Introduction: Stranger Things: the Flea and the Acrobat

"Picture an Acrobat, standing on a tightrope..." - Mr. Clarke

If you have watched the show Stranger Things then these words should be familiar to you. If you haven't watched Stranger Things I highly recommend that you do, also parts of this won't make as much sense.

The Flea and the Acrobat is the analogy which the science teacher, everyone wishes they had, Mr. Clarke explains alternate dimensions to the main characters. The analogy goes the top of the tightrope is our dimension, and the bottom of the rope is another dimension. There are rules for each of the dimensions. The Acrobat represents humans and the flea represents something else. The Acrobat can only move forward and back on the tightrope and can never travel to the other side of the tightrope. The flea can travel on the forward and back on the tightrope but it can travel to the side and underneath the rope.

I wanted to try making a practical 3d version of this concept which a teacher might use in a classroom. I came up with making a 3d Rope model with a metal core then adding a magnet to the "Flea" so it could travel on the side and underneath the rope. The Acrobat isn't magnetic so it can only move forward and back on top of the rope.

Note: Of course making it in 3D brings up one obvious point, the Acrobat can fall off the rope.

Step 1: What You'll Need

1. 3D Printer

  1. Filament:
    • Wood: I used wood based filament for the rope and two of the tree for a decent effect.
    • Black: I used this for the other two trees and the Flea which I'll go into later for the steps.
    • Grey: You can use whatever color you want for the Acrobat I just wanted something different.

2. Threaded metal rod: or something smaller/bigger depending on how large you want to scale it.

2. STL Files: it's my first time trying to make STL files from scratch, please be kind.

  1. Rope: I used Blender 3d with the Oscurant Chain Rope maker to generate the rope. Oscurant AddOn
    1. I flattened the top of the rope model so the acrobat model could stand unassisted on top.
    2. I then used Meshmixer to add a hole through the center of the rope model for the threaded rod. The included Rope file is a little under 6'' because I trimmed both ends in order to make 3d printing easier. I printed the rope upright to help prevent the center hole from deforming.
  2. Flea: The flea is intentionally simple since depending on the scale many of the details will be lost. Also it needs to be sturdy if you have a powerful magnet.
  3. Acrobat: It's just another simple model I created which should be printed upright with support.
  4. Trees: I used the tree generator on Thingiverse to create these.
  5. Base: I generated these off of the trees which I will go into detail later in the steps.

3. Magnet: I would scale the rope first and have an idea of how large you want to make this. I would then print a small rope model with a hole through the center to take with you to find a magnet and whatever you're using as the metal core. Even using a fairly powerful rare earth magnet I was surprised how weak it was through the 3d printed rope.

4. Black Acrylic paint

5. Glue Gun or a strong adhesive.

6. MeshMixer: (optional if you have a preferable program that lets you add holes to STL files) : MeshMixer

6. LED (Optional)

  1. White or Yellow LED
  2. Black Wire
  3. Resistor
  4. Heat Shrink Tubing
  5. Battery
  6. Drill

Step 2: 3D Print: Rope Model

I would scale and print the Rope first because it's the easiest way you can gauge how large the other pieces will have to be.

Rope Model:

1. Rope_Threaded.stl: is the file I used for this example. A threaded rod with the measurements 1/4in-20x12 fit very nicely.

2. Rope.stl: is the same file just without the hole through it to allow you to scale and add whatever sized metal core you want.


I trimmed the ends on both models to help with the printing, however, keep an eye on this especially if you're using wood filament. I had a few failures because I printed it upright and it detached from the bed. Printing with a raft would help reduce the risk of detachment.

Post work (optional):

Since the rounded side of the rope is supposed to be in the "Upside Down" I added a little black acrylic paint and sanded it once it was dry to make a "decayed" effect.

Step 3: 3D Print: Adding a Hole to a Model With MeshMixer

This is a quick tutorial for adding a hole to your STL file with MeshMixer.

  1. Download the file that you want to add a hole through.
  2. Open MeshMixer and click Import
  3. Select the STL file you downloaded and Import it.
  4. Once the file has been imported click Edit->Add Tube
  5. You should see at least one red dot and a green tube appear in your model (see picture).
  6. The settings for a straight tube are
    1. Spline (inside)
    2. Combine Mode: Boolean
  7. If you need to re-position the tube then click on one of the red dots and drag that to re-position it.
  8. Change the radius in the Add Tube menu until it matches or is slightly bigger then what you're using as your metal core.
  9. Click Accept
  10. If there's now a hole in your model that looks like what you wanted (see picture) then it should be good to go.
  11. Click File->Export and name your new STL file.

