Drawing an ellipse

[crupiea]

Got into ellipses here recently and if you have done these before you will know that there really are no tools to draw the things like there is a compass for circles.

Sure, you can draw one of you have an engineering degree and two compasses, a slide rule and some other stuff but man its confusing.

I am just relegating myself to using one of those green plastic things, taking a pic of it, emailing it to myself then fiddling with it, 

There really should just be a $20 tool for this. 

 

[jerry1939]

Will this help?  (Inkscape).  https://www.google.com/search?ei=0ue0XameAcO-tQWexoyIBw&q=inkscape+make+an+ellipse&oq=inkscape+make+an+ellipse&gs_l=psy-ab.3..0i30.90867.98753..102318...0.2..0.118.1510.12j4......0....1..gws-wiz.......0i71j0i7i30j0i5i30j0.RxW0clIS0hE&ved=0ahUKEwipz7GymrvlAhVDX60KHR4jA3EQ4dUDCAo&uact=5#kpvalbx=_Oei0XY20KZKesQXM3rEQ27

jerry

[jollyred]

there is a technique for drawing an ellipse, using two nails and a piece of string.  Look on Youtube for videos on how to do it.

[munzieb]

I made a "do Nothing machine" or trammel of Archimedes about a year ago for a project that needed an ellipse. There are several plans on the web. The narrow width is about 4". I made the groves with a router but there several ways to hold the sliding blocks in place. I hold it down with 2 sided tape and a rubber grommet to hold the pencil. If you decide to make one and you need a smaller ellipse, draw out the smallest one you can on card stock and then use a compass and then trace out a smaller dimension and cut out with a scissor and use as a template.

Edited October 27, 2019 by munzieb

[jerry1939]

Try this:  http://tavmjong.free.fr/INKSCAPE/MANUAL/html/ix01.html    (Don't know why, but you will need to Copy/Paste the link).

Scroll to ellipse.

jerry

[teachnlearn]

If it makes you feel better, I will send you two brad nails and a loop of string for 20 dollars. I've got an engineering degree and apply KISS in my designs and projects. RJF

 

[OCtoolguy]

31 minutes ago, teachnlearn said:

If it makes you feel better, I will send you two brad nails and a loop of string for 20 dollars. I've got an engineering degree and apply KISS in my designs and projects. RJF

 

Is there some formula for deciding the "size" of your ellipse? How do you go about that?

 

[Woodmaster1]

I cheat and use AutoCAD when I substitute at the local Vocational School and use the plotter to print it at 1:1 scale. The string method and the homemade device works great too. When I taught drafting precad we use the major and minor axis to draw them with a compass.

Edited October 27, 2019 by Woodmaster1

[JimErn]

13 minutes ago, octoolguy said:

Is there some formula for deciding the "size" of your ellipse? How do you go about that?

 

here ya go Ray, wrap your head around this one

What is the equation for an ellipse?

Use the standard form (x−h)2a2+(y−k)2b2=1 ( x − h ) 2 a 2 + ( y − k ) 2 b 2 = 1 . If the x-coordinates of the given vertices and foci are the same, then the major axis is parallel to the y-axis. Use the standard form (x−h)2b2+(y−k)2a2=1 ( x − h ) 2 b 2 + ( y − k ) 2 a 2 = 1 .

ROFLMAO

Seems easier to me to use the circle widget in inkscape, draw out an ellipse (default drawing) and on the tool bar set the width and height

[OCtoolguy]

1 minute ago, JimErn said:

here ya go Ray, wrap your head around this one

What is the equation for an ellipse?

Use the standard form (x−h)2a2+(y−k)2b2=1 ( x − h ) 2 a 2 + ( y − k ) 2 b 2 = 1 . If the x-coordinates of the given vertices and foci are the same, then the major axis is parallel to the y-axis. Use the standard form (x−h)2b2+(y−k)2a2=1 ( x − h ) 2 b 2 + ( y − k ) 2 a 2 = 1 .

ROFLMAO

Seems easier to me to use the circle widget in inkscape, draw out an ellipse (default drawing) and on the tool bar set the width and height

Thanks, I'm going to sit here and drink a beer while I digest all those x's and o's. I used to be pretty good in math but that was over 60 years ago. I forgot every bit of algebra that I ever knew. But thanks for all that anyway.

 

[jerry1939]

Crupiea - Scroll up and reread the post from "teachnlearn".  For 20 bucks he would send you 2 nails & a piece of string.

WAIT and he will probably double the offer.  You just pay separate S&H.

jerry

[teachnlearn]

https://www.mathopenref.com/ellipse.html

Look at the first ellipse picture on the site. The point on the ellipse moves with the mouse. Notice the line a is from one point in the middle line. Just think of one brad nail being point a, the line a is going to be the string from that brad nail to the outside of the circle. The line b is the string from the other brad nail, point b. When you move the outer string point, less say a  to the line that goes through the two brad nails, you get the outer point. That going to be the outer end of the ellipse left of brad a. Move the string point to the line that goes through the brads, say b and go to the right side you get the end of the ellipse from brad nail b. Move the point around the ellipse and remember, point a is a brad nail, point b is a brad nail. The line a is the length the string will reach to the ellipse from nail a. The line b is the string that will reach the ellipse from nail b.

 

Play with the picture, that grab some cardboard, two brad nails and different loops of string, As you move the brad nails closer and further from each other your going to see the ellipse flatten and expand. The string loop will always be the same until you make a different size. A whole group of string loops and you can make an ellipse on the living room floor with the right length. RJF

[teachnlearn]

7 hours ago, jerry1939 said:

Crupiea - Scroll up and reread the post from "teachnlearn".  For 20 bucks he would send you 2 nails & a piece of string.

WAIT and he will probably double the offer.  You just pay separate S&H.

jerry

 

BUT WAIT THERES MORE!!!! If you send cash before the end of the day, I'll include a putt putt scoring pencil! RJF

[John B]

On 10/28/2019 at 5:20 AM, teachnlearn said:

If it makes you feel better, I will send you two brad nails and a loop of string for 20 dollars. I've got an engineering degree and apply KISS in my designs and projects. RJF

 

This is the way we learnt at tech, when I was doing my apprenticeship. Oval coffee tables and dinning tables where  the thing and we marked out the tops like this. Simple and accurate.