Subject:
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Re: LD4DStudio sample suggestions
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Newsgroups:
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lugnet.cad
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Date:
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Wed, 24 Jun 2009 22:15:56 GMT
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Viewed:
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10119 times
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In lugnet.cad, Eric Albrecht wrote:
> In lugnet.cad, Roland Melkert wrote:
>
> > lol, i went for the first one (small 1.3MB gif fragment):
> >
> > http://www.ld4dstudio.nl/img/ld4d/engine.gif
>
>
> Very nice work! There are a fair number of complex constraints going on
> here. The linear portion of the crank is easy enough (rotation around fixed
> axis). But the connecting rods have to have one end stay connected to the
> crank and the other end stay coincident with the axis of a cylinder. This
> means they need both an oscillating translation and rotation. Finally, the
> pistons need to have pure translation but still stay attached to the moving
> ends of the rods (guided). I like it.
Thanks, actually I did cheat a bit. I made sure the cylinder heads are
perpendicular to the crankShaft. With that in place the motion comes down to
fairly basic geometry. First step is to calculate the pistonRound angle by
reducing the whole thing to a triangle like:
pistonRoundAngle
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| \
| \ pistonRodLength
\ \
\ \
\ \ pistonRodAngle
| x
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crankElementLength
x=sin(crankShaftAngle)*crankElementLength
pistonRoundAngle=arcSin(x/pistonRodLength)
And finally you get the pistonRodAngle thanks to the fact all triangle angles
add up to 180 degrees
pistonRodAngle=180-crankShaftAngle-pistonRoundAngle
do note some additional 'playing' with angle offsets was needed to get it all to
work for this specific engine.
>
> I've only just started playing with LD4DStudio so I am hardly qualified to
> comment. But I make a lot of Technic LDRAW models, make a lot of technical
> renders, and I make a lot of photographic stop motion animations for
> <http://www.ericalbrecht.com/technic/ Technicopedia>. I can imagine this
> tool being incredibly useful once I figure out how to use it.
I love your site, it has tons of background information and helps in selecting
candidates for animation. I'm thinking on doing the
http://www.ericalbrecht.com/technic/850.html model for my next sample.
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Message is in Reply To:
 | | Re: LD4DStudio sample suggestions
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| (...) The linear portion of the crank is easy enough (rotation around fixed axis). But the connecting rods have to have one end stay connected to the crank and the other end stay coincident with the axis of a cylinder. This means they need both an (...) (15 years ago, 24-Jun-09, to lugnet.cad, FTX)
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