Aligning a parabolic curve tangent to two points

[pneal231]

I have come up with a parabolic curve from a 'Sag Chart' program for calculating wire sag between Utility Poles. I now need to place this curve into my Profile that has the poles laid out in it. I need to make the curve Tangent at each attachment point between two poles. The best I can do as of now is eyeball it in there which will get me the sag distance pretty closly but as any Autocad user knows if it isnt exactly aligned it will drive you nuts. I made a rough sketch of what im trying to do.

 

[Tyke]

How do you ant to deal with the difference in levels of the end points of your catenary? Can you not give this information into your software that calculates the catenary and let it calculate the asymmetrical catenary that you require. You could then make a block of the catenary and scale it on insertion to take account of the vertical exaggeration of your profile.

[pneal231]

I do not have the software that came up with the catenary. I was only given the appropriate catenary for three different types of wire. The levels of all the end points will vary span to span depending on the grade of the ground and pole height. There are several hundred spans in this particular projects.

[JD Mather]

Attach dwg files here, not image files.

Does LT have Parametric tab (Geometry Constraints)?

 

And I think you mean coincident, not tangent. Show your "eyeball solution" so that the design intent is clearer.

[pneal231]

2123389 16-E3R2.dwg

 

Attached is a portion of the file.

[Mike_Taylor]

Attach dwg files here, not image files.

Does LT have Parametric tab (Geometry Constraints)?

 

And I think you mean coincident, not tangent. Show your "eyeball solution" so that the design intent is clearer.

 

LT does not have the bility to create constraints.

[JD Mather]

You didn't answer the question about LT having Parametric functionality.

There is no point in me trying to work out a Geomtry Constraints solution if LT doesn't have that functionality.

 

Edit. Well now I see that it is reported - no constraints in LT.

[pneal231]

Yes, there is a Parametric Tab Autocad 2013 LT.

[JD Mather]

Yes, there is a Parametric Tab Autocad 2013 LT.

Well then, I guess we are back on.

It will probably be best to put a Fixed Constraint on all line endpoints that don't move. I don't norally work quite like this, but it will be an easy way to get started.

The next step will be to get some points for coincident constraints on curve at known spread distance between pole contact points. (you will probably want a construction layer for hiding some stuff to keep it from getting too confusing)

I will try to post example tomorrow.

[BIGAL]

if you google catenary there is lots about the formula so could build a equation in excel and import the point values into LT by pasting to command line pretty sure this still works with LT just copy the column of x,y after typing pLine

 

The excel needs to use the contactenate command =CONCATENATE(A1,",",B1)

 

PLINE

123.45,456.89

125,456.7

127,455.23

[eldon]

I think there may be a simple solution to the problem.

 

First place a copy of the catenary on the top of each tower. Then move one catenary using the intersection with the next catenary as the base point, to the top of the next tower. And so on down the line of towers