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Parametric Curve not generating LD-Haack curve

alex_ramirez327
alex_ramirez327 Member Posts: 2 EDU
in Community Support
I tried writing the LD-Haack equation that is in the wikipedia page, into the y variable of the parametric curve function but it keeps saying it can't regenerate properly. I made sure there isn't any unit conflicts and tried to divide the function into two parts, one in the x variable and the other in the y. Do you guys have any tips or know how to do it properly? The dimensions of the curve, has a radius of 6 inches and its maximum height is 1.5 meters, or 59.055 inches.

This link takes you to the document Im working on. 
https://cad.onshape.com/documents/7b2bde7228785d9873741e76/w/b57f355fb8b142c2e73359d7/e/bbbfbe62b73820f43a5840a0

Best Answer

Answers

  • mahir
    mahir Member, Developers Posts: 1,324 ✭✭✭✭✭
    Looks like there are some unit issues going on with your formula for Y. Acos() does not take angle input. It requires a unitless number. I may have also found a bug with how sqrt() is processed by the featurescript (or possibly Onshape itself). I can plot the output of a sin(), but not sqrt(sin()) or (sin())^.5.

    @ilya_baran can you take a look?
  • ilya_baran
    ilya_baran Onshape Employees, Developers, HDM Posts: 1,273 image
    @mahir I tried and don't see an issue.  Do you have a doc you can share that illustrates it?
    Keep in mind that sin has a tendency to go negative sometimes, in which case sqrt will throw.
    Ilya Baran \ VP, Architecture and FeatureScript \ Onshape Inc
  • mahir
    mahir Member, Developers Posts: 1,324 ✭✭✭✭✭
    @ilya_baran I think you're on to something with the negative sin(). Onshape doesn't support imaginary numbers... go figure. 

    ¯\_(ツ)_/¯ 
  • alex_ramirez327
    alex_ramirez327 Member Posts: 2 EDU
    Yes this is exactly what I wanted, Thank you. The parametric program is difficult to use, but I'm still trying to learn.
  • flavio_trifoni632
    flavio_trifoni632 Member Posts: 2 EDU
    thanks so muck, I had the same issue and you solved it

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