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December EDU Project: Hot Tub + Hour Of Code


December EDU Project: Hot Tub + Hour Of Code

As the chilly winter weather sets in across the nation, we thought this would be a welcome subject for this month's Thornburg EDU Project. At the end of this month's EDU Project, we've got a challenge in conjunction with the #hourofcode initiative, so be sure to check that out as well! Now, on to Dr. Thornburg's lesson!


Hot tubs are relaxing! They come in a wide variety of models, but the main concepts are the same. Unlike swimming pools, hot tub users generally just sit and relax in warm water with small jets blowing bubbles and water streams on your back. After a half-hour, you emerge from the tub well relaxed with aches in your joints pretty well dissipated. The therapeutic value of hot tubs is why they are in training rooms for athletic teams, but a lot of people have installed hot tubs in their homes.

Hot Tub Image Source: Morguefile

Hot Tub Image Source: Morguefile

This project involves the design and building of a hot tub suitable for inclusion in a doll house. This project involves a lot of mathematics, and even explores the concept of water pressure. While it doesn't have any jets in it, you can add those if you want, and make a nice place for your fingers to relax, since our model is pretty small. Normally, hot tubs are about 2.5 meters across. Ours has an outside dimension of only 13 cm.

As with the other projects we've explored so far, this one will be done using Tinkercad.

Step-By-Step Design

1. The first step is to put the ruler on the workplane, and drag a Polygon from the Basic Shapes area of the screen onto the workplane. The shape of this polygonal prism is hexagonal ― just what we want.

2. Our next step is to resize this shape to represent the interior of the tub. The original dimension is 20 mm corner to corner, and 17.32 mm across the faces. The goal is to maintain the aspect ratio and resize the hexagon to 120 mm corner to corner. The face to face size will be 120 x 17.32 ÷ 20 which is 103.92 mm. Next, set the height to 40 mm.

3. Next, we'll make the outer part of the tub. Select the hexagonal prism, copy it, and paste it. To keep from being confused later, make the new shape a different color.

4. Move the interior piece up by 5 mm. You can pull it up with the black arrow, or enter 5 mm in the base position field on the left of the screen, just below the height setting.

5. Now it is time to change the size of the outer piece. Select it, make the corner to corner dimension 130 mm, and adjust the face to face dimension proportionately. In this case, the size will be 130 x 103.92 ÷ 120 which is 112.58 mm.

6. Now we need to align the two pieces so they are centered. Select both pieces, choose the align tool and click on the center button for both the X- and Y-axes. This might be easier for you to see if you use the Top view of the workplace.

7. When you are done, the pieces are centered like this.

8. Next, select the interior piece and choose the Hole tool to the right of the workplace.

9. Select both pieces, and click on the Group button to the top right of the workplace. This gives us the finished view of the tub itself.

10. Now we need to add seats to the tub. Drag a cylinder to the interior of the tub.

11. Change the seat size to 30 mm in diameter, with a 20 mm height. Finally, raise the seat 4 mm from the base. As before, this kind of movement can be done with the black arrow, or by entering 4 mm into the field below the height field.

12. Now move the seat to one of the corners so it makes a tight fit.

13. Copy the seat, and paste five more of them to the interior of the tub. Position them to the remaining corners, and you're done.

14. If you choose the Home view of the workplane, you can see a nice view of the tub. Export everything to an STL file and you're ready to print!

Printing & Assembly

Print a copy of your tub and check to make sure there are no holes in your model from which water can leak.

Things To Do & Notice

Calculate the volume of your tub. Here are some hints: A hexagon is made from six equilateral triangles. In our case, these triangles are 65 mm on each side. The tub is 35 mm deep, and you need to subtract the volume of the six cylindrical seats, each of which has a diameter of 30 mm and a height on 19 mm.
Using a measuring cup, fill your tub with water and compare the volume you found with the volume you calculated. If the numbers are different, how do you account for this?
Our tub has a wall thickness of 5 mm. Water exerts pressure on the walls of its container. Since the density of water is one gram per cm3, what is the pressure inside a full tub in newtons (N) per cm2? Where is this pressure the highest? Where is it the lowest. How thin do you think you can make the tub walls and still safely hold a tub full of water?

