Modelling Rail Track

[tfhill]

We are currently looking at how to model rail track in Revit to avoid a Bentley solution (Microstation / MX). A piece of track curves left and right in plan and up and down in section whilst at the same time twisting. We can ignore that it is track, effectively alll want to do is extrude a shape along a 2 axis curve whilst twisting the shape.

 It is possible to use a swept blend to create a twist along one curve in either axis, but not both axes as far as I have worked out. To make this more difficult the swept blend will also only let you sweep along one curve at a time, so if it was snaking in plan on a flat surface each curve would need to be set up and sweep over and over which is not really a suitable solution.

Does anyone have any suggestions? we are using Revit Architecture, Structure and Inventor.

[kathryn.langan]

Hi Tom,

You should be able to achieve this in the conceptual massing environment. You might want to take a look at the Sweeps and Swept Blends documents for more information.

If you want your rail to be something other than a mass, you can use the Model By Face tools in the Massing & Site tab, or you could use a dummy mass to create a sweep path and use the standard shape tools (see Set the Massing Tools Free(ish)).

I hope this helps! If you have any questions about the above please let us know!

[tfhill]

Hi,

Despite having used conceptual mass for sometime now I didnt know it could do this. I have tried it and I would say we are half way there. I can draw a curved path and use the element point to sweep several different profiles along it which is great, however, as soon as I introduce another curve to the path I get an error with no explanation. If I make the profiles all circles it works, however, any other shaped profiles and it gives me an error. If I have a path of multiple curves and draw a spline over those curves then it works with any profiles.

Also these paths are on one plane (flat) and I am unsure how this can be altered to make the path follow 2 planes, ie, it curves in plan and section.

Thanks for your help this is something we have been trying to solve for some months now using all software packages and Solidworks looked to be the only solution. If we can get Revit to do it then that would be the ultimate solution.

[kathryn.langan]

Hi Tom,

It might help to be able to see what you're trying to do - do you have an image or a sample sketch that shows what kind of path this will follow and how the profile should adjust?

[tfhill]

Hi,

As its for the modelling of all rail track in many future projects and not any project in particular I cannot really sketch it. Basically we need to extrude / sweep a shape along a path. The path will need the ability to bend infinitely in all directions in plan and section whilst twisting along the extrusion. We will only be modelling a section for each scheme, but every piece of every scheme will  be different.

Another way to look at it would be that we need to model the track of a rollercoaster......... just not to such an extreme path.

Thanks

[kathryn.langan]

A single profile sweep can be created along a multi-segmented path, but a blend cannot. Can you achieve the path you need by manipulating a spline?

[tfhill]

Spoiler

I can achieve it, however, I am not sure how accurate it is and as a track consists of 2 parallel paths I am not sure if this will work as I dont think a spline can be offset? I am trying to achieve this as Bentley have cornered this market for all rail schemes. This is an add-on that Autodesk need to write or they will loose customers to Bentley as Network Rail are pushing for all rail schemes to be done using Bentley products such as Microstation and Navigator rather than Navisworks / Revit. 

[ccollins]

It can be done using Revit Conceptual Massing.

Profile of rail swept thru spline thru points. Reference points can be adjusted in plan/section/ 3D.

Spline can be copied to create 2nd rail.

Ties can be placed between rails by creating a form, dividing the surface and applying an Adaptive Component.

( FWIW--Revit's Conceptual Massing code and UI was "borrowed" from Bentley when their guru programmer came to Adesk.)

cheers

[kathryn.langan]

Hey Tom,

As Cliff mentioned, the spline could be copied, but not offset in the conceptual environment.

[tfhill]

Hi Guys,

Copying it would not give the correct geometry, it would need copying and then altering to suit, it doesnt appear that there is an accurate efficient solution that would convince our track designers to switch from Microstation. Unfortunately I think we will have to model it in Bentley as is currently standard then link it in to the Revit / Navisworks model.

Thanks for your help.

[kathryn.langan]

I'm sorry that we weren't able to come up with a better solution. I would suggest providing some comments to the Revit Development group at the Product Feedback site - input on your workflow would be helpful for them to improve this in the future.

[tfhill]

Thanks for this link, I will submit something to them.