Subject:
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Re: Lego AT-AT (secrets revealed)
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Newsgroups:
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lugnet.starwars
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Date:
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Fri, 8 Dec 2000 18:56:50 GMT
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Viewed:
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1137 times
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In lugnet.starwars, Jason J. Railton writes:
> In lugnet.starwars, David Eaton writes:
> 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 all stop-motion animation, and I doubt the movie models
> have much of an interior. Is that seriously what you were expecting? How
> about the pros and cons of fitting a working Repulsor-Lift in a minifig
> Landspeeder then?
Um.. I'm not really arguing that an AT-AT not done to my exacting
specifications wouldn't be cool or neat or anything, I was just clarifying
my position.
Actually, throughout this message it seems I've offended you or something,
or perhaps you thought I was insulting your walking model by saying it's not
absoloutly perfect and canon. Sorry if I insinuated anything like that.
Lemme take another shot at it.
I'm a modeller. *MY* primary concern in building *MY* AT-AT is to get a
model that looks good. Getting it to move and stuff is only a secondary goal
to me. Hence, my priority is building an AT-AT that LOOKS like it should
look. If I can get it to move and act like a "real" AT-AT, cool. All the
better. And I'll even try. But not at the expense of the other goals of the
project, unless for some reason, I decide to change those goals.
People often ask me if I'm going to make it walk, since they've seen other
models walk, etc. Up until about 6 months ago, I'd say "yeah, I've thought
about trying to do it, and maybe I'll figure something out one of these
days." Then I started actually examining the problems involved and
calculating exactly what I'd demand in an AT-AT walking mechanism for my
model. Again, without comprimising what I've felt has been my primary goal
of the model. And after examining the problems involved, I pretty much
convinced myself that I couldn't do what I wanted, and that it may in fact
be impossible.
It was never my intent to say that a wonderful AT-AT model with some
comprimises on authenticity and looks in exchange for functionality couldn't
exist. And as such, I'm not trying to attack you. Actually, I think your
model is really cool. And were it my goal to make a walking AT-AT, I'd try
and copy it. Actually, I may anyway, since it really does intreuge me.
Mostly I was just responding to you saying that I thought that what you were
doing was impossible, and I just wanted to more clearly say what I thought
was impossible, because you seemed to think I was suggesting that a walking
AT-AT was impossible, and I wanted to clarify. But in short, sorry if I
offended.
> > Problem 1. Leverage. When in minifig scale, the body is HEAVY...
>
> Well, you wrap strings around a large solid drum for the leg. Remember it
> only has to bear the weight of the body in a fixed position. Once it's
> ready to move, you only have to lift the leg, not the whole body. I'm not
> saying you could do it in that space, but it's not impossible.
Hmmm.. an interesting thought... perhaps a flex rod extended into the
undercarriage attaching at the lower hip, released when the upper hip is
raised could be hidden and still be able to support the weight... Dunno
about the space issue though... interesting thought...
> I don't know how reliable the newer pneumatics are, but that's probably not
> worth even trying. You'd need some pretty solid bell cranks linked to the
> leg.
Yeah, I haven't actually tried the pneumatic method yet-- but that was going
to be my next attempt. However, if I can support it with some sort of flex
system/strings like you suggested, perhaps the joints won't need to be quite
as strong. Actually, I wasn't really counting on pneumatics much, since even
if they're strong enough, they're really hard to time accurately :(
> > 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...
>
> For the accurate walk, you need to move one leg at a time. This means that
> each foot steps forward for 1/4 of its cycle, then sweeps back (at 1/3 the
> speed) for the other 3/4 of its cycle (as the other 3 feet take a step).
> This is how large quadropeds (elephants, hippos) move around slowly, and is
> incredibly hard to do mechanically from a single drive.
Tell me about it. That's a lot of why I gave up on it-- it was really overly
complicated and seemed to reuqire way too much space to time well, etc. As
for the method, that's exactly how the makers of ESB designed the AT-AT's
walking mechanism. They closely studied large animals, most notably
elephants, walking slowly.
> > 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...
>
> Well, use more bits of string down the leg.
Exactly. A flex system of sorts would be the way I'd do it (I actually tried
a couple things to that effect, but quicly ran out of pieces that could hide
the flex tubes).
> Don't have this... checking Brickshelf...
> Eh? It's nothing like it! Look a bit closer - that one can't even raise
> or lower its legs. They're pinned to the body at the top. It must rely on
> rocking about to raise a leg clear of the ground. If anything, mine's like >the wobbling dog from the very first 8888 ideas book, but with levers instead
> of sliding pivots for the legs.
Sorry- it's been a while since I've seen that walker, and granted I'm still
not overly clear on exactly how your mechanism works.
[snip neat description of joints]
> > ... 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...
>
> Doesn't work like that. Think about it - what you've just described
> actually entails lifting two legs at once. Instead, you have to position
> three of the legs so that they balance on their own, then you can raise
> the redundant one.
I'm not exactly sure what you mean here-- basically the idea I was trying to
suggest is that the three feet down will balance the weight on their own
when the lifting leg is raised. Hence, if you've got:
(1 = just planted, 4 = about to lift)
1
3
2
4
you'll shift the weight of the body more toward the leg on 3 so that when
the 4th is lifted, the rest will support the weight. And as the 4th gets
placed, you shift away from the leg currently on 3 (it's now about to be
lifted anyway), and back onto 4, now being the one that's just been planted.
And to that effect, if (during this lift phase) leg 3 is shortened, there's
less chance that the AT-AT will tip towards the raised leg. Basically,
trying more to stable it like a tripod. Let me know if I'm way off base
here, too... This has all been theoretical for me so far, as I haven't
designed a 4 cycled walker to actually experiment on...
> > 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.
>
> Yeah, well, I don't buy that for a minute.
Quite wisely so. Although I think 50 feet was the scale Lucas originally
played around with for walkers, which is why I think that number even
exists. It's quite obviously wrong from watching the movies...
> Mine's small. I can live
> with that. What do you use as minifig scale anyway? And I don't mean
> in studs...
I usually go by 7mm = 1 minifig foot. That's based on a minifig being
roughly 42mm tall (Really it depends on the head, hair, and any neck gear)
and that translating to roughly 6 feet tall. And as such, since studs are
8mm, 7 studs is 8 minifig feet.
> And as for '60 km/h over level terrain' - that means all four
> legs would have to move in a complete cycle every second! Right...
Yep. That's rather silly, I think, but if you watch the movie, it's about a
complete cycle every 2 or 3 seconds (not really sure), and the "explanation"
is of course that it wasn't moving at top speed on Hoth. Although I still
don't really buy that it could go 60 kph... that'd just be ridiculous...
> Well, it's interesting to see that the DSDK AT-AT is the first walker set
> LEGO have done, despite putting one in most of the ideas books (see
> Brickshelf, 8888-8891). The dinosaur looks the neatest one. Note that
> it only raises the rear legs - the front legs just swing, and it relies on
> a rocking motion to raise them clear of the ground.
I'll have to check that out... I don't think I've seen that before...
DaveE
Dunno where to FUT... I guess SW is ok... maybe .technic or .build...
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Message has 1 Reply:
 | | Re: Lego AT-AT (secrets revealed)
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| (...) I'm not offended or insulted. But, you made some pretty disparaging remarks about making a walking AT-AT. Then, you clarified this by saying that you meant a fully operational one, with neatly hidden actuators and a detailed interior, would be (...) (24 years ago, 9-Dec-00, to lugnet.starwars)
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Message is in Reply To:
| | Re: Lego AT-AT (secrets revealed)
|
| (...) 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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