Doin' The Twist

comments (0) January 24th, 2009 in blogs

DaveRichards David Richards, contributor
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One of our readers asked about how to put a twist in a square spindle or leg. Here's a method to do that. There are certainly other ways to do this but I think this is fairly straightforward and understandable.


We'll start with a square. It's green because that's my back face color. The face orientation isn't important for this part of the drawing. I made it 12"x12" for this example. We can scale it down later.

We'll select the square and copy it upward. Use Ctrl+Move (Option on Mac) to do this. I copied the square up 2" and made 15 copies. This is done by starting the move direction in the correct direction. Then we let go of the mouse and type 2, Enter, *15, Enter. We're going to create 90° so we need to choose a factor of 90 for the number of copies.

After making the copies, use the Tape Measure tool to put a couple of diagonal guidelines on the top square. Then we'll select all but the original square. The easiest way to do this is to orbit  so that you are looking at the edges of the squares making sure there's a gap between the lowest two squares. Then drag a selection box around the top fifteen squares.

Get the Rotate tool and using the intersection of the guidelines as the center of rotation, rotate the selected squares 6°. That's 90 divided by 15.

Get the Select tool, hold Shift and double click on the lowest of the selected squares.

And the rotate the remaining selection 6°.

Continue deselecting squares and rotating the remaining selection 6° until you get to the top.

When you've completed all the rotations, select all of the squares and make a group of them. Leave the guidelines. We'll use them again shortly.

Get the line tool and draw line segments between corners of neighboring squares. Select these lines and copy/rotate them 90°. Center the rotation on the intersection of those guidelines. To copy and rotate at the same time, get the Rotate tool and hit Ctrl (Option on Mac) to toggle on the Copy function. At this point we're finished with the group of squares so we can either hide or even delete them.

Next we'll select both of these curves and use the Skin plugin to quickly fill in the faces between. It is possible to do this without the plugin by drawing the lines between the vertices on each of the curves. You can see the lines in the following image.

After the skinning is completed, we'll soften the diagonals. I used Ctrl+Eraser (Option+Eraser on Mac) but you can also select the geometry, right click and choose Soften/Smooth Edges.

Next, triple click on the twist with the Select tool. Get the Rotate tool and copy/rotate it 90° and make three copies. Start the rotation, type 90, Enter, *3, Enter.

We now have the 90° of twist. We'll select it all and make it a component. Then we can copy it at many times as needed to create the rest of the length of the twist. If needed, we can scale this before making the component so that the dimensions are correct.

After copying the twist section as needed, hide the seam lines between the components. Open one of them for editing, get the Eraser and hold Shift while clicking on the seams. To complete the spindle draw squares on the ends of the twist and use Push/Pull to extend the spindle. Make sure to draw the squares outside the twist component. Hide the seam lines as needed and make those sections of the spindle components and copy the spindle as needed.

This twist component could be saved for future use as desired.





posted in: blogs, Sketchup, , twist

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