Floating Tensegrity Helix

thingiverse

This is a stunning tensegrity sculpture composed of two intertwining helices that appear to float above one another without touching. Four tensile members support the upper structure, while the base and top of each helix form a regular tetrahedron. I recently came across a similar tensegrity structure made from wooden blocks on Reddit, which inspired me to create this piece with some unique requirements: using only triangular shapes, a single line or string for simplicity, and hiding the string within the structure so it's not visible until someone examines it closely. Even upon closer inspection, the sculpture remains puzzling. The entire weight of the upper tetrahedron is suspended by a single line in the center, while the three lines on the corners prevent the upper tetrahedron from tipping over by applying tension against any rotation. Printing Notes ========== This model will print without supports but may turn out better with them. I set "Support Overhang Angle" to 60 degrees and placed blocks in a few locations so that there was only one support. See this photo:  I recommend setting "Minimum Layer Time" to at least 10 seconds so the helix doesn't print too quickly. Assembly ===== To assemble, follow these steps: 1. Print one "top" and one "bottom". 2. You'll need approximately 90cm of transparent monofilament fishing line. Cut more than this, as the ends can be trimmed later. 3. Tie a large knot in one end of the line using an improved clinch knot, which is a standard fishing knot for tying on a hook (but no hook here). 4. Starting from the "top" piece, run the other end of the line through the vertical holes in the center of both pieces. See this picture:  5. Continue running the line down the channel in the center of the "bottom" piece's helix until it comes out of the other end. 6. Push the line through one of the closest holes in the bottom piece (at the midpoints of the base). It doesn't matter which hole is used. 7. Align the top and bottom pieces as pictured/desired:  8. Push the line from one corner of the "top" to another through the hidden channel. It doesn't matter which direction is taken. 9. Continue running the line down and up between the pieces through different holes until it's fully connected.  10. The line must turn a corner on the bottom piece, so ensure it's placed completely in the channel (there is a notch in the corners to prevent it from falling out). 11. Note that for final connection between the bottom and top, the line should have exited a hole near one of the previous connections. 12. Tension the line, and arrange the model to the correct height. It doesn't need to be perfectly level at this point, but the height does need to be accurate. 13. Tie off the tag end of the line to the upright line near it using a simple overhand knot. You don't need to keep the sculpture upright while doing this. 14. Slowly pull the top and bottom pieces apart to tension all of the lines and tighten the knots. If the top and bottom are not level with one another, simply rotate the pieces and the lines will follow. 15. Cut off the excess line on both ends. 16. Optionally glue the line to the bottom piece in the center of the sculpture. You'll be unable to place any weight on the sculpture unless you do this.