Pizza Themed Tensegrity Structure!

Summary Section: 

This is a one of a kind, pizza themed, tensegrity structure! Originating in Italy, the Pizza Tensegrity Structure was forged by the grandmasters of pizza. The Super Mario Brothers, Leonardo DaVinci, and the Little Caesars Pizza Guy. Together, they came together and forged one of the most ultimate pizza structures in the world. The pizza tensegrity structure is a completely floating pizza structure made from two pizzas, two pizza peels, two handles, hooks, and strings! It can be used as a table, or just a cool structure you want to show off! It has a 14cm diameter and is 18cm tall.  It can also hold up to 5lbs. This was made in collaboration with Devin Barker. You can find his Printables page here: https://www.printables.com/social/405775-devin-barker/about

Lesson Plan and Activity:

With a partner, you will design and create a single custom Tensegrity Structure of equal complexity or greater as the tables depicted above (as determined and approved by the instructor).

Parts List: 

Assembly/Construction Instructions:

You will need to buy these screws: https://tinyurl.com/SmallScrewEyePins 

Additionally, you will need to buy fishing line such as this: https://tinyurl.com/StrongFishingLine

Assembly Instructions for Tensegrity Structure - Tools Recommended: Very small screwdriver (Phillips), small needle nose pliers, hammer, and scissors, small ruler, marked in centimeters.

Extra Parts required: 12 Small Hooks (depicted below), any fishing line, or small string. 

Optional Parts: Hot glue gun, sandpaper, drill, and leveler

Step 0) Before you start…

Lay the parts down and make sure you have all the parts that you will need.

If needed, sand the peg and/or L Shaped Wing if they do not perfectly fit. If the nozzle to your 3D Printer isn’t precise enough, you may need to sand down some of your parts. Sand until they all fit together nicely. 

Step 1) Connecting the Peg, L Shaped Wing, and Peel

Connect the L-Shaped wing and Pizza Base using the peg. If needed, sand the peg in order to get a better fit. After you connect all three parts ensure that it is a stable connection by pushing them together. You can use some super glue or hot glue for a more permanent fit. You should have one of these arms for each complete base.

Step 2) Look on both peels for a small indent where you will be making your hole. Next, either use a drill or a hammer and screwdriver to make your holes. A drill is highly recommended, but if you do not have one, use a hammer and screwdriver carefully.

Do not make it deep. The hole should only be about 0.5-1 cm deep. Do the same for the other peel. Then screw the screw into the pizza peel where your hole was. Do this for both pizza peels. (You can also do this step before attaching it to the wing, if easier)

Step 3) After, put the entire part (L-Shaped wing connected to Pizza Peel) into the base. Make sure that it fits properly, and use sandpaper if it was printed slightly too large. It should look like this:

This is not permanent, we are just making sure the part fits before we move on. We want to make sure it is sanded properly.

Step 4) Then, use your drill to make a hole in only the top part of the base. Identify the pre-cut holes.

If you don’t have a drill, you can use a screwdriver and punch a hole in it using a hammer. However, this is not ideal since it is slower and takes more time. The hole should go all the way through the top half of the base. Then do the same for the other base.

If you are using a screwdriver, then make sure you do not hit too hard. Otherwise, the base will break.

Step 5) One the bottom part of the base, identify the pre-cut holes and lightly make an indent with the hammer. This is so that the screw goes through both bases and does not make a void where the screw did not go through.

1. Next, glue both two sides of the pizza peels together using either hot glue or super glue. Make sure the bases are aligned before gluing. Remember, Bottom 1 and 2 go together, and Top 1 and 2 go together. This is very important for the aligning of the holes.

Make sure to align the hole on the top, and the indent on the bottom before the glue dries.You can use a pencil to make sure the holes line up correctly.

You can also use the wing so that the indent is flush with the hole. This is only temporary, just to make sure that the bases are aligned correctly.

