GH
Gene Heskett
Thu, Apr 29, 2021 5:58 PM
On Thursday 29 April 2021 09:06:32 Michael Möller wrote:
// 3 "eccentric"s
module disc(r) { cylinder(r=r,h=2) ; }
module rod() cylinder(h=4,r=2) ;
translate([60,0,0]) {// A circle is a circle. Can't be anything else
// if you rotate elsewhere than its centre, then it's motion is
eccentric rotate(360*$t) translate([5,0,0]) disc(20);
rod() ;
}
This below is almost precisely what I wanted, thank you Michael.
translate([-60,0,0]) {
// An elongated circle is mathematically the same as an ellipse
// if you rotate it about its center it has two "lobes" in Genes
parlance translate([0,40,0]) {
rotate(360*$t) scale([1.2,1,1]) disc(20); // ellipse 40x48
rod() ;
}
One final question: Once the circumference has been determined, do I
subtract an equal amount from Y that I added to x to keep the
circumference unchanged as I make it into an ellipse? Or is there some
trig needed?
IOW if I change the scale arguements to 1.03,.97,1 will the circumference
remain unchanged from the 1,1,1 condition?
Thank you. A fresh copy of the piece that will be flexed by this ellipse
is about a 4.5 hour build, about 3 hours into it now, and then I'll have
something to measure and test fit against. This is not the same printer
so the finished sizes of the parts may easily be a major fraction of a
millimeter different. Probably requiring I adjust and rebuild. This
piece building now in particular as I made the first one on a different
printer out of translucent PETG, but this printer is loaded with black
PETG, and despite its not showing anything but a hi res cylinder for an
inner wall in openscad, the bases of the splines are seriously "printing
thru". Something I could not see in the translucent PETG at all. That
may predict an early failure.
// you can rotate it about one of the foci, in which case it has one
"lobe". focus = (sqrt(201.2201.2-2020)); // distance of focus from
center translate([0,-40,0]) {
rotate(360*$t) translate([focus,0,0]) scale([1.2,1,1]) disc(20);
rod() ;
}
}
// a "hull" round two circles (with plenty of overlap) is a
traditional "cam" as in camshaft
rotate(360*$t) hull() {disc(20); translate([0,18,0]) disc(8);}
rod() ;
Best viewed as an animation, f.eks. FPS 5, steps 25
[image: image.png]
On Thu, 29 Apr 2021 at 14:29, Will Hardiman
bill.hardiman1995@gmail.com
wrote:
It seems to me that Gene is describing an ellipse:
it needs to be like the usual woodworkers ellipse
layout tool, consisting of 2 pins and a string loop to fix the
reach, the string is dropped over the two pins, and a pencil is then
used to make the outline mark by using the string as a "thats as far
as I can reach" and stay inside the string.
A video of this technique:
https://www.youtube.com/watch?v=Et3OdzEGX_w
In which case the answer has already been posted by Nop Head (module
ellipse(xr, yr) scale([1, yr / xr]) circle(xr); ), and any confusion
about lobes or asymmetry is just that.
On Thu, 29 Apr 2021 at 13:05, jon jon@jonbondy.com wrote:
Gene:
Can you make the shape you want by using hull() on two circles or
cylinders of different diameters spaced a bit apart?
On 4/29/2021 7:59 AM, doug@milmac.com wrote:
Gene, I’m afraid it’s still far from clear (to me, at least) what
exactly you’re trying make. Ellipses don’t have “lobes”. Perhaps
you could post a hand-drawn sketch of what you want to make?
Gene Heskett wrote:
…That looks as if it should do it except that will make a single
lobe … so the ellipse will have two lobes
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
On Thursday 29 April 2021 09:06:32 Michael Möller wrote:
> // 3 "eccentric"s
>
> module disc(r) { cylinder(r=r,h=2) ; }
> module rod() cylinder(h=4,r=2) ;
> translate([60,0,0]) {// A circle is a circle. Can't be anything else
> // if you rotate elsewhere than its centre, then it's motion is
> eccentric rotate(360*$t) translate([5,0,0]) disc(20);
> rod() ;
> }
>
This below is almost precisely what I wanted, thank you Michael.
> translate([-60,0,0]) {
> // An elongated circle is mathematically the same as an ellipse
> // if you rotate it about its center it has two "lobes" in Genes
> parlance translate([0,40,0]) {
> rotate(360*$t) scale([1.2,1,1]) disc(20); // ellipse 40x48
> rod() ;
> }
One final question: Once the circumference has been determined, do I
subtract an equal amount from Y that I added to x to keep the
circumference unchanged as I make it into an ellipse? Or is there some
trig needed?
IOW if I change the scale arguements to 1.03,.97,1 will the circumference
remain unchanged from the 1,1,1 condition?
