rookie37 Posted August 25, 2011 Posted August 25, 2011 When I write mathematical equations in the parameters, I get an error I think the problem is syntax. Thats because when I write part of the equation, Inventor accepts it. When I try to multiply by a power, I get an error. Example 5^2 (five to the power of 2) Will somebody help me with my equation? A bit of background I'm drawing an ellipse. I want to change the size of the ellipse. However, I don't want the focal point to move C=( ( 1-( (MINORradious*2) / (MAJORradious*2) )^2 ) ^0.5) * MAJORradious I have this equation on the attachment and color coded for easier reading Eccentricity.docx Quote
JD Mather Posted August 25, 2011 Posted August 25, 2011 Attach your ipt file here. Do you want that point to move (the one you labeled DOES NOT MOVE)? Do you want it to stay on the ellipse? If so, add a coincident constraint. In your ^2 do you have units or are all of your numbers unitless (ul). If you are squaring units (for example mm) this will not work for a linear dimension. (example I would expect MAJORradious and MINORradious to have length units. You must put something in your formula to cancel out these units so that they are not squared) Right the formula out by hand including all units with the magnatudes and you will see the problem. Quote
rookie37 Posted August 26, 2011 Author Posted August 26, 2011 JD I have drawn it again. this time without any attempt at changing the parrameters. I have a jpg that explains it better that I'll attach with another email. It tried to attach it this this one but it won't for some reason ellipse1.ipt Quote
rookie37 Posted August 26, 2011 Author Posted August 26, 2011 JD I want to be able to change the size of the ellipse as shown in the jpg. I want the focal point to be fixed. Just a bit of refrence. I copied these formulas from a spreadsheet In the sreadsheet I have majoraxis (major diameter) Inventor will only dimention the radious of the ellipse. This is why I wrote (MAJORradius * 2) instead of majoraxis Eccentricity=(1-(minoraxis/majoraxis)^2)^0.5 focal point = Eccentricity*majoraxis/2 Quote
rookie37 Posted August 26, 2011 Author Posted August 26, 2011 More explanation about the jpg and my equation focal point = 51702 in the black ellipse focal point = 46985 in the blue ellipse Quote
JD Mather Posted August 26, 2011 Posted August 26, 2011 Inventor will only dimention the radious of the ellipse. Construction lines. Have you read this document? http://home.pct.edu/~jmather/skillsusa%20university.pdf Quote
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