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Thread: Complex Truss to build....help

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    Default Complex Truss to build....help

    Hello all

    I am trying to build a complex roof truss and am sort of stuck as to how to make it. It isn't a simple single plane truss, but rather has two top chords with one bottom chord, making some of the segments having rotation in both the x/y plan as well as the x/z plane. I have attached a quick sketch of the truss to get a better idea. To add to this problem, i would really like it to be adjustable, since the dimensions may change.

    I believe the answer to the major problem of this truss (making the segments that aren't planar in the x,y,or z planes) lies with using reference lines, however i don't have a lot of experience with refernce lines. I may be wrong with that however.

    Any help anyone could give me would be most appreciated.
    Thanks
    Gord
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    Active Member wildcat_714's Avatar
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    Default Re: Complex Truss to build....help

    Heres quickie for ya. Im going to try doing it a slightly different way also since this would probably be tubes correct?
    Peter-
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    Default Re: Complex Truss to build....help

    Thanks for the reply. Unfortunately i'm still using Revit 7, so i couldn't open your family. Is there any way you'd save it down to 7?

    Also, does anyone know of the proper syntax for using the trigonometric 'sine' formula?

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    I could stop if I wanted to ita's Avatar
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    Default Re: Complex Truss to build....help

    February 2001 Cadalyst had an excellent tutorial called "Create parametric trusses in the Revit Family Editor" by Richard Rundell - which is probably what you want. I have a copy but it does not export - it is corrupted somehow! Somebody may have a copy or know where the article is on a site. RevitCity had a copy but I could not find it in a search. Best of luck.

    And . . . look up "Valid formula syntax" in the help file. Its all there!
    Last edited by ita; 2005-08-30 at 09:24 PM. Reason: Added the syntax help message

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    Revit Technical Specialist - Autodesk Scott D Davis's Avatar
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    Default Re: Complex Truss to build....help

    I might use a void to drive the truss geometry for your sjetch, if I've understood it correctly. Looks like a type of spaceframe, or a '3-sided' truss?

    If so, you can build a void to the shape that you need and then attach the truss members as sweeps using the edges of the void as sweep paths. The void doesn't actually cut anything, it is just used as a 'place holder' and wont show when you load it into the model.

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    I could stop if I wanted to ita's Avatar
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    Default Re: Complex Truss to build....help

    Gordgraff, I have managed to turn the tutorial into a pdf document in a binder - attached below. It is somewhat dated but the principles still apply.

    Whjooops the order of the threads has got reversed. How about that
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    Last edited by ita; 2005-08-30 at 09:54 PM. Reason: Thread reversal

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    Revit Arch. Wishlist Mgr. Wes Macaulay's Avatar
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    Default Re: Complex Truss to build....help

    Quote Originally Posted by gordgraff
    Thanks for the reply. Unfortunately i'm still using Revit 7, so i couldn't open your family. Is there any way you'd save it down to 7?

    Also, does anyone know of the proper syntax for using the trigonometric 'sine' formula?
    Sure Gord - it's sin in Revit. So sin(30) will give the value of 0.5

    The others are cos, tan, atan, acos and asin.

    That truss you were building... as a R7 project I would cut a section crosswise across the truss, and create two ref planes for the angled sections. Name the ref planes and then set your plane to one of the named planes. Then you can draw model lines in those planes, and then sweep along the model lines.

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    Active Member wildcat_714's Avatar
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    Default Re: Complex Truss to build....help

    Sorry, Revit cant save down and I no longer have 7 on this machine. Out of curiosity why arent you using 8 or 8.1? And Scott nailed the other way I was going to build it. By using a mass (in this case a void) it would be pretty easy to control while flexing, and the cleanups would probably be handled better.
    p-

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    Default Re: Complex Truss to build....help

    Thank you for all your help. I will try the void option next, but at the moment i'm trying one involving reference planes that rotate based of length changes (in order to ensure it always lines up with the proper joint). Anyways, i need to use the tangent comand in a formula to set the angle, but haven't used it before. I tried searching for 'valid formula syntax' but i couldn't find the source. Could someone possibly direct me to the thread/page that describes proper formula syntax for tangent.

    Actually, what i need is tangent ^-1 (inverse), can Revit do this formula?

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    Active Member wildcat_714's Avatar
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    Default Re: Complex Truss to build....help

    This site is pretty popular for math formulas. Might have what you need.
    http://www.mathforum.org/

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