Gear looks weird

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Gear looks weird

Rainer Glaschick
Using the code
> include <MCAD/gears.scad>
> gear(number_of_teeth=10,circular_pitch=200);
I get the picture as enclosed, where the teeth do no show a nice curve, and even seem to be larger at the tip than at the bottom.
What did I make wrong? Shouldn't it look like the involute at Wikipedia, i.e. like  
    http://en.wikipedia.org/wiki/Involute_gear

Rainer

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Rainer Glaschick, Paderborn, Germany


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Re: Gear looks weird

MichaelAtOz
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Perhaps you want involute_gear_tooth()?
Admin - email* me if you need anything,
or if I've done something stupid...
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Re: Gear looks weird

Rainer Glaschick
On 11.05.2015 13:38, MichaelAtOz wrote:
> Perhaps you want involute_gear_tooth()?
Well, the function/module gear() uses involute_gear_tooth() to create the tooth, and I think this is a more or less internal subroutine.

The module test_gears() just uses gear(), but the gears produced look also not encouraging.

So my question is if someone has already successfully created nice working gears with the library, and how this is done.

Rainer


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Re: Gear looks weird

MichaelAtOz
Administrator
Perhaps you want MCAD\involute_gears.scad

Admin - email* me if you need anything,
or if I've done something stupid...
* click on my MichaelAtOz label, there is a link to email me.

Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work.
Obviously inclusion of works of previous authors is not included in the above.


The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
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Re: Gear looks weird

cacb
On 2015-05-11 14:36, MichaelAtOz wrote:
> Perhaps you want MCAD\involute_gears.scad
>
> <http://forum.openscad.org/file/n12619/involute_gears.jpg>

I think that is a good idea. I used it some time ago with success, see
example at
http://arnholm.org/printing-3d-gears/

I found that the terminology of gears is somewhat (completely?)
inconsistent and depending on "who you talk to". It makes it hard if you
have not done this before as was the case for me.

In the example on that page I managed to print a gear that successfully
replaced a stripped plastic gear in a car ventilation system. It still
works :-)

Carsten Arnholm

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Re: Gear looks weird

Chow Loong Jin
In reply to this post by Rainer Glaschick
On Mon, May 11, 2015 at 02:17:50PM +0200, Rainer Glaschick wrote:
> On 11.05.2015 13:38, MichaelAtOz wrote:
> > Perhaps you want involute_gear_tooth()?
> Well, the function/module gear() uses involute_gear_tooth() to create the
> tooth, and I think this is a more or less internal subroutine.
>
> The module test_gears() just uses gear(), but the gears produced look also not encouraging.
>
> So my question is if someone has already successