Eccentric Sphere Gears

by whosawhatsis, published

Eccentric Sphere Gears by whosawhatsis Feb 18, 2011

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27406Views 9785Downloads Found in Interactive Art


This is a sphere made of gears. The hub of the gears is off-center so that the surface breaks up when the gears turn.

This is based on emmett's cube gears ( http://thingiverse.com/thing:6073 ), but with a lot of improvements to the script. Rendering still takes a long time at first (as much as 10 minutes for this version), but I've added caching so that you don't have to wait that long every time. The render statements I used to do this also stop the OpenCSG renderings from looking like something homicidal impressionist clown with dyslexia painted during an earthquake. I also made the animation work, though even with the caching it won't exceed a few fps. The most important thing, though, is that I added a module to the parameters section to define the shape to cut into gears. You can now make gears out of any STL just by dropping the "import_stl" into this module.


The gears are pretty similar, but it will only become a smooth sphere if it is assembled just right, so you should number them as you finish printing them. While looking at the center with any four faces visible, mark one of the large faces with a 1, then 2-3 moving clockwise from there. Face 5 is adjacent to 1 and 4, and if you turn the center piece so that side 5 and the remaining three sides are visible, you can number them in a counter-clockwise direction. You can also place them by identifying them in the OpenCSG rendering; gears 1 and 2 are grey, gears 3 and 4 are red, gears 5 and 6 are green, and gears 7 and 8 are blue (even-numbered gears are small, odd-numbered gears are large).

You can assemble them by threading M3 screws into the plastic of the center block. Use 16-18mm screws for the large gears and 18-20mm screws for the small gears.

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Hey there, I am really trying to make this into a motorized version. I am trying to bring the scad file into freecad so I can export an iges or step file. When I run the code in freecad I get a lot of errors. I can get the center to come out but all the gears fail. Any ideas? Or could you post gear 1 or 5 in an iges format

I use unigraphics to model in and really need the center and one gear so I can alter them and add a motor to make it rotate.

I've attempted to take OpenSCAD files into freecad before, but it never worked. Trying to convert OpenSCAD files to other cad formats seems to be a losing proposition.

I got it figured out. In freecad there was a problem with frustrum second diameter being set to zero in every gear first unite command. I changed them all to .01mm and all works well except for gear 1. But I was able to get iges and step files to import to nx without a hitch for all the gears and the center hub.... Other than gear 1. I have been working on maki,g motorized version. Will be posting soon.

"An Excellent Sphere"

-Chef Excellence

I get the following error messages when processing the sphere center file in Slic3r:

"Warning: The input file contains a hole near edge 14.000000-85.000000 (not manifold). You might want to repair it and retry, or to check the resulting G-code before printing anyway."

And then afterwards, this:

"Warning The model has overlapping or self-intersecting facets. I tried to repair it, however you might want to check the results of repair the input file and retry."

That worked great. The part now prints perfectly. Thanks!!! What does that program do to the file?

This is f*d up. The center piece is not at all right, it doesn't look anything like the drawing (it is 5 sided rather than 6 sided and doesn't have symmetry). What's going on with this?

I'm new to thingiverse and have been constantly perplexed by the off center gear hub in all these great kinetic sculptures. I'd like to learn more about how to design off center hubs with varying numbers of gears. Most of the things on this site seem to come from a standard 8 sided hub. Could you point me in a direction to learn more about the method of creating unique solutions or is there a reason most projects utilize the 8 sided hub? 

I've printed a few gear hearts now and would really like to start making more complex assemblies.

Basically, 8 cone-shaped gears protrude from that 8 sided hub. Then, those gears are cut into a nifty shape. The "off center hub" pretty much means that a sphere shape has been cut from this gear set, but the sphere was offset from the center.

I am trying to assemble these sphere gears that I printed. Can't seem to get it together right. So I downloaded the scad file. What do I have to do to this scad file to make it display the fully assembled, color coded sphere that you describe in the instructions? Every time I try to render it, it shows me the center piece and then 8 cylinders going in the different directions, I don't get any color coded gears. I have eightgears() //render full assembly uncommented.

Also, any tips for figuring out how to line up the gears?

That line should render it as described, I'm not sure why it wouldn't. What do you see when you render using CGAL? This should show you the complete assembly without the colors.

As for lining up the gears, it's just trial and error. Screw one in, then place one of the adjacent gears in its place (without a screw until you find the right orientation, and rotate the two until it feels like a smooth sphere. If it doesn't become smooth, move the loose gear one tooth over and
try again, and once you've got it, insert the screw for that gear. Repeat until you've got them all in.

You should also be able to just see latitudinal and longitudinal lines due to the tessellation of the sphere, at least on the larger gears, so you can use them to align those gears.

In OpenSCAD I get this 8 times:

WARNING: Ignoring unkown module 'bevel_gear'.

Ah, you need MCAD! Sorry, forgot about the dependency. I've uploaded a zip file that has everything you should need to make it work.

"homicidal impressionist clown with dyslexia painted during an earthquake

I love technical descriptions!

Thanks for raising the bar higher for me - I've got a lot to learn on OpenSCAD. This will be fun to print.

That's awesome! I can't wait to take a look at your script; I didn't even know what you're talking about was possible with openSCAD. Well done.

This looks great, I'm going to print this! 8-)

That's great, be sure to post pics.