# Laser cut carboard planetary gear

### Build Info:

Gears made using the gear extension in inkscape. The inside gear or ring gear was also made with this extension but I inverted it. I’ll be making a video tutorial on how to do this in the near future. The ring gear has 42 teeth, the 3 ‘planet’ gears have 12 teeth and the central ‘sun’ gear has 18 teeth. This website has lots of useful info on the mechanics and calculations involved in making a planetary gear. The main points to note are:

To get the gears to mesh properly, all teeth have the same pitch/spacing. Also use this equation to calculate the number of teeth required per gear so everything fits correctly:
R = 2 × P + S

R Number of teeth in ring gear
S Number of teeth in sun (middle) gear
P Number of teeth in planet gears

Finally, if you want the 3 ‘planet’ gears to sit at 120 degrees from each other, then both your sun gear and ring gear need to be evenly divisible by the number of planets. Follow these constraints and you are golden!

All line widths in the svg file are set to 0.01mm. Depending on your vector graphics editor the svg file may appear blank when you first open it. You will need to switch to outline mode to see anything. In Inkscape this is done by clicking View > Display Mode > Outline.

Here is a png image of what the svg file drawings look like:

(Edit)- made another vid just showing the gears rotating…..so…..hypnotic…cant….stop……watching

## 14 thoughts on “Laser cut carboard planetary gear”

1. wattnotions says:

I’m working on a two stage version atm – it’ll be at least twice as hypnotic!

1. Tomm says:

Heya!

Just stumbled across this while looking to design a planetary gear myself, and it looks fantastic! I was just wondering if you ever put up anything about how you made the ring gear in Inkscape? I’ve not found anything about how to make that part around, so any help would be massively appreciated.

Tom

1. wattnotions says:

Hey Tom,

It’s been quite a while since I did it so I’m a bit rusty on the exact steps. I remember using the built in gear generator extension in inkscape to make the planet and sun gears. For the ring gear it was a bit more complicated, I think I used the gear extension to make the ring gear and then I somehow inverted it so the teeth were facing inwards. I’ll try to do it again this evening and if I get it working I’ll make a post about it.

Shane

2. wattnotions says:

Hi Tom,

I’ve made a youtube video showing how to make the ring gear. It’s currently uploading but it will be available at this link in the next hour or two: https://youtu.be/Y-ympot2pms

1. Tomm says:

Hey again,

That’s brilliant, thanks very much! I’ll definitely take a look at it this evening then. Incidentally, While I was digging around yesterday, I also found this, which might be useful for you in the future:

http://www.freewarefiles.com/Planetary-Gear-Designer_program_103311.html

If can save the designs in SVG which can then be imported into Inkscape, but I’ve not idea how well they mesh in reality!

Tom

2. Tomm says:

Just a quick note to say thanks again for the video! I just watched it and it’s very clear. So clear in fact I feel a touch silly about needing to ask!

Cheers again!

1. wattnotions says:

No worries, meant to make that video months ago you just reminded me 🙂 Thanks for that link to the gear generator program…..can see it coming in handy!

All the best,
Shane

2. I absolutely love this! Thank you for making this video and sharing your file. I will be making projects with the kids using this as the base.