#HourOfCode Challenge

From December 5th to the 11th, multiple companies, schools, and organizations are participating in the Hour Of Code program to encourage students to learn and experiment with code. We'd like to get in on the action with this monthly lesson. Can you reconstruct this month's EDU lesson using the code based CAD program, BlocksCAD? If you send us a screenshot of your code solution with an image of your final model, and we will put your name in the hopper to win a 1kg roll of PLA filament in the color of your choosing! We will select a winner from the submissions on January 1st, so you have nearly a whole month to fit in an hour of code! Best of luck everyone!


Haunted Halloween Challenge Tutorial


Haunted Halloween Challenge Tutorial

A 3D Printed Jack O Lantern with an LED candle inside lights up the whole print!

A 3D Printed Jack O Lantern with an LED candle inside lights up the whole print!

We've just launched the Haunted Halloween Challenge! This challenge is a little different than previous ones — we'd like you to make a design that should be lit up from the inside! It seemed like a great opportunity to help out our students and teachers with a little tutorial.

Due to the fact that excessive heat and finished 3D Prints don't mix too well, we suggest that you use a flameless LED candle to make your prints light up. As evidenced by the adjacent photo, it works really well! You can find inexpensive, flameless LED candles at most major stores, especially during this Halloween season.

To make a hole big enough for a flameless candle in your model, first you'll need to measure the candle you'd like to insert. Our candle, for the sake of the tutorial, was roughly 1.5" (38mm) in diameter and 1.5" (38mm) tall. To ensure enough room inside the print, we decided that making a slightly larger cylinder of 1.75"D (44mm) x 1.75"H (44mm) would work best. We suggest that you also make the hole slightly bigger than your candle to be safe. 

Now you'll need to create the spooky model you'd like to illuminate. That part is entirely up to you and we look forward to seeing your design! For our tutorial, we've started with a basic, not-so-scary pumpkin in the center of the workplane. We first raised the pumpkin to make some space beneath it. Next, we created the cylinder and scaled it to the proper size using the control handles on the model.

With the cylinder finished, we lowered our pumpkin model on top of the cylinder so that they overlapped. To ensure that the hole works in printing, we extended the base of the cylinder past the workplane using the control handles. Then with the cylinder selected, we changed it from "Color" to "Hole" and grouped the pumpkin and cylinder hole together. This creates a pumpkin with the proper candle hole inside! 

Once you've crossed this point with your design, you can save it in TinkerCAD and download the STL file for printing. When you upload your design to the Polar Cloud for printing, we suggest you use a small "Infill Amount" in your Cura settings (5-10%). This will allow more light to shine through from your candle! Finally, be sure you have support material turned on to ensure your candle hole doesn't cause your part to collapse during printing. With those settings in place, you can press print and watch it go!

Once your design has printed, simply remove the support material and insert your LED candle! Take a picture of your design all lit up and send it to us, and we'll be happy to share your spooky creations. Best of luck to everyone in this challenge and have fun printing!


Introducing: Educational Projects By David Thornburg


Introducing: Educational Projects By David Thornburg

Today we're starting something that we think you'll love. This is the first in a monthly series of projects in the STEAM (science, technology, engineering, arts, and mathematics) education areas written by David Thornburg, that we want you to try with your class! They involve the design and construction of projects that can be used to explore a variety of topics. 

Our emphasis is on the design process and we'll primarily focus on two excellent free design tools suitable for students at most grade levels: Tinkercad and BlocksCAD. These entry-level tools are cloud-based, and accounts are free. 

As you work with these projects, we want to hear from you! Especially if you have cool ideas for new projects, and ways you have extended these projects in your own schools. Have fun and enjoy David's first project: Sea Shell Spirals!



