From: nasato@wiliki.eng.hawaii.edu (Neil Asato)
Newsgroups: rec.games.frp.misc
Subject: Re: Military Mechs? Hexapod
Date: 30 Jul 92 09:02:11 GMT
Organization: University of Engineering, College of Engineering

In article <RATINOX.92Jul29101842@splinter.coe.northeastern.edu> ratinox@splinter.coe.northeastern.edu (Richard Pieri/Stainless Steel Rat) writes:
>>>>>> On 28 Jul 92 18:16:51 GMT, wcalderw@nmsu.edu (William A. Calderwood)
>>>>>> said:
>
>WAC> Insectoid Mechs:
>WAC> (low profiles, streamlined) hmm sounds like a tank to me.
>WAC> (more armot and heavier weapons) more legs more weight can be
>WAC> supported. But why do this when all ya have to build is a tank.
>WAC> (getting a system to cordinate all those leg movements and supply
>WAC> enough power to keep the whole thing moving might slow it down in the
>WAC> end)
>
>Take a look at the Hexapod program funded by the US military. The ultimate
>goal is to build a six legged "tank" that can walk at 35 mph and step over
>tank traps. Right now the testbed framework and software has it "running"
>at around 10 mph and it can climb steps with two meter risers.
>
>A walking tank has the benefit of being able to step over obstacles that
>would stop a tracked tank.
>
>--Rat
>
     This sounds interesting. The one thing that I have wondered
since everybody keeps saying that insect-tanks are superior, I was
wondering how they solved some nagging problems that I see.
     How did they solve the shear stresses that would occur from the
knee to the body? and what about the creep effects (mechanical 
engineering term) on the legs? Is the leg an exo-skeleton with the
muscles on the inside like an insect, or on the outside like an endoskeloton?
     How do they perform maintenance work on the muscles (technical interest,
please do not just refference it) (do they have to rest it on platform,
if it can "sit straight down" how does it get up without ripping
up the floor of the maintenance floor and how does it get the friction
to stand up on the legs without just uselessly making furrows in the
ground) ?
     How much does the tank weigh? How much armor does it have?
How much armor does it have on its various sides (the bottom seems
like an obvious target and would be better protected than a normal
tank)?
     How does it distribute that weight on its legs? Does it have 1+ meter
radius disks at the end of the legs? This question deals with the problem
of the tanks legs sinking into the ground requiring the tank to pull
its stuck legs out of the ground.
     How does the energy expenditure compare between the tracked tank
and the legged tank ( use the engineer's use of the term efficiency
not that salesman version of efficiency [if they say it is over 30%
energy efficient I would be amazed, it they say over 50% I would
say that they are above TL12(BTRC terminology) and got the technology
from aliens :-) .(by the way BTRC TL12 is technology from the year 2000 AD).
     What type of motor system did they use? If they used hydraulics,
how did they solve the leakage problem? If they used some linear motor,
which type of linear motor did they use?

     By the way I throw the above questions to anyone who believes that
a legged tank is as good as they seem to make it out to be.
I personally think any large legged vehicle (massing more than 1000 kg)
would be relatively slow in reality due to stresses (especially shear) and
creep effects if the limbs move fast (thought example: spider tank
has a race with an M-1, after going 100 meters the legs are severely
warped. After 1 kilometer, the spider tank is running on its knees...)
I am interested in what the real world (note the lack of quotation 
marks around the two previous words) machines would be like, and
it seems like a lot of people around here are arguing based on solid
knowledge of what the engineering solutions are (or not).