ceramic, Super Kevlar. The Abrams uses ablative armour over its hull armour, most folks forget the hull of the Abrams is rolled whole as a solid piece of armor, then they add the abblatives and now the new armour coming out so again while there are dense portions the composite desighns are bulkier but tend to weigh less, the Abrams is far better at stopping incoming rounds than WW2 Era tanks that were much heavier.

[Boymonkey]

Yawn ...I just got up . Iam glad I made an interesting thread and hey thanks for the maths lessons everyone