Thank you. A fresh copy of the piece that will be flexed by this ellipse
is about a 4.5 hour build, about 3 hours into it now, and then I'll have
something to measure and test fit against. This is not the same printer
so the finished sizes of the parts may easily be a major fraction of a
millimeter different. Probably requiring I adjust and rebuild. This
piece building now in particular as I made the first one on a different
printer out of translucent PETG, but this printer is loaded with black
PETG, and despite its not showing anything but a hi res cylinder for an
inner wall in openscad, the bases of the splines are seriously "printing
thru". Something I could not see in the translucent PETG at all. That
may predict an early failure.
> // you can rotate it about one of the foci, in which case it has one
> "lobe". focus = (sqrt(20*1.2*20*1.2-20*20)); // distance of focus from
> center translate([0,-40,0]) {
> rotate(360*$t) translate([focus,0,0]) scale([1.2,1,1]) disc(20);
> rod() ;
> }
> }
> // a "hull" round two circles (with plenty of overlap) is a
> traditional "cam" as in camshaft
> rotate(360*$t) hull() {disc(20); translate([0,18,0]) disc(8);}
> rod() ;
>
> Best viewed as an animation, f.eks. FPS 5, steps 25
> [image: image.png]
>
>
> On Thu, 29 Apr 2021 at 14:29, Will Hardiman
> <bill.hardiman1995@gmail.com>
>
> wrote:
> > It seems to me that Gene is describing an ellipse:
> > >it needs to be like the usual woodworkers ellipse
> >
> > layout tool, consisting of 2 pins and a string loop to fix the
> > reach, the string is dropped over the two pins, and a pencil is then
> > used to make the outline mark by using the string as a "thats as far
> > as I can reach" and stay inside the string.
> >
> > A video of this technique:
> > https://www.youtube.com/watch?v=Et3OdzEGX_w
> >
> > In which case the answer has already been posted by Nop Head (module
> > ellipse(xr, yr) scale([1, yr / xr]) circle(xr); ), and any confusion
> > about lobes or asymmetry is just that.
> >
> > On Thu, 29 Apr 2021 at 13:05, jon <jon@jonbondy.com> wrote:
> >> Gene:
> >>
> >> Can you make the shape you want by using hull() on two circles or
> >> cylinders of different diameters spaced a bit apart?
> >>
> >>
> >> On 4/29/2021 7:59 AM, doug@milmac.com wrote:
> >>
> >> Gene, I’m afraid it’s still far from clear (to me, at least) what
> >> exactly you’re trying make. Ellipses don’t have “lobes”. Perhaps
> >> you could post a hand-drawn sketch of what you want to make?
> >>
> >> Gene Heskett wrote:
> >>
> >> …That looks as if it should do it except that will make a single
> >> lobe … so the ellipse will have two lobes
> >>
> >> _______________________________________________
> >> OpenSCAD mailing list
> >> To unsubscribe send an email to discuss-leave@lists.openscad.org
> >
> > _______________________________________________
> > OpenSCAD mailing list
> > To unsubscribe send an email to discuss-leave@lists.openscad.org
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>
NH
nop head
Thu, Apr 29, 2021 7:12 PM
On Thursday 29 April 2021 09:06:32 Michael Möller wrote:
// 3 "eccentric"s
module disc(r) { cylinder(r=r,h=2) ; }
module rod() cylinder(h=4,r=2) ;
translate([60,0,0]) {// A circle is a circle. Can't be anything else
// if you rotate elsewhere than its centre, then it's motion is
eccentric rotate(360*$t) translate([5,0,0]) disc(20);
rod() ;
}
This below is almost precisely what I wanted, thank you Michael.
translate([-60,0,0]) {
// An elongated circle is mathematically the same as an ellipse
// if you rotate it about its center it has two "lobes" in Genes
parlance translate([0,40,0]) {
rotate(360*$t) scale([1.2,1,1]) disc(20); // ellipse 40x48
rod() ;
}
One final question: Once the circumference has been determined, do I
subtract an equal amount from Y that I added to x to keep the
circumference unchanged as I make it into an ellipse? Or is there some
trig needed?
IOW if I change the scale arguements to 1.03,.97,1 will the circumference
remain unchanged from the 1,1,1 condition?
Thank you. A fresh copy of the piece that will be flexed by this ellipse
is about a 4.5 hour build, about 3 hours into it now, and then I'll have
something to measure and test fit against. This is not the same printer
so the finished sizes of the parts may easily be a major fraction of a
millimeter different. Probably requiring I adjust and rebuild. This
piece building now in particular as I made the first one on a different
printer out of translucent PETG, but this printer is loaded with black
PETG, and despite its not showing anything but a hi res cylinder for an
inner wall in openscad, the bases of the splines are seriously "printing
thru". Something I could not see in the translucent PETG at all. That
may predict an early failure.
