I’ve spent the last week printing and assembling a prototype gearbox made from PLA. If you were curious at all about my mystery print from last weekend, you can see it inside of the gearbox here:

The entire gearbox is made up of about 18 different printed pieces totaling about half a kilogram in weight. Just for fun, I calculated that I used about 200 meters of filament to print the whole thing.

Here is a photo of the top half of the gearbox case after finishing the print:

And here is the fully assembled gearbox screwed shut:

This experiment is mostly to see if one can make a complete mechanical assembly like this entirely from 3D printed parts. (With the exception of the 4 screws and nuts to hold it closed.) This includes not just the gears, but also the shafts, the bushings, and the case.

In case you are wondering, the black tape on the left and right ends are just there to make it easier to see the shafts spinning.

The other purpose of this assembly is as a prototype for an idea I have for a lateral thruster. This is a dual propeller part on the ferry boat we will use for moving around in the pond. (And getting to the floating house from the edge of the pond.) The concept is that the motor will be up in the boat pointing downwards and will drive the top of the four shafts. The bevel gears will transmit the power to the left and right shafts on which will be 2 propellers spinning in opposite directions. (The propellers would need to have opposite pitch, so that they create a thrust in the same direction when they spin opposite to each other.) The bottom gear and shaft is only there for balancing out the forces and holding the other three gears in place.

Subjectively, I would say it is a complete success. When I turn one shaft by hand, the other 3 shafts turn correctly. Even after applying grease to the moving parts, it has a slight catch once every turn which I assume is some slight imperfection in the plastic I can’t see, but I am also assuming that if it gets used for real, these imperfections would naturally wear away. It is really fairly minimal and doesn’t prevent turning.

Here is a video of it in action:

 And one more video where I use a hand drill to power it: