What combat role could a mech play on a real battlefield?

[OutOnTheOP]

 

Explicitly, out of the second citation:

 

"...driving moment. In this particular case the muscle's contribution is the least of the three. The forward deceleration of the knee joint (caused by extensor deceleration at the hip) and the gravitational forces contribute about 80% of the moment required to accelerate the shank forward. This will explain the limited EMG activity of the knee extensors (quadriceps) at this time. During the latter half of swing the inertial load reverses; and also do the three components. They all contribute in varying degrees to the deceleration of the shank. However, in this case the muscle moment contributes about 80% of that re- quired. This is in agreement, in normals,with the considerable hamstring activity seen during the latter half of swing, and also explains why an above-knee amputee requires a shock absorber in his knee mechanism to decelerate his prosthetic limb..."

 

So, 20% conservation of energy during walking is understated, but I chose this for the running torque because this can be, theoretically, considered the "running peak" torque.

 

You seem to be overlooking this part:

During the latter half of swing the inertial load reverses; and also do the three components.

[Malleolus]

You seem to be overlooking this part:

 

What, that it says during the driving portion that gravitational forces perform 80% of the work, then when the gait is reversed muscles do 80%? And I said that 20% of the energy can be attributed to external forces independent of the prime mover, and that you could downsize the engine more than 20% but since half the gait is under 80% power by the prime mover this can be considered the "peak running" torque and the motor, I choose, should be sized to run at this load?

[Malleolus]

Ok, so the walking gait wastes a bunch of energy, but out of that energy wasted, 70.8% is recovered. And? That's still a bunch of energy wasted.

 

How much energy, excluding regenerative braking that isn't included in most vehicles, is retained in a tracked or wheeled vehicle in between stops, starts, accelerations, and decelerations? That would be... none. Seriously, you don't know what the hell you're even saying.

[shagrat]

That is why vehicles need to burn fuel... if they were as efficient as humans or horses a liter of Red Bull or a bag of oats would do wonders!

Edited June 16, 2014 by shagrat

[shagrat]

Hmm, what is the percentage of energy (from burning fuel) wasted in heat when burning it? How much energy created is then wasted when braking? So it is more than 60%??? So the 30% is more efficient even with tires, perfect concrete road and wind channel optimized chassis? Guess so...

[shagrat]

To give you an idea:

http:// http://www.fueleconomy.gov/feg/atv.shtml

"Only about 14%-30% (...) is used to move it down the road"

I guess an APC, IFV or Tank is far worse...?

So please don't try to fool people in believing a vehicle is more energy efficient than an animal or human.

I could partially agree with the acceleration arguments, but now it gets utterly ridiculous.

A combustion engine plus a non-hybrid wastes a lot more energy than any walking being on this planet!

[shagrat]

...and considering an M1 A2 Tank with its Turbine engine(!!!) it is so devastating energy inefficient it hurts!

The waste heat is a real pain so can't even ride on the tanks top and the fuel efficiency so "good" that it mostly waits for the tankers... 3 Gallons per mile?!

[Bushmanni]

With wheels on I can do about 20km/h on average compared to 7km/h on legs. That's with additional weight of the bike and friction of the bearings and wheels. I don't know if that gives any kind of representative figure for the efficiency of wheeled and bipedal locomotion but I'd like to hear what you guys think of it.

[shagrat]

How fast are you on a field? In a lightly packed wood? On a rough hillside? It's not speed it's agility...

[OutOnTheOP]

What, that it says during the driving portion that gravitational forces perform 80% of the work, then when the gait is reversed muscles do 80%? And I said that 20% of the energy can be attributed to external forces independent of the prime mover, and that you could downsize the engine more than 20% but since half the gait is under 80% power by the prime mover this can be considered the "peak running" torque and the motor, I choose, should be sized to run at this load?

 

You're reading their message wrong: it doesn't mean that it takes 80% muscle to walk backwards... it means that during the "up" phase of the stride, 80% of the power is provided by muscle, 20 by inertia assist. During the "down" phase of the stride, 80% is gravity, 20% muscle. That says nothing about the overall efficiency of the stride, only about the relative use of muscle during select PARTS of the stride

[OutOnTheOP]

How much energy, excluding regenerative braking that isn't included in most vehicles, is retained in a tracked or wheeled vehicle in between stops, starts, accelerations, and decelerations? That would be... none. Seriously, you don't know what the hell you're even saying.

