Introduction: Magnetic Geodesic Planetarium
Hello all! Id like to walk you through my process of creating a geodesic planetarium held up with magnets and crafting wire! The reason for using this magnets is for ease of removal in times of rain or less than ideal weather conditions. This way you save time and preserve the condition of the inner cloth that is the projection screen.
Step 1: The Frame
This part of the process was rather simple and fun thanks to the kind people at zip tie domes! I ordered a 17ft diameter 3v 5/8ths dome for this specific project, but you can feel free to use whatever size and frequency dome suits your needs!
Step 2: Cutting Fabric for the Screen
In this process for the 3v 5/8ths dome there are two different sizes of triangles to cut out. Zip tie domes has a wonderful calculation tool and does a great job of color coding the struts for the specific sizes. For this project there were 75 large blue triangles and 30 smaller red triangles. This took about 75 yards of black out cloth. The fastest way I found of doing this is to create two stencils for each triangle and calculate how much slack you'd like to have for the inside of the dome. At the end of this tutorial I'll go over some improvements that can be made and things I learned throughout the process. Once you've cut out your triangles you are ready to sew!
Step 3: Sewing
This is one of the most challenging phases of the build. For this depending on the size of your dome, you will need an industrial sewing machine. I was fortunate enough to gain access to a sewing lab at UC Davis due to me being a design major. The best way of sewing is to break the dome up into five tessellation's of the triangle shown in the images i've attached. Once all five are sewn together you can begin to work your way down to the bottom. this part was one of the more challenging and time consuming parts. This starts to become a rather large heavy and cumbersome mass of cloth to work with, so remain calm and remember to take deep breaths! It can become very frustrating but keep in mind the outcome is worth it! I did this process on my own and it took approximately 35 hours. I would highly recommend working with a team if you can! Now, thats often easier said than done so if your tackling this project on your own, stock up on caffeine.
Step 4: Magnetic Dowels
So here is where I took a different approach with the project. I got a few 6ft 3/4inch wooden furring strips and chopped them down to about 5 inches. I also drilled a small hole on each dowel on the side opposite of where the magnet would attach. I then bout neodymium magnets with a draw force of about 3 lbs. The idea here is that I can attach the screen easily with magnets and when rain inevitably arrives I can take the cloth down easily. These magnets were fastened to the dowels using a two part epoxy mix left to dry for 24 hours. After they dried I then plasti dipped the magnetic parts to add an extra layer of protection as neodymium magnets are very brittle. For the cloth screen I found the most inexpensive way to make the cloth magnetic, was to epoxy steel bolts at each of the connection points of the seems. Once finished you'll want to grab some crafting wire and tie the magnetic rods to the center of the hubs of the pvc frame.
Step 5: Raise It Up! and Set It Up!
Once everything has dried and you've attached your dowels to the frame its time to attach the screen to the frame! This did not pan out exactly how I had intended and I had to wrap the 6 bolts at the zenith of the dome in crafting wire and secure the tarp to the frame by wrapping wire from the screen to the hubs. The screen was very heavy so the magnets couldn't do much at this point. However once the very top of the dome was secured the rest of it just clicked into place! So while its not 100% magnetic it's 90% and that sure sped up the set up process! the next part was to make the dirt floor disappear inside so I bought a 20x20 heavy duty tarp and managed to snag some carpet samples for free from a local flooring warehouse!
Step 6: Setting Up the Mirror Ball Projection System
There is a wonderful resource online I will refer you to by Paul Bourke. He talks in depth about how to set up a rather inexpensive mirror ball projection system. I would recommend getting a good quality sound system as that is the other side to creating an immersive experience. I used an Optoma HD27 for the projector and it seems to do a nice job. there are better projectors and I would recommend spending some time researching and reading Paul Bourke's page on what specs you need for a projector. Not all projectors work for this project so take your time researching!
Step 7: Closing
Credit to the film "Mayan Archeoastronomy" by the CONACYT. At the end some things I would do differently is to use metal hooks for the top of the screen to create a stronger and much more efficient bond at the top. Another thing is the size of my tarp is quite large so that why it has a pillowy effect. I will be working on making the surface more taught by adding velcro to the struts or finding some way to solve the issue of "slack". This was true learning experience and this is a project that will constantly have room for improvement! Total cost came to about $2000 and that includes the following:
-Zip tie Dome Kit
-Wood for dowels
-Rulers, cloth scissors, thread
If you have any questions or comments feel free to send em my way! Thank you and I hope this tutorial helped!
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