UFO Tensegrity Structure

IMPORTANT NOTES:

1. Be extremely careful if you plan on printing in PETG, the eye-hooks can easily get caught and snap in half while you're inserting them into the parts.
2. I apologize for the image quality & cropping, for whatever reason it is Printables isn't allowing me to properly crop my images.
3. This was made in partnership with MD3377.

Summary:

This mind-boggling tensegrity table uses tension and compression to create the illusion of a floating table sure to impress your friends and act as a fantastic conversation starter! Being only 15x15x20 (l*w*h) centimeters once assembled, it’s small enough for everyone to print! Designed by MD3377 and myself, we can guarantee you’ll love this design (once you get past the frustration of assembly)! 

Besides your filament of choice, you’ll also need some fishing line and miniature screws.

Lesson Plan & Activity:

With a partner, you will design and create a single custom Tensegrity Structure of equal complexity or greater as the tables depicted above

Parts List:

1x Day_BottomBase_V2.3mf

1x Day_BottomBeam_V2.3mf

1x Day_TopBeam_V2.3mf

1x Day_TopBase_V2.3mf

8x Eye-Hooks

4x pieces of string/fishing line

Assembly/Construction Instructions:

Assembly Instructions for Tensegrity Structure - 

Step One - Preparation

Tools Recommended: Small Phillips head screwdriver, Pair of small needle nose pliers, mini wire/string cutters, a small ruler (marked in millimeters), a leveler that you could use an app on your phone for, and a pencil, and a friend (trust us, this will be important).

Extra Parts required: 8 Small Hooks (depicted below), any fishing line or small string. In the case that something breaks and you do not want to reprint or use extra screws, have a hotglue gun on hand or super glue. The hot glue gun will also cauterize the string so you will have no give at the ends of your knots. You will also need a leveling device. Most smartphones will have a tool like this on them.

Step Two - Base Setup

1. Once all parts are printed, flip the top base, which is the UFO, upside down so you can see the indented guide holes on the bottom.  You will insert your 3 screws into these said holes (insert picture). Also find the indented guide holes on the top of the mountain base (insert photo). And insert your 3 screws into these holes aswell (insert photo).

1. If you have difficulties getting your screws to fit in, take your small screwdriver and hammer a slightly deeper hole into each pre-existing slot or use the corner of a a flat hhead screwdrivers edge to force a hole into the base. Repeat this process for the bottom base where the indented holes are. (insert a gif of a screwdriver being hammered into the base)

1. Take your 6 screws out of the box and screw them into each indented hole one at a time, pressing them lightly into the holes and turning with your fingers.

1. If you have difficulties turning the screw into the bases, you can use pliers to continue to tighten it, but we were able to turn them by hand. Repeat this for the remaining 5 screws.

Step Three - Beam Setup

1.  For the beams use the smallest Phillips-head screwdriver you can find to indent a guide hole within the pre-existing slot for the screws if needed. 
2. You should first push into the point until a very shallow hole has formed, then continue pushing and occasionally twisting into the point until it is deep enough.
3. It is also possible to use a hammer to hit the screwdriver to create a hole, but make sure to be extra careful not to use too much force with it to ensure the piece doesn’t break, as happened in the example below. Hot glue was used here to repair the damage. 

1. Once the guide hole is ready, you will choose one of your screws and carefully twist either the screw around on the beam or the beam around while keeping the screw in place. 
   1. You may also use a screwdriver if you so, please. 

Step Four - Beam Insertion

1. At this step, it is time to insert the top curly beam into the top base and the bottom c beam into the bottom base. 
2. As there is a tight fit when you insert the beams into the bases, you may need to sand down the beams just slightly depending on your printer calibration, to ensure they can slide into the base with a snug fit. Make sure not to have them too loose (or loose at all) or you will end up needing the hot glue, messing up the illusion.  

Step Five - Tying the String

1. The next step is to measure out your string. You will need four pieces of string minimum, but expect to use more. You’ll need at least one piece that’s two centimeters long, but with at least ten (recommended 15) centimeters extra to tie the knots. You will also need three pieces of string that will be approximately sixteen centimeters long once tied, so you’ll need around thirty centimeters (one foot) of string to tie it together with ease. It is possible to do with less waste, however, it is incredibly difficult.
2. To begin, turn both the connected parts on its side. Take the smaller string and connect the two beams using a knot of choice.  You will tie the knot around each hook to maintain a minimalistic look. If this is not important to you, you can tie only one knot by looping the fishing line through both screws and tying the ends together. No matter which way you do it, the stability will not be affected, only the final looks of the design. We recommend a fishing knot on the UFO, and then a square knot on the base. This way, you can easily adjust the design with the bottom knots, and the top will be completely secured.
3. Once the center wire is complete, do the same with the three larger strings. With the larger strings you should tie a fisermans knot first on the top base, and then once tight, you will then loop the string through the hook on the bottom base but instead of a fishing knot, do a single box knot. Once all strings have the top fishing knot and one bottom box knot you can loosen the box knot to finalize the orientation and make sure the structure is flat on the top and bottom. When to your liking you will do another box knot so you will have double box knots all around for the bottom base.