 

How much of the energy you spent accelerating yourself to a dead sprint is conserved after you come to a stop? ALSO none.

[OutOnTheOP]

Hmm, what is the percentage of energy (from burning fuel) wasted in heat when burning it? How much energy created is then wasted when braking? So it is more than 60%??? So the 30% is more efficient even with tires, perfect concrete road and wind channel optimized chassis? Guess so...

 

And now you're arguing about the efficiency of the powerplant, NOT about the efficiency of the motive method. We have to assume, when comparing the efficiencies of wheeled/ tracked motion versus legged, that both are drawing power from the same powerplant technologies. If you can make "myomer" muscles to drive legs, you can also use them to drive "pistons" in a reciprocating engine.

[shagrat]

Nope! Read it again and in full: the wasted energy OVERALL is 80%plus... 60% of that 80% from the engine alone...

[OutOnTheOP]

To give you an idea:

http://www.fueleconomy.gov/feg/atv.shtml

"Only about 14%-30% (...) is used to move it down the road"

I guess an APC, IFV or Tank is far worse...?

So please don't try to fool people in believing a vehicle is more energy efficient than an animal or human.

I could partially agree with the acceleration arguments, but now it gets utterly ridiculous.

A combustion engine plus a non-hybrid wastes a lot more energy than any walking being on this planet!

 

I call BS. Apples to apples, here. You have to assume, when making comparison, that the power plant technology is available equally to walkers or conventional vehicles.

 

That said, a cursory look at an exercise calculator website (https://www.healthstatus.com/perl/calculator.cgi) indicates that 60 minutes each of the following exercises have these caloric (energy) requirements:

 

14-16 mph cycling, 960 kcal

4 mph walking, 468 kcal

12-14 mph cycling, 792 kcal

12 mph running, 2,028 kcal

8 mph running, 1,224 kcal

 

This means that, in terms of energy efficiency, as measured in kcals per mile (total calories burned in an hour divided by distance covered in 60 minutes) you get:

 

13mph cycle= 61 kcal/mi

12 mph run = 169 kcal/mi

 

15mph cycle= 64 kcal/mi

4mph walk= 117 kcal/ mi

8mph run= 153 kcal/mi

 

That means you can move at the same speed on a bicycle for 37% as much energy as required to run that speed, or you can move the same distance THREE TIMES FASTER on a bicycle for approximately half the energy expended even to walk it- which is much more efficient than running, as has been pointed out.

 

And all this is based not on a machine designed to move wheels, but rather on a machine designed to (rather inefficiently) transfer energy from a machine designed to walk (your legs) into power to drive wheels. So it's STILL not quite apples-to-apples, because there's an unnecessary level of mechanical friction (all the gears and axles of the bike in addition to the inefficiency of your legs) working against the bicycle.

 

Are you QUITE SURE walking is as efficient as you think it is?

Edited June 16, 2014 by OutOnTheOP

[OutOnTheOP]

Nope! Read it again and in full: the wasted energy OVERALL is 80%plus... 60% of that 80% from the engine alone...

 

Gee, I wonder why they're that inefficient?

 

the percentage of energy (from burning fuel) wasted in heat when burning it?

 

Oh, RIGHT! The POWERPLANT is inefficient. That has NOTHING to do with the drivetrain. And if you accelerate to a sprint, then come to a stop, exactly as much energy is wasted in deceleration as is wasted to do the same on wheels without regenerative braking: ALL of it.

[OutOnTheOP]

How fast are you on a field? In a lightly packed wood? On a rough hillside? It's not speed it's agility...

 

With wheels exerting the same ground pressure as the human foot? Exactly the same. Now, if I need to climb over some REALLY bad terrain, sure... but "really bad terrain" for a 2-wheeled, human-scale bicycle != "really bad terrain" for a low-stance 20+ ton vehicle. Brush that would stop a human bicyclist is inconsequential to a HMMWV or tank.

[OutOnTheOP]

To give you an idea:

http://www.fueleconomy.gov/feg/atv.shtml

"Only about 14%-30% (...) is used to move it down the road"

I guess an APC, IFV or Tank is far worse...?

