Empathy List Archives

F

FourthDr

Sun, Sep 2, 2018 9:47 AM

I see in the documentation how to create a sphere. But how would I create an
oval shape?

--
Sent from: http://forum.openscad.org/

I see in the documentation how to create a sphere. But how would I create an oval shape? -- Sent from: http://forum.openscad.org/

NH

nop head

Sun, Sep 2, 2018 10:12 AM

Use scale() with different scale factors on each axis on a circle, cylinder
or sphere.

On 2 September 2018 at 10:47, FourthDr who_doctor@hotmail.com wrote:

I see in the documentation how to create a sphere. But how would I create
an
oval shape?

--
Sent from: http://forum.openscad.org/

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

Use scale() with different scale factors on each axis on a circle, cylinder or sphere. On 2 September 2018 at 10:47, FourthDr <who_doctor@hotmail.com> wrote: > I see in the documentation how to create a sphere. But how would I create > an > oval shape? > > > > -- > Sent from: http://forum.openscad.org/ > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

F

FourthDr

Tue, Sep 4, 2018 5:20 AM

Hi Nophead:

I'm actually looking to create an ogive nose cone with a spherical point.
There was a model on Thingiverse someone made that included what looked like
a nice set of cones snub ogive, ogive, and conical, plus a few others. But
when I tried to cut it to fit my printer it crashed OpenSCAD. Upon closer
inspection, the model was full of errors that where not easily fixed. So I
thought I'd try and make my own. I'm looking to create the cone plus a base
that fits a body tube and includes a loop to attach a shock cord for a model
rocket. See attached model: nosecone.zip
http://forum.openscad.org/file/t1425/nosecone.zip

Model Rocket Kit https://www.thingiverse.com/thing:685617

--
Sent from: http://forum.openscad.org/

Hi Nophead: I'm actually looking to create an ogive nose cone with a spherical point. There was a model on Thingiverse someone made that included what looked like a nice set of cones snub ogive, ogive, and conical, plus a few others. But when I tried to cut it to fit my printer it crashed OpenSCAD. Upon closer inspection, the model was full of errors that where not easily fixed. So I thought I'd try and make my own. I'm looking to create the cone plus a base that fits a body tube and includes a loop to attach a shock cord for a model rocket. See attached model: nosecone.zip <http://forum.openscad.org/file/t1425/nosecone.zip> Model Rocket Kit <https://www.thingiverse.com/thing:685617> -- Sent from: http://forum.openscad.org/

CM

christophe malvasio

Tue, Sep 4, 2018 7:04 AM

the nosecone of this rocket does not look oval
basic : hull( ){translate([0,0,($Z-$1_
diameter])sphere($1_diameter);cylinder($2_diameter);}
printers are not very good with spheres
Le mar. 4 sept. 2018 à 07:21, FourthDr who_doctor@hotmail.com a écrit :

Hi Nophead:

I'm actually looking to create an ogive nose cone with a spherical point.
There was a model on Thingiverse someone made that included what looked like
a nice set of cones snub ogive, ogive, and conical, plus a few others. But
when I tried to cut it to fit my printer it crashed OpenSCAD. Upon closer
inspection, the model was full of errors that where not easily fixed. So I
thought I'd try and make my own. I'm looking to create the cone plus a base
that fits a body tube and includes a loop to attach a shock cord for a model
rocket. See attached model: nosecone.zip
http://forum.openscad.org/file/t1425/nosecone.zip

Model Rocket Kit https://www.thingiverse.com/thing:685617

--
Sent from: http://forum.openscad.org/

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

the nosecone of this rocket does not look oval basic : hull( ){translate([0,0,($Z-$1_ diameter])sphere($1_diameter);cylinder($2_diameter);} printers are not very good with spheres Le mar. 4 sept. 2018 à 07:21, FourthDr <who_doctor@hotmail.com> a écrit : > > Hi Nophead: > > I'm actually looking to create an ogive nose cone with a spherical point. > There was a model on Thingiverse someone made that included what looked like > a nice set of cones snub ogive, ogive, and conical, plus a few others. But > when I tried to cut it to fit my printer it crashed OpenSCAD. Upon closer > inspection, the model was full of errors that where not easily fixed. So I > thought I'd try and make my own. I'm looking to create the cone plus a base > that fits a body tube and includes a loop to attach a shock cord for a model > rocket. See attached model: nosecone.zip > <http://forum.openscad.org/file/t1425/nosecone.zip> > > Model Rocket Kit <https://www.thingiverse.com/thing:685617> > > > > > > -- > Sent from: http://forum.openscad.org/ > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

T

Troberg

Tue, Sep 4, 2018 7:21 AM

How I would have done the nose cone:

A succession of spheres of appropriate sizes (just calculate the diameter at
different heights), hull() them together. It doesn't take many spheres to
get a good, smooth surface.

Then, of course, cut off the bottom with difference().

If you want it hollow, make another, scale it down a bit, and use
difference() to hollow the first one out.

