Re: [OpenSCAD] Help with two problems with SCAD
In the general setting of the photo, rotate_extrude and linear_extrude has
little value. The natural solution would be to define the tube path by
interpolating splines and build the tube by sweeping a ring along that
path. That is a completely distinct approach though.
2017-05-14 12:38 GMT-03:00 Carsten Arnholm arnholm@arnholm.org:
On 14. mai 2017 16:26, Marijan Pollak wrote:
It is Gravity motor, but I did not
asked for help with that, only in creating round pipes or cylinders which
I
can made difference from cylindrical plate to get pipes inside.
I would recommend something like below for creating pipes, instead of
subtracting cylinders. This avoids the problem that the inner cylinder has
to extend at both ends, to avoid numerical problems:
$fn=30;
module StraightPipe(ro=10, th=1, l=100)
{
linear_extrude(l)
difference() { circle(ro); circle(ro-th); }
}
module CurvedPipe(ro=10, th=1, radius=100, angle=60)
{
rotate([90,0,0])
translate([-radius,0,0])
rotate_extrude(angle=angle,$fn=60)
translate([radius,0,0])
difference() { circle(ro); circle(ro-th); }
}
translate([-50,0,0]) CurvedPipe();
translate([+50,0,0]) StraightPipe();
The angle parameter in rotate_extrude requires a recent version of
OpenSCAD.
Btw. the "PerpetumMobius" photo or the model you made with hoses imply
non-planar bent pipes. That isn't possible with rotate_extrude in OpenSCAD.
Carsten Arnholm
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On 14. mai 2017 19:09, Ronaldo Persiano wrote:
In the general setting of the photo, rotate_extrude and linear_extrude
has little value. The natural solution would be to define the tube path
by interpolating splines and build the tube by sweeping a ring along
that path. That is a completely distinct approach though.
It is true for OpenSCAD, you cannot create that model with either of the
above methods using built-in functions directly.
For the fun of it I tried to replicate the photo using only my variants
of linear_extrude, rotate_extrude plus 'transform_extrude' (i.e. not in
OpenSCAD). See image of model generated with xcsg. In principle it is
doable with similar functions.
Being able to sweep a general cross section along a spline path is
something anyone would like to have, I totally agree with that.
Carsten Arnholm
I wouldn't be so pessimistic. Any trajectory for this will have a piecewise
definition. With rotate_extrude() circle() plus cylinder() OpenSCAD offers a
viable piecewise solution, in form of the method every plumber would use. It
is not at all difficult and even render time will be acceptable.
What I severly doubt is that any closed loop pipe will ever squeeze out a
pico Watt of power from gravity ...
Ronaldo wrote
In the general setting of the photo, rotate_extrude and linear_extrude has
little value. The natural solution would be to define the tube path by
interpolating splines and build the tube by sweeping a ring along that
path. That is a completely distinct approach though.
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Hi, Ronaldo, thank for Your help and pesimism. I on other hand am quote
optimistic of outcome. People look at things different way and usually see
what they think they see, not reality, usually. so if You think my 3D Max
pocture would not work, You are right, since it should be put verticall not
on horizontal plane. If You say that in regard to photograph I sent You of
actuall device,which nearly worked but missed anti sliding mechanism which I
cannot make by bare hands, then I must tell You hat thing is not static but
describe very complex trajectories. When things would be working I shall
sent You a recording by camera.
In regard to non manifold problem I would suggest simple solution in which
surfaces that coincide or edges that are same be replaced in order they are
created by duplicates.
Else following advices written I made complete mess of turbine and at least
80% of surfaces dissapearred, so I have to revert to versions that were
allmost good just slow in rendering.
in regards to problem of pipes I would try to use Mr. Kabakov routines for
helical extrude of circle. The rest I would do with straight cylinders, or I
may find some solution in Your Macaroni maker example. Once more, thank a
lot!
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BTW, knot theory gives us a trajectory function commonly known as "figure
eight knot" that can produce something quite useful for this task. It needs
some playing with the parameters to get other interesting figures (of course
one can also play with the function). I implemented a simple sphere plot
routine to show it. Doing a sweep upon this trajectory will be straight
forward.