1. After all four strings (three exterior and one center) are in place, turn the contraption so it sits upright.

Step Six - Corrections

1. Stand the assembly up, and take the level. Put it on the top of the UFO and check to see if any particular sides are lower than others. If they are, tighten the screws that are on the side that are loose. This will evenly distribute the weight of the water bottle, candle, or whatever the object of choice is.

Step Seven - Enjoy!

Congratulations! You now have a tensegrity UFO that you and all your guests can enjoy and be amazed by.

Design Choices:

After watching multiple videos about tensegrity, we were tasked to create a tensegrity structure of our own. After creating some sketches, Max (MD3377) and I decided on a UFO design that would act as a cup or candle holder as our primary “attraction”, or top base.

Because of the size constraints, we decided to make the bottom base use the entire 15x15cm and then add fillets to the edge to make it feel more polished. Then we’d make the top smaller to make the illusion that the UFO isn’t the same size as the land (even though they are incredibly close). The beams are then meant to illustrate the “tractor beam” from the UFO and the ground being lifted up and into the UFO.

Top Base:

The internal hole was designed to hold a cup, as stated above, and was measured based on a Hydroflask sitting at our table while we were designing (thanks Valerie). The beads around the exterior were added late into V1, after our first assembly, because it felt incredibly bland.

Bottom Base:

Originally, this design was made up of layered extrusions with different shapes at each level. Eventually, we were shown how to use the freeform tool to create the current base, with flowing hills and a much more pleasing visual. The base also consists of a base extrusion to place the entire design on a pedestal and add security to the overall structure.

Beams:

Both beams were meant to look like tractor beams or something being torn up by a tractor beam. In my mind, the top beam also illustrates the sky and the wind that it’s pushing as it leaves the land. This is also why it’s blue. The bottom beam was the tip of the mountain getting extracted from the ground and looping inside the beam, which is why we chose to have the bottom beam actually connect from the top with an internal string instead of connecting with an external string on either beam. We also created fillets around every edge to create a futuristic vibe and, in the image to the right, increase the overall strength of the beam.

Version History:

Between Version One and Two we had… a few changes that needed to be made. Here are the changes.

1. Cosmetic Changes
   1. Bring UFO circles up a tad more and also make them slightly larger 
      1. 
2. Functionality Changes
   1. Make the fits slightly (0.01)  looser to get a better fit between the bases and beams
      1. 
   2. Make the top base .25cm deeper and .25cm wider to allow it to hold a water bottle more securely
      1. 
   3. Make both beams wider and thicker
      1. 
   4. Potentially add holes to beams and bases for screw
      1. 
   5. Make the bottom base thicker so screws wont protrude out the bottom.

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If you are interested in seeing our Solidworks instructions that we created and followed in the creation process, here they are:

1. Top Base
   1. Start by creating a constraint box of 15 by 15cm
   2. Then create two construction Centerpoint circles on the origin on the top plane. One should be 15cm in diameter, and one should be 9.
   3. Make a sketch on the front plane off of the two circles, one line that goes from the origin to the outermost circle, one from the inner circle up 3cm, and then an arc that connects the two endpoints. Make sure these are all dimensioned.
   4.  revolve 360 degrees to form a UFO shape.
   5. Create a sketch on the inner circle of the UFO, and make a 1cm by 1cm centerpoint rectangle on the origin.
   6. Extrude this rectangle so it creates a hole completely through the base to leave a spot for the top beam.
   7. Tight and Loose fits - Adjusted the dimensions on either side to make them 0.04cm larger than the beam in order to create a tight fit
2. Top Beam
   1. Start with a constraint box of 10.5 by 4cm
   2. Make a vertical construction line down from the center point
   3. Create a corner rectangle from the top center of the constraint box measuring 1cm by 1cm for the insertion piece of the top plate.
   4. From this top rectangle, use the circular lines to make a “sweeping” line to the left and then a loop on the right side back into another sweeping line that is curved to the right.
   5. After, you offset the line that is made by 0.5cm bi-directional.
3. Bottom Beam
   1. Start with a constraint box of 8 by 4cm
   2. Make a vertical construction line up from the center point.
   3. Create a corner rectangle on the bottom of the constraint box that is centered within the box, and 1cm by 1cm for the insertion piece of the bottom base.
   4. From the bottom rectangle, make a “sweeping” line that sweeps right and then left, ultimately ending back on the origin line.
4. Bottom Base
   1. Start with a constraint box of 15 by 15cm
   2. Draw the first box then extrude
   3. Create another constraint box offset by approximately 1.5cm for the next section and then draw the new design and then extrude that one as well.
   4. Repete this step again.
   5. Repeat one more time but offset by 1cm. 
   6. On top of the last design, you will want to extrude cut on the CenterPoint down 1cm.
   7. Tight and Loose fits - Adjusted the dimensions on either side to make them 0.04cm larger than the beam in order to create a tight fit

