Malleolus

BTW... I'm baaaaaack

Conveniently, I'm an armorsmith. Joint protection is not a major hurtle, and fully armored joints were commonplace in the later suit's, just look at the Maximillian styled armors. This is a suit, there's flesh, muscle, and fat in the way. If anything it'd be far easier to armor a mech where the armor is integral.

That's hilarious, yet sad at the same time... so no one else can be civil?

Wow, how did the appearance of mods shut this down?

Sorry boss man

The only person that put forward actual debate was ShuRugal, but human gait is vastly more multidimensional than what he covered, and you know what? He took it for what it is and I'm going to trust that he ACTUALLY IS GOING TO READ the information put forward. I've been working on biomechatronics for 15 years twit. If he still has consternation after reading it, I'm perfectly fine with that.

Thank you. All peer reviewed, scientifically backed research from accredited sources I would expect to be beyond your capacity to understand. As previously stated, you saying it's an apples to apples comparison means you have no idea what you're saying nor attempted, or lack the capacity to understand, that you are making an assumption about a multi-bodied non-linear system based off a linear single bodied system. I never brought in metabolism and the actual efficiency of human muscles, that was another person. I've been taking about the mechanics of human gait.

Ok, let's make this as simple as possible... yes, at any one time 80% of ONE HALF the cycle is powered by the muscles. Meaning one leg is under 80% power half the time. My little world is called reality, how about you?

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.

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.

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.

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.

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.

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?

It's actually a very fun read, and yeah, but I did say shits and giggles.

Hmmmm... ok. Let's just get this out of the way, since you intend on being an ass rather than being at least partially respectful: you are comparing a single body linear force flow to a multi-bodied nonlinear force flow. This is, well, stupid as hell. Where you did the most basic force calculations, which out of respect I didn't pick apart because you didn't show your work on single order levers, but I couldn't do a decent force flow diagram of human gait on three pages of this forum. But, why don't we just go ahead and do a little citing, as requested. http://reedlab.eng.usf.edu/publications/handzic2013validation.pdf Just to save you the trouble: "The PDW model and human horizontal reaction forces switch from resisting to assisting forward progression at the same time during stance. However, the maximum forces are slightly different. The PDW model’s horizontal reaction forces have a maximum backward force of 48 % of the walker mass at heel contact and a maximum forward force of 37 % of the walker mass at toe off. The human data shows smaller forces: maximum backward force is 23 % of the body mass at 8 % of the gait cycle and the forward force is 26 % of the body mass at 53 % of the gait cycle." And, btw, there's this too: http://jeb.biologists.org/content/213/5/790.full Saving the trouble, again, is: Recovery of potential and kinetic energy Walking is characterized by a pendular exchange of gravitational potential and forward kinetic energy during each step (Cavagna et al., 1977). We suspected that walking digitigrade might in some way decrease the transfer of kinetic and potential energy. We found that the mean percentage recovery was 70.8±6.1% (mean ± s.d.) when the subjects walked with plantigrade posture and 64.8±6.4% when they walked with low-digitigrade posture. The mean difference in percentage recovery for the eight subjects was 6.0±5.8% (P=0.025, one-tailed). Thus, walking with low-digitigrade posture appears to reduce the pendular transfer of kinetic and potential energy. and https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=12&cad=rja&uact=8&ved=0CG8QFjAL&url=http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F22475510_Joint_torque_and_energy_patterns_in_normal_gait%2Ffile%2F79e4150de3fb249715.pdf&ei=qHaeU5X7OqTJsQTbyILYDA&usg=AFQjCNFew8bG96aiEjLerGLDNeasb5WOIg&sig2=GAcVEwKfuUrASiUqnnN43w&bvm=bv.68911936,d.cWc 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 (quadri- ceps) at this time. During the latter half of swing the inertial load reverses; and also do the three com- ponents. 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 mecha- nism 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. Now, on to the efficiency of compliant actuators vs. stiff actuators ftp://xsee.ene.unb.br/Projects/rleg/protese/materiais/variable%20stiffness%20actuators/compliant%20actuator%20designs.pdf "Walking and running robots: an actuator with adaptable compliance extends the capabilities of these devices. The setting of the compliance can be used to maximize the amount of energy, which can be stored during touchdown of the feet and released during push-off. In addition, by varying the stiffness of the joints, the natural The equilibrium position of a compliant actuator is defined as the position of the actuator where the actuator generates zero force or zero torque. 82 IEEE Robotics & Automation Magazine SEPTEMBER2009" This simple statement alone says the greatest benefit of compliant actuation. Tuneable compliance, and with more elaborate schemes than SEA, offer higher fidelity. So, again, one can either downsize the motor to running torque with the compliance in mind, or have extremely extended peak powers, and still save on energy. I cannot legally post information that I have purchased, nor my own work. These tidbits should be enough to sate your thirst, however. Just for shits and giggles, high beta fusion reactor from lockheed martin: "Public reactions describe the announcement of their activities on nuclear fusion remarkable, because Lockheed Martin doesn't usually make public announcements about Skunkwork projects unless they have a high degree of confidence in their chances of success. The developement timeline indicates plans to have a prototype 100-megawatt nuclear fusion machine of Lockheed Martin tested in 2017, and that a fully operational machine should be grid-ready ten years from now."

