spiral flutes

[kodama@austin.rr.com]

I need to model some columns with spiral flutes in VW12. I have had no luck. Can some one steer me in the right direction?

Wayne Locke

[grant_PD]

sounds like a job for nurbs/ extrude along paths....

[islandmon]

1) Determine Flute Cycle Rate = degrees of turning within column

2) Determine Flute Angular Separation = frequency of fluting per cycle.

3) Divide, FCR / FAS to determine number of nodes

4) Divide column length by number of nodes to get pitch angle.

now you can :

5) create a single 2d section with the fluted profile then convert that to NURBS curve.

6) Dup & Rot per nodes & pitch angle

7) Loft the nodes of one dihedral to create a NURBS Solid

Here's one I just created for you using a 15? separation @ 90? cycle,

note the 6 blue NURBS sections rotated 15? each. This module can then be stacked as symbols to create multiple cycles of 90?:

Hope this helps ; )

[kodama@austin.rr.com]

Islandman,

That's precisely it. I have some questions? What is the Flute Cycle Rate and how did you determine it? Does a 90? Flute Cycle Rate mean that a flute spirals 1/4 of a full turn? I use the term pitch to mean the column length reqired for a complete spiral, i.e 12" pitch means a complete spiral in 12". Does this fit into your explanation anywhere?

I also don't understand "Flute Angular Separation = frequency of fluting per cycle".

If you could explain your example a little more to me I would appreciate it. I'm an English major/Woodworker not a mathmatician or engineer.

Thanks,

Waayne

[Kevin]

EJ, this is amazing work. My question is how long did it take you to make this? It would help me understand how complex an operation this process is.

[islandmon]

As you can see, it's all really very quick & easy ...

requiring only the original fluted section as a NURBS curve duplicated

& lofted to any degree of twist. In the illustration I use 15? increments with a pitch height= 1/2 of the radius of the section:

[Travis]

Thanks, Armstrong, this tutorial is very helpful. Wonder if you might post it on the TechNotes/HowTo board.

Happy New Year!!

[kodama@austin.rr.com]

I made a, in this case 6" X 36" column, with a solid extrude. Then I made a line and used the "spiral-helix " command and "extruded along path" a 1" radius circle, then did a duplicate array and solid subtraction. The result was very good and fairly fast.

I am less familiar with lofting nurbs but was less satisfied with the results. If I attempted to loft vertically more than 6" I got the beginning of an hourglass shape and there was a lot of duplicationg and rotating. I liked the approach and would like to know if you could make the top and bottom nurbs, rotate the top 180?, and loft it without getting the hourglass.

Wayne