Sea shells are amazing objects to explore.  Young children enjoy finding them, exploring their colors and shapes.  They even hold large ones to their ears to “hear the ocean.”  This project explores the spiral shape of many shells, with special focus on shapes similar to that of the chambered nautilus― a cephalopod whose shell is an equiangular spiral.  In this project, you will build 3D-printable shapes of quarter circles with different sizes based on Fibonacci numbers (connecting this activity to math) that, when assembled, produce a spiral similar to that of the chambered nautilus.  These shapes will be made using Tinkercad.

Fibonacci numbers are generated from a simple calculation and show up quite commonly in nature.  Starting with the numbers 1 and 1, the next number in the series is the sum of the previous two numbers.  This gives us 1, 1, 2, 3, 5, 8, 13, 21, and so on.  Our project will use quarter circle pieces whose width is based on Fibonacci numbers.  We will start with two quarter circles 10 mm across, and add more from there.

If you'd like to download the entire lesson as PDF for usage in the classroom, use the link below!

SEA SHELL SPIRALS : Step-By-Step Design

1. Using Tinkercad, drag a cylinder to the workplane and drag the ruler tool onto this plane as well.  The reason for using the ruler is that it lets us enter numbers for sizes as text rather than having to drag a corner of a shape by hand which sometimes is hard to control accurately.

2. Make the cylinder 20 mm in diameter by entering these numbers in the text field associated with each side on the x-y plane.


3.  Change the height of the cylinder to 5 mm and drag a box onto the workplane.

4.  Set the box dimensions to 25 mm on a side, with a height of 7 mm.

5.  Use the black triangle at the top to lower the box beneath the workplane by 1 mm.

6.  Using the arrow keys, move the box so the left edge is at the center of the cylinder.  If you don't get it the first time, you can fix it later.


7.  Copy and paste the box and use the arrow keys so the upper edge is at the center of the cylinder.


8.  Select both boxes and turn them into holes by clicking on the hole button in the Inspector window near the top right of the workplane window.


9.  Select all three objects and choose the Group button at the top of the screen.  This will leave you with just the visible quarter circle.


10.  If the dimensions are not exactly 10 mm by 10 mm, Ungroup the object, move the boxes to the right place, and Group everything again.

11.  Change the piece height to 3 mm.  This completes your basic piece, and everything else is made from copies of this.


12. Copy and paste your first shape, move it to the right and click on the rotate symbol (the red curved arrow shown below) and drag the piece by 90º.

13.  Use the arrow keys to move the piece to the right, leaving a small gap with the first piece.


14.  Copy and paste this piece and move it down a bit.

15.  Change the dimensions to 20 mm, rotate the piece 90º, and move it to clear the pieces you already made.


16.  Repeat this process with a size of 30 mm.


17. Repeat this process with a size of 50 mm.


18. Repeat this process with a size of 80 mm.


19.  You now have enough pieces to fill your build plate.  Change your view so you are looking at the model from the top and adjust any pieces that are too close together.


20.  Export your model as an STL file for printing.

Printing & Assembling The Model

Print a set of shapes in any color you wish and put them together into a spiral.  To my eye, this pattern is very pleasing to the eye.  As you can see, using Fibonacci numbers makes everything fit perfectly!


Things To Do & Notice

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     Chambered Nautilus Shell Section Source: Wikipedia

Chambered Nautilus Shell Section Source: Wikipedia

Assemble the shapes as shown in the photograph.  What would the dimension of the next shape be?  If you want, design and build the next shape in the sequence.  It will be so large that only one of them fits on the build plate.

Compare your shape with that of the chambered nautilus shell cross-section shown below.  In what way is this shape similar to that of the Fibonacci spiral you created?  In what way is it different? 

Fibonacci numbers are quite common in nature, but they don't seem to exactly match up for the spiral in the chambered nautilus shell.  Why do you think that is?

What about garden snails?  Are their shells similar to what we made?  If you have access to a shell collection, see how many different examples of spirals you can find.

Spirals of the kind we just made are called equiangular spirals.  For further learning, you can explore the math of these spirals with some help from Wikipedia.