Automatic Seasonal Clock (uses a clock motor)

Hey there! So, I made this project because it popped into my mind. I was looking for project ideas to 3D model and came upon the concept of an orrery. So I thought "hey, what if you made an automatic orrery that's always accurate?" then when that idea gradually became even more impossible i was like "hey. let's do a seasonal clock instead. So here it is!

I used the superior software: Fusion360 to make this. The gears were made with  the SpurGear extension, and the screw holding the earth wand to the base gear was made with the fasteners tool of fusion360. You can 3d print the one in this fie or buy one.

I created it by researching stuff about gear ratios. 

The way it works is with a motor that turns once per hour. The entire gear train creates a reduction of 1/876. It was supposed to have a gear reduction of 1:8760, but I'm apparently terrible at math and missing another 1:10 reduction. In a future iteration, I could probably use a 20 tooth gear as well as a 50 tooth gear. However, if you alter a clock motor to tick once every 10 hours, this model works for any year that is NOT a leap year. So, here's what I learned about gear trains, gear reduction, and all that.

When you have two gears interlocked, their ratio is the driven gear over the driving gear. So, if a 10 tooth gear turns a 30 tooth gear, the ratio is 3:1. Now, say you attach a motor to the 10-tooth gear that turns once per minute. So, the 10-tooth gear will turn completely in 1 minute, while, since the ratio is 3 to 1, it will take 3 minutes for the 30-tooth gear to turn. Now, let's apply this logic to my project! I also learned that stacking gears means you need to multiply the gear ratios to get the overall reduction of the gear train.

So, the clock motor turns once per hour and has a 10-tooth gear on it. It takes 1 hours for that gear to make a full rotation.

Driven by this 10-tooth gear is a 40-tooth gear. So, the 40-tooth gear makes a full rotation once every 4 hours. Now, the 40-tooth gear has a 10-tooth gear attached to it under it. These two move at the same speed, as they both rotate 360 degrees at the same time. So, it takes 4 hours for the small 10 tooth gear under it to turn a full rotation.

Now, if we link a 50 tooth gear with this 10 tooth gear, sine the ratio is 5:1, the 50 tooth gear takes 20 hours to make a full rotation.

Now, there's also a 10-tooth gear atop the 50-tooth gear that moves at the same speed and is interlocked with the 60-tooth gear. So, since the 10-tooth gear moving is the same speed, it takes 20 hours to turn fully. Since the ratio between the 60-tooth gear and the 10 tooth is 6:1, then, the 60-tooth gear takes 120 hours to turn, and so does the 10-tooth gear under the 60-tooth gear.

Finally, we reach the 73 tooth gear. It is linked to the 10-toothed gear of the 60 toothed gear that rotates completely in 120 hours. So, the ratio between these two gears is 1:7.3. So, we multiply the speed of the 10-tooth gear (120 hours) by 7.3 and this gives us a gear that turns once every 876 hours!