Subject:
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Re: Part: Plate 2 x 2 with hand rail
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Newsgroups:
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lugnet.cad
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Date:
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Thu, 1 Apr 1999 04:52:23 GMT
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Viewed:
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573 times
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In lugnet.cad.dat, Tim McSweeney writes:
> Ok Here's my first attempt at modeling an Ldraw part. It's the 2 x 2 plate • with grab rail, commonly seen in the divers sets
>
> I only have one issue with it (that I know about), On the diagonal arms, the • intersection with torus in the corners is Drawn as a
> perfect circle but in fact it should be some sort of funky Ellipse. Is this • acceptable as is? if not is there an easy way to
> calculate what the correct shape is?
I've been thinking about this for a while, and I even searched unsuccessfully
for a bagel to use as a model.
I think the shape you are looking for is an ovoid, like the cross-section of
an egg, in your case lying on its side.
You'll have to use two 2-4edge.dats, one stretched horizontally, and the other
squeezed horizontally.
OK, let's see... I'm assuming the torus of the bar has a thickness of 8, but
I don't know the inner radius of the torus, so let's call it r. I'm not sure
of the thickness of the bracket, either, so let x=1/2 thickness of bracket.
The elongated half of the ovoid will point inward. Its y-axis radius will be
4, and its x-axis radius will be calculated thus:
sqrt((r+4)^2-x^2)-sqrt(r^2-x^2)
The shortened half of the ovoid points outward. Its y-axis radius will also
be 4, but its x-axis radius will be calculated:
sqrt((r+8)^2-x^2)-sqrt((r+4)^2-x^2)
Of course once you have your ovoid edge, it will have to be rotated 45
degrees, and placement might be a bit difficult. If this doesn't make sense
to you (or me, for that matter) then maybe I'll take a crack at it tommorrow.
Thanks for posing such an interesting question.
-John Van
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Message has 1 Reply:
 | | Re: Part: Plate 2 x 2 with hand rail [DAT]
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| Well, I was almost correct. The shape is actually an elipsoid, since the original circle is stretched horizontally on both sides, though by different amount. The formulas worked perfect, though. Try this for one of the corners: 1 16 -34.503 2 (...) (25 years ago, 1-Apr-99, to lugnet.cad)
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