Introduction: Tensegrity - Desk Top Model
The concept of "Tensegrity" (Tensional Integrity) is basically hidden suspension. This model appears to have to layers of structure with no physical support between them. Although there are some excellent models on the internet, I wanted to make one small enough to fit on a desk for a conversation piece. I can tell you from experience it does draw a lot of attention. It is easy to build, uses everyday common materials and does not require a high level of skill.
1. 3/8" wood - about 12" x 4"
2. 1/4" wood dowel - about 2'
3. String - Your choice (Seet step #6)
4. Superglue - preferably small tubes that pour easily and dry quick
1. Band saw
2. Drill press
Step 1: Base Plate
There are two identical assemblies so make two of everything wood.
The base is made from 3/8" (#1). The wood can be anything you have. It could be any material you want but I'm a wood worker so mine is wood. I used Poplar because that's what I had on hand. Cut two pieces 3" x 3" (#2).
Step 2: Base Corner Holes
Each string will be wedged in place with a round toothpick. My round toothpicks are ~3/32" in diameter. I used a 5/64" hole for the corners to allow the toothpicks to wedge the string without falling through.
The location of the corner holes is shown in illustration #3. All four corner holes have the same dimensions (#4).
Step 3: Base Main Holes
There are two main holes in the base plate. One is a 1/4" hole for the post and a 1" hole for access to attach the center string to the horizontal platform (#5).
The 1" hole is in the center. It is important to locate the 1/4" hole exactly as shown to allow proper line-up of the center string.
At this point you can round off all four corners. Sand all the outside edges as well as the edges of the 1" hole (#6).
Step 4: Posts and Small Platforms
In the center of this structure there are two identical horizontal platforms with a piece of string between them. The platforms are 3/8" thick. Placement of both holes in the platform is important. The larger hole is 1/4" diameter. The smaller hole is the same size as the corner holes (5/64") on the base plates. Both holes are centered from the sides. illustration #7 shows the platform dimensions.
The post is 1/4" wood dowel 2 7/8" long (#8).
Round the end of the platform with the 5/64" hole (#9).
Step 5: Assembly
All of the wood pieces are now complete and ready for assembly. Glue the platform to the post. The platform should be flush with the top of the post (#10).
When the glue dries, insert the post into the base. The post should be flush with the bottom of the base (#11).
It is also important to make sure the hole for the string in the platform is centered over the 1" access hole in the base. If the platform is parallel to the base side, the string hole will be on center. Use a scrap piece of wood to set beside the platform. Use a small square to ensure the platform is parallel to the sides of the base (#12).
Glue the post in place on the base.
Do both base assemblies. The base assemblies should be identical.
Step 6: String
The ideal string would be less than 5/64" in diameter, strong, and does not stretch. Finding string that does not stretch is difficult. However, all of the pieces of string are relatively short so some possible options are normal household string, paracord strands, fish line, upholstery thread, etc.
I used 5/32" Paracord from a local home improvement center. The Paracord has 7 inner strings. Cut a piece of Paracord ~8" long. Remove the 7 inner strings.
The first challenge is to thread a string through the 5/64" hole in the base. The strings have a tendency to unravel. You can burn the ends with a match but that only seals the tip of the end. The strings can still unravel.
I used a small dab of wood glue on the last 1/2" - 3/4" of the string. Then I rolled the string to mix the glue into all the threads of the string. That provided a somewhat rigid tip and minimized the unraveling.
Step 7: Attach Strings
To attach the string to the base, I use wood round toothpicks wedged in with the string (#13). I used superglue to attach the strands to the base. Do not attach any string yet.
We will start with a practice session getting the strings attached to the base and center platform.
Cut a piece of scrap wood 3/8" thick. For the practice session, cut another piece of the Paracord and remove the strings. Prepare the ends of the strings as described in step #6.
Drill several 5/64" holes in the scrap piece of wood. Insert a round toothpick into one of the holes. It should not fit through the hole. My toothpicks are ~3/32" diameter. The hole is 5/64". Although the toothpick will not fit all the way through the hole, the tip of the toothpick will extend beyond the surface of the wood (#14). Cut the excess off the tip of the toothpick.
Insert a string into one of the holes. Pull the string through far enough so all glue and any unraveling is on one side.
Insert the toothpick back into the hole with the string in the scrap wood. When you are sure the toothpick is the correct length, pull the toothpick back out.
Although my superglue has a set time of ~3 seconds, it is long enough to allow excess glue to absorbed partially up into the exposed end of the string. If glue is allowed to be absorbed partially up the exposed end it becomes rigid and immediately obvious and distracts from the suspension mystery of this project. To avoid this, apply the smallest drop of glue possible. Keep in mind you have less than 3 seconds to insert the toothpick. Insert the toothpick as tight as you can get it. It should have a very rigid connection and no obvious absorption on the good end of the string.
Using a wire cutter or utility knife, cut the excess toothpick and string. Pull on the string again to make sure it is still a solid connection.
After you have perfected your technique of the string attachment on the scrap wood, it's time to attach the strings on the project.
Thread a string through a hole in a base plate. The toothpicks will be inserted from the bottom. Have the toothpick ready to insert. Drop a dab of glue onto the hole with the string in it. Insert the toothpick to wedge the string in place (#15).
Do the same thing with the other three holes.
After all 4 corner strings are in place, add the string for the center horizontal platform. Note that it is in the opposite direction as the four corner strings (#16).
After all the glue is dry, which could be almost instantly depending on what type of glue you use, use a utility knife or wire cutters to snip off the string and toothpick flush with the bottom of the base. Sand the bottom of the base to provide a smooth surface.
Step 8: Second Base Plate Attached
The strings are attached to the second base plate in the same way that we did the first base plate. However, we have to keep the strings tight while we apply the glue. To simplify the process we can add two scrap wood blocks in between the base plates to maintain the exact same length of string on all four corners. The blocks should be 3 1/4" long. They can be any width as long as they fit between all the strings and wood parts. I cut a 3 1/4" piece of 2 x 4 and then sliced it into two pieces (#17).
Insert the center string into the other horizontal arm. Temporarily attach a piece of tape to the end to prevent it from getting pulled out.
Insert each of the four corners strings into their corresponding holes on the other base plate. Temporarily attach a piece of tape to each string to prevent it from getting pulled back out of the hole (#18).
Step 9: Final String Attachment
With the strings in place, put the two 3 1/4" wood spacers in place (#19).
Note that the end of the center string from the horizontal arm is brought out through the side. That will allow the bottom base to sit flat on a surface while gluing the strings in place.
Place the side of your hand on top of the top plate to make sure the plate is tight against the spacers. With two fingers grab any one string and pull it tight. Place a drop of glue in the hole with the string and quickly insert a toothpick beside it. Do the same thing with the string in the opposite corner. Now finish the other two corners (#20).
Cut the excess string and toothpick on all corners (#21).
Step 10: Final Assembly
With all four corner strings in place, all we have left to do is attach the middle string.
Pull the middle string through the access hole in the base. Set the project upright on the opposite base. Remove the spacers (#22).
Pull on the top middle string until all four corners are tight. You should be able to feel that the assembly is going to stand on its own once the middle string is attached.
Using a toothpick wedge, glue the center string in place from the top (#23). Snip off the excess string and toothpick.
Your project is complete (#24)!