## Turbo Talk => General Discussion => Topic started by: Kevin Taylor on December 05, 2017, 02:35:07 PM

Title: What am I doing wrong with these angles?
Post by: Kevin Taylor on December 05, 2017, 02:35:07 PM
I am trying to do a simple 1" x1" square steel tube frame that has some compound angles.
The side rails where my compound angles are seem to be wrong somehow, and I cannot figure anything out.
They should be parallel when all said and done, but they are off by just enough to mess everything up.

This is what I have done:
I simple extrude it
I draw a line at the angle I need
I simple extrude that line
I move the origin of the simple extruded line so I can rotate the y axis to the angle I need to make it a compound angle
I do a 3d slice
3 point assembly
everything looks good at first glance, but they are off..as in not parallel as they should be.

I have no idea what I am doing wrong, and I cant take it anymore. Ive redone it a 100 times and in different ways all producing the same result, I need help on what I am doing wrong.

platinum '16
Title: Re: What am I doing wrong with these angles?
Post by: Henry Hubich on December 05, 2017, 04:27:22 PM
I'd suggest that you delete the two red members and then replace them as follows: Establish a Workplane By Facet on the front face of the rear member, as shown in the first attachment below. Then draw a 1" square with the starting corner on one vertex of the mitered face of the rear member, as shown in the second attachment. Extrude this square and adjust its length to overlap the rear member and the inclined member. Adjust the length of the rear member and of the inclined member to overlap the new extrusion. Working carefully by eye in zoomed-in views, 3D-Slice the three members to create mitered joints.

HOWEVER, I noticed that the rear member is not quite level, being tilted about 0.09 degree. I strongly recommend that you redraw that part before following the procedure suggested above.

Henry H
Title: Re: What am I doing wrong with these angles?
Post by: Kevin Taylor on December 05, 2017, 04:39:26 PM
Thanks Henry.
I am going to try that out. Couple of things however:
For the future, when I need to do exact compound angles like this, how do I go about doing it?
In the example I posted, those rails have an incline of 20 degrees and go outwards for a total angle of 170 degrees or an 85 degree miter on each piece and a 10 degree bevel.

I want to be able to just use the angles I have, rather than draw stuff out and see what angles come as a result of that. So how do you go about that knowing the angles you want to have?

BTW, I knew the back end was out of whack, I almost deleted it before posting the file. I didnt want to start trying to fix it until I figured out the side rail issue.

Thank you for the reply Henry.
Title: Re: What am I doing wrong with these angles?
Post by: Henry Hubich on December 05, 2017, 06:04:08 PM
Thanks Henry.
I am going to try that out. Couple of things however:
For the future, when I need to do exact compound angles like this, how do I go about doing it?
In the example I posted, those rails have an incline of 20 degrees and go outwards for a total angle of 170 degrees or an 85 degree miter on each piece and a 10 degree bevel.

I want to be able to just use the angles I have, rather than draw stuff out and see what angles come as a result of that. So how do you go about that knowing the angles you want to have?

BTW, I knew the back end was out of whack, I almost deleted it before posting the file. I didnt want to start trying to fix it until I figured out the side rail issue.

Thank you for the reply Henry.

One way: In World Plan view, Workplane by World, draw a line (anywhere, any length) at an angle of 85° and Extrude it. Go to Front view, Workplane by View, and rotate the extrusion 10° CCW about the Z axis. Place the extrusion where you want the top cut of the slanted member and 3D Slice it, using Slice by Plane (or Slice by Surface if your version offers that option).

Henry H
Title: Re: What am I doing wrong with these angles?
Post by: Alvin Gregorio on December 05, 2017, 06:22:21 PM
...
For the future, when I need to do exact compound angles like this, how do I go about doing it?
In the example I posted, those rails have an incline of 20 degrees and go outwards for a total angle of 170 degrees or an 85 degree miter on each piece and a 10 degree bevel.

I want to be able to just use the angles I have, rather than draw stuff out and see what angles come as a result of that. So how do you go about that knowing the angles you want to have?
...

Trigonometry, I would guess.  I don't know trig.
This reminds me of figuring out the angles for and cutting crown-molding.

So, for the math folks-- I guess the question is how would one mathematically calculate the compound cut angles in kevbo's example.
Title: Re: What am I doing wrong with these angles?
Post by: Kevin Taylor on December 05, 2017, 06:48:50 PM
Thanks Henry.
I am going to try that out. Couple of things however:
For the future, when I need to do exact compound angles like this, how do I go about doing it?
In the example I posted, those rails have an incline of 20 degrees and go outwards for a total angle of 170 degrees or an 85 degree miter on each piece and a 10 degree bevel.