// you can rotate it about one of the foci, in which case it has one
"lobe". focus = (sqrt(201.2201.2-2020)); // distance of focus from
center translate([0,-40,0]) {
rotate(360*$t) translate([focus,0,0]) scale([1.2,1,1]) disc(20);
rod() ;
}
}
// a "hull" round two circles (with plenty of overlap) is a
traditional "cam" as in camshaft
rotate(360*$t) hull() {disc(20); translate([0,18,0]) disc(8);}
rod() ;
Best viewed as an animation, f.eks. FPS 5, steps 25
[image: image.png]
On Thu, 29 Apr 2021 at 14:29, Will Hardiman
bill.hardiman1995@gmail.com
wrote:
It seems to me that Gene is describing an ellipse:
it needs to be like the usual woodworkers ellipse
layout tool, consisting of 2 pins and a string loop to fix the
reach, the string is dropped over the two pins, and a pencil is then
used to make the outline mark by using the string as a "thats as far
as I can reach" and stay inside the string.
A video of this technique:
https://www.youtube.com/watch?v=Et3OdzEGX_w
In which case the answer has already been posted by Nop Head (module
ellipse(xr, yr) scale([1, yr / xr]) circle(xr); ), and any confusion
about lobes or asymmetry is just that.
On Thu, 29 Apr 2021 at 13:05, jon jon@jonbondy.com wrote:
Gene:
Can you make the shape you want by using hull() on two circles or
cylinders of different diameters spaced a bit apart?
On 4/29/2021 7:59 AM, doug@milmac.com wrote:
Gene, I’m afraid it’s still far from clear (to me, at least) what
exactly you’re trying make. Ellipses don’t have “lobes”. Perhaps
you could post a hand-drawn sketch of what you want to make?
Gene Heskett wrote:
…That looks as if it should do it except that will make a single
lobe … so the ellipse will have two lobes
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
Good luck trying to calculate the circumference of an ellipse. There is no
formula. See https://www.youtube.com/watch?v=5nW3nJhBHL0
On Thu, 29 Apr 2021 at 18:58, Gene Heskett <gheskett@shentel.net> wrote:
> On Thursday 29 April 2021 09:06:32 Michael Möller wrote:
>
> > // 3 "eccentric"s
> >
> > module disc(r) { cylinder(r=r,h=2) ; }
> > module rod() cylinder(h=4,r=2) ;
> > translate([60,0,0]) {// A circle is a circle. Can't be anything else
> > // if you rotate elsewhere than its centre, then it's motion is
> > eccentric rotate(360*$t) translate([5,0,0]) disc(20);
> > rod() ;
> > }
> >
> This below is almost precisely what I wanted, thank you Michael.
>
> > translate([-60,0,0]) {
> > // An elongated circle is mathematically the same as an ellipse
> > // if you rotate it about its center it has two "lobes" in Genes
> > parlance translate([0,40,0]) {
> > rotate(360*$t) scale([1.2,1,1]) disc(20); // ellipse 40x48
> > rod() ;
> > }
> One final question: Once the circumference has been determined, do I
> subtract an equal amount from Y that I added to x to keep the
> circumference unchanged as I make it into an ellipse? Or is there some
> trig needed?
>
> IOW if I change the scale arguements to 1.03,.97,1 will the circumference
> remain unchanged from the 1,1,1 condition?
>
> Thank you. A fresh copy of the piece that will be flexed by this ellipse
> is about a 4.5 hour build, about 3 hours into it now, and then I'll have
> something to measure and test fit against. This is not the same printer
> so the finished sizes of the parts may easily be a major fraction of a
> millimeter different. Probably requiring I adjust and rebuild. This
> piece building now in particular as I made the first one on a different
> printer out of translucent PETG, but this printer is loaded with black
> PETG, and despite its not showing anything but a hi res cylinder for an
> inner wall in openscad, the bases of the splines are seriously "printing
> thru". Something I could not see in the translucent PETG at all. That
> may predict an early failure.
>
> > // you can rotate it about one of the foci, in which case it has one
> > "lobe". focus = (sqrt(20*1.2*20*1.2-20*20)); // distance of focus from
> > center translate([0,-40,0]) {
> > rotate(360*$t) translate([focus,0,0]) scale([1.2,1,1]) disc(20);
> > rod() ;
> > }
> > }
> > // a "hull" round two circles (with plenty of overlap) is a
> > traditional "cam" as in camshaft
> > rotate(360*$t) hull() {disc(20); translate([0,18,0]) disc(8);}
> > rod() ;
> >
> > Best viewed as an animation, f.eks. FPS 5, steps 25
> > [image: image.png]
> >
> >
> > On Thu, 29 Apr 2021 at 14:29, Will Hardiman
> > <bill.hardiman1995@gmail.com>
> >
> > wrote:
> > > It seems to me that Gene is describing an ellipse:
> > > >it needs to be like the usual woodworkers ellipse
> > >
> > > layout tool, consisting of 2 pins and a string loop to fix the
> > > reach, the string is dropped over the two pins, and a pencil is then
> > > used to make the outline mark by using the string as a "thats as far
> > > as I can reach" and stay inside the string.
