158 replies to this topic

[Ray Mason]

The point is that the mass cancels out so in a situation when you're not slipping it doesn't matter (the forces are in equilibrium). Heavier mech would crash harder due to the mass but as longs as it's not slipping it will be ok. As you can see it's not so difficult to have a "driving" system limit your acceleration as you go, basically preventing you from slipping, it would do the math on the fly.

As to the "100T would make the ground crumble", the taller and heavier you are, the bigger your feet are. The feet are designed so that their size mitigates the weight. If you made yourself proportionately larger and heavier the pressure of your feet would be identical. Bridges are something completely different as they are built on a limited number of pillars. A road is not limited in such way. And as it's been mentioned, spikes can be used to increase friction.

[Nik Van Rhijn]

In the "fluff" it often says that the main roads in cities and inter city highways are constructed with mech traffic in mind. I think turning circles should be linked to speed, bearing in mind that mechs can "lean" into turns using their gyros for balance. Mechs should be able to assess the forces involved and "govern" your speed to prevent slipping normally.

[Fachxphyre]

Dlardrageth, on 30 November 2011 - 11:07 PM, said:

Walk != run. To my knoweledge noone even suggested a given mech shopuld skid/slip while going at leisurely patrol pace. Yeesh, why do I get the impression most/half the people already don't get the point of the rule/mechanics in question again? It is the same as a friggin' tank in real life. No, a tank going at 10 kph isn't likely to skid. One going 60 kph much more so.

So if this would become a game mechanic, your light Mech going at 20 or 30 kph won't be affected, if it goes 110+ kph though and you think you can run slalom without consequences, well, say hello to skidding into the next building and eventually even throught it. And no, I really don't think many light Mech pilots use super glue to counter that, not even hardcore munchkins.

actually, if you stop and consider the actual physics involved, as well as some basic engineering, tanks and mechs are basically nothing alike from this standpoint. tanks had to be deliberately designed to reduce ground pressure (the distribution of the mass of the vehicle over the "footprint" of the vehicle) in order to be able to perform in sandy or swampy environments without digging their tracks in and simply becoming an expensive armored gun emplacement. if it helps, picture a human wearing snowshoes.

now, on the other hand, we have a bipedal robot that may well weigh more than a 60 ton abrams MBT. it has partially articulated foot pads (thus allowing it to run). i invite you to take a quick jog around whatever building you live in. notice that only a portion of one foot is actually in contact with the ground at any given time (and you're totally out of contact with the ground for a bit as well), and if you're really booking it you're probably only making contact with the balls of your feet and toes. this has the effect of drastically increasing the ground pressure (the effect ot 2.5-3x bodyweight divided by the reduced area of a portion of one footpad).

The listed ground pressure of an M1A2 abrams tank is roughly 15 psi (roughly 100kPa). in comparison, let's use a bipedal figure, me. i weigh 100kg and wear size 13 shoes (US sizing). breaking out a ruler to get rid of idiotic measurement systems, the approximate area of the ball of my right shoe is roughly .01m (10cm by 10cm) which is a conservative overestimate. now to get the vertical force we take the accepted measure of roughly 2.5 times my body weight (250kg) multiplied by the gravitational constant (9.8m/s^2), yielding 2450N (this represents the peak force of my bodyweight landing on the foot, which gets into more complicated acceleration measurements which i want to skip. so 2450 Newtons of force divided by .01m of area gives us a whopping 245,000 Pa, or 245kPa, well over the ground pressure of a tank!

If I were to be concerned about anything, it wouldn't be mechs sliding around, it would be their feet punching right through road materials that aren't meant to take those loads. And as for the people talking about stocking feet and linoleum vs metal and concrete, go look up some standard coefficients of friction and stop making me doubt humanity

[Fachxphyre]

Datum, on 16 March 2012 - 09:41 PM, said:

Force of friction is equal to the friction coefficient times normal force.
F(fr)=Coef(fr)*N
(N being Normal force being Mass * Gravitational Acceleration)
So F(fr)=Coef(fr)*Mass*Accel(grav)
Force=mass*accel, so accel=force/mass
assuming a flat surface, we can substitute the force of friction to be accel=[Coef(fr)*Accel(grav)*mass]/mass
the masses cancel out and we have the equation for maximum acceleration:
Accel=Coef(fr)*Accel(grav)

On earth, multiply your friction coefficient by 9.8m/s^2 to get your max acceleration. Say my rubber shoes have a coefficient of .4 on carpet. I multiply that coefficient by 9.8m/s^2 to get 3.92m/s^2 of acceleration before I slip.

