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The US Army spent millions developing giant, six-legged walking trucks in 1980s

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Re: The US Army spent millions developing giant, six-legged walking trucks in 1980s

#161

Post by js2 »

Meph504 wrote: post #136
ganafagol wrote: post #126

Earlier quoted context omitted.

That's not really accurate. It depends on the tree type, but the growth cycle is somewhere between 50 to 100 years for optimal results. It's true that most forests today are not old growth anymore. They have been cut (usually clear cut) and then either replanted or just naturally reseeded and are now essentially waiting for the next cut. There are some areas where they are monocultural tree farms with not much else g…

I'm guessing you aren't from the U.S. but in the southern U.S. growing newer species of Pine (variants of Loblolly Pine). A standard lease is 20 years from seedling to harvest, some older variants can go 30 to 50, but you don't see that being planted any longer and that's all leases maturing. And here, I can assure you they are very much mono culture, evenly spaced, engineered species of trees, almost nothing else ha…

> in the southern U.S. they clear cut nearly everything in the 1800s. There is very little old growth left.

Linville Gorge being a notable exception:

https://en.wikipedia.org/wiki/Linville_Gorge_Wilderness

Re: The US Army spent millions developing giant, six-legged walking trucks in 1980s

#162

Post by 0xffff2 »

Meph504 wrote: post #136
ganafagol wrote: post #126

Earlier quoted context omitted.

That's not really accurate. It depends on the tree type, but the growth cycle is somewhere between 50 to 100 years for optimal results. It's true that most forests today are not old growth anymore. They have been cut (usually clear cut) and then either replanted or just naturally reseeded and are now essentially waiting for the next cut. There are some areas where they are monocultural tree farms with not much else g…

I'm guessing you aren't from the U.S. but in the southern U.S. growing newer species of Pine (variants of Loblolly Pine). A standard lease is 20 years from seedling to harvest, some older variants can go 30 to 50, but you don't see that being planted any longer and that's all leases maturing. And here, I can assure you they are very much mono culture, evenly spaced, engineered species of trees, almost nothing else ha…

Interesting. I've never seen anything like that in the Northwestern US.

Re: The US Army spent millions developing giant, six-legged walking trucks in 1980s

#163

Post by bigiain »

imtringued wrote: post #132
bigiain wrote: post #100

Earlier quoted context omitted.

These days delivering that sort of payload with a hexacopter is only a "stupidly expensive hobby grade" project. (Though I'm not aware of any homebuilt multi rotors up in the 485lb plus a ~170lb pilot range. Yet.)

These days? Car sized hexacopters have been vaporware for several decades.

Person carrying multicopters are common enough on YouTube videos (at least some of which probably aren’t fraudulent).

Give me $30k, and I’ll build you a multicopter capable of delivering a 500lb payload 1km away made mostly out of hobby parts. It’s no longer rocket science.

Re: The US Army spent millions developing giant, six-legged walking trucks in 1980s

#164

Post by robomartin »

bigiain wrote: post #102
robomartin wrote: post #18

I have many books on on robotics and AI from Stanford and MIT from that era, back when I started to get deeply involved in the field. My son is about a year away from graduating with degrees in CS and Robotics. He was quite surprised to realize that much of what he is learning today isn't new at all. Tremendous work was done decades ago in both domains. Put simply, you can only get so far with neural networks when yo…

> I don't think there's anything in a Roomba that did not exist in the 1980's other than far greater computing power at a very low cost. High energy density batteries as well. My off-brand Roomba clone uses 4 18650 lipo cells @40-50g each, a total of ~40WHr for under 200g. That 40WHr would need about 1kg of lead acid battery, or maybe 7-800g of NiCad battery.

Yup. Correct. I did mention high energy density storage in my original comment.

Re: The US Army spent millions developing giant, six-legged walking trucks in 1980s

#165

Post by andbberger »

TaylorAlexander wrote: post #144
andbberger wrote: post #79

Earlier quoted context omitted.