> > >
> > > A video of this technique:
> > > https://www.youtube.com/watch?v=Et3OdzEGX_w
> > >
> > > In which case the answer has already been posted by Nop Head (module
> > > ellipse(xr, yr) scale([1, yr / xr]) circle(xr); ), and any confusion
> > > about lobes or asymmetry is just that.
> > >
> > > On Thu, 29 Apr 2021 at 13:05, jon <jon@jonbondy.com> wrote:
> > >> Gene:
> > >>
> > >> Can you make the shape you want by using hull() on two circles or
> > >> cylinders of different diameters spaced a bit apart?
> > >>
> > >>
> > >> On 4/29/2021 7:59 AM, doug@milmac.com wrote:
> > >>
> > >> Gene, I’m afraid it’s still far from clear (to me, at least) what
> > >> exactly you’re trying make. Ellipses don’t have “lobes”. Perhaps
> > >> you could post a hand-drawn sketch of what you want to make?
> > >>
> > >> Gene Heskett wrote:
> > >>
> > >> …That looks as if it should do it except that will make a single
> > >> lobe … so the ellipse will have two lobes
> > >>
> > >> _______________________________________________
> > >> OpenSCAD mailing list
> > >> To unsubscribe send an email to discuss-leave@lists.openscad.org
> > >
> > > _______________________________________________
> > > OpenSCAD mailing list
> > > To unsubscribe send an email to discuss-leave@lists.openscad.org
>
>
> Cheers, Gene Heskett
> --
> "There are four boxes to be used in defense of liberty:
> soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> If we desire respect for the law, we must first make the law respectable.
> - Louis D. Brandeis
> Genes Web page <http://geneslinuxbox.net:6309/gene>
> _______________________________________________
> OpenSCAD mailing list
> To unsubscribe send an email to discuss-leave@lists.openscad.org
>
MM
Michael Möller
Thu, Apr 29, 2021 7:20 PM
As nophead wrote : https://en.wikipedia.org/wiki/Ellipse#Circumference ...
if you just want to read rather than watch.
The article gives a relatively simple formula for an approximation, and the
error bounds. It may be enough for you.
Put that into a spread sheet or something and adjust a,b until they fit
your circumference requirement and eccentricity.
On Thu, 29 Apr 2021 at 21:13, nop head nop.head@gmail.com wrote:
On Thursday 29 April 2021 09:06:32 Michael Möller wrote:
// 3 "eccentric"s
module disc(r) { cylinder(r=r,h=2) ; }
module rod() cylinder(h=4,r=2) ;
translate([60,0,0]) {// A circle is a circle. Can't be anything else
// if you rotate elsewhere than its centre, then it's motion is
eccentric rotate(360*$t) translate([5,0,0]) disc(20);
rod() ;
}
This below is almost precisely what I wanted, thank you Michael.
translate([-60,0,0]) {
// An elongated circle is mathematically the same as an ellipse
// if you rotate it about its center it has two "lobes" in Genes
parlance translate([0,40,0]) {
rotate(360*$t) scale([1.2,1,1]) disc(20); // ellipse 40x48
rod() ;
}
One final question: Once the circumference has been determined, do I
subtract an equal amount from Y that I added to x to keep the
circumference unchanged as I make it into an ellipse? Or is there some
trig needed?
IOW if I change the scale arguements to 1.03,.97,1 will the circumference
remain unchanged from the 1,1,1 condition?
Thank you. A fresh copy of the piece that will be flexed by this ellipse
is about a 4.5 hour build, about 3 hours into it now, and then I'll have
something to measure and test fit against. This is not the same printer
so the finished sizes of the parts may easily be a major fraction of a
millimeter different. Probably requiring I adjust and rebuild. This
piece building now in particular as I made the first one on a different
printer out of translucent PETG, but this printer is loaded with black
PETG, and despite its not showing anything but a hi res cylinder for an
inner wall in openscad, the bases of the splines are seriously "printing
thru". Something I could not see in the translucent PETG at all. That
may predict an early failure.