Shurugal, the dynamics of human gait cannot be compared in any but the most basic way. Inverted pendulum also accounts for the majority of the force that lifts the leg vertically. All the data is experimentally derived, theoretically the efficiency numbers are greater still. Like it or not, in actuator efficiency alone you can undersize your motors by over 30% over stiff actuators if you use antagonistically oriented variable inductance actuators.

I can't speak for Endo steel per say, but I'd point you to stacked electro-active polymer actuators and iron matrix nickle-coated carbon fiber metal matrix plating.

Uh, just on a side note here, look up high-beta fusion reactors.

All your math is flawed, when applied to a walking system. These things are true for tracked and wheeled systems (except the segwey), but not true for walking systems. Tracked and wheeled systems require power to be delivered constantly to both sides (with exception to pivoting the tracked system). This is not true for a walking system, especially a bipedal system. Bipedal systems use, primarily, 2 systems to decrease load requirements, or increase efficiency, that is not available to any other system. This is the inverted pendelum and off-center gravity, or "falling forward gait", as well as your muscles being compliant actuators. I will reference the most simple mechanical version we have for the majority of this, a series elastic actuator, but will mention the most appropriate at the end. First of all, we'll work off your following work: "Now, since we've got two legs to spread the load over, we can say that each leg only needs to provide 90,000 N of force 90,000 Nm on a 1-meter lever. But, each leg consists of 2 levers which must both produce that torque at the same time, so our total torque per leg... 90,000 * 2 = 180,000 Nm. Right, so to get out AGT1500 to output 180,000 Nm, we need to gear it down 47.95:1. This gives us an output rotation of 62.6 RPM, or 37.5 deg/s. To stand up from a full crouch would take about 2.25 seconds, and you're going to need a second gear to do it." Do something before you finish reading this: Stand up without leaning forward AT ALL. Back totally erect at 90*. Second time, stand up normally. The second time, normally, there's several things going on. You lean forward, inducing a momentum that builds the faster you throw your torso forward and the more you stand up. This momentum imparts, independent of your prime movers, a centripetal force on your hips and knees, which induces an assistive torque. The more you stand up, the less torque is required, which conveniently mirrors the loss in momentum. You use 50% less energy because of this momentum. For arguments sake, we'll say it takes 10% the weight of your upper torso to initiate this momentum gain in the torque load, and because you're not pivoting against a solid surface, both gravity and mass take over once your torso moves past 90* progressively building momentum until you begin to straighten out, reducing your momentum conveniently as your torque requirements diminish. So, right off the bat, unless you're doing squats in a mech, you're back to 90,000Nm. As previously stated, series elastic actuators increase any given actuators efficiency by including a compliant element in series with the actuator because of the, in this case, passive elastic compliant components spring constant, this efficiency gain being roughly 15%, meaning that the spring does 15% of the work usually. So, we're now sitting at 63,000Nm. So, now you can do two things, lower the draw from your power source, or increase the system forces. Still coming up short of your 180,000Nm by 30%, you have doubled either your load or your speed. Even with pretty bad friction losses, you can still come up short easily. "In the case of forward walking, where the entire leg operates as a single lever, the power transfer to the ground is mathematically identical to a wheel: we need a torque between the base of the lever and the body, and the leg then transfers that torque into the ground. For a human-proportioned mech of 14' height (4.2m), you're going to have 7' (2.1m) legs (from hip joint to heel, human legs are roughly 50% of total height). To accelerate a 20 ton (18000 kg) object at 3.5m/s^2, we use Force = Mass * Acceleration, and we see that you need to deliver 63,000 newtons (14,000 lbf) to the ground. For a 2.1m leg to deliver that force, we need to produce 132,300 Newton Meters (97,579.5 ft lbs) of torque around the hip joint. The Honeywell AGT1500 out of the Abrams produces 3,754 Nm (2,750 FtLbs) of torque at 3,000 RPM. To provide 132,300 Nm, we need to gear that down 35.25:1, giving us a max rotation at the leg of 85 RPM. With a 2.1 meter leg, this gives us a maximum speed of about 1 km/min, or about 35 mph. In reality, the top speed will probably lose at least 10mph, depending on leg travel, because when the leg is at any angle other than perpendicular to the ground, the engine has to hold a portion of the mech's weight as well as provide motive power. I can do the math on that loss if your really want me to." No, it's not. Whereas wheels or tracks have to provide the running torque constantly on both sides, each leg on a bipedal system is only using running torque 50% of the time in a stiff actuator drive train, then you also have to include the phenomenon of "fall forward" gait and inverted pendulum. At most, with your math, it would only require this force on the first step, excluding, again, using your body this time (ankle to ground vs. ankle to head single order lever arm). Realistically, this takes a pitiful amount of initiating force to induce a cascade of momentum multipliers (head leading, arms, as well as shifting your center of mass over the balls of your feet rather than over the heels of your feet, hence why it's called falling forward), but in the end we can say that this is going to be 8-10%, experimentally (more like 15% theoretically), your anticipated torque requirement, with a system conservation of 20% after your forces play out per step. Your running torque just dropped to 78078 ft-lbs. Including the series elastic actuator rather than a stiff actuator, this decreases again to 62243.7ft-lbs. Basically, for the same power requirements, a bipedal locomotion can use 35% less the anticipated running torque of tracked or wheeled vehicles using proper gait and the most basic compliant actuator scheme, and only have to employ running torque on one half the entire actuator system per step. Not to mention all the mechanical advantage structures you could include. On a side note this system is an endurance optimized bipedal locomotion system. Find me a tracked or wheeled robot of the same dimensions that can go over 14 miles on $.03USD of electricity and I'll delete my account. "We have this field of science call "engineering". With it, we can make astonishingly accurate predictions about all sorts of things mechanical, even if they've never been built and tested. I'll be doing just that in just a minute, if you care to stick around." In engineering we have these fields called mechatronics and biomechatronics that specialize in systems like this. We take the time to look into actuation and articulation schemes that lie well outside what conventional mechanical engineering is used to. "Well, now you're talking numbers that make sense, I wonder If we could do that with a wheeled system..." And how long does it take to exchange a package for another? A mech can theoretically do this on the order of minutes. "sinking in isn't the problem. the problem is asking a tiny patch of dirt to hold 130 kilonewtons of transverse force. Protip: it won't." If transverse forces were the only forces at play here, I'd agree. Furthermore, texturing the feet can increase both purchase and surface area. I'm not questioning your intellect, nor am I going to say that I know that mechs can definitely play a significant enough role in the combat theatre to implement them immediately, but it cannot be proven yes or no until it is trialed. I am saying that you are attempting to analyze this system in a relatively 2 dimensional mindset, but it's extremely multi-dimensional.

