Introduction: Pythagoras Cylinder With Sketchup to STL

My inspiration for this project came from a youtube video titled Pythagoras Cup filled with Mercury. As a physics teacher that teaches fluids, I wanted a measurable version of this. I know there are Pythagoras Cups out there, but I also wanted to Make It Myself!

With some basic Geometry and a reference to how large I wanted it, I was able to make a sketch and use Google Sketchup to make a digital model of my design. 3DHubs allows me to get a physical copy without me having a 3D printer. I needed to make sure that Sketchup would output the 3d model format that 3dHubs accepts. A quick search led me to find me to www.guitar-list.com for a plugin that allowed for exactly what I needed.

3dHubs.com site allowed me to drag and drop my stl file to find a printer near me. In the Dallas area, there are many printers willing to provide 3d printing services. With my large sized model, there was one printer available. I modified my fist design because the original size was beyond my price point. Size matters. Once I shrunk my cylinder to half its height, the price went down, but more importantly, the number of people available to make a smaller print grew many times over, to over 70 printers.

Step 1: Google Sketchup Highlights

Picture of Google Sketchup Highlights

Especially since my object is circular, I placed the center of the object at the origin of the workspace. I needed to reference the center Alot for this model.

I started with a bottom base view of my object and push/pulled from there. I chose to work in mm for precision, easy calculations and easy conversion to mL since I am making a container to hold fluids.

I painted my model transparent, because I want the final object to be transparent and painting it transparent allowed me to see what will be material in my model.

When looking at the bottom, I realized I did not have a 3D object because the base was 2 dimensional. I pushed the edge. Since the empty circle is a flat plane in the middle of what I had pushed out, i drew a line across the flat enclosed region and a the empty plane space was filled with its shape.

In the center column I have a u tube that falls all the way through the bottom of the glass on one side and out the side of the lowest point of the center column. I tried using the follow me tool with a guide, but the model was incomplete and fragmented. To make a curved tube, I made identical arches (Half circles were the easiest to reference) across each angle of the two "circles". Then I line tooled all the connections to get the planes across each piece of the u tube. It did not take as long as I thought it would.

By rick clicking and selecting hide on an outside surface, I could check to see that I did not have any interior planes that might confuse or mess up the 3D printing process.

The last image is evidence of this. I zoomed to move inside the material of my model and found a circle plane that may have caused a problem with my model allowing water to flow through it.

I double checked my surfaces to make sure that they were the exterior of the plane on the outside. Right click and select Reverse Face on the surface you want flipped.

Step 2: Sketchup --> .STL --> 3dHubs.com

Picture of Sketchup --> .STL --> 3dHubs.com

A quick google search led me to find a way to export Sketchup to STL files and more.

www.guitar-list.com has en export plugin that allows you to select your units and DFX options.
The options are polyface mesh, polylines, triangular mesh, lines and STL.
I had to make sure to type in the ".stl" extension for the file name when saving the export.

3dHubs has a drag and drop STL feature that will show you a thumbnail image of your model if it is a stl model with the stl extension. It was here I realized that Sketchup has a surprise for me. The default Sketchup person model has a speech bubble that is hidden unless hidden geometry is checked in the View menu bar.

Jarrod from Burleson's Print Hub took care of my print and is in the Dallas/Fort Worth area. My first model has small stands for feet and caused an obstruction when printed. Jarrod had some really good ideas and was willing to create a 3d model of my idea in AutoCad Fusion 360. The model suggested was smooth without the polylines that my skecthup file was littered with. After some modifications to my sketchup file, Jarred printed the second copy with no extra charge as well as a stand that he designed to help my physics demonstration. 3dHubs has an easy and effective way to communicate ideas, revisions and files through their order system.

Step 3: The Finished Product

Picture of The Finished Product

Jarrod contacted me on where to pick it up and I had a pleasant experience as he handed off my part to me.

I the future I am going to give AutoCad Fusion 360 a try. Printers and manufactures may not be able to see the vision of your product just from the stl file. Many do not use Google Sketchup much, if at all, because the free version does not allow for easy exports and they already have a good comprehensive CAD program. My experience has been that fabricators do not treat Sketchup files as a standard format for printing 3D models and can be blind to whether the design is sound until after it is printed.

I am happy with my model and design. The model works as designed. When a liquid is below the center column, no fluid leaks out. When the liquid is above the center column, all the liquid will then fall through the bottom center hole.

Jarrod has excellent customer service and treated my part well. I will probably look into a CAD program that easily exports to IGES, STEP or DWG for future fabrications.

Comments

verence (author)2015-06-23

Bah! If Pythagoras' students were clever, they'd put their pinky up the central hole, blocked the wine and have the full cup! ;-P

'part from that, interesting project. Is there an option to make the cylinder more round? That looks more like a 24-gon.

Is there a plugin for Firefox or Chrome to see *.stl files?

Manolov4 (author)verence2016-01-06

Pythagoras made this cup for those who always want to have more. In this way, he taught his students that the one who wants more, loses everything. Wich in most cases is trye... He also wanted to teach equality. My origin is from Samos, Greece, the island wich is claimed to be his homeland. :-)

Zachariah (author)verence2015-06-23

To my understanding, that is a limitation of the free sketchup. I could have represented the circle with many more sides to make it rounder, but i did not.

I googled stl viewer and found many, even for phones.

verence (author)Zachariah2015-06-23

> To my understanding, that is a limitation of the free sketchup. I could have represented the circle with many more sides to make it rounder, but i did not.
Ah, okay,

> I googled stl viewer and found many, even for phones.
Yes, I know about external, stand alone viewers. But as a lot of intructables have stl files included, I would like to see them inside the browser. So I was (and still am) especially looking for a browser plug-in.

ccyclone (author)verence2015-07-03

There isn't any limitation on Sketchup to produce higher sided cylinders, you just have to type the number in when you draw the circle for the cylinder.

Instructables has a web based STL viewer that used to work on Chrome but now it seems to have a spot to view the STL but sits there with a loading animation forever. Something must be broken.

Malkaris (author)2015-06-29

this is the same mechanism used in aquaponics, but I always heard of it as a bell siphon, I always figured it was invented in more modern times.

Zachariah made it! (author)2015-06-22

Fun build and demonstration piece holds 425 mL

Zachariah (author)Zachariah2015-06-23

The container's volume is 425. It will hold 250

tomatoskins (author)2015-06-23

I've never heard of a Pythagoras Cup but this is pretty awesome!

Zachariah (author)tomatoskins2015-06-23

Thanks! Neither did I before this project.

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