// you can rotate it about one of the foci, in which case it has one
"lobe". focus = (sqrt(201.2201.2-2020)); // distance of focus from
center translate([0,-40,0]) {
rotate(360*$t) translate([focus,0,0]) scale([1.2,1,1]) disc(20);
rod() ;
}
}
// a "hull" round two circles (with plenty of overlap) is a
traditional "cam" as in camshaft
rotate(360*$t) hull() {disc(20); translate([0,18,0]) disc(8);}
rod() ;
Best viewed as an animation, f.eks. FPS 5, steps 25
[image: image.png]
On Thu, 29 Apr 2021 at 14:29, Will Hardiman
bill.hardiman1995@gmail.com
wrote:
It seems to me that Gene is describing an ellipse:
it needs to be like the usual woodworkers ellipse
layout tool, consisting of 2 pins and a string loop to fix the
reach, the string is dropped over the two pins, and a pencil is then
used to make the outline mark by using the string as a "thats as far
as I can reach" and stay inside the string.
A video of this technique:
https://www.youtube.com/watch?v=Et3OdzEGX_w
In which case the answer has already been posted by Nop Head (module
ellipse(xr, yr) scale([1, yr / xr]) circle(xr); ), and any confusion
about lobes or asymmetry is just that.
On Thu, 29 Apr 2021 at 13:05, jon jon@jonbondy.com wrote:
Gene:
Can you make the shape you want by using hull() on two circles or
cylinders of different diameters spaced a bit apart?
On 4/29/2021 7:59 AM, doug@milmac.com wrote:
Gene, I’m afraid it’s still far from clear (to me, at least) what
exactly you’re trying make. Ellipses don’t have “lobes”. Perhaps
you could post a hand-drawn sketch of what you want to make?
Gene Heskett wrote:
…That looks as if it should do it except that will make a single
lobe … so the ellipse will have two lobes
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
As nophead wrote : https://en.wikipedia.org/wiki/Ellipse#Circumference ...
if you just want to read rather than watch.
The article gives a relatively simple formula for an approximation, and the
error bounds. It may be enough for you.
Put that into a spread sheet or something and adjust a,b until they fit
your circumference requirement and eccentricity.
On Thu, 29 Apr 2021 at 21:13, nop head <nop.head@gmail.com> wrote:
> Good luck trying to calculate the circumference of an ellipse. There is no
> formula. See https://www.youtube.com/watch?v=5nW3nJhBHL0
>
> On Thu, 29 Apr 2021 at 18:58, Gene Heskett <gheskett@shentel.net> wrote:
>
>> On Thursday 29 April 2021 09:06:32 Michael Möller wrote:
>>
>> > // 3 "eccentric"s
>> >
>> > module disc(r) { cylinder(r=r,h=2) ; }
>> > module rod() cylinder(h=4,r=2) ;
>> > translate([60,0,0]) {// A circle is a circle. Can't be anything else
>> > // if you rotate elsewhere than its centre, then it's motion is
>> > eccentric rotate(360*$t) translate([5,0,0]) disc(20);
>> > rod() ;
>> > }
>> >
>> This below is almost precisely what I wanted, thank you Michael.
>>
>> > translate([-60,0,0]) {
>> > // An elongated circle is mathematically the same as an ellipse
>> > // if you rotate it about its center it has two "lobes" in Genes
>> > parlance translate([0,40,0]) {
>> > rotate(360*$t) scale([1.2,1,1]) disc(20); // ellipse 40x48
>> > rod() ;
>> > }
>> One final question: Once the circumference has been determined, do I
>> subtract an equal amount from Y that I added to x to keep the
>> circumference unchanged as I make it into an ellipse? Or is there some
>> trig needed?
>>
>> IOW if I change the scale arguements to 1.03,.97,1 will the circumference
>> remain unchanged from the 1,1,1 condition?
>>
>> Thank you. A fresh copy of the piece that will be flexed by this ellipse
>> is about a 4.5 hour build, about 3 hours into it now, and then I'll have
>> something to measure and test fit against. This is not the same printer
>> so the finished sizes of the parts may easily be a major fraction of a
>> millimeter different. Probably requiring I adjust and rebuild. This
>> piece building now in particular as I made the first one on a different
>> printer out of translucent PETG, but this printer is loaded with black
>> PETG, and despite its not showing anything but a hi res cylinder for an
>> inner wall in openscad, the bases of the splines are seriously "printing
>> thru". Something I could not see in the translucent PETG at all. That
>> may predict an early failure.