So please don't try to fool people in believing a vehicle is more energy efficient than an animal or human.

I could partially agree with the acceleration arguments, but now it gets utterly ridiculous.

A combustion engine plus a non-hybrid wastes a lot more energy than any walking being on this planet!

 

No one, repeat NO ONE has argued that current-technology powerplants are more efficient than animal metabolisms. We have argued that the MOTIVE TECHNOLOGY, IE DRIVETRAIN, IE LEGS are inherently less efficient than wheels. If you use animal metabolism to drive wheels instead of legs (like, oh, I don't know, a BICYCLE?), it is much more efficient than using your legs to walk. Same powerplant efficiency, better drivetrain efficiency.

[Malleolus]

You're reading their message wrong: it doesn't mean that it takes 80% muscle to walk backwards... it means that during the "up" phase of the stride, 80% of the power is provided by muscle, 20 by inertia assist. During the "down" phase of the stride, 80% is gravity, 20% muscle. That says nothing about the overall efficiency of the stride, only about the relative use of muscle during select PARTS of the stride

 

No, you are reading it wrong. It is saying that when the stride reverses, as the cycle of gait reverses the direction of the leg to push the body forward, the legs reverse direction... it's WALKING. Legs don't constantly move forward, their direction reverses, cycles, every step. Do you actually READ things, and think about it before you reply? Human gait constantly reverses, this doesn't mean they walk backwards.

Edited June 16, 2014 by Malleolus

[Malleolus]

With wheels on I can do about 20km/h on average compared to 7km/h on legs. That's with additional weight of the bike and friction of the bearings and wheels. I don't know if that gives any kind of representative figure for the efficiency of wheeled and bipedal locomotion but I'd like to hear what you guys think of it.

 

Wheeled vehicles are more efficient on extremely hard surfaces. In fact, a modern train is over 2 orders of a magnitude more efficient than walking... on hardened steel rails. This phenomena is because very hard surfaces reflect forces well, requiring little work to move. The softer the surface, efficiency of wheeled vehicles drop dramatically. Even on dry, but soft soil, like driving on packed soil, efficiency drops below that of a human. In situations where you consistently have very hard surfaces and properly maintained vehicles, it's more efficient. This isn't true for most cases, especially in the military.

 

This is also why blacksmiths anvils are through hardened.

[Malleolus]

Sha, he's being a twit, but human muscles are energy inefficient, as is metabolism. Fat has insane energy density, and produces glucose that cells burn with oxygen that produces energy and acids. If I remember correctly, net oxygen usage in humans, which is a byproduct of energy use, is over an order of a magnitude more than a wheeled vehicle. HOWEVER, this does not compare to human gait. Human GAIT is very efficient and uses several mechanisms to store and expend forces while walking rather than constantly use muscle force to provide constant power. Fuel also improves the longer the hydrocarbon chain it consists of, which is burned with oxygen to produce carbon monoxide and dioxide. The longer the chain, the more energy is available when it is split and oxidized.

Edited June 16, 2014 by Malleolus

[Exorcet]

Wheeled vehicles are more efficient on extremely hard surfaces. In fact, a modern train is over 2 orders of a magnitude more efficient than walking... on hardened steel rails. This phenomena is because very hard surfaces reflect forces well, requiring little work to move. The softer the surface, efficiency of wheeled vehicles drop dramatically. Even on dry, but soft soil, like driving on packed soil, efficiency drops below that of a human. In situations where you consistently have very hard surfaces and properly maintained vehicles, it's more efficient. This isn't true for most cases, especially in the military.

 

This is also why blacksmiths anvils are through hardened.

Wouldn't the penalty apply equally? With soft surfaces, energy is wasted deforming the surface. Legs act just like wheels/treads in this regard. Walking through deep snow can be a pain, yet tracked vehicles can get through it pretty well.

[Malleolus]

Wouldn't the penalty apply equally? With soft surfaces, energy is wasted deforming the surface. Legs act just like wheels/treads in this regard. Walking through deep snow can be a pain, yet tracked vehicles can get through it pretty well.

