One of my favorite concept drawings uses a tellurion mechanism. A couple years back I figured out the math for the necessary gear ratios, but now I thought it was time to cut some (a lot of) gears to test my math, and make sure everything works as it should. It’s a little crude, but certainly adequate for a mock-up.
A quick breakdown…
-This display mimics the movement of the earth and moon around the sun. Because it moves in a one year cycle, it also indicates the months, and the solstice/equinox.
-The center of the carriage will have a sun on it, as you can see from the drawing of the clock. The entire carriage, along with the earth and moon, will rotate once every 365.25 days. I used that number so that it aligns with a Julian style perpetual calendar mechanism.
-The earth rotates so if you were to draw a line through the place you live, it would point directly at the sun at noon each day.
-Then the moon moves around the earth with its synodic cycle. If you note the location of the moon in relation to the earth and sun, you can see what phase it’s in. If it’s directly between the earth and sun, it’s a new moon. If it’s on the other side, it’s a full moon.
The math for this mechanism was deceptively tricky, for me at least. That center gear needed to turn .99726215 each day. Then the carriage, which works off that gear, needed a .99726215 to .002737850 gear ratio. This necessitated some very strange gear tooth counts.
After a lot of work, I finally (nervously) turned the 1/day gear through it’s yearly cycles, and I’m happy to say everything is working perfectly!
Now, should I get the opportunity to move forward with this design, I’ll know it’s good to go!