The Antikythera Mechanism Episode 5 - The Input Crown Wheel Assembly

In this video I make the small assembly that enables the user to drive the mechanism.

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Cameras used in this video:
Panasonic GH5 - https://amzn.to/2rEzhh2
Panasonic X920 - https://amzn.to/2wzxxdT

Tools & Shop Products:
"Solidworks 2013 Bible": http://amzn.to/2FObS1D
"Gears From The Greeks", Derek de Solla Price: http://amzn.to/2pii4ZD
"A Portable Cosmos: Revealing the Antikythera Mechanism, Scientific Wonder of the Ancient World" https://amzn.to/2NoLgIR
Dormer A190202 Jobber Drill Set, 1.0 mm - 6.0 mm x 0.1 mm Size: https://amzn.to/2DR5fdb
YG1 NC Spotting Drill 8% Cobalt HSS 1/8 to 1/2" 120 Degree 5 Pc Set CNC Machine: https://amzn.to/2G7ylv6
Hegner Scroll Saw: https://amzn.to/2IhteVW
Kaowool 24" X 12" X 1" 2400 F Ceramic Fiber Insulation: http://amzn.to/2pfsM3d
Tix Flux 1/2oz: http://amzn.to/2G85OEZ
Tix Solder: http://amzn.to/2G4lUiE
Dykem 80300 Steel Blue Layout Fluid, Brush-in-Cap (4oz): http://amzn.to/2HGPaJJ
Generic Dial Indicator 0.001": http://amzn.to/2FOFTyF
Blue Matador Abrasive Paper - https://amzn.to/2IAFiBT

Abbreviated Transcript:

0:00:56 Now much like the main solar drive wheel, from our modern perspective, this is clearly not the easiest way to construct the part. So again the question naturally arises, why did The Maker choose this more difficult method?
03:08 Taking care to reheat the work as soon as it started to cool down, and also being careful to not to overheat it. It doesn't take much to melt a small piece of brass like this. A light skim cut on the lathe created a uniform surface, and widened the inside diameter to be a close fit with the central cylinder formed earlier. A touch of soft solder bonds the two parts together, and fills the join in the perimeter of the band.
06:57 Gradual increases in the depth of cut on either side of a single tooth, eventually leave a small triangular land at the tooth apex. At which point the carriage can be locked, and all of the teeth cut at the same setting. I took a light skim cut of the perimeter to remove the small exit burr left by the fly cutter, and then marked out the rectangular hole that will receive the driving arbor.
09:49 I've found that around 0.4 of a millimeter gives a good tight radius to the bend, and allows the metal to bend easily without cracking. The inside corner on the indexing arm, that I made in a previous video, serves as a convenient square reference.
12:27 The wheel assembly could be held up to B1 with a toolmakers clamp, depthed, marked and then permanently fixed in place. But I'd also like to have the back surface of the bracket flush with the side of the main plate, without having to trim that plate after the fact. So that meant making my best guess at the correct depthing at the planning stage, and essentially locking it in at the start of the project.
13:18 With the input assembly position located, the bracket and underlying main plate were drilled out to accept a pair of steady pins. The steady pins now ensure the the accuracy and repeatability of the bracket position. And once clamped firmly, I drilled out the hole for the bracket retaining pin. A quick tidy up of the holes, and that's the bracket complete for now.
16:44 I opened up the matching rectangle marked out in the center of the crown wheel, taking care to ensure a close fit. With the crown wheel assembled on its driving arbor, I marked the retaining pin position, which will ensure a small clamping force from the taper pin once its inserted.
19:05 The friction is quite low, with both wheels showing free and smooth movement. And the gear interaction feels good too, much better than I expected from a triangular tooth form. In fact based on the feel alone, there's not much to give away the fact that its not a modern tooth profile.

References:

Gears From The Greeks - Derek de Solla Price: http://amzn.to/2pii4ZD

The CT and PTM data that the AMRP have made publicly available can be found here: http://www.antikythera-mechanism.gr/data

Gear schematic can be found in Tony Freeth's 2012 research paper:
http://dlib.nyu.edu/awdl/isaw/isaw-pa...

The Antikythera Mechanism Episode 5 - The Input Crown Wheel Assembly