1. Bottom Base Circle
2.  Create a constraint box of 15X1cm
3. Create a vertical line that goes up by 0.25cm from the origin point
4. From the top and bottom of the 0.25 line create two horizontal parallel lines that go out by 7.5cm and at the end of the two horizontal lines connect them vertically with another line
5. From here you will revolve this shape across the y-axis. This will create your bottom circle
   1. Bottom Circle Fillet
6. Open up the fillet button and click on the top edge of the circle and set the fillet parameters to symmetric and 1.5cm. 
   1. Boss Extruded shapes
7. Create a sketch of a shape of your liking.
8. For the first shape only create it within the fillet of the bottom circle.
9. Extrude the created shape by  0.25cm
10. Continue this step as many times as you would like. 
    1. Cut Extrude
11. When your base is completed the last step is to cut and extrude a shape preferably a square for your beam to fit into. 
12. Create a shape on the top extrusion of your base. For ours, we did a 0.5X1cm square and then cut extruded by 1 cm down through the sketch plane.

Version Two Edits:

1. Top Base
   1. Take the sketch that is forming the bubbles on the side underneath the revolve and add more space between the bottom and centerpoint of the circle sketch. This is to push the circles up and make the UFO feel more original.
   2. Go into the original sketch and change the depth of the inner circle from 1.25cm to 1.5cm so there’s more depth and room to hold objects.
      1. After doing this, the arc changes and therefore we need to stay in the original sketch and change the diameter to 15.25. Even though this is larger than the 15cm that’s allowed, because of the fillets it will shrink down to 14.89cm.
   3. Enter the cut extrude and make the 0.64cm dimension 1.04cm for the new dimension.
   4. Triangulate the places for each screw using equalateral triangles and equidistant circles to make the 0.1cm diameter.
      1. After this extrude cut the 0.6cm into the top base for the screw to sit in.
2. Top Beam
   1. Go into the boss extrude and make the design thicker (0.6cm → 1.0cm). This is to prevent hte design from cracking when pressure is put onto it.
   2. After making the design thicker, go int othe sketch of the extrude, and make the top portion that will have the hook insertion point thicker (0.5cm →0.8cm).
      1. Because of this, the arc will become thicker on the bottom and thinner near the ovangular loop in the center. To add some strength back, put a fillet in the crevice that is 0.2cm.
   3. Adjust the height of the connection piece that’s attached to the top base from 1.0cm to 1.25cm as to prevent the curved part from inserting itself in the base.
3. Bottom Beam
   1. Go into the boss extrude and make the design thicker (0.6cm → 1.0cm). This is to prevent the design from cracking when pressure is put on it.
   2. After making the design thicker, go into the sketch of that extrude, and make the top bit that will have the hook thicker. Originally it’s 0.5cm thick, and change it to 0.8cm.
      1. Once doing this, the arc will also thicken due to it being tangent to a line affected by the thickness change.
   3. Adjust the cut extrude 0.64cm dimension to 1.04cm to adjust for the new beam dimensions.
4. Bottom Base
   1. Under Revolve 1, enter the sketch and change the height value from 0.25cm to 0.5cm. This is to allow more space for the screws to go into.
      1. When this is done, a few things happen.
         1. The fillet is now incredibly steep. Go into Fillet 1 and change the value from 0.5cm to 0.6cn.
         2. The hole for the beam is now hidden due to the height change. Go into the Cut-Extrude and change the offset value from 2.68cm to 2.88cm. This is adjusting for the 0.25cm height difference and also to make the tallest point 1.0cm, as the previous version wasn’t exact.
   2. Create a fillet on each corner of the cut extrude to maintain the same shape as the base and a snug fit.
5. Triangulate the places for each screw using equalateral triangles and equidistant circles to make the 0.1cm diameter.
   1. After this extrude cut the 0.6cm into the top base for the screw to sit in.
   2. Alongside this, offset the extruded cut

If for whatever reason the Printables page does not want to show gifs, proper formatting, or anything else that could possibly go wrong, here is a link to the google doc this was created on.

https://docs.google.com/document/d/1yBMPDKDU-RhR804VN0iGr2VVsSq9yj-GoFxN_AUBbeo/edit