Inspired by large 20 plus foot rhythmic metal wind sculptures, I've been trying to design and build a small, somewhat similar kind of kinetic wind sculpture using traditional construction methods such as metal and polymer clay. The designs have failed because it is difficult to visualize the kind of balanced, rotating, yet rhythmic design I want to create, and the construction of such a sculpture by traditional methods is not trivial.
Therefore, I recently I began to explore the use of 3D software to develop the sculptures I envision. This has proven very successful as a design tool because animating the sculpture allows me to see exactly how the sculpture will look when it is rotating. A 3D model also has the added benefit of being 3D printer build ready.
So, with the advent of powerful open source software such as Blender 3D, and affordable 3D desktop printers, a new generation of kinetic wind sculptures can be realized.
This sculpture requires a computer, 3D software and a 3D printer. The design is not limited to a specific size, which depends on the printer and/or the segmentation of the final sculpture. For this instructable I will show the design and pre-flight build process for a small kinetic wind sculpture, discuss adjustments to the design and then show an example of how to scale it up in size.
Here is an animation of the model I will be reviewing.
Step 1: Load and Learn a 3D Software Package
I decided to use Blender 3D because it is free open source software, has hundreds of online video tutorials, has a virtual physics lab for wind testing and it can export objects in the file formats used by 3D printers. However, there are a variety of other very capable software packages that can be used for this project so explore the package of your choice.
I spent many hours running through the online tutorials until I felt comfortable with the UI and many of the features. Because the design is somewhat organic in style, I paid particular attention to the bezier curve in relation to lofting and lathing. These techniques are used for most of the design elements.
Step 2: Identifying the three components of the assembly
The kinetic sculpture is designed and built in three separate pieces: the sculpture, the turbine and the stand.
The sculpture and turbine will be glued together after they are printed. Designing the turbine and sculpture separately has two main advantages; first, any modification to improve the performance of the turbine will not compromise the aesthetics of the sculpture and secondly, the separation allows for a taller final sculpture because the two are stacked. Additionally, the bottom of the sculpture and the top of the turbine are flat, this means the turbine can be built by the 3d printer with little or no supports if it is built upside down.
Step 3: Design the sculpture's wings
The first screen shows the tall wings. These were modeled using a multi-point bezier curve as shown. While modeling the wings, I applied a three count array modifier with a 120 degree spread. This type of visualization is extremely powerful in the overall design because collisions are obvious. As I sculpt the control wing, the other two immediately follow the same curving and twisting.
Here is a 2 minute video of how it looks in real time as one wing is adjusted while the others follow.
The other two screen shots show the smaller wings and the bezier edit.
In addition to modeling the curve as shown, there is also a bezier curve for the overall shape that permits the wings to be tapered to a point at the end, and there is also a closed curve for the shape of the circumference of the wing. This setting allows the wing, in this case, to be flattened on two sides.
Step 4: Design the sculpture's central column
Next, the sculpture's central column is modeled. It provides an aesthetic element as well as a structural member for the wings.
For this component, the piece consists of a lofted closed circle using a bezier curve. Because the shapes are only relative in size, this object is scaled to easily combine with the wings. Note that although the wing support arms are shown in this image, they were added after the wings were in place.
What is not shown in this image is the interior of the column which is also a lathed object that will act as a pivot point for the sculpture.
Step 5: Assemble the sculpture
Next the wings and central column are combined and the wing support arms are added. These parts are converted to mesh objects and joined into a single exportable unit which then becomes a printable object.
Step 6: Design the turbine blades
The sculpture rotates because of wind energy, and rather than compromise the sculpture's design with turbine capabilities, I elected to design and build the turbine separately. In this way changes to sculpture or turbine are mutually exclusive.
For the blade design, I once again used bezier curves that were joined to form the outside of the blade, and another one on the interior to provide a handle to shape the cup part of the blade. These closed curves were connected and then filled as a plane object. The second image shows the process of pulling the center out to form a cup to catch the wind.
When the shape is complete it is visually re-sized, smoothed, solidified and a 6 element array modifier is applied.
Step 7: Design the turbine column and assemble
The column was designed to have a hole running through the center so the stand would fit through it and up into the sculpture's center column. The technique was to extrude a simple circle object while controlling its height and size. The sharp angles are then smoothed with a subsurface modifier.
When complete, the blades and column are converted to mesh objects and joined into a single exportable object for fabrication.
Step 8: Design the stand
The stand was also designed using a simple circle extrude method, however a lofted closed circle using a bezier curve similar to the sculpture center column would also work. Not shown is a compartment in the bottom of the stand that would accept a filler to help weigh the stand down.
I've also included a color rendered view that shows the opening in the turbine column for the stand.
Step 9: Print a scale model and test
Each one of the three components are exported as an object file or stl file for fabrication. The design may need to be built with overhang support because of the aggressive curves on the wings. The final determination will have to be made prior to the build and is likely based on how the object is positioned in the build volume; and the experience of the builder.
The parts would be printed to produce a small 8 inch total sculpture. This would be useful for final wind testing and adjusting any elements that need further refinement. It will also make a great desktop kinetic sculpture.
This is an image of MakerBot's MakerWare application with the sculpture imported as an OBJ file and ready to build.
Step 10: Considerations for a larger sculpture
If the sculpture is printed at a diagonal within the printer's build volume, it can be scaled to a larger size. For example, if the build volume is an 8x8x8, the diagonal is approximately 11 inches. The final printing can take advantage of this diagonal length.
The sculpture design is based on two sets of thirds, three tall wings and three short wings set approximately 60 degrees apart. This means the base can be divided into six 60 degree pie shaped pieces. Each of the pie pieces would provide a base for the wings. In this figure, a simple 60 degree pie piece was added to the tallest wing and exported as a single tall wing object.
Additionally the short wing is also modified to include a 60 degree pie piece, and finally, a single turbine blade is attached to a single 60 degree pie piece..
All of these post build pieces would then be glued together to create the sculpture and turbine.
Step 11: Realizing a larger scale sculpture
I'm using MakerBot's MakerWare application as an example.
Here I've imported the pie and tall wing shown in the last step as a single object
Showing in the MakeWare application is the wing scaled and tilted to take advantage of the diagonal print space. Also note this build would require build supports, which is a simple check box in the MakerWare options dialog.
The final version would require a build of 3 tall wings, 3 short wings and the central column with supports. The turbine would need 6 blades and pies. The stand would only require a single build.
I would expect the final version to be a total height of somewhere between 15 and 17 inches.