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  • Sun, Earth and Moon Model (Tellurion / Orrery) With 3D Printed Parts

    Thank you for the reply. I know what it feels like trying answer questions a few years after you've left a particular zone - Ha!.I am attracted to your design because the basic unit of rotation is the day. Most traditional tellurium designs i’ve seen are based on the year, so the crank handle spins the earth rapidly like a top. Because of that, good luck trying to get a particular location on the earth aligned properly with the moon (as in eclipse path demonstration.)The trade-off is that your crank handle (or knob) orbits the sun, which is a little awkward, and it takes a lot of turns to get it all the way round the year.The other attraction is the simplicity and elegance of your gear train, but that will somewhat diminished after i add an extra set of gears for synodic rotation - ha!R...

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    Thank you for the reply. I know what it feels like trying answer questions a few years after you've left a particular zone - Ha!.I am attracted to your design because the basic unit of rotation is the day. Most traditional tellurium designs i’ve seen are based on the year, so the crank handle spins the earth rapidly like a top. Because of that, good luck trying to get a particular location on the earth aligned properly with the moon (as in eclipse path demonstration.)The trade-off is that your crank handle (or knob) orbits the sun, which is a little awkward, and it takes a lot of turns to get it all the way round the year.The other attraction is the simplicity and elegance of your gear train, but that will somewhat diminished after i add an extra set of gears for synodic rotation - ha!Right now i’m working on a more typical design based on the calculations (but not the engineering) of C.H. Balleisen’s 1938 paper in which he corrects the sidereal vs. synodic mistakes of another paper that same year by R.K. Marshall. You have probably seen those papers - they come near to the top of a google search for orrery. Both papers deal with 2 different “inexpensive” orreries using standard gears. I just completed building a 6-planet orrery inspired by those papers, but with completely different gear trains and two more planets. Thank heavens that Balleisen wrote the correcting paper! The Marshall mistakes were the very same one’s you mentioned.In my current tellurian project i’m using a layout similar to one by Staines & Sons (all over YouTube) which also has a design simplicity as well as apparent symmetry. They are selling a finished product and provide no technical information (clock makers are historically and currently secretive.) So after trying to lay it out with the same number of gears in the same configuration i realized that at least one gear pair (lunar nodes) has to be non-unity module to achieve concentricity with the output shafts. Now - that is a lot easier for you to do with 3D printing than for me cutting metal teeth the old school way! I’m satisfied that i can hack that using a standard gear cutter though, since it’s close to a standard pitch. Mechanical efficiency in power transfer is not a major worry on these slow moving gears.Anyway after that i’m probably going to revisit your design and see if i can add anything to it.I’ll post what i come up with.thanks again.

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