>>
>> > // you can rotate it about one of the foci, in which case it has one
>> > "lobe". focus = (sqrt(20*1.2*20*1.2-20*20)); // distance of focus from
>> > center translate([0,-40,0]) {
>> > rotate(360*$t) translate([focus,0,0]) scale([1.2,1,1]) disc(20);
>> > rod() ;
>> > }
>> > }
>> > // a "hull" round two circles (with plenty of overlap) is a
>> > traditional "cam" as in camshaft
>> > rotate(360*$t) hull() {disc(20); translate([0,18,0]) disc(8);}
>> > rod() ;
>> >
>> > Best viewed as an animation, f.eks. FPS 5, steps 25
>> > [image: image.png]
>> >
>> >
>> > On Thu, 29 Apr 2021 at 14:29, Will Hardiman
>> > <bill.hardiman1995@gmail.com>
>> >
>> > wrote:
>> > > It seems to me that Gene is describing an ellipse:
>> > > >it needs to be like the usual woodworkers ellipse
>> > >
>> > > layout tool, consisting of 2 pins and a string loop to fix the
>> > > reach, the string is dropped over the two pins, and a pencil is then
>> > > used to make the outline mark by using the string as a "thats as far
>> > > as I can reach" and stay inside the string.
>> > >
>> > > A video of this technique:
>> > > https://www.youtube.com/watch?v=Et3OdzEGX_w
>> > >
>> > > In which case the answer has already been posted by Nop Head (module
>> > > ellipse(xr, yr) scale([1, yr / xr]) circle(xr); ), and any confusion
>> > > about lobes or asymmetry is just that.
>> > >
>> > > On Thu, 29 Apr 2021 at 13:05, jon <jon@jonbondy.com> wrote:
>> > >> Gene:
>> > >>
>> > >> Can you make the shape you want by using hull() on two circles or
>> > >> cylinders of different diameters spaced a bit apart?
>> > >>
>> > >>
>> > >> On 4/29/2021 7:59 AM, doug@milmac.com wrote:
>> > >>
>> > >> Gene, I’m afraid it’s still far from clear (to me, at least) what
>> > >> exactly you’re trying make. Ellipses don’t have “lobes”. Perhaps
>> > >> you could post a hand-drawn sketch of what you want to make?
>> > >>
>> > >> Gene Heskett wrote:
>> > >>
>> > >> …That looks as if it should do it except that will make a single
>> > >> lobe … so the ellipse will have two lobes
>> > >>
>> > >> _______________________________________________
>> > >> OpenSCAD mailing list
>> > >> To unsubscribe send an email to discuss-leave@lists.openscad.org
>> > >
>> > > _______________________________________________
>> > > OpenSCAD mailing list
>> > > To unsubscribe send an email to discuss-leave@lists.openscad.org
>>
>>
>> Cheers, Gene Heskett
>> --
>> "There are four boxes to be used in defense of liberty:
>> soap, ballot, jury, and ammo. Please use in that order."
>> -Ed Howdershelt (Author)
>> If we desire respect for the law, we must first make the law respectable.
>> - Louis D. Brandeis
>> Genes Web page <http://geneslinuxbox.net:6309/gene>
>> _______________________________________________
>> OpenSCAD mailing list
>> To unsubscribe send an email to discuss-leave@lists.openscad.org
>>
> _______________________________________________
> OpenSCAD mailing list
> To unsubscribe send an email to discuss-leave@lists.openscad.org
>
GH
Gene Heskett
Thu, Apr 29, 2021 8:40 PM
On Thursday 29 April 2021 15:20:16 Michael Möller wrote:
No wonder, yee Gods etc, that the guys during Apollo wanted to know if
Katherine checked their orbits, she may have been the only person on the
planet that understood all that stuff.
The article gives a relatively simple formula for an approximation,
and the error bounds. It may be enough for you.
Simple? I don't want to know your definitiion of complex.
Put that into a spread sheet or something and adjust a,b until they
fit your circumference requirement and eccentricity.
The last spreadsheet I used was dynacalc for os9 in '86, to print it all
out and prove to the state income tax folks that they had finally
managed to write an income tax law that ate its own tail, and without
changing a thing, it calculated about 20% greater liability everytime
you hit the recalc key, I mailed them the printouts of that whole
hairball and said you calculate it, I can't get a straight answer. Took
them about 5 months to issue a refund for more than I'd ever seen out of
dynacalc. And the intructions for the next year were simple enough I
could do it a 4 banger $12 calc. One of those that said 2X2 was
3.999999. And they bought it!
Life can be seriously funny, and it would be fun if it didn't end with a
death sentence anyway. :-)
Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
On Thursday 29 April 2021 15:20:16 Michael Möller wrote:
> As nophead wrote : https://en.wikipedia.org/wiki/Ellipse#Circumference
> ... if you just want to read rather than watch.
>
No wonder, yee Gods etc, that the guys during Apollo wanted to know if
Katherine checked their orbits, she may have been the only person on the
planet that understood all that stuff.
> The article gives a relatively simple formula for an approximation,
> and the error bounds. It may be enough for you.
Simple? I don't want to know your definitiion of complex.
> Put that into a spread sheet or something and adjust a,b until they
> fit your circumference requirement and eccentricity.
