Solid Core Compound Planetary Gearbox (customizable)

thingiverse

To build upon earlier designs, targeting less extreme gear ratios leaves us room for more creative choices in our gear selection. Specifically, incorporating fused sun gears in both stages would allow us to distribute drive force over a larger contact surface, ease initial post-print processing, and boost efficiency. A fused sun gear introduces a constraint that the sun gear teeth are a multiple of the corresponding planet gear teeth, effectively mirroring the planet gears and allowing the two stages to turn in unison with the planets at a 1:1 ratio. Despite this constraint, we can still achieve absurd gear ratios (up to 616:1 within the specified range), but around 50:1 to 100:1 seems a more practical target based on existing designs. Incorporating a three-layered approach from https://www.thingiverse.com/thing:3210223 and https://www.thingiverse.com/Gear_Down_For_What/about will make this gearbox more functional. Eventually, I'll adapt this gearbox to work with other models, but for now, I'm focusing on arranging the gears. This design diverges from the usual teeth relationship of R=S+2P by allowing some flexibility in our ring gear tooth count through dropping teeth and stretching the ring gear (which is easier than compressing and maintaining clearance). This flexibility gives us more options when choosing gear combinations. This model requires a bit more care when inputting values. Use [this spreadsheet](https://docs.google.com/spreadsheets/d/1hqFEOytS_mmBg6_0ydeiAXPRqUPBqH1xZYJIOtOm-4M/edit?usp=sharing) to select appropriate values. In summary, this design brings the following benefits: 1. Customizable for various gear ratios and dimensions 2. Single-piece sun gear, increasing efficiency, strength, and load distribution 3. Potentially more available gear ratios by violating R=S+2P constraint 4. Print-in-place fully assembled, potentially allowing multiple degrees of freedom in a robot arm printed in one pre-assembled unit. (One last note: The scad is a bit of a mess, I know. I've been making changes to experiment with different ideas. It probably has bugs too. I'll tidy it up eventually when I settle on a final design.)