I want to be able to just use the angles I have, rather than draw stuff out and see what angles come as a result of that. So how do you go about that knowing the angles you want to have?

BTW, I knew the back end was out of whack, I almost deleted it before posting the file. I didnt want to start trying to fix it until I figured out the side rail issue.

Thank you for the reply Henry.

One way: In World Plan view, Workplane by World, draw a line (anywhere, any length) at an angle of 85° and Extrude it. Go to Front view, Workplane by View, and rotate the extrusion 10° CCW about the Z axis. Place the extrusion where you want the top cut of the slanted member and 3D Slice it, using Slice by Plane (or Slice by Surface if your version offers that option).

Henry H

Interesting, i am going to try it out. Sounds like pretty much what I was doing in my first post, but I am going to see if your way results in what I need.

Thanks for the info.
Title: Re: What am I doing wrong with these angles?
Post by: Kevin Taylor on December 05, 2017, 06:54:09 PM
...
For the future, when I need to do exact compound angles like this, how do I go about doing it?
In the example I posted, those rails have an incline of 20 degrees and go outwards for a total angle of 170 degrees or an 85 degree miter on each piece and a 10 degree bevel.

I want to be able to just use the angles I have, rather than draw stuff out and see what angles come as a result of that. So how do you go about that knowing the angles you want to have?
...

Trigonometry, I would guess.  I don't know trig.
This reminds me of figuring out the angles for and cutting crown-molding.

So, for the math folks-- I guess the question is how would one mathematically calculate the compound cut angles in kevbo's example.

I didnt explain that very well, Henry posted an example in post #3.
Basically I used an angle finder to determine the angles, so I know what they are. I just need to put them in turbocad correctly. I am using the correct angles, But they are just not coming out correctly for me.

So in the example I had a 20 degree incline on the rail that also comes out. This creates a compound angle, overall angle is 170 degrees with a 20 degree incline (thats really hard to explain in words). So its a 85 degree miter with a 10 degree bevel. I just have to figure out how to input that in turbo cad.
Title: Re: What am I doing wrong with these angles?
Post by: Dean on December 06, 2017, 04:07:40 AM
I am trying to do a simple 1" x1" square steel tube frame that has some compound angles.
The side rails where my compound angles are seem to be wrong somehow, and I cannot figure anything out.
They should be parallel when all said and done, but they are off by just enough to mess everything up.

This is what I have done:
I simple extrude it
I draw a line at the angle I need
I simple extrude that line
I move the origin of the simple extruded line so I can rotate the y axis to the angle I need to make it a compound angle
I do a 3d slice
3 point assembly
everything looks good at first glance, but they are off..as in not parallel as they should be.

I have no idea what I am doing wrong, and I cant take it anymore. Ive redone it a 100 times and in different ways all producing the same result, I need help on what I am doing wrong.

platinum '16

Not sure if this helps but a quick and easy fix to your problem was to loft 3D polylines.
Title: Re: What am I doing wrong with these angles?
Post by: nikkipollard on December 06, 2017, 05:23:52 AM
Excellent Idea Dean

I really battled with the slice tool (specifically the slice by 2 points) when I first started to use it. The thing to remember is that it slices perpendicular to your current camera view. Which means that you need to be looking straight at it. So if you are in a skewed view  it never slices the way you would expect it too.

If this was my drawing I wouldn't have started with a cross section of the tubing. I would have drawn it in plan or elevation (depending on the bend) and extruded that and shelled it - to make it hollow.
Title: Re: What am I doing wrong with these angles?
Post by: Henry Hubich on December 06, 2017, 09:37:38 AM
Those inclined members are trickier than they look at first glance.

Henry H
Title: Re: What am I doing wrong with these angles?
Post by: Henry Hubich on December 06, 2017, 12:30:11 PM
Another way: I drew a 3D Polyline along the axes of the frame members, one segment for each frame member, taking care to get the lengths and angles of the various segments correct. Drew a set of 3D Boxes, one for each member, 1” x 1” and a bit longer than the corresponding frame member. Rotated each Box through the appropriate angle(s) and snapped its default Reference Point to the midpoint of the proper Polyline segment (first attachment, below). Drew a short 2D Line and extruded it to create a zero-thickness object. Rotated it as required for the cutting plane between two adjacent frame members and snapped its Reference Point to the Polyline vertex where the two frame members are to be connected. Repeated for each joint (second attachment).  At each joint I 3D-Sliced by Surface each of the two members and deleted the extraneous pieces. Repeated for each joint. Third attachment shows the result.

Henry H