--
Sent from: http://forum.openscad.org/

How I would have done the nose cone: A succession of spheres of appropriate sizes (just calculate the diameter at different heights), hull() them together. It doesn't take many spheres to get a good, smooth surface. Then, of course, cut off the bottom with difference(). If you want it hollow, make another, scale it down a bit, and use difference() to hollow the first one out. -- Sent from: http://forum.openscad.org/

NH

nop head

Tue, Sep 4, 2018 8:03 AM

I had to look up https://en.wikipedia.org/wiki/Ogive. Looks like you can
rotate_extrude the intersection of a circle and a square.

On 4 September 2018 at 08:21, Troberg troberg.anders@gmail.com wrote:

How I would have done the nose cone:

A succession of spheres of appropriate sizes (just calculate the diameter
at
different heights), hull() them together. It doesn't take many spheres to
get a good, smooth surface.

Then, of course, cut off the bottom with difference().

If you want it hollow, make another, scale it down a bit, and use
difference() to hollow the first one out.

--
Sent from: http://forum.openscad.org/

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

I had to look up https://en.wikipedia.org/wiki/Ogive. Looks like you can rotate_extrude the intersection of a circle and a square. On 4 September 2018 at 08:21, Troberg <troberg.anders@gmail.com> wrote: > How I would have done the nose cone: > > A succession of spheres of appropriate sizes (just calculate the diameter > at > different heights), hull() them together. It doesn't take many spheres to > get a good, smooth surface. > > Then, of course, cut off the bottom with difference(). > > If you want it hollow, make another, scale it down a bit, and use > difference() to hollow the first one out. > > > > -- > Sent from: http://forum.openscad.org/ > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

F

FourthDr

Tue, Sep 4, 2018 9:32 AM

Troberg:

Not quite sure I visualize how you are suggesting I code up a cone. Would
that produce a true ogive? And then how would I add a spherical tip instead
of the usual point? Have some example code?

--
Sent from: http://forum.openscad.org/

Troberg: Not quite sure I visualize how you are suggesting I code up a cone. Would that produce a true ogive? And then how would I add a spherical tip instead of the usual point? Have some example code? -- Sent from: http://forum.openscad.org/

NH

nop head

Tue, Sep 4, 2018 10:31 AM

From the diagram on Wikipedia I saw that half the cross section of an ogive

is the intersection of a circle and a rectangle.

To blunt the point you need to position another circle that is tangential
to the first one and truncate the ogive at the tangential point and then
hull it with a semi circle.

Using the formula here: http://mathworld.wolfram.com/TangentCircles.html

On 4 September 2018 at 10:32, FourthDr who_doctor@hotmail.com wrote:

Troberg:

Not quite sure I visualize how you are suggesting I code up a cone. Would
that produce a true ogive? And then how would I add a spherical tip instead
of the usual point? Have some example code?

--
Sent from: http://forum.openscad.org/

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

>From the diagram on Wikipedia I saw that half the cross section of an ogive is the intersection of a circle and a rectangle. To blunt the point you need to position another circle that is tangential to the first one and truncate the ogive at the tangential point and then hull it with a semi circle. Using the formula here: http://mathworld.wolfram.com/TangentCircles.html On 4 September 2018 at 10:32, FourthDr <who_doctor@hotmail.com> wrote: > Troberg: > > Not quite sure I visualize how you are suggesting I code up a cone. Would > that produce a true ogive? And then how would I add a spherical tip instead > of the usual point? Have some example code? > > > > -- > Sent from: http://forum.openscad.org/ > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

C

cbernhardt

Tue, Sep 4, 2018 3:00 PM

Or, if you have access to a CAD program that creates DXF files you could draw
the ogive shape as a cross section of a shell and import it.
http://forum.openscad.org/file/t1309/ogive.jpg

--
Sent from: http://forum.openscad.org/

Or, if you have access to a CAD program that creates DXF files you could draw the ogive shape as a cross section of a shell and import it. <http://forum.openscad.org/file/t1309/ogive.jpg> -- Sent from: http://forum.openscad.org/

J

jsc

Tue, Sep 4, 2018 3:44 PM

On the subject of rocket nosecones, I created an OpenSCAD model some time ago
to generate Haack series shapes:

https://www.thingiverse.com/thing:804129

These shapes are calculated to minimize drag in supersonic flows, so not
something that is functionally useful for model rockets. Still, I thought it
might be of interest.

Some work would need to be done to make it suitable for fitting to a rocket.

--
Sent from: http://forum.openscad.org/

On the subject of rocket nosecones, I created an OpenSCAD model some time ago to generate Haack series shapes: https://www.thingiverse.com/thing:804129 These shapes are calculated to minimize drag in supersonic flows, so not something that is functionally useful for model rockets. Still, I thought it might be of interest. Some work would need to be done to make it suitable for fitting to a rocket. -- Sent from: http://forum.openscad.org/

discuss@lists.openscad.org

Ovals