Worlds Smallest K'nex Orbital Gear Assembly




Introduction: Worlds Smallest K'nex Orbital Gear Assembly

About: I have an Associates Degree in Electrical Engineering Technology and I am currently working as a manufacturing Engineer. I have many interests which are ever expanding, but one of the things which I love do...

Welcome to my Instuctable on how to build the smallest possible orbital gear assembly out of k'nex!

I originally built this to be part of a transmission, however, despite its small size, it was too large for my needs. I thought others would be able to find some use for it, so I decided to post an instructable on it for you!

Step 1: Parts List

Parts required:

2 circle connectors

1 1" grip gear

1 blue spacer

1 peg connector

1 tiny wheel

2 ladder connectors

14 white sticks

12 half slotted connectors

4 slotted connectors

2 yellow sticks (you can also use red or grey sticks instead for longer shafts)

4 light blue or brown 1" gears. (note: they must be light blue or brown which spin freely on a stick)

12 green sticks

1 medium toothed gear

Step 2: The Planetary Carrier

This is the planetary carrier which houses all the gears.

Step 3: The First Shaft

This is the first shaft attached to the sun gear. Slide it through the center of the planetary carrier.

Step 4: The Planet Gears

Place the light blue and brown gears on the diagonal green sticks so that they link with the sun gear. These are the planet gears.

Once the planet gears are in place, slide the small wheel on the rotor over the sun gear. This secures the planet gears in their places.

Step 5: Planetary Carrier Part 2

This is the the second half of the planetary carrier which will hold the ring gear in contact with the planet gears.

Step 6: The Ring Gear

The medium yellow toothed gear will act as the ring gear. Place the ring gear at the very end of the second shaft with teeth pointing out and slide inside the second half of the planetary carrier.

Step 7: Final Assembly

Connect the two halves ensuring the teeth of the ring gear grab the planet gears. Then slide the large gear on the second shaft so that it locks on the white sticks on the planetary carrier.

Congratulations for completing the smallest k'nex planetary gear assembly! Thanks for viewing my project, I hope you enjoyed it. Be sure to check out my other Instructables!

If you post an instructable which uses something from one of my instructables, let me know, I'll post a link to your 'ible in my applicable 'ible



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23 Discussions


2 years ago

Awesome! I didn't think this was possible with k'nex! Voted. :)

6 replies

Thanks for the vote! glad you like it. It is quite possible, I made a larger version using the large gear for the ring gear, but it had a tendency to jam a lot.... which led me to design this one! It is also possible to simulate orbital gears using a differential. I will be posting something that will explain how soon. Please subscribe if you don't want to miss it! :)

Alrighty, you got my subscription! :D

That's awesome! I'll put a link to it in my 'ible. :)

It looks cool but what is an orbital gear assembly and what is it used for?

12 replies

An orbital gear assembly is basically a differential with unequal gearing for each side. Automatic transmissions use them to change gears.

I recommend watching this video on how orbital gears are used in an automatic transmission.

This video explains it really well! Thank you.
Great instructable, if you would have added a short video to show how the gears move (and how smooth they move, I'm curious about that), then it would have become featured I'm sure.
But keep posting things like this, great! I'm going to make one when I get home, just to see how it works

(I'm in agreement)

Thanks for the advice! The gears are not extremely smooth when turning, the small gears tend to have some resistance between the teeth. This may be reduced slightly by using only 2 planets. I would recommend that you not lubricate it (i tried that) as it causes the sun gear and stopper to slip and the shaft will fall out.

I'm going to make it right now! And... I would not lubricate my knex gears, hehe.
I forgot to tell that I voted for you in the contest btw :)

I appreciate it! Oh! your the one who made the smallest differential! I'm using quite a few of those in my current project. I plant to post my project when its done. I will be sure to give you full credit for them :)

You're welcome. It's always good to see a knex project win a contest ^^
And, that's correct ^^
woa really!? a few of them? And they work good? I sometimes had a little trouble with them, when the axles weren't colinear, but if the structure is right, it should work.
What kind of project is it? Something very mechanical, I'm sure :D

Oh, one more thing. I build it yesterday, and I couldn't get it to work smoothly. That may be the tightness of my gears, though, I haven't abused them (yet).

they work well enough as long as they dont experiance too much torque for the sticky gears. im using a total of 5 diff's in my project which is a awd car with a dual differential cvt.

Are you using the non friction gears? (Light blue or brown)

Oh cool :o But is it going to be something big, or still relatively small? You know, I'm just a fan of small, so I always like to see things as small as possible :P But then again, with lots of functionality in them. Maybe give an indication how large the model now already is :P

No, I don't have those new frictionless gears (are they really labelled like that?) I used the dark blue ones, they're older, I guess. I only have 1 of those light ones, but I could try different dark blue ones to see if some have less friction than others. (jee... 5 differentials... O.o)

it is as small as I could make it while being functional and proportional to a normal car. My current model is about 24" x 50.5". Here is a photo of the car from about a week ago. I'm working on the transmission and gearbox now. Once I have those sorted out I will post instructions for it.

I don't know what k'nex calls them. I just call them frictionless because they don't stick to the rods like the other small gears


Oh... that's pretty huge :o
I think one day I'm going to try to make a car, but this would be the maximum wheel size. It will lack certain functionality such as a full independent suspension or a proper gearbox... Perhaps I will use Arduino to make it RC. It will have a mini dummy motor :P Just like in the Maxima set, but keep it up! Don't forget to include a lot of footage about what moves, so it's understandable for more people.