Step 4: 3D Print: Flea Model

Once you have the Rope printed and scaled the Flea. I would make the Flea with a infill 50% or higher before printing it. Especially if you decide to make a hole in the flea to hide the magnet. I used a rounded magnet, glued to the bottom of the model.

There are more powerful magnets then what I used which could easily break a low infill model.

Step 5: 3D Print: Acrobat Model

The Acrobat model was an easy print upright with support. I scaled it after the rope so it fit on top of the rope without being too big or too small. I found adding a little electrical tape to the bottom of the model's feet really helped to steady it.

As to the filament color of the Acrobat that is entirely up to you. I made him a different color to help show there is a difference between the Acrobat and the Flea.

Step 6: 3D Print: Tree/Base Models

The Tree models should be scaled according to taste and whatever you're using as the metal core of the rope. The Base Models need to be large enough so you can run the metal core through them.

Trees: Regardless of if you use the models I provided or generate your own you'll need to print two of each and preferably with black filament for the trees the model stands on. Reason is the "Upside Down" dimension is a decayed mirror of our world so the tree models should mirror each other and the black filament is for the decayed effect.

Links to my generated trees:

Note: Using black acrylic paint on a wood filament tree would be another good way to show the decayed nature of the "Upside Down".

Base: If you create your own trees then you'll likely need your own bases or modify it to accommodate the metal core. If you use the included base files, then you will need to add a hole to the base for your metal core. I added the files I used which have a "_Threaded" at the end of each filename.

A. Meshmixer: I imported my tree STL file into the program then clicked on Edit->Plane Cut

  1. I rotated the Plane Cut 180 degrees and moved it down to make sure the base has a clean cut (See pictures)
  2. I opened the Object Viewer (View->Show Object Viewer) to select the base object and move it up slightly.
  3. I clicked Edit->Transform->Uncheck Uniform Scaling then modified the Size Y until I had the height I wanted to run the metal core through it. Once you're done click Accept (See pictures)

Step 7: Gluing the Magnet to the Flea

Glue the magnet to the Flea model then let it dry a full 24 hours away from anything metal. Especially if you're using an extremely powerful rare earth magnet, you want it to be fully cured before using it.

If you are using a slightly larger magnet, like I did, I suggest painting the magnet whatever color the Flea is to help hide it.

Step 8: Optional: Add a Temporary Gate

If you haven't watched Stranger Things then this isn't going to make much sense and you should go watch it.

I thought I used the concept of a gate more as how the Demigorgon makes them. Which fit perfectly with the tree models.

The Demigorgon can create temporary gates to travel from the "Upside Down" to our world which it does in a tree at one point during Season 1. When it makes the gate it essentially tears it's way through so the gate is ragged.

If you want to add a gate to your display then take a drill bit which is the diameter of your LED or at least for the "Upside Down" Tree you're going to need a hole big enough for your LED to fit in.

  1. Take the two prints of one of the tree models and decide on which side is your display side.
  2. Drill a hole completely through the tree trunk at roughly the same spot on both.
  3. If you want to add a LED then add it to the "Upside Down" Tree only because there's very little light in the "Upside Down". I used scotch tape in front of the LED to soften the light and make it look a little less like a LED.
  4. I used black wire to hide it a little better and keep the battery out of sight.

Note: I tried creating a better gate effect using fiber optics. I wanted to be able to shine a light into the "gate" on either side and with the fiber optics it would shine out the other hole. Unfortunately any fiber optics I bought, which would be big enough, I have serious doubts I could bend it to suit my needs. If there is a type of fiber optic flexible enough to suit my needs I'm sure it's very expensive.

Step 9: Align All of the Pieces

Put all of the pieces together temporarily (scotch tape worked well for the trees) to make sure everything looks how you want it to.

If the model isn't stable on it's own I would suggest either the green foam, from a craft store, to sit it on. You can always clamp something onto the base or the metal core, if it sticks out, to stabilize the model too.

If there's too much movement with the metal core and the bases I found wrapping the metal core with a rubber band works very well. You can wrap it as thin or as thick as you need to so it'll work on all sizes.

Step 10: Glue the Pieces Together

Once you're happy with how the trees look then glue them to the bases. I used a hot glue gun which worked but you have to be very quick or the glue partially hardens and it's not going to be flat.

When it's cured assemble everything together and you're done!

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