Broken Heart

by GregFrost, published

Broken Heart by GregFrost Nov 7, 2010

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Broken Heart by GregFrost is licensed under the GNU - GPL license.

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A kinetic sculpture made using my parametric bevel gear script inspired by this: http://www.brainblog.to/item/2008/11/herz-aus-zahnraedern
I modeled the entire thing from scratch in OpenSCAD, starting with the Parametric Involute Bevel and Spur Gear script I posted some time ago. I have added an additional complexity to the movement because not only do the gears spin, but the axes of the gears rotate too.

Being a kinetic sculpture, you really need to see it in motion:

Be warned that before you attempt to print this, an improved technique for attaching the gears to the central mount is really needed.

I have the openscad files for everything, although there are so many parts that it is a bit of a process generating the STLs from them.

If someone wants to collaborate on a better way to mount the gears, let me know.


Vitamin Parts:
3/16 threaded rod, nuts and washers
M4x40 cap screws, and half nuts.
10mm aluminium tube.

trap 5 nuts between heart_centre_middle and heart_center_top parts.
Repeat and screw both of these onto the threaded rod.
Attach 10 and 15 tooth inner gears to the centre pieces with the M4 cap screws. I also put a nut on the outside of the centre to clamp the screw in place. This is the bit that I am least happy with because the screws can wiggle loose and after you have glued the outer parts of the gear in place you cant tighten them again. I would strongly suggest modifying the design somehow before attempting to build this. Any ideas on how to better attach the gears in the centre?
Then glue all of the gear outers in place.
Cut a slot at the top and bottom of the aluminium tube so that it can grip the bottom gear and the top drive gear.
Slide the walls over the tube.
Add the top drive gear (10 teeth) so that it engages with the aluminium tube and screw a nut on to hold it up.
Install the crossmount.
Install the drive gear shaft (again using 3/16th threaded rod) and the drive gear with nuts either side of it. The shaft goes into the crossmount to hold the drive gear at the right angle.
This is a bit fiddly.
Add the last gear (15 tooth gear).
Screw the handle onto the driver shaft.
Attach the knob to the handle. I used a bearing for this so that the knob spins nice and smoothly.

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I've printed many of the parts in this build. The handle is definitely not in the zip as well as a bottom part of the base. I can get by without any detailed instructions, but please, Mr. Frost, a mere list of how many of each part to print would be extremely helpful.


One of each of the gear outer parts. They are all unique. Each gear needs an inner part with a matching tooth count. I think the one for the bottom is unique but the others with the same tooth count are the same. The other parts are all unique. You should be able to generate the handle from the openscad.

I see! Thanks, much!

Hello, thank you for share your design, I actually printed all the parts, but I have glue every parts before to put the inner gear around the center, so I can't identify which the orden of each one, can you tell me the order of the outer parts?. thank you very much

Awesome work,

how about a zip with all the files?

Hi Greg,

We've printed your parts out using one of our SLS Machines, but were having significant trouble assembling the whole thing. I take it there's multiples of a few parts, but its not described as such here? Otherwise I think I might just be a bit slow :s

Anyway - I noticed you were in Adelaide - so
are we. I also noticed you wanted to collaborate on a better way to mount the gears. I think we can help each other out here. Shoot me an email, crsdfr at gmail dot com.

Thanks Greg! Fantastic design you have here.

So I've started printing off the parts so that I can make one of these for myself, but I can't seem to find the handle.

Could you upload that as well please?


This weekend I visited the Science Museum of Minnesota and they have a working (=movable) model of a cube made from 8 unusually shaped gears. I think the cube is modeled after work by Kamikara as ljudmila cites below.

The inner assembly looks like a truncated octahedron - 8 hexagonal faces and six smaller square faces. Each hexagonal face has an embedded/trapped bearing to hold a gear axle. This sounds similar to the do-decahedron bearing mount you are trying to make - so I think you are onto the right track with trapped bearings.

Have you finished a new bearing mount? I'd love to see it.

Thanks for sharing your hard work!


p.s. I didn't have my camera at the museum, but my sister did take some pictures with her new phone. If she can figure out how to get them downloaded, I can post or e-mail you pictures of the geared cube.

Kamikara / Haruki Nakamura is the original artist, working in paper. More great stuff at his website: http://www.geocities.jp/kamikara1967/paperart.htmhttp://www.geocities.jp/kamika...

Another clone of this heart is by Thehumanhive at shapeways: http://www.shapeways.com/model/29355/gear_heart.htmlhttp://www.shapeways.com/model...

Greg, this looks great. Will you post all the scad sources needed to produce the parts? I guess it could work with some other shapes besides a heart too.

im planning on posting the scad files, but they are not really in a fit state yet. When I have them cleaned up a bit more I'll post them.

Hi...I'd love to help with the finetuning of this.

Do you have the files in IPT or IGS or any other format than STL?

I can't load STL into Inventor to work with them.



I added my heart scad file (just for the heart shape). The way I modeled it, there are some discontinuities at the equator. If you are good with 3d design, an improved heart model would be a great help.

As stated elsewhere, this is modeled in OpenSCAD. I am working on a do-deca bearing mount to replace the roundish one in the STL files (the heart_centre files) where it has trapped bearings instead of a trapped nut. My bearings are ID5 OD10 H4 mm. I was thinking to make the gears click into the firmly held bearings by using an M5 pan head with most of the head filed off and a deep cross slot cut into the head so that the remainder of the pan head can bend inwards. I was thinking of putting rubber cut from an inner tube in the slots so that the head springs out again and holds in the bearing when inserted. The M5 can then be screwed directly into the gear to a precise depth.

AWESOME. insight into the process of making this? how did you know it would work? could you simulate it in software or are you a freak of nature :-P

This is really amazing!

At first, when I saw all the parts needed and the long instructions, I thought it would be too much trouble. But then I saw the video! It might be a while, but I definitely want to make one. Thank you for posting this!

Which 3D printer did you use?

Did you use support material?

I use a printer that started as a TechZone Laser Cut Mendel, but I have replaced the whole X axis with the exception of the carriage, the Z Pulleys and the wooden gears on the extruder with parts printed by itself.

No support material was used.

verflucht nochmal awsome !!! geared allseeing eye or gonzofist would be cool!

This might be one of the more amazing things I have seen on here.

I saw this before, are you the original artist, or did you move it to this medium?

The idea came from this: http://www.brainblog.to/item/2008/11/herz-aus-zahnraedernhttp://www.brainblog.to/item/2...

I modeled the entire thing from scratch in OpenSCAD, starting with the Parametric Involute Bevel and Spur Gear script I posted some time ago. I have added an additional complexity to the movement because not only do the gears spin, but the axes of the gears rotate too.

Seems great! :)

Can you please provide some details how to assembly it and what materials are needed?