Problem making 3x3 square tube diagonal bracing

[Luke_Y.AGII]

Here is the problem:

How do I make accurate 3x3 diagonal braces, where the top lands 1.5 inches below the top of the post and the bottom lands 1.5 inches above the bottom of the opposite post. 

Allign would work perfectly, but not without knowing the exact length.

ive tried making  a long 3x3 and attaching it to the bottom and rotating it using the bottom center as a rotation point (and then slicing the ends off). This gets me close, but it isnt accurate. 

Is there a way to do this that doesnt require me to dust off my trigonometry text books?

 

[dany_rochefort]

@Luke_Y.AGII  Just draft everything out in 2d, then extrude it to 3d. Rather than trying  to ''slice to fit'' 3d elements. 

[Kent1Cooper · Accepted solution]

Assuming you mean you want the top face of the diagonal 3x3 to hit the inboard face of the right vertical at that distance from the top, and the bottom face of the diagonal likewise to hit the left vertical that far up from the bottom....

A and B are the ends of your diagonal Line in the image [red here].  With a UCS set in the plane of the overall frame at the red Line, OFFSET the red line by 3" down-rightward [yellow Line].  Draw a CIRCLE centered at A and passing through B [dashed green].  ROTATE the red and yellow Lines, with A as the rotation base point, and using the Reference option.  The Reference direction will be from A to C, which is the INTersection of the yellow Line with the green Circle [not the end of the yellow Line], and the new direction will be to B.  The right side above is after that rotation.  OFFSET either the red or yellow Line by 1 1/2" toward the other, for the center-line path to EXTRUDE or SWEEP your 3x3 along.

[imadHabash]

Hi,

Click on below image and follow commands to complete your issue .. 

- Ucs command >> ZAxis 

- draw a rectangle by Rectang command .

- Extrude command >> Path 

[Luke_Y.AGII]

you could do the same thing with SWEEP, the problem here is that the white line you are using as a path (if it is a copy of the line i used to connect the two horizontal lines)  is not the correct path. Move the object into place and you will see it doesnt land correctly. 

[Luke_Y.AGII]

Yeah, that does work, but I was hoping for a quicker way to do it. thank you.

[Washingtonn · Accepted solution]

Draw a diagonal line segment between posts (from low point to high point).

At the mid-point of this line segment, draw a circle having a diameter equal to the tubing outside dimension.

Draw a perpendicular line passing through the mid-point of the original line intersecting the circle.

This is the angle for the tubing between the posts. move the line to the center of the circle, extend to the other post.

Adjust the tubing length to account for angle trimming.

[Luke_Y.AGII]

this is very similar to the solution that I came up with as well. i just wish there were an easier way to move about the 3D objects and trim them up, instead of having to draw a 2D version of each new instance.

[imadHabash]

LOFT command .

[Luke_Y.AGII]

the profile of a 3x3 sq tube cut on an angle will terminate in a rectangle, not a square , the height of the brace you created is less than 3". Since you don't know the height of the profile the brace will make at the post, you cant really use this method. But I appreciate you trying to help!

[Kent1Cooper · Accepted solution]

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@Washingtonn wrote:

....

Draw a perpendicular line passing through the mid-point of the original line intersecting the circle.

This is the angle for the tubing between the posts. ....

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It's not quite clear to me from the description, but if by "This" you mean that the direction from the INTersection-of-perpendicular-Line-with-Circle to the top end of the original diagonal is the angle, that's not correct.  For an exaggerated example, that would be the green here, when what you want is really the magenta:

You can do it by drawing a Circle at the mid-point of the original diagonal, but if that's the approach, then skip the perpendicular Line, and instead draw one of the magenta Lines, from the original endpoints [A & B here], TANgent to that Circle, to get the correct direction for the diagonal tube.  Move that to the center-of-Circle/midpoint-of-original-diagonal, and Extend/Lengthen it as needed for the mid-line path to Extrude/Sweep along.

[Patchy]

Rotate is the precise way.

Same as in the shop, hold one end of the tube and rotate the other end, no mistake about it.

[Luke_Y.AGII]

this would result in a width or height of larger than 3". You dont need a circle at all, just a line that is 1.5 inches on either side of the connecting line that is perpendicular to the line. 

 

[Kent1Cooper]

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@Luke_Y.AGII wrote:

this would result in a width or height of larger than 3". You dont need a circle at all, just a line that is 1.5 inches on either side of the connecting line that is perpendicular to the line. 

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Not so, because what you suggest will give you the green Line in my previous image twice, and the perpendicular distance between those two, which should be the desired dimension of the tube, will be less than that dimension.  Not by much at the size of the OP's image, but still less, as the exaggerated situation illustrates.  EDIT:  Measure the distance perpendicularly between your Lines that meet the ends of that 3" Line, with sufficient precision to show the difference, and you'll see.

[Luke_Y.AGII · Accepted solution]

Please see the attached video.

[Kent1Cooper]

You didn't do it with high enough precision to see the difference, as I suggested.  Using your technique [yellow Lines], the perpendicular distance between is, and in fact must be, less than 3":

whereas drawing them TANgent to a 3"-diameter Circle at the middle:

As I said, it's not very much less in your approach at comparatively large size [and how much less will vary with the ratio of the diagonal length to the desired width], but it is less.  A more exaggerated example, with the desired dimension larger in relation to the overall size of things, so the difference, in Aligned Dimensions taken perpendicularly between, is clear even at lower precision:

[Washingtonn]

Kent is technically correct regarding the dimensions being less than 3" for the method shown in Luke's video - BUT  consider the following:

1. Existing manufacturers' allowable tolerances of all the steel members (both brace and posts)

2. Measuring and cutting tolerances of the steel in the shop/field.

3. Welding tolerances when components are assembled together in the shop/field.

4. Acceptable assembly installation tolerances.

Conclusion:

Luke's method is the correct one to use for the task at hand as it is the easiest/quickest to implement.

[Luke_Y.AGII]

I see what you mean. Thank you for your input!