>
The last spreadsheet I used was dynacalc for os9 in '86, to print it all
out and prove to the state income tax folks that they had finally
managed to write an income tax law that ate its own tail, and without
changing a thing, it calculated about 20% greater liability everytime
you hit the recalc key, I mailed them the printouts of that whole
hairball and said you calculate it, I can't get a straight answer. Took
them about 5 months to issue a refund for more than I'd ever seen out of
dynacalc. And the intructions for the next year were simple enough I
could do it a 4 banger $12 calc. One of those that said 2X2 was
3.999999. And they bought it!
Life can be seriously funny, and it would be fun if it didn't end with a
death sentence anyway. :-)
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>
JB
Jordan Brown
Thu, Apr 29, 2021 10:19 PM
On 4/29/2021 9:43 AM, Gene Heskett wrote:
In which case the answer has already been posted by Nop Head (module
ellipse(xr, yr) scale([1, yr / xr]) circle(xr); ), and any confusion
about lobes or asymmetry is just that.
I believe thats correct, however ellipse is not listed in the cheat
sheet, so where do I find its docs?
There is no built-in ellipse module.
What's shown above is the definition of an ellipse module:
module ellipse(xr, yr) scale([1, yr / xr]) circle(xr);
Once you have that, you can say "ellipse(3,5);" to get an ellipse with a
"radius" in X of 3 and in Y of 5. (I don't know whether that's a good
definition of "radius", but it's sort of understandable.)
On 4/29/2021 9:43 AM, Gene Heskett wrote:
>> In which case the answer has already been posted by Nop Head (module
>> ellipse(xr, yr) scale([1, yr / xr]) circle(xr); ), and any confusion
>> about lobes or asymmetry is just that.
> I believe thats correct, however ellipse is not listed in the cheat
> sheet, so where do I find its docs?
There is no built-in ellipse module.
What's shown above is the *definition* of an ellipse module:
module ellipse(xr, yr) scale([1, yr / xr]) circle(xr);
Once you have that, you can say "ellipse(3,5);" to get an ellipse with a
"radius" in X of 3 and in Y of 5. (I don't know whether that's a good
definition of "radius", but it's sort of understandable.)
DE
David Eccles (gringer)
Fri, Apr 30, 2021 11:04 AM
alternatively / equivalently:
module ellipse(xr, yr) scale([xr, yr]) circle(1, $fn=64);
--
Sent from: http://forum.openscad.org/
alternatively / equivalently:
module ellipse(xr, yr) scale([xr, yr]) circle(1, $fn=64);
--
Sent from: http://forum.openscad.org/
D
doug@milmac.com
Fri, Apr 30, 2021 1:24 PM
Unfortunately, this is no more clear than any of your other explanations.
If you would just please post a hand-drawn sketch of what you’re trying to achieve, that will make things so much more clear.
Gene Heskett wrote:
[…]
Take a 4" circle made out of rubber, pin the left edge at its ID then
pull it out of round by a by stretching over another pin 3/16" larger
than the circles diameter. This will be a pretty close approximation of
what I want.
Unfortunately, this is no more clear than any of your other explanations.
If you would just please post a hand-drawn sketch of what you’re trying to achieve, that will make things so much more clear.
Gene Heskett wrote:
> \[…\]
>
> Take a 4" circle made out of rubber, pin the left edge at its ID then
> pull it out of round by a by stretching over another pin 3/16" larger
> than the circles diameter. This will be a pretty close approximation of
> what I want.
NH
nop head
Fri, Apr 30, 2021 5:24 PM
Sounds like a harmonic gear except they are not made from rubber. They have
a cylindrical metal tube with gear teeth on the outside that is deformed by
two bearings that rotate in the middle. I don't think it is exactly an
ellipse. The shape would be the minimum energy curve.
On Fri, 30 Apr 2021 at 16:51, doug@milmac.com wrote:
Unfortunately, this is no more clear than any of your other explanations.
If you would just please post a hand-drawn sketch of what you’re trying to
achieve, that will make things so much more clear.
Gene Heskett wrote:
[…]
Take a 4" circle made out of rubber, pin the left edge at its ID then pull
it out of round by a by stretching over another pin 3/16" larger than the
circles diameter. This will be a pretty close approximation of what I want.
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
Sounds like a harmonic gear except they are not made from rubber. They have
a cylindrical metal tube with gear teeth on the outside that is deformed by
two bearings that rotate in the middle. I don't think it is exactly an
ellipse. The shape would be the minimum energy curve.
On Fri, 30 Apr 2021 at 16:51, <doug@milmac.com> wrote:
> Unfortunately, this is no more clear than any of your other explanations.
>
> If you would just please post a hand-drawn sketch of what you’re trying to
> achieve, that will make things so much more clear.
