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Seemingly basic drafting question


HCb

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Hey, all, this may be stupid-simple but I cannot figure it out (I'm a builder, not a draftsman...so far). If I need to post this somewhere else, please let me know.

 

Attached is a file. I'm trying to draw a truss I'm going to build a number of. I want to throw in a diagonal brace between a couple of uprights on each side. I want the brace piece to have square ends, not diagonal cuts. I want the brace piece to fit into the space between two parallel vertical pieces and the horizontal and diagonal piece with, hopefully, all four corners of the rectangular brace piece touching the bounding pieces (I'm not sure this is possible). I'm not sure how to go about drawing the brace piece (shown in magenta in the file on the PurlinSupports layer). I've tried a number attempts but modifying the position/angle at one end mucks up the other end. If this is possible to draw it right in one try (without a bunch of hack work) then it's probably something sexy/simple (like bisecting a line with a compass) but I haven't figured it out. My hacking attempts are on the left in the drawing, my depiction of what I'm looking for as a final product are on the right in the drawing.

 

I'd love some help. Thank you.

 

--HCTrussTest.dwg

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What are you using to construct your truss? Wood or steel? If you are using steel, what structural shape will be used for the chords, verticals and braces?

Edited by ReMark
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HCb, since your file was made with an educational version of AutoCAD, I don't think a lot of people will be opening it (something about the educational stamp infecting AutoCAD so it shows up on EVERY drawing). If possible, can you post a JPEG or attach a PDF of what you're trying to do?

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HCb, since your file was made with an educational version of AutoCAD, I don't think a lot of people will be opening it (something about the educational stamp infecting AutoCAD so it shows up on EVERY drawing). If possible, can you post a JPEG or attach a PDF of what you're trying to do?

 

Oh gosh. That is simply perpetuating a myth.

 

That is only true for drawings that have objects or data copied to them from an educational version. It stops people from making money off a free product. Most of us actually have no issues at all in opening or even downloading educationlly generated drawings. Most of us also know better than to copy parts of them into something we want to get paid for.

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(something about the educational stamp infecting AutoCAD so it shows up on EVERY drawing).

 

Not possible.

Fine to post edu files here.

Anyone familiar with AutoCAD can open your file without concern.

 

But if you are a student - why aren't you doing this with the Frame Generator in Autodesk Inventor - much much much easier.

Students can get Inventor for free from http://www.autodesk.com/edcommunity

 

If for some reason of torture you must use AutoCAD - this tutorial might help http://home.pct.edu/~jmather/content/CAD238/AutoCAD%202007%20Tutorial%208.pdf

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The geometry that you are trying to construct does not have a simple solution in basic AutoCAD, although some different versions may be able to do what you want (someone may mention Inventor). If you are at an educational establishment, you could download it for free.

 

Structurally, what you are drawing goes against the premise that the centre lines of all members at a joint pass through a common point, otherwise there is an out of balance force at the joint.

 

I wonder why no-one has thought of this layout before? Perhaps the geometry is too tricky for techniques available until now. Probably your easiest solution would be to try a full scale set up, so that your square ended timber takes up its own position at one end, whilst you mark up the other end :D

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I'm still trying to figure out if this is supposed to be a wood or a steel truss. Looks like the OP has incorporated some channel in the design.

 

Is this what you are trying to do? I'm not recommending it. Saved in 2000 file format.

 

TrussTest-1[rev].dwg

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I'm still trying to figure out if this is supposed to be a wood or a steel truss. Looks like the OP has incorporated some channel in the design.

 

The OP needs to clarify the design intent if all sections are the same or not.

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What are you using to construct your truss? Wood or steel? If you are using steel, what structural shape will be used for the chords, verticals and braces?

 

Thank you for the reply.

 

I'm using 2x4 rectangular steel tubing, 11ga. I'm thinking that there should be a way to draw a maximum-length piece of the same material in the diagonal position shown in the file without a bunch of trial and error. I'd like to be able to do this for multiple projects, each one with different roof pitches and vertical brace spacing.

 

--HC

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I read it that the OP wanted something like this, so that all the braces could be cut square. :?

 

Those added braces, if cut square like that would have to be applied to the outside of the truss, covering the existing joints to have any structural value at all.

