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--- projects:glass_sphere:housing [2019/01/05 02:19] – tjhowse
+++ projects:glass_sphere:housing [2019/02/24 22:54] (current) – tjhowse
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+{{indexmenu_n>2}}
 ====== Material selection ======
-Glass is pretty good. When tempered and treated it's pretty shock-resistant, can handle a wide range of temperatures, handles radiation.
+=== Glass ===
+Glass is pretty good. When tempered and treated it's pretty shock-resistant, can handle a wide range of temperatures, chemically stable, and handles radiation without degrading too much.
+== Sourcing ==
+For my initial experiments I want to use recycled glass. I have lots of mirror scraps, some blown glass bottles, and a glass tabletop. I need to solve a few problems:
+  * Removing the silvering on the mirrors,
+  * Blown versus float glass,
+  * Smashing the glass into frit,
+    * Particle size,
+    * Wash versus non-wash.
+  * Fusing the glass into solid chunks.
+    * Temperature profile,
+    * Flux.
+== Toughening ==
+Tempering glass makes it strong. I've done this already on the leaf-in-glass project. Also soaking in molten potassium nitrate at 300 degrees for a while. This [[https://patents.google.com/patent/US3445208|patent]] describes a process which uses all kinds of nasties dissolved in the liquid KNO<sub>3</sub>. I'm not going to risk fluoride poisoning.
+====== Geometry ======
+== Overall ==
+I think the most robust shape would be a sphere. Every other shape has points or edges that would lead to higher peak stress when dropped.
+== Assembly ==
+It's gotta have a hollow bit in the middle for the electronics, but I want it to be as close to solid as possible. My current plan is to create the sphere in two unequal halves, one with a void in the centre for the electronics and the other part caps off the hole.
+{{:projects:glass_sphere:pasted:20190105-090354.png}}
+== Joining ==
+The join will be the weak part. I would like to fuse the two bits of glass into one, however that would require around 800 degrees celsius, which would destroy the electronics.
+My current plan is to lap the two joining surfaces very very smooth and [[https://en.wikipedia.org/wiki/Gauge_block#Wringing|wring]] them together. I'm currently hoping the two halves will cold-weld together. This way I can avoid using adhesives which would degrade over time.
 ====== Shielding ======
-Leaded potting compound, or lead sheets wrapped around the electronics.
+Some of the cooler options for electronics inside the sphere require microcontrollers and flash storage, which would have their effective lives extended with some radiation shielding. I'll use a leaded potting compound (if it exists), or lead sheets wrapped around the electronics.