Station equality in middle of alignment

[annw2]

Shifting gas line alignment - stable in the middle - moving on the ends.

I have corridors, profiles, profile views, off set alignments all set.

Can I add a station equation in the middle at this points without undoing all of the above?

Will this keep my profile views in the middle stable so I can get decent plots in the middle, while the end keeps moving or will this not help?

Has anybody used this feature?

[Joe-Bouza]

Not sure, but were the calculation for the gas line minimum radii acceptable?

[Jason.Hickey · Accepted solution]

You can do what I just did - test it on fake data and see. The results weren't as I had hoped they'd be.

I had an ailgnment that ran from 0+00 to 62+84. At station 30+00, I added a station equation with a station back of 30+00 and a station ahead of 300+00. The profile looked good, the alignment looked good, life was good.

Next, I adjusted the start point of the alignment and the end point - the staion equation remained gometrically in the same location, but the station values changed - your zero moves when the beginning of the alignment moves, so the station back changes as well. The profile also shifted since the whole thing is station based and I changed the stationing.

What you MIGHT try is using a reference point instead of a station equation. In the alignment properties, set a reference point at the station that you don't want changing. That will hold that station at that point no matter how you edit the alignment.

[annw2]

If I have time, I prefer to ask here rather than risk losing the data set.

I was going to try keeping a copy of my file, then changing the  station reference point to see what happens.

Thanks for the heads up about the station equality shifting.

Yes.  The fillet length also works fine.

Thank you for all the help, and why does the accept as solution not always show?  It would help if it was an option in this window as well.

[andrewpuller3811]

If you put 2 station equations in the alignment, one at the start of the alignment before the area to hold, but after the first curve and the other at the end of the alignment, after the area to hold but before the last curve, seems to work as you want.

If you move the start of the alignment or the end, the profile stays fixed with respect to the existing surface, as long as there is always some space between the start of the alignment and the start of the profile.

[annw2]

Just getting back to this issue after being on hold for months.

What happens if the station equalities SHORTHEN the alignment and you have two station 200+00's for instance?

How would 3d know to keep the profile views straight?

My boss wants the overlap to reduce drafting time on the ends that aren't changing, but I'm not sure that would work.