//traj = knot(720, 2, 3, 4); //Figure eight knot
traj = knot(720, 2, 1.5, 2);
//traj = knot(720, 2.5, 1.5, 2.5);
//traj = knot(720, 2, 2.5, 2);
//traj = knot(720, 1, .5, 0);
for(i=[0:len(traj)-1]) translate(traj[i]) sphere(10); // plot trajectory
function knot(N=360, a=2, b=1.5, c=2, r = 100) = [for (t=[0:N]) r *
[(a+cos(at))cos(bt), (a+cos(at))sin(bt), .2sin(ct)]];
http://forum.openscad.org/file/n21554/knot.png
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Thank You for example. As I need smooth pipes i would try to use cylinders
instead, or maybe
hull
https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Transformations#hull()instruction
can make pipes smooth?
On Fri, May 19, 2017 at 3:32 PM, Parkinbot [via OpenSCAD] <
ml+s1091067n21554h80@n5.nabble.com> wrote:
BTW, knot theory gives us a trajectory function commonly known as "figure
eight knot" that can produce something quite useful for this task. It needs
some playing with the parameters to get other interesting figures (of
course one can also play with the function). I implemented a simple sphere
plot routine to show it. Doing a sweep upon this trajectory will be
straight forward.
//traj = knot(720, 2, 3, 4); //Figure eight knot
traj = knot(720, 2, 1.5, 2);
//traj = knot(720, 2.5, 1.5, 2.5);
//traj = knot(720, 2, 2.5, 2);
//traj = knot(720, 1, .5, 0);
for(i=[0:len(traj)-1]) translate(traj[i]) sphere(10); // plot trajectory
function knot(N=360, a=2, b=1.5, c=2, r = 100) = [for (t=[0:N]) r *
[(a+cos(at))cos(bt), (a+cos(at))sin(bt), .2sin(ct)]];
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You may try my library https://justinsdk.github.io/dotSCAD/ .
include <rotate_p.scad>;
include <polysections.scad>;
include <path_extrude.scad>;
include <bezier_curve.scad>;
include <circle_path.scad>;
function knot(N=360, a=2, b=1.5, c=2, r = 100) =
[for (t=[0:N]) r * [(a+cos(at))cos(bt), (a+cos(at))sin(bt),
.2sin(ct)]];
traj = knot(720, 2, 1.5, 2);
shape_pts = circle_path(radius = 25);
path_extrude(shape_pts, traj);
http://forum.openscad.org/file/n21561/traj.jpg
http://openhome.cc
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Yes, Yes! That is more like it. Little Kinky but most important parts are
there.
But Sorry to say. I am near totaly blind on left eye and my right eye is
also giving up from
overuse. No matter how I look, I cannot see from where to Download this
DotSCAD library.
Can You give hyperlink to download page?
On Sat, May 20, 2017 at 12:58 PM, caterpillar [via OpenSCAD] <
ml+s1091067n21561h97@n5.nabble.com> wrote:
You may try my library https://justinsdk.github.io/dotSCAD/.
include <rotate_p.scad>;
include <polysections.scad>;
include <path_extrude.scad>;
include <bezier_curve.scad>;
include <circle_path.scad>;
function knot(N=360, a=2, b=1.5, c=2, r = 100) =
[for (t=[0:N]) r * [(a+cos(at))cos(bt), (a+cos(at))sin(bt),
.2sin(ct)]];
traj = knot(720, 2, 1.5, 2);
shape_pts = circle_path(radius = 25);
path_extrude(shape_pts, traj);
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Thank You, I have been there, just I did not click on Maintained by
JasonSDK.
Hopefully additions are included in .zip file.
On Sat, May 20, 2017 at 12:58 PM, caterpillar [via OpenSCAD] <
ml+s1091067n21561h97@n5.nabble.com> wrote:
You may try my library https://justinsdk.github.io/dotSCAD/.
include <rotate_p.scad>;
include <polysections.scad>;
include <path_extrude.scad>;
include <bezier_curve.scad>;
include <circle_path.scad>;
function knot(N=360, a=2, b=1.5, c=2, r = 100) =
[for (t=[0:N]) r * [(a+cos(at))cos(bt), (a+cos(at))sin(bt),
.2sin(ct)]];
traj = knot(720, 2, 1.5, 2);
shape_pts = circle_path(radius = 25);
path_extrude(shape_pts, traj);
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and 20th Centuries, Engineer Nikola Tesla!
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There's a "Clone or download" button (the green one) at the right side.
http://forum.openscad.org/file/n21564/%E6%93%B7%E5%8F%96.jpg
http://openhome.cc
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