Now, these battles are not going to be on earth, so we get to have the fun of using different local gravity for this equation.
Say on Eaglesham (for the sake of argument) we have an 8m/s^2 grav constant. Your mech is sprinting on concrete with a static friction coefficient of .7 (mech cleats or something). We multiply the two and get a max accel of 5.6m/s^2 before slipping.
Let's say we have a Jenner sprinting along at 33 meters/second, pulling as tight as it can go without slipping with said max accel of 5.6m/s^2. Assuming a circular turn, it has a max turn rate of about 9.7 degrees/second. Depending on the surface that can vary from a bare minimum of steel-on-ice 5.5 degrees/second to cleated-talons 15 degrees/second at full speed. At lower speeds we have a much greater rate of turning, obviously.

Now, this puts fast mechs into a point-to-point run if they are to stay upright, while slower mechs are free to turn with impunity, unless on ice or giant air-hockey tables.

Now, these could be tweaked from planet to planet as well as surface to surface. A planet with stronger gravity will, in fact, allow for tighter cornering and more responsive throttle (thought it may also limit top speeds mechanically). Conversely, one with weaker gravity, like on a moon, means slower turning to the tune of Blue Danube.

Also, depending on the mech's foot, you could potentially purchase different treading "modules", like buying mech cleats that improve off-road grip at the cost of worse concrete performance, or vice versa with a flat rubber sole or something.

Perhaps with the mechs, you could have an electronic limiter to turn speeds and acceleration rates, just so long us madmen can override it and drift our flocks of Jenners

If done right, this could add more environmental variety to the different planets as well as tactical choices.
-My two cents

and there humanity goes and TOTALLY REDEEMS ITSELF! liked, seconded and so forth, further proof that some people might have remembered high school physics.

[Bluey]

one word

LOL

[cinco]

change the poll option. this has nothing to do with realism or arcade.

in fact, it's more stupid and arcade to expect that there would be ground without any fiction or that mechs don't have some type of frictional material under their feet.

Fachxphyre, on 17 March 2012 - 02:01 PM, said:

and there humanity goes and TOTALLY REDEEMS ITSELF! liked, seconded and so forth, further proof that some people might have remembered high school physics.

and then you remember we're talking about giant robots fighting on different planets and thus mechs would obviously have to be designed not to slip. derrr...

Edited by cinco, 17 March 2012 - 02:14 PM.

[Naughtyboy]

well..ofc, when you run it should affect your running if you take a 90 degree turn in full speed..like with a car today..

[Insidious Johnson]

Caballo, on 01 December 2011 - 03:18 PM, said:

Have you ever seen the marks a rim w/o tire leaves in the asphalt? well, imagine a 20 ton battlemech pushing it's whole weight on one foot when moving, I haven't got to make any maths to assure it will leave a mark.

Asphalt, concrete, etc are not granite solid. they are conglomerates, so if you hit them with 50 tons in a 10m2 square, i doubt the surface would take that brutal pressure w/o brokening down, Ergo the mech will not "Slip" on those surfaces, it will thread them.

More than that, on hot days asphalt just literally melts. It is a petrolium based suspension of oils, tars, and gravel. But this stuff in BT is ferro crete. That should cover the streets wanting to act like sticky soup on a hot day with PPC's blaring. The maps in MW4 had 'footfalls' i.e. different effects could be assigned to different textures and then used on a map. I made a volcanic map at one time and spent time researching how to do it. So you step in lava, the temperature rises, you step on rock, you hear it crunch, you step on packed dirt, you hear a thud. I'm sure there is something better in MWO.