Thank you!

It will only play any one role at any given time. The idea is that you can use the mechs in place (to augment) of some other units. Instead of having to transport 100 of every vehicle you might need, transport 50 of each, then 50 mechs with their requisite cache. They can be mixed and matched as needed, reducing logistical nightmares. There's also TROPHY, ARENA, and IRON FIST. Having a 360* field of radar coverage is not a new idea, and we're shooting RPG's, not magic missile. Any of these countermeasures would be able to identify and eliminate magic missile too, and alert the pilot to the location the fire originated from. Not from a dead stop, and only if the tank is oriented in the direction that it can do so. This is the beauty of a side step, you can be fully commited but can move side to side without having to pivot. Won't be a problem... because 90 psi is for a dirt bike, not a mountain bike or other human powered bike. Furthermore, at 12'-14', you're realistically looking at closer to 20-25t, or 44-47 psi. Plus, compaction increases resistance on all but the most loose terrain, so "sinking in" won't be quite as bad as you'd think.

I was hoping you'd understand I don't want it doing anything on the battlefield better, just be able to do multiple things well, as needed. I'm not saying it's going to pull a Neo. I'm saying whereas wheeled/tracked vehicles have to pivot to change direction, a mech can literally sidestep behind cover. Or, WITH ENOUGH RANGE, step out of the way or twist out of the way, whereas a tank would have to absorb the blow. A 12-14 foot mech at a whopping 40t, well above what it would realistically weigh (half that maybe), would be at 88psi. Heavy, but not ground breaking, and that's if you have human scaled feet.

I'm still not suggesting total replacement.

I would call it agile. Cars/tanks are significantly faster than horses and humans, but can't accelerate nearly as fast. Actually, humans can accelerate faster than racehorses under adrenaline or they're athletes. Agility is a derivative of acceleration. If you can fit two to three mech "tools" on one transport vehicle, you reduce the need to have a platform for every possible scenario anticipated. One mech can replace any one piece of equipment at a time. Only in scenarios where you need all the possible scenarios at once will a shortage exist. Two vehicles (a mech transport and it's cache transport) versus 5 or more.