spiral around cylinder

[JHEarcht]

VW2010 on Windows XP

I vaguely remember seeing this done somewhere, but not how it was done. I want to create a series of spirals around a cylinder. It's basically a rotate-while-extruding process. But the demo I saw simply drew vertical lines on the surface of a cylinder, and then rotated one end to spiral the lines connecting top and bottom.

The example may have been in SketchUp, but does anyone know how to do it in VW2010?

[Benson Shaw]

The Helix command in the Model>3d Power Pack should work for you. Draw a line to limit the overall height, then invoke the tool and set the diameter and pitch. It creates NURBS which have no thickness, but they can also be paths for Extrude Along a Path.

-B

[MullinRJ]

You can also use the Sweep command, which is also under the Model menu.

Place a locus to the side of the object you want to sweep by at least the radius of the cylinder you want it to wrap around. This assumes you want it wrapped around the outside of the cylinder

Select both the locus and your object and invoke the Sweep command.

To get it to spiral up, enter a positive value for the pitch.

For the number of wraps, enter 360 * 7 (for 7 full turns). This saves you from having to do the math in your head, or elsewhere.

Render in OpenGL or better to see it as a solid. You may have to assign colored fills to see detail.

Raymond

[bcd]

Where did you see the 'line to limit the overall height' trick. I've been bashing against this tool forever!. Now so easy. Thanks

[Kevin McAllister]

I discovered the "line" defining length and direction can also be an arc.

KM

[JHEarcht]

Thanks for the information. I tried both the Helix and the Sweep commands, but I couldn't figure out how to set the vertical dimension. When I set the "thickness" it didn't do what I expected. The help files and tech manual said nothing about an upward spiral.

Should I draw the limit line vertically from locus upward, or horizontally at the upper end?

Anyway, I eventually used a Spring tool in the Mechanical toolset to create the spirals. It worked simply and easily because the extension length was obviously a variable.

Is there a way to rotate one end of a cylinder independently from the other end? I'm sure I've seen that done somewhere. I tried the Reshape tool, but no luck.

[Benson Shaw]

Pat Stanford recently reminded us in the Twist Drill thread.

It's certainly in VW Help. Here is the first part of the entry:

Creating Helix-Spirals

The Create Helix-Spiral command creates a helix-shaped or spiral-shaped 3D object from one or more path objects. The paths can be 2D objects or NURBS curves.

To create a helix or spiral:

1. Select the object(s) to use as the path.

2. Select Model > 3D Power Pack > Create Helix-Spiral.

The Helix-Spiral Creation dialog box opens.

-B

[Benson Shaw]

Should I draw the limit line vertically from locus upward, or horizontally at the upper end?

Which locus do you mean? I drew the 2d line in Front View, made the helix, and then switched to top view and created a cylinder as an extruded circle inside the helix.

Is there a way to rotate one end of a cylinder independently from the other end? I'm sure I've seen that done somewhere. I tried the Reshape tool, but no luck.

You can loft a couple NURBS circles on parallel planes, but it looks like a cylinder, even if the circles have relative rotation. You would see the rotation if the starting shapes have some irregularities, or if the planes are not parallel. Is that what you mean?

-B

Edited August 9, 2010 by Benson Shaw