 

You'd think, and when I get home I'll cite if you want, but human gait has evolved to walk through soil/etc and not on hard surfaces... This is why it has so many force recycling means, they recycle force consistently. The force lost to shocks on soft soil is just that, lost, muscle recycles this. A penalty accrues, but not nearly as rapidly as wheeled/tracked vehicles. How well, actually? Yes, it can, but at huge fuel consumption unless the tracks are designed to give the greatest purchase on snow... then you can argue snow shoes.

Edited June 16, 2014 by Malleolus

[OutOnTheOP]

No, you are reading it wrong. It is saying that when the stride reverses, as the cycle of gait reverses the direction of the leg to push the body forward, the legs reverse direction... it's WALKING. Legs don't constantly move forward, their direction reverses, cycles, every step. Do you actually READ things, and think about it before you reply? Human gait constantly reverses, this doesn't mean they walk backwards.

 

You DO realise you just said the EXACT same thing I did, only with different words? The point is that during half the stride cycle, it's 80% gravity. During the other half (the "up phase I mentioned; when the leg is lifting your mass up to the top of the pendulum cycle), the muscle is doing 80% of the work. Either way, you were trying to say that gravity does 80% of the work for the entire stride, and that is entirely incorrect.

[OutOnTheOP]

Wheeled vehicles are more efficient on extremely hard surfaces. In fact, a modern train is over 2 orders of a magnitude more efficient than walking... on hardened steel rails. This phenomena is because very hard surfaces reflect forces well, requiring little work to move. The softer the surface, efficiency of wheeled vehicles drop dramatically. Even on dry, but soft soil, like driving on packed soil, efficiency drops below that of a human. In situations where you consistently have very hard surfaces and properly maintained vehicles, it's more efficient. This isn't true for most cases, especially in the military.

 

This is also why blacksmiths anvils are through hardened.

 

And yet walking magically allows that same surface to bear higher transverse loads, applied in relatively sharp impulses, rather than the steady push of a track or wheel? There's some interesting physics in your little world...

[OutOnTheOP]

Sha, he's being a twit, but human muscles are energy inefficient, as is metabolism. Fat has insane energy density, and produces glucose that cells burn with oxygen that produces energy and acids. If I remember correctly, net oxygen usage in humans, which is a byproduct of energy use, is over an order of a magnitude more than a wheeled vehicle. HOWEVER, this does not compare to human gait. Human GAIT is very efficient and uses several mechanisms to store and expend forces while walking rather than constantly use muscle force to provide constant power. Fuel also improves the longer the hydrocarbon chain it consists of, which is burned with oxygen to produce carbon monoxide and dioxide. The longer the chain, the more energy is available when it is split and oxidized.

 

 

You know what? Get stuffed. You are a brick wall. NOTHING gets through to you, and your debate technique consists of:

 

"nuh uh! Your math is bad! Here, I'll disprove it by posting misleading and mis-applied sound-byte quotes cherrypicked from random websites, without actually mathematically or scientifically backed work presented! I'll mislead you by insisting evolution always picks the most efficient engineering solution! Animals are more efficient at creating energy than internal combustion engines, unless you try to argue that the reason animals are so much more efficient overall is more efficient energy processing, in which case I'll TOTALLY reverse what I JUST SAID, and insist that the gait is what makes them most effficent, despite having JUST been shown that the energy required to make the same movement is lower when the same muscles are driving wheels instead of legs. The totally-efficient animal metabolism processes are now inefficient when it's convenient to my argument, even though it has nothing to do with anything in the debate about powertrain efficiency, but MECH IS BEST!".

 

I guess they will be best, if they equip the mecha with Reality Shielding as efficient as that you have employed.

 

I'm done arguing this. A whole PARADE of folks have come through and posted on why this is not practical or efficient in comparison. We have shown you the math. We have shown you real-world, apples-to-apples comparisons. MOST of the posters here were downright dismissive, and blew off the very idea as a joke. I at least tried to enlighten you on the reasoning behind it.

 

You cannot, or do not want to, get it through your head- nor do you even dignify it with a real response. You claim "omigawd, your maths are SO wrong", but never actually disprove them. Everyone that has posted on here, other than you two, has agreed it's a silly idea, mechanically speaking.

 

You two are fanboy zealots, and no amount of reality will change that. I see my effort is wasted, and therefore withdraw from this entire asinine endeavor. I have no doubt that you will pat yourself on the back at your "victory" in the debate.

Edited June 16, 2014 by OutOnTheOP