I strongly believe that this is the best 3D printable gear configuration. It has very little friction and does not require hardware or bearings to run for a long time at 1000+ RPM. With some of my newer remixes of this, this type of gearbox can be mounted to a NEMA 17 Motor and with more modules and interconnecting ever other sun gear the backlash nearly disappears completely

I have made a lot of newer, better gearboxes (with some HUGE gear ratios) like this one! Check out my other "Things"

Updates!
4/7/14- Video of gearbox driving knee joint on InMoov. Legs https://m.youtube.com/watch?v=Ah7cCeW9HrY
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Please Check out my Youtube Video Below!

This design has two different gear ratios depending on which sun gear is driven. The large ring gears have a different teeth but the OD and notches are the same meaning you can choose which way you insert it into the capsule, this is how the gear ratio is changed, along with using different sun gears. Please note that you actually don't need the other sun gear or the mounts just to try it, but it will not work as well without it. Also, make sure you don't couple the two sun gears together, won't work that way.

These parts have all been printed and proven to fit. I ran this on with a drill at full speed for 3 minutes had the gearbox held up very well, i suspect that with a couple dabs of grease this gearbox could handle 1700 RPM input speed for hours.

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PRINT INSTRUCTIONS:

You will need 3 or 4 planet gear's, those are the long double gears. 4 is best.

you will need a large carrier ring, and the small carrier ring.

For the 37:1 gear ratio setup you will need the "Drive Sun 37:1" and the "Driven Sun 37:1"

For the 49.something:1 gear ratio setup you will need the "Drive Sun 51:1" and the "Driven Sun 51:1"

if you plan to use it for anything more than demonstration you will also want to print the NEMA 17 mount and the end cap that mates with it.

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PLANET GEAR PHASING INSTRUCTIONS------------------IMPORTANT!

The planet gears are technically dual gears. They are two gears attached together and have a different number of teeth, after some studying i realized that this means they must be assembled so that they are "relative" to each other, Theres a picture in the files to help you do this properly.

I included the Fusion 360 project files, and if you want you can modify this and stack the planetary gears to give this gearbox 4 or 8 modules for use in high torque applications, i would also suggest that you interconnect every other sun gear to do this.

Thanks for checking this thing out!

Update 3/27/17- I figured out how to calculate the gear ratios on these gearboxes, So i wrote a arduino program to spit out the best teeth combinations. I'm currently working on making one that will be a gear ratio of 1,400:1 and that is with the largest number of teeth being a 53 tooth ring gear. I will include this program with my gearboxes.

For More Cool Projects and Upgrades, Don't forget to Follow Me on Thingiverse and Subscribe to my Youtube Channel, Gear Down For What?https://www.youtube.com/c/GearDownForWhat