Community
Civil 3D Forum
Welcome to Autodesk’s Civil 3D Forums. Share your knowledge, ask questions, and explore popular AutoCAD Civil 3D topics.
cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

Transition types/equations

3 REPLIES 3
Reply
Message 1 of 4
azontanou
388 Views, 3 Replies

Transition types/equations

Hi,

I am currently working on a rail project and i’m having a problem with the formula of cubic parabola. I would appreciate if you could give me any tips/advice.

 

Here is my problem:

For the spirals i have to use the cubic parabola type.

C3d 2014  supports  the formula for cubic parabola, but  the simplified one: y=(x^3) / (6*R*L)   

Unfortunately  this formula is not acceptable for my client .

The formula that needs to be applied is: y=(x^3) / [6*R*l* (cos^(3) τ)]

 

Have anyone faced a similar situation before?

I am wondering  if  there is  a way to modify the current equation of cubic parabola, or if a third-party plug-in is developed  for that purpose.

 

Thank you in advance.

 

3 REPLIES 3
Message 2 of 4
doni49
in reply to: azontanou

Forgive me as I've never used a "cubic parabola" before (or spirals in C3D) but the only real difference I see between the two formulas is instead of L, you've got (cos(3)*t).  So is that just more accurate than L?  Meaning is L that number but rounded?  If so, can't you somehow adjust the rounding that the formula uses?



Don Ireland
Engineering Design Technician




If a reply solves your issue, please remember to click on "Accept as Solution". This will help other users looking to solve a similar issue. Thank you.


Please do not send a PM asking for assistance. That's what the forums are for. This allows everyone to benefit from the question asked and the answers given.

Message 3 of 4
wfberry
in reply to: doni49

Don:

 

I think you may have overlooked something.  I believe that is a lowercase "L" he typed in that one formula.  All I know about it, but it must be somewhat significant.

 

Bill

 

 

Message 4 of 4
azontanou
in reply to: doni49

I would like to thank you very much for your prompt responses. Time is very critical for us, so in order to make myself more clear, i am attaching images explaining all about the equation (in English).

As mentioned before, Civil 3d uses the simplified formula to solve cubic parabola, but for my client the only acceptable equation is the complicated one (in the green box).

 

And i am still wondering:

Have anyone faced a similar situation before?

Is there a way to modify the current equation of cubic parabola in civil 3d?

Or is it possible a third-party plug-in to have been developed for that purpose?

 

 

 

 

Can't find what you're looking for? Ask the community or share your knowledge.

Post to forums  

Rail Community


Autodesk Design & Make Report