Subject:
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Re: Lego AT-AT
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Newsgroups:
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lugnet.starwars
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Date:
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Thu, 7 Dec 2000 14:24:58 GMT
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Viewed:
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894 times
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In lugnet.starwars, Jason J. Railton writes:
> Now you're making fun - and DaveE doesn't believe it's possible.
Well, I've gotta come in and clarify. I don't think it's possible to achieve
a walking model made of Lego parts (not counting future miracle parts) that
walks as an AT-AT is "supposed" to walk (using all the joints as shown in
the movie, not necessarily timed the same, but probably not that far off
from it), while at the same time being both to minifig scale and also having
a believeable minifig-scale interior.
Here's why.
Problem 1. Leverage. When in minifig scale, the body is HEAVY. To make the
upper hip joint (where the leg connects to the body) "correctly", it's got
to fit the mechanism to turn that joint within a roughly 6x6 area, 4 studs
deep, with as much as 2 studs worth of space on the actual upper hip
section. A technic axle just won't cut it. The leverage simply bends or
snaps an axle, not to mention that even if it didn't, getting it raised
requires lots 'o torque and would have to be pretty slow. A technic
turntable won't cut it cuz it's just too big. That makes it no longer to
scale. A flex system probably won't do either at this joint, (though I
concede this MIGHT work... dunno... haven't played around with it enough)
mainly because there's not a lot of room for leverage to lift the leg in
that little 6x6 area, and again, that means lots of torque, and thus really
slowed down. That pretty much leaves pneumatics. That could work. But timing
it JUST right would be difficult (perhaps impossible, I dunno) given the
impreciceness of Lego pneumatics.
Problem 2. Inconsistant rate of speed. At least one of the joints in the
model needs to work at a varying speed through the walking cycle. And
probably the best system for that is a mechanical system, driven by
pneumatic. I think as I figured it, the joint that probably NEEDS the change
in speed is the standard hip joint (connects upper hip to lower hip),
although I haven't played around with it enough to promise that it's
possible that the other two joints could be the ones using variable speed.
But the big problem here is that such a mechanism takes up valuable space in
a leg that's at a maximum supposed to be 2 studs wide (actual knee joints
are a little wider, and actual hip joints are a little wider, but minimally
so). So fitting it in is really tough.
Problem 3. Space. Well, ok, I've already mentioned it, but the space
requirement is really tough. Any mechanism to control the movement of the
lower hip or knee joint has to go THROUGH the upper hip section, and the
knee joint needs to go through that AND the lower hip section (in order to
be accurate from a modelling perspective). So 1st off, you've got problems
fitting it INTO the leg. 2nd, timing those movements (especially if you're
using pneumatics which would require lots of pumps) takes up space, so
assuming it WAS possible, you can't fit the mechanism into the AT-AT and
still leave room for a believeable minifig-scale interior.
Anyway, admittedly, my constraints are rather silly. And as is probably
obviated, I'm valuing accuracy to the "real thing" above all else. After
all, I am a modeller :)
> Well, I've
> always started with the walking mechanism and built the detail on to that.
> If you don't believe me, look here:
>
> http://www.joefish.cwc.net/bricks/scifi/atat/
Very cool! Actually, the walking mechanism (especially the '2nd' AT-AT
model) looks remarkably similar to the one used in the 8890 technic idea
book, although the brace is placed horizontally rather than vertically, if I
recall correctly. Any more insight into how the knees on the '3rd' AT-AT
model were done? You say it's got "two cranks and spring-controlled knees
and ankles"... how does that work exactly?
> Then Lego did the Dark Side Developer's Kit AT-AT, with knees. Well, I
> could see it wouldn't walk much like an AT-AT, and someone at TVLF accused
> mine of wobbling too much (but have you seen a DSDK AT-AT walk - yuk!).
Yeah, when calculating where the strides should be, I figured that to some
extent it would need this (assuming 1 leg is lifted at a time, rather than
2), since when one leg is lifted, the weight has to be shifted off of this
leg. And the easiest way to do that of course is to simply shift to the
weight to the opposite leg, and potentially even shorten the opposing leg
(bend the knee more or something) on that stroke so the body actually leans
away from the raised leg...
> So, at the bottom of the page you can see two shots of my latest walking
> mechanism, now up to 14 inches tall and awaiting some bodywork.
Cool! Minifig scale is roughly 20 & 2/3 inches high, although 14 inches
would be accurate to the often reported "50 feet" height of the AT-AT.
(There's been some debate on the issue, but bottom line is that the ESB
AT-AT's just aren't nearly that short-- roughly 75 feet has been the more
commonly 'accepted' height. Used to be that older references said it was
50ft tall, now references pretty much all say "over 50 feet tall")
> All these
> models have been driven by a single motor, and this latest one is my first
> to carry it's own batteries. At some point I'll get a Mindstorms RCX and
> try for an even bigger one.
Can't wait to see it! Walking mechanisms have always fascinated me... I have
to say, though, that the Dark Side Developer's mechanism (though very cool)
is kinda silly looking... It'd be interesting to be able to build your
design and see how you did certain things...
DaveE
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Message has 1 Reply:
 | | Re: Lego AT-AT (secrets revealed)
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| (...) Well - okay - can't argue with that. But the question remains: SO? I mean, we've yet to see the interior of an AT-AT in any film (apart from the cockpit footage in ESB) - and not even George Lucas came up with an actual walking one; they're (...) (24 years ago, 8-Dec-00, to lugnet.starwars)
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Message is in Reply To:
| | Re: Lego AT-AT
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| (...) Now you're making fun - and DaveE doesn't believe it's possible. Well, I've always started with the walking mechanism and built the detail on to that. If you don't believe me, look here: (URL) why my models aren't up to full minifig scale or (...) (24 years ago, 7-Dec-00, to lugnet.starwars)
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