Parametric Curve not generating LD-Haack curve

alex_ramirez327

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

mahir

@alex_ramirez327
It took some doing, but here's a functional version. Looks like OS was hiccuping on adding an angle to a non-angle, so I had to divide by "rad" in one spot. Take a look.

<a rel="nofollow" href="https://cad.onshape.com/documents/806fd3a0e7926db94f37794d/w/27cbe82bc35c7cf9267e6a01/e/4b66ed7509d6c90d8d02b282" title="Link: https://cad.onshape.com/documents/806fd3a0e7926db94f37794d/w/27cbe82bc35c7cf9267e6a01/e/4b66ed7509d6c90d8d02b282">https://cad.onshape.com/documents/806fd3a0e7926db94f37794d/w/27cbe82bc35c7cf9267e6a01/e/4b66ed7509d6c90d8d02b282</a>

mahir

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

@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.

mahir

@ilya_baran I think you're on to something with the negative sin(). Onshape doesn't support imaginary numbers... go figure. 

¯\_(ツ)_/¯ 

mahir

@alex_ramirez327
It took some doing, but here's a functional version. Looks like OS was hiccuping on adding an angle to a non-angle, so I had to divide by "rad" in one spot. Take a look.

<a rel="nofollow" href="https://cad.onshape.com/documents/806fd3a0e7926db94f37794d/w/27cbe82bc35c7cf9267e6a01/e/4b66ed7509d6c90d8d02b282" title="Link: https://cad.onshape.com/documents/806fd3a0e7926db94f37794d/w/27cbe82bc35c7cf9267e6a01/e/4b66ed7509d6c90d8d02b282">https://cad.onshape.com/documents/806fd3a0e7926db94f37794d/w/27cbe82bc35c7cf9267e6a01/e/4b66ed7509d6c90d8d02b282</a>

alex_ramirez327

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

thanks so muck, I had the same issue and you solved it