Modelling a gear (cogwheel)

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Hello there,

I am trying to model a gear, but am struggling with the most basic problem.
I modeled one tooth and want to distribute it to faces of a tube.
That´s the theory.
Should look something like this:



I took a geometry node, with a tube inside. Drawing a curve for the tooth and copied them to selected points on the tube. It works almost fine, but the teeth are not oriented correctly. So I tried to use the normal of the primitive, to attach the tooth, but all things I tried didn´t bring me to the correct result.


I watched some tutorials but nothing helped. Even this one is not solving my problem:
Forum Post [www.sidefx.com]


Could you guys help me? I am having a hard time, getting into Houdini as an old school MAX user.

thanks…d.
Edited by 3dclassen - May 23, 2020 09:20:33

Attachments:
GEAR_wrongOrientation.jpg (30.9 KB)
GEAR_correct.jpg (55.8 KB)

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Hi,

here is a setup using two methods, to create a simple gear. The first method is grouping the smaller side primitives and extruding

them. The other method is using the prim centers (of the smaller primitives) and creates orientation attributes using the primitive

normals. After this “copy to points” can be applied, to transform the teeth to the desired position (with the correct orientation).

Attachments:
simple_gear.hipnc (101.1 KB)

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In the simplest form, it is just a polyextrude on a cylinder.
Edited by Island - May 23, 2020 10:23:14

Attachments:
gear.hiplc (89.1 KB)

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Hey Aizatulin,

thank you very much for the solution - this works perfectly!
I haven´t thought that such a simple task needs so much effort. As I am not the scripting guy (yet), I try to understand your attribute wrangle.

many thanks for the fast answer!!!

Kind regards,
Daniel
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Island
In the simplest form, it is just a polyextrude on a cylinder.

Thanks Island!
the problem with gear-wheels the shape is very special. So I have to distribute the shape around the circle, perpendicular. In the beginning I had the same idea as you, but this is not working for me.
construction of gear [en.wikipedia.org]

Thanks anyway…d.
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Could you just use a group range? I modified this to allow a gear with a different size to move with the larger gear. There is no code in this except time animation. If that is not close enough, you can add more than one extrude with individual transforms of extruded front to shape the teeth (rather than increase divisions in a single extrude), but to get a perfect gear, you would do better in a CAD program/solidworks anyway (where there are no polygons).
https://vimeo.com/421959451 [vimeo.com]
Edited by Island - May 23, 2020 15:56:16

Attachments:
gear.hiplc (179.0 KB)
gears.jpg (51.7 KB)

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3dclassen, my guess is that you want to use cogs of potentially different diameters…right? But with (at least somewhat) similar teeth size, to work together.

One simple option then, going this “let's avoid dealing with copy instances point attributes atm” route (ok for learning the basics, but unavoidable going further), and as shown here using polyextrude mainly, is to just set the initial number of columns relative to the tube radius. possibly multiplied by a user picked number to set the teeth “density”, so to speak.

and then “cheat” with a more simple copy and transform node. that'd be the gist of if.

I'm still at work atm, and frustratingly can't send files, but here's a screencap of what I tried in my last break, hopefully the comments might help.

Attachments:
2020-05-23_182500.jpg (320.1 KB)

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lol, I could also have just tried polyextruding by individual elements! Overcomplicating things…
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how about this, where the concave/vex profiles actually complement each other.

Attachments:
gear.jpg (67.4 KB)
vu_gear.hiplc (98.4 KB)

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That is simple and elegant! Attached is a multiple extrude gear which would better fit a real spur gear.
Edited by Island - May 26, 2020 13:46:18

Attachments:
GearMultipleExtrude.hiplc (167.4 KB)

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