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Thank you for the reply.

 

I'm using 2x4 rectangular steel tubing, 11ga. I'm thinking that there should be a way to draw a maximum-length piece of the same material in the diagonal position shown in the file without a bunch of trial and error. I'd like to be able to do this for multiple projects, each one with different roof pitches and vertical brace spacing.

 

--HC

Oh, OK. Then what you want is a dynamic block of the part you need. This block would have a lengthwise stretch action. You could insert the block, stretch it, then rotate it into place, or add a rotational action to the block too. Another way would be to simply draw a rectangle of the required size, and rotate it into position.
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Might be able to help if you saved your drawing back to a earlier version of autocad, not all of is have the latest versions of autocad

 

Hey, Sparky, sorry, I wasn't trying to be thoughtless. I'm attaching the same file saved for R14 which seems like it goes back to the late 90's.

 

Thanks for your reply and help.

 

--HCTrussTestR14.dwg

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Not possible.

Fine to post edu files here.

Anyone familiar with AutoCAD can open your file without concern.

 

But if you are a student - why aren't you doing this with the Frame Generator in Autodesk Inventor - much much much easier.

Students can get Inventor for free from http://www.autodesk.com/edcommunity

 

If for some reason of torture you must use AutoCAD - this tutorial might help http://home.pct.edu/~jmather/content/CAD238/AutoCAD%202007%20Tutorial%208.pdf

 

Hey, JD, thanks for the reply.

 

I'm using AutoCAD, quite honestly, because I didn't know any better than to not. I've been doing CorelDRAW for years, as mentioned, but not doing extensive design work with it. I was taking a college course for something unrelated and decided to take advantage of the ability to get a legal license for the product which I could use for a while to try to learn it. I had downloaded a trial before but got so frustrated (not thinking to look for tutorials online) that I had given up on it. When I got the chance to get a license legally for a longer period of time I thought I'd give it a shot. Glad I did and when the edu license expires I'll buy a commercial license. In the meantime I'm learning it on my own.

 

I'm going to check out that link, thank you.

 

--HC

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The geometry that you are trying to construct does not have a simple solution in basic AutoCAD, although some different versions may be able to do what you want (someone may mention Inventor). If you are at an educational establishment, you could download it for free.

 

Structurally, what you are drawing goes against the premise that the centre lines of all members at a joint pass through a common point, otherwise there is an out of balance force at the joint.

 

I wonder why no-one has thought of this layout before? Perhaps the geometry is too tricky for techniques available until now. Probably your easiest solution would be to try a full scale set up, so that your square ended timber takes up its own position at one end, whilst you mark up the other end :D

 

Hey, Eldon, thank you for your reply.

 

I'm no longer a student so I cannot download the edu licensed Inventor. Maybe a 30-day trial or something.

 

Structurally, I'm not a professional engineer. I have an engineer who has defined the materials to be used and the diagonal and horizontal parts of the truss are more than adequate (he tells me) for the compression and tension loading on the respective members. The material comes in 24 foot lengths and, when cut to length, gives me a few drops. I'm trying to use some of the drop to add additional bracing to the truss. I have done what you suggest (set up a full-size piece and cut to fit), but I was thinking there might be a way to do it in CAD so I know ahead of time. I've built trusses that clearspan 48 feet using the same basic principle and which have handled a 6+ inch snow load on a 3:12 pitch. I cut those diagonal members (there were more of them in my longer trusses) in the manner you suggest...lay it up there and mark it.

 

Thanks again.

 

--HC

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Hey, ReMark, the structure is all steel rectangular tubing (for the structure of the truss). The channel depicted are parts from my full drawing I did not remove for the sample file I submitted. They represent Cee purlin which will support the roof panels which will run from one truss to the next (away from the view point you see in the file I submitted). I have since also submitted a R14 version of the file.

 

--HC

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The OP needs to clarify the design intent if all sections are the same or not.

 

Hey, JD, the truss itself is comprised of the members on the Trusses layer (shown in green) with the diagonal parts I'm trying to draw shown on the PurlinSupports layer in magenta. All the truss pieces (green) and the diagonals (magenta) are of the same material: 2x4 11ga mild steel.

 

--HC

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