>
> Gene Heskett wrote:
>
> […]
>
> Take a 4" circle made out of rubber, pin the left edge at its ID then pull
> it out of round by a by stretching over another pin 3/16" larger than the
> circles diameter. This will be a pretty close approximation of what I want.
>
> _______________________________________________
> OpenSCAD mailing list
> To unsubscribe send an email to discuss-leave@lists.openscad.org
>
GH
Gene Heskett
Fri, Apr 30, 2021 7:39 PM
On Friday 30 April 2021 13:24:01 nop head wrote:
Sounds like a harmonic gear except they are not made from rubber. They
have a cylindrical metal tube with gear teeth on the outside that is
deformed by two bearings that rotate in the middle. I don't think it
is exactly an ellipse. The shape would be the minimum energy curve.
On Fri, 30 Apr 2021 at 16:51, doug@milmac.com wrote:
Unfortunately, this is no more clear than any of your other
explanations.
If you would just please post a hand-drawn sketch of what you’re
trying to achieve, that will make things so much more clear.
With the list owners permission, I could post pix, but the best jpeg
compression limits those to a minimum of about 350k by the time they get
expanded by base64'ing them for email attachments, and it would take 4
or 5 pix to really explain what I'm doing. The printed plastic parts are
about done, but the housing is lathe and mill work, and will be a week
or so cuz I'll have to write the gcode to do it.
I'm even printing my own ball bearings, in whatever diameter is needed
using bb's for the balls, so this won't be as smooth and quiet running
as the $2000 and up commercial ones, but hopefully will be strong enough
to get the job done. A test for size disc I made early this morning only
needed a fraction of a mm tweak, so the real version is about 15% done,
then the alu carving begins.
This idea is, because the hi priced versions also break, is a pre-broken
one, removing the place where the steel ones break in favor of a sliding
joint. How it wears remains to be determined.
Gene Heskett wrote:
[…]
Take a 4" circle made out of rubber, pin the left edge at its ID
then pull it out of round by a by stretching over another pin 3/16"
larger than the circles diameter. This will be a pretty close
approximation of what I want.
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
On Friday 30 April 2021 13:24:01 nop head wrote:
> Sounds like a harmonic gear except they are not made from rubber. They
> have a cylindrical metal tube with gear teeth on the outside that is
> deformed by two bearings that rotate in the middle. I don't think it
> is exactly an ellipse. The shape would be the minimum energy curve.
>
> On Fri, 30 Apr 2021 at 16:51, <doug@milmac.com> wrote:
> > Unfortunately, this is no more clear than any of your other
> > explanations.
> >
> > If you would just please post a hand-drawn sketch of what you’re
> > trying to achieve, that will make things so much more clear.
> >
With the list owners permission, I could post pix, but the best jpeg
compression limits those to a minimum of about 350k by the time they get
expanded by base64'ing them for email attachments, and it would take 4
or 5 pix to really explain what I'm doing. The printed plastic parts are
about done, but the housing is lathe and mill work, and will be a week
or so cuz I'll have to write the gcode to do it.
I'm even printing my own ball bearings, in whatever diameter is needed
using bb's for the balls, so this won't be as smooth and quiet running
as the $2000 and up commercial ones, but hopefully will be strong enough
to get the job done. A test for size disc I made early this morning only
needed a fraction of a mm tweak, so the real version is about 15% done,
then the alu carving begins.
This idea is, because the hi priced versions also break, is a pre-broken
one, removing the place where the steel ones break in favor of a sliding
joint. How it wears remains to be determined.
> > Gene Heskett wrote:
> >
> > […]
> >
> > Take a 4" circle made out of rubber, pin the left edge at its ID
> > then pull it out of round by a by stretching over another pin 3/16"
> > larger than the circles diameter. This will be a pretty close
> > approximation of what I want.
> >
> > _______________________________________________
> > OpenSCAD mailing list
> > To unsubscribe send an email to discuss-leave@lists.openscad.org
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>
AH
Adrian H
Fri, Apr 30, 2021 8:52 PM
One final question: Once the circumference has been determined, do I
subtract an equal amount from Y that I added to x to keep the
circumference unchanged as I make it into an ellipse? Or is there some
trig needed?
On Thu, Apr 29, 2021 at 1:58 PM Gene Heskett <gheskett@shentel.net> wrote:
> One final question: Once the circumference has been determined, do I
> subtract an equal amount from Y that I added to x to keep the
> circumference unchanged as I make it into an ellipse? Or is there some
> trig needed?
>
Here are some approximations for the perimeter of an ellipse, with the last
one being "exact". It's actually way more complicated to compute than that
of a circle.
https://www.mathsisfun.com/geometry/ellipse-perimeter.html