[Ryuu Tetsuhara]

bishop, on 03 March 2012 - 01:48 PM, said:

First of all this poll is absolutely stupid, just because it is or isn't canon doesn't mean it's unrealistic; we need to keep in mind that mechs do not exist and battletech is not the all holy bible on what would be realistic for a 100 ton mech.

Now think about this, is a 100 ton mech slamming his foot down into concrete likely doubling the amount of force being applied to the concrete going to simply slide along like a gundam? Absolutely not. And to that point, if sliding is in any way shape or form in MWO upon release; I will be severely disappointed because if I wanted to slide around in a building sized steel robot then I would go play armored core.

Also we can look to modern day tanks for the answer to this, going 45 miles per hour they do not simply slide along if they stop.

Agreed, nothing more to say about this ...

[David McCarthy]

Mech Engineering student speaking here

I think, it would depend to a large extent on whether your concrete was designed to take mech weight without deforming. we know some, like solaris underground tunnel system, probably are. others, probably not.

if your concrete deformed an appreciable amount, then, I would say, no. no skidding. but if it didn't, then most definitely yes, you would skid.

[Mason Ventris]

Slip you ******* SLIP!!!

[HighlandWolf]

if youre trying to take corners at high speed, you pay the price if you cant handle the mech..or reverse for that matter at high speed..though i'd rather think the engine might have something to say about that...mechs have grip on the bottom of the feet ..theyre not shiny smooth..but still..it should be there to some degree i think

[Rigamortice]

Dont forget these Mechs are huge weight a heep, concrete and asphalt will buckle and break prior to a slide. Now in a snow or ice yes I say slip.

[Carl Wrede]

We should absolutely have the skidding!

[Ravana]

If they implement different ground types will they be taking into account that certain streets in a city are designed for mechs? In the books they listed streets that were specially reenforced for mech travel. Those that weren't would get torn to shreds as the mech walked on them. (You see this even in modern days. Roads designed for heavy semi travel. Or roads saying that only 5 ton trailers and below are allowed) If they state that all roads in a city will be for mech travel then yes I can see slippage coming into play. I would also expect this from ice covered terrain that can withstand the weight of a mech. However I would also expect that mech designers would compensate for this with the gyroscope in the mech such as leaning into turns. A tank can't lean into a turn, hence why it skids. If not all roads are designed for mech travel I would expect that you would have more sure footing on them due to you sinking in with each step, like walking on sand, but I would also expect that you would not be able to go as fast due to the surface moving under you.

Edited by Ravana, 26 March 2012 - 08:13 PM.

[LordDeathStrike]

forget pavement, what happens on cold worlds when its icey or theres freezing rain? benny hill mechs? (aka chain slipping flailing and breakage of assbones)

[VarietyOfCells]

LordDeathStrike, on 26 March 2012 - 08:26 PM, said:

forget pavement, what happens on cold worlds when its icey or theres freezing rain? benny hill mechs? (aka chain slipping flailing and breakage of assbones)

Actually, do you know what people do to create traction on ice? They put metal links on the soles of their shoes. Know why? Metal melts ice, so the metal diggs in deeper creating traction. A mech with treads on its feet will have little trouble on ice.

Also, I agree with everyone who says tanks and mech are different. The surface area and center of balance is all very different. Mechs won't slide, and I'm sure would have all manner of gyros and programs to keep them from sliding. Even cars now days can tell when there's less traction.

Edited by VarietyOfCells, 26 March 2012 - 08:57 PM.

[That Guy]

wile i must admit that i am about to sin (posting with out reading the whole thread), but shouldn't we be more worried about mech slippage on loose and rocky ground, rather than firm grippable ground? try to walk up a large hill made of loose gravel. now try running.

in my not-a-physist-mind wouldnt a mech (or any body) be more likly to slip if the surface is loose? like highly compressed dirt with lots of loose debris on top?

[William Petersen]

I always thought that was kind of a ridiculous rule. It's a 20-100 ton machine putting all that weight into two concentrated pressure points, how would that *not* sink in and make 'foot prints' on roadways?!