Step 6) After making all your holes, start screwing your screws into your base. Make sure you screw through both plates. Once the screw is too hard to turn anymore, use pliers to tighten it more. There should be 8 screws needed for both bases.

If you made the holes too wide when drilling, use hot glue for a better stick.

It should end up looking like this for both sides.

Step 7) Stick the wing into the base. Use hot glue so it sticks properly.

Step 8) Next, use pliers to cut the hook on one of the two peels.

Step 9) Then, hold, one pizza (with the base, L-shaped wing, and peel) upside down, and connect the hooks of both pizzas

Step 10) Get around 40 cm of string.

Make sure someone is holding the pizza for you so you  can tie the knots. Let the pizza hang by the middle, but still be held so it doesn't fall over.

Step 11) Loop a string through the bottom hole, then top hole and use a square knot to tie a loose knot between them. Here is a video showing how to tie a square knot. https://tinyurl.com/HowToTieASquareKnot. It doesn't have to be too tight, because we can just pull on the square knot later to tighten it. 

Step 12) Make sure the string does not have much slack. If it does, you can always do it again. Repeat these steps with each corner of the bases.  Make sure to use pliers to really tighten the string so there is the least amount of slack as possible.

Step 13) If your structure is uneven, start tinkering to see where it is leaning. Use your leveler to help you! You need to find the place where it is tight or loose, and fix it. 

Step 14) Once you are satisfied with the tightness, move the knot to the bottom and use some hot glue to lock the knot in place. Then cut the excess string.

Step 15) After this, you are done!

Design Choices:

These were our original blue prints for the model. We originally designed the wing to be it's own peperoni piece, not something separate coming out of the pizza. We also had the peel combined with the L-Shaped Wing. These were removed to give the structure more balance.

Shortly after, we modeled the arm system that we were going to use. This is vastly different from the model we know have. We originally thought it would be better to have the peg combined with the wing. But this made our structure to easy to break, and hard to print. As you can see, we have a sperate peg, wing, and peel.

Even our pizza model changed. Originally, wanted to have just one base. But because of the pizza's unique textured bottom, we need two parts. The printer would be unable to properly place the filament properly for the textured bottom without the base breaking. 

When creating the model in Solidworks, the main problem was that our wing was not even and could have broken. So we made it uniformly thick throughout only after many tries.

When we were making the structure in Solidworks, we initially made the design on the left.

But, you can see the middle structure that used this design failed. The left one looks like it is about to break.

The reason was that there was too much pressure on the arms causing bends and breaks. You can see that the model on the left is very unlevel and is about to fall. To fix these problems we came up with a number of solutions. 

First, we stopped using a string for tension in the middle of the structure. It created too many weak points that caused to the whole thing to structurally fail. You can see the gaps and bends in the arms. Our new structure instead just has a connection with the arms in the middle. There is no bend in the arms the structure is much more level.

Second, we made a support piece so that the arms don't bend forward. We had to spread it out as much as he could so that the arm is stable.

Another design choice was making pre-drilled holes in our base. Before, we had to use a ruler to find where the holes needed to be. Now, we just have to make the holes where the pre-drilled holes are. This was to increase the stability of our structure, as now, the parts were aligned instead of randomly placed. The pre-drilled holes also allowed us to prevent breaks in the screw. Usually, the screw was going through straight plastic, but with the holes, there was a clear guideline of where the screws could go.

Our final main design choice was to use the square knot instead of the fisherman's knot. The square knot could be adjusted and readjusted for tightness as many times as needed. The fisherman's knot was a one-and-done. If you messed it up, you would have to start over.

Other than that, the only other changes we made were how we built our structure. Most notably, we used a drill to create the perfect holes in the screws instead of a hammer. When we used a hammer, our base broke multiple times.

The drill prevented that as instead of slowly hitting the weak points, it went straight through. The drill also took much less time and saved us from going back to try and deepen the holes.