| Topic: |
Science > Physics |
| User: |
"Dobri Karagorgov" |
| Date: |
25 Feb 2005 01:17:41 PM |
| Object: |
Ellipser - a tool for mechanical drawing ellipses |
I am looking for partner in this innovation:
www.geocities.com/dedaNoe/ellipser.html
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| User: "Brian Webb" |
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| Title: Re: Ellipser - a tool for mechanical drawing ellipses |
16 Apr 2005 06:43:15 PM |
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"Dobri Karagorgov" <dedanoe@yahoo.com> wrote in message
news:845f8859.0502251117.561cf60@posting.google.com...
I am looking for partner in this innovation:
www.geocities.com/dedaNoe/ellipser.html
The following book contains numerous mechanisms
for creating curves, including ellipses.
"Mechanisms for the Generation of Plane Curves"
I. I. Artobolevskii
Pergamon Press, 1964
- Brian
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| User: "CWatters" |
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| Title: Re: Ellipser - a tool for mechanical drawing ellipses |
26 Feb 2005 04:23:14 AM |
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"Dobri Karagorgov" <dedanoe@yahoo.com> wrote in message
news:845f8859.0502251117.561cf60@posting.google.com...
I am looking for partner in this innovation:
www.geocities.com/dedaNoe/ellipser.html
Just one slight problem...
In this computer age who draws on paper? Really high quality drawing
instruments made between the wars can be had for a few dollars in junk
shops.
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| User: "CWatters" |
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| Title: Re: Ellipser - a tool for mechanical drawing ellipses |
26 Feb 2005 04:30:12 AM |
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"CWatters" <colin.watters@pandoraBOX.be> wrote in message
news:m6YTd.21143$uH3.2671644@phobos.telenet-ops.be...
"Dobri Karagorgov" <dedanoe@yahoo.com> wrote in message
news:845f8859.0502251117.561cf60@posting.google.com...
I am looking for partner in this innovation:
www.geocities.com/dedaNoe/ellipser.html
Just one slight problem...
In this computer age who draws on paper? Really high quality drawing
instruments made between the wars can be had for a few dollars in junk
shops.
Putting that aside for the moment....
Frequently when you want to draw an ellipse you are trying fit a curve
between several points that will end up on the ellipse - eg you don't know
where the center or focus are located. Perhaps it would be better if you
could come up with a method that didn't rely on knowing R1 and R2.
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| User: "Keith A. Lewis" |
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| Title: Re: Ellipser - a tool for mechanical drawing ellipses |
25 Feb 2005 03:27:48 PM |
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(Dobri Karagorgov) writes in article <845f8859.0502251117.561cf60@posting.google.com> dated 25 Feb 2005 11:17:41 -0800:
I am looking for partner in this innovation:
www.geocities.com/dedaNoe/ellipser.html
Your | characters are coming out funny in Mozilla.
é ù
Anyway, what is the advantage of your device over a string connected to two
fixed pins?
--Keith Lewis klewis {at} mitre.org
The above may not (yet) represent the opinions of my employer.
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| User: "tadchem" |
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| Title: Re: Ellipser - a tool for mechanical drawing ellipses |
25 Feb 2005 02:19:51 PM |
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Nasir al-Din al-Tusi (1201-1274 A.D)
<http://www.google.com/search?hl=en&lr=&as_qdr=all&q=linkage+epicycle&btnG=Search>
described epicycles in the "Ilkhani Tables" and the "Tadhkirah".
They were devised in an effort to compensate for the inadequacies of
Ptolemaic astronomy during the work-up to Copernical astronomy.
As described in the link:
"Nasir al-Din, by properly placing such a couple at the end of a vector
emanating from the Ptolemaic equant center caused the vector to
periodically expand and contract. The period of its expansion being
equal to that of the epicycle's rotation about the Earth, the end-point
of the couple carries the epicycle center with it and traces out a
deferent which fulfills all the conditions imposed upon it by Ptolemy's
observations. At the same time, the whole assemblage is a combination
of uniform circular motions, hence unobjectionable, and it preserves
the equant property, also demanded by the phenomenon itself."
Not quite 800 years ago...
It did not work for astronomy because it was not forseen that the
physical center of the orbit would be one of the foci and *not* the
geometric center. Kepler's Laws (1605-1618) corrected that problem:
http://www.kepler.arc.nasa.gov/johannes.html#anchor784359
and epicycles were promptly forgotten.
You may find some help here:
<http://www.roymech.co.uk/Useful_Tables/Drive/Epi_cyclic_gears.html>
or google "Epicyclic gears".
There are many marvelous devices dor drawing ellipses:
<http://www.google.com/search?hl=en&lr=&as_qdr=all&q=device+draw+ellipse&btnG=Search>
Tom Davidson
Richmond, VA
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