Topic: Spiral on alignments

[therock003]

I guess this is a noob question but i havent figured it out yet,so here goes.

Lets say i create an alignment from polyline.After i choose edit alignment geometry,how can i add spirals before and after the curve and define the a parameter?

[mjfarrell]

Rock,


You might need to try a few different values, unless you have already calculated the proper geometry or when you enter your [A] value C3D will return a NO SOLUTION FOUND error. So you might experiment with using the LENGTH value first, and then using the Tabular view of the Alignment to verify your [A] value if that is the controlling factor. I typically cover this type of alignment geometry editing in all of my classes.

[therock003]

No of course i have considered the lengths and parameters,what i need though now is to draw the spirals.

As i said,if i draw a polyline and define an alignment from polyline,civil creates a default curve as well.If i select edit alignment geometry,i can see some options about spirals but i dont know how to add them in a curve.Also if i select the alignment grid view,a panorama appears where i can view information about the tangents and the curves,and edit some values,but there's no option to add the clothoids there either.

[mjfarrell]

First; is your polyline that you converted into an alignment drawn PI to PI? IF yes then follow the steps below. If not you may want to try creating your geometry over drawing ONLY to the PI's. There are some 'other' special issues when one works with alignments created from polylines as well.

Second, the order of operation is to chose your desired Spiral types.
The command prompts will appear as follows:

Command:
Current spiral definition: Clothoid

Select entity before to attach to: (Here you select the incoming Tangent)



Select entity after to attach to: (Here you select the out going Tangent)


Select spiral type [Incurve/Outcurve] <Incurve>: (Here you select wether it is an Inside or Outside curve)

Specify spiral length or [A]: 25 (Here you select to specify Length, or A value)

Here is the Procedure:

To add a free spiral-curve-spiral (between two entities)

Click Alignments menu Edit Alignment Geometry.
On the Alignment Layout Tools toolbar, click .
Select the entity from which you want to add the spiral-curve-spiral.
Select the entity to which you want to add the spiral-curve-spiral.
Select the spiral-in length by picking two points in the drawing or by entering a spiral-in A value.
Select the spiral-out length or enter a spiral-out A value.
Specify the whether the curve solution angle is either greater than or less than 180 degrees.
Enter a radius value or select two points in the drawing to specify the radius.
To display a curve preview you must either pick a point in the drawing or enter a coordinate value. Then, rubber band is drawn to the cursor from the selected point and the curve preview is displayed.

Note If you enter an A value for either the spiral-in or the spiral-out value, then the curve preview is not displayed when you specify the radius.

(If you can send me only the polyline/alignment you are working with in a DWG I will happy to apply your edits, spiral values and report back on whether it works, or fails and why.)

[mjfarrell]

No of course i have considered the lengths and parameters,what i need though now is to draw the spirals.

As i said,if i draw a polyline and define an alignment from polyline,civil creates a default curve as well.If i select edit alignment geometry,i can see some options about spirals but i dont know how to add them in a curve.Also if i select the alignment grid view,a panorama appears where i can view information about the tangents and the curves,and edit some values,but there's no option to add the clothoids there either.

First let me say I should have read you quoted post MORE carefully.

When you convert ANY polyline geometry into an alignment be sure to toggle OFF the ADD CURVES option.

For two reasons.

First that IS the geometry you wanted for your alignment otherwise why did you draw it that way. (The polyline)
Second you typically do NOT want to place the same Radius curve at ALL locations and most important in most instances the user will not know what the DEFUALT radius is set at.

[therock003]

Thank you for your repliew my friend.

So what is the ADD curves option good for?I have toggled it off since you advised me too.

I tried the fres piral-curve-spiral and it did work.

Two more questions.Since english is not my native language,i dont understand some technical terms.What is the difference between free and fixed options?

Also what did you mean when you asked if i drew from pi to pi?(I know pi means point intersection,but what does drawing pi to pi mean)?

Thanks again!

[mjfarrell]

Don't worry about not understanding the terms used to describe the curves, or spirals. As autodesk chose to use very obscure terminology in their definitions.

FIXED, implies that the geometry is 'locked' in place and changes to the incoming, or out going tangents, result in a NON-tangential curve or spiral.

FLOATING, implies that the geometry is 'locked' to the first attachment point (entity) and changes to the that first object maintains it's tangency however the other end 'floats' and will most likely also become NON-tangential.

FREE, implies that the curve is FREE to alter it's geometric properties to remain tangent should either the incoming OR outgoing tangent geometry be altered.


One sets the Curve/Spiral geomtry settings on the Alignment Toolbar using the little arrow drop down next to the very first Icon on the Left. It is the Last entry titled Curve and Spiral Settings....

The above is all covered in 'lesson 1' for alignments in my classes. Apologies for using PI (Point of Intersection) abbreviation without explanation.

The ADD curves option would ONLY be good (my opinion) if it actually followed geometric rules and altered the radius, etc, instead of using a single default value at all locations.  Even with the 'rule set' in 2009, the geometry Does NOT follow the rules it merely alerts the user when IT(Civil3D) allowed them to break the rules.
What is your native language, as I could attempt to post both the English version of solutions for you and your language.(If supported by Babblefish)

[therock003]

One sets the Curve/Spiral geomtry settings on the Alignment Toolbar using the little arrow drop down next to the very first Icon on the Left. It is the Last entry titled Curve and Spiral Settings....

Is that the "drawing PI to PI" method?

As for the free/floating/fixed explations you provided i concluded that the free is the best since you can easily change the alignment geometry and keep the curves tangentials to the lines.I cant think for now reasons to use fixed or floating...

My native language is greek but plz dont bother with translation,i may as weel ask specifically for any technical term i dont comprehend,other than that i can follow the language. 

As for the lessons you mentioned you teach.What kind of leasons are there?Is it kind of a workshop,or online courses.If there are workshops taking place in the U.S. then of course i wont be able to participate,but if there's any convenient method,i will seriously consider it.

[mjfarrell]

When I use the term PI to PI, the actual command is Tangent-Tangent (No Curves)

My classes are typically at the invitation of the user's Employer, or Agency. In your case that would most likely involve a flight across the Atlantic. My passport is ready, and as I would get a lot out of such a trip, I might actually charge your company only for the flight and a hotel room, and give you the course at no additional charge. (There is more to life than money)

At this point I am off to the airport, to fly home. I will most like be offline until very much later today depending on Internet access, and flight schedules. Have a Great Day!

[therock003]

Wow that is so generous,but sadly I am not currently employed at the moment since i haven't graduated yet (I have passed all of my courses but my degree is pending on my thesis).And then there's the 12 month period service to the army, which here on Greece is mandatory.So 2010 will be the year I will be looking for a job i guess!

[mjfarrell]

I understand your situation; I too performed military service after school, and prior to embarking in my profession.
That being said; when and or if you return to the Civil world the offer stands with no expiration date.

[therock003]

Thank you very much,i appreciate it,and i will certainly be back!

Till then,see ya in the forums!