Once you've got everything printed, you may need to sand the 'arm' tubes so that they rotate freely inside each other.
- The Mercury arm should rotate freely around the 1/8in steel rod.
- The Venus arm should slide and rotate freely around the Mercury arm
- The moon ring shaft should rotate freely around the Venus arm
- The Earth arm should rotate freely around the moon ring shaft
- And finally the Mars arm should rotate freely around the Earth arm.
I found it easiest to assemble the arms then slide them into place onto the base.
Start by placing the earth arm into the mars arm, tube sides down.
Then put the moon ring shaft into the earth arm, tube side up.
Then press fit the big moon gear onto the tube end of the moon ring shaft.
Finally put the Mercury and Venus arms tube side down into the moon ring shaft.
Then just press fit the corresponding gears (not square holes) onto their tubes and slide the whole thing onto the 1/8 in steel rod in the base, and use a sheet metal screw to secure the little moon ring arm near the gears to the base.
Then just press fit the motor into the slot on the base (and use tape if necessary), attach the keyway to the motor shaft, and slide the driving gears onto the square key.
The last thing to do is to cut pieces of 1/16 in steel rod to hold the planets.
You may need to use a drill to drill out the holes to 1/16 inches in both the arms and the planets. Make the planets sit at about the same center-line as the sun, and hot glue to a graduation cap!
Nesting arms with out gears
How the moon ring attaches to the base
My dad once showed me a model orrery online and said, could you make one of these? I've been obsessed with designing them ever since. I make them mainly out of brass as shown below, but wanted a working one on my graduation cap for college. This is the design I made in the few extra days after having no final exams this last semester.
I use fusion 360 for the majority of the design, but used gearotic motion (https://www.gear2motion.com/) to spit out the gear teeth size/shape and for checking gear ratio accuracy.
I calculated gear ratios with this awesome tool: http://scientific601.altervista.org/gear/gearcalc.html