Add 5 degree upward twist ONLY to the ends of a cross bar on a Christian Cross

[emailgaryw]

Hello community!

I'm trying to add an approximate 5 degree twist to the ends (only) of the cross bar on a christian cross.

This cross bar has compound angles both bending forward and downward. 

I know how to use lofting to add a twist to a column but I don't know how to use this method when the

column or bar has compound angles.

The center of the cross bar member needs to remain as is but the ends of this bar needs an upward twist

of approximately 5 degrees without twisting the center section of the bar. 

I've included my .f3d . The two bar sections have been created as separate components. A Vertical bar

and a Horizontal bar. They are then combined in a final component build with both bars. 

I've tried many different approaches to solving this challenging problem. Mainly, trying to use Lofting

with no success as yet. 

Thanks , in advance for any and all help!

Gary

[etfrench]

Guide rails in a loft should get  you there.  Can you post a marked up picture of the desired result?

[emailgaryw]

I need to clarify that 5 degree twist. With the cross sitting flat, arched down, the twist would be a clockwise rotation of each end of the cross bar. 

I've uploaded a pic of a large metal version that my smaller version is based on. You can see the slight twist in the ends of the cross bar.

Thanks,

Gary

[davebYYPCU]

More like a 10 degree twist for the same appearance, 

Solid Loft, with (4) 3d tangent, twisted spline curves.  (Right hand end before mirror and combine)

Take the centre line profile, and the end profile is an 8mm square,

Patch loft the centre line profile to the left, dummy body to supply the tangential reference.

Sketch the end profile - 8mm square, aligned to the centre lines in your set out sketches.

(with in my photo it's 10 degrees,) rotate clockwise.

Create a 3d sketch, use Project > Include 3d Geometry, and select the 4 edges of the extruded centre profile body, and the 4 corner vertexes, from the end profile.  Connect a 3d spline to the projected edge, and respective vertex.

Make the centre end of this spline tangent to the projected edge.  Repeat for the other 3 rails.

solid loft the two profiles with 4 rails.  Mirror then Combine.

Might help

[davebYYPCU]

Oops, 

Patch loft Extrude the centre line profile to the left, dummy body.....

[emailgaryw]

Hello Dave,

I'm having a difficult time trying to follow your suggestion.  Can you add your design to my f3d file.

It's the cross bar that has 2 complex curves 90 degrees to each other. The ends of that cross bar are twisted clockwise slightly (you said it's looks like approximately 10 degrees relative to the picture) while the center of the cross bar remains stationary. 

Just for practice, I created a rectangular bar using lofting but was unable to put a twist in the end of that bar.

I can put a twist in a lofted column if it's made using a polygon but not with a square shape. The cross bar is basically a square rectangular shape but has those 2 curves added to it.

Thanks Dave!

Gary

[davebYYPCU]

Yes, will send you the file, much later tonight, it wasn’t saved to the cloud.

In the meantime, go back to my wireframe picture,  each rail is a 3d curve, you will need 3d curves turned on, in Preferences, and the sketch pallette.

You need a profile on the centre line, mine was sized from your two sketches.

you need the two profiles in place to make the rails, you can’t twist them as an after manouvre.

Second profile is on an offset plane from the centre, but I used a Plane at Angle from the layout sketch, giving me the length of the bar.  Sketch on this plane, project the two centre line end points into this sketch, and construction Lines to find the profile centre position, sketched the square, removed the vertical / horizontal constrains, and replaced them with perpendicular ones.  Rotate the square (without the construction lines) for me it was 10 degrees.

To make the rails, tangent at the centre line, you need a short extrusion to the left. Patch Extrude the centre line profile.  

Create a 3d sketch.  Project > Include 3d Geometry, and select the four corner points in the outside sketch, and the four edges of the Patch body.  Should have total of 8 purple articles, when everything other than this sketch is hidden.

With 2 point Splines, connect the two profiles, making the inside end of the spline tangent to the edge.  Four of those, and the Loft will work.

[davebYYPCU]

Apologies for the delay, 2 days with ISP call centres and I fixed here myself, go figure....

Let me know if your still stuck....

[emailgaryw]

Hello Dave,

Thanks for all your hard work and helping me find a solution to this problem.
I’m going through your design solution. I haven’t used most functionality in fusion 360
so a lot of this is new to me.

It does look like you put the twist in the vertical bar instead of the cross bar but I should be
able to translate that over to the cross bar.

Again, thanks for helping me. I’ll let you know my progress after I’ve spent some time looking
and trying all the steps to your solution.

Regards,

Gary

[emailgaryw]

Hello Dave,

Well, I gave it a try and I'm stuck big time!

I have attempted to model the cross bar with a twist. I was able to put a twist on the ends of the cross bar

but I couldn't figure out how to add the other curve after I made the 10 degree twist to each end of the bar.

My attempt is under the component name: "Oct 24th CROSS BAR". It looks like you added the twist to the "Vertical 

Bar" instead of the "Cross Bar". The Cross Bar has 2 curves that are 90 degrees to each other. 

How do I add that other sketched curve to this bar that I sketched on that component. Am I even close to getting this thing right?

Thanks for all your help, Dave. I've included your file with my newly added attempt of which is named "Oct 24th CROSS BAR". This is my biggest challenge so far using Fusion 360. 

Thanks,

Gary

PS

I've included a pic of my attempt

[davebYYPCU]

I have taken some presumptions from your file, 

that being that the top and front sketches do not take the twist into account.

changed some lines to construction in your sketches to clarify the shape

There are usually many ways to get it done, your end plate sketching is not clear what part should be used, so sketched a different way in this file, taking your lead...

I have found the centre point of the twisted face, by developing the construction lines in my Sketch 10.

Add the square profile, twisted 10 degrees.

That done, I have extruded the dummy body, 4 rails in 3d, that are tangent to the dummy body.  Loft and mirror, but not done the combine in case you want to edit that final shape.

I have put my stuff in the timeline before your loft, so you can still see where you were.

Might help.....

[davebYYPCU · Accepted solution]

Got the PM, don't need the stl, have done the twisted cross bar, with and without splayed ends, 

will let you move and position the two together, if not in the right place....

Might help...

[emailgaryw]

Dave,

It looks great!
Thank you very much for all your help!
You’ve gone above and beyond helping me with the solution to this project.

Best Regards,

Gary

[emailgaryw · Accepted solution]

Hello Dave,

Wow! You did it!

You've gone above and beyond in helping me with the solution to this project!

I can't thank you enough.

Best Regards,

Gary