The kinematics are the tricky part. Trajectory planning is still quite difficult today even with our speedy modern CPUs

Trajectory planning what? Actually solving the inverse kinematics of 3dof manipulators is trivial. I did so 20 years ago using a Basic Stamp microcontroller for my 18 servo hexapod. I was 15. Planning foot placement is a bit harder but I would say the compute heavy part today would be perception.

Trajectory planning for foot placement.

Re: The US Army spent millions developing giant, six-legged walking trucks in 1980s

#166

Post by sho »

foobarbecue wrote: post #14

I know someone who worked on a big radial hexapod robot for dod recently, and he said everyone involved in the project felt it was pointless (hexapods are just not a good platform for doing much of anything), but it was well-funded so they did their best.

> hexapods are just not a good platform for doing much of anything

Care to expand on this? There's an awful lot of insects with six legs that seem to do OK. Maybe I've watched too much Patlabor/GitS but I would have thought it a viable candidate for any number of mechanical platforms.

Re: The US Army spent millions developing giant, six-legged walking trucks in 1980s

#168

Post by octoberfranklin »

hutzlibu wrote: post #134
octoberfranklin wrote: post #128

Earlier quoted context omitted.

> because from a ecological perspective the walkers are superior You sure about that? Soil compaction is the most serious long-term damage caused by timber harvesting. It's why only tracked harvesters driven by highly-paid fellers are allowed off the gravel. The masses of everyday log-truck drivers (and their wheeled vehicles) are not allowed on the dirt. You want the ground pressure spread out as much as possible, n…

I am not sure about compaction compared to a tracked forester. Physics implies that tracked ones are better, for that, yes. But they rip up even more surface. I believe it is a question, how often the specific path has to be passed by by a forester. "It's why only tracked harvesters driven by highly-paid fellers are allowed off the gravel." And this is sadly not true for germany or other parts of europe I know about.…

> But they rip up even more surface.

Compaction is much, much worse. It takes a century or more to undo in temperate rainforests like the Olympic Peninsula.

Re: The US Army spent millions developing giant, six-legged walking trucks in 1980s

#169

Post by octoberfranklin »

24gttghh wrote: post #155
hutzlibu wrote: post #134

Earlier quoted context omitted.

I am not sure about compaction compared to a tracked forester. Physics implies that tracked ones are better, for that, yes. But they rip up even more surface. I believe it is a question, how often the specific path has to be passed by by a forester. "It's why only tracked harvesters driven by highly-paid fellers are allowed off the gravel." And this is sadly not true for germany or other parts of europe I know about.…

This is a good example of the range of equipment I have seen: https://www.mainecustomwoodlands.com/maine-custom-woodlands-... Only thing non-tracked that goes off the gravel logging roads would be the Skidder (it literally drags bunches, or 'hitches' of trees to the transport vehicles). And even that might be partially or fully-tracked. The feller, slasher, excavator, bulldozer, etc. are all tracked from what I've se…

> Mandatory? Doubtful. But they are most practical in the rough terrain.

I didn't mean to imply there was a government mandate. It's the large forestland owners who demand it of their contractors.

Re: The US Army spent millions developing giant, six-legged walking trucks in 1980s

#170

Post by TaylorAlexander »

andbberger wrote: post #165
TaylorAlexander wrote: post #144

Earlier quoted context omitted.

Trajectory planning what? Actually solving the inverse kinematics of 3dof manipulators is trivial. I did so 20 years ago using a Basic Stamp microcontroller for my 18 servo hexapod. I was 15. Planning foot placement is a bit harder but I would say the compute heavy part today would be perception.

Trajectory planning for foot placement.

I think of “trajectory planning” as: you have a known target position and you have to figure out how to get there. That’s not hard with a 3dof manipulator.

But figuring out where to place the feet, which I consider a perception problem, is very hard. But I think that’s what you’re talking about and I just use different terminology. That’s why I was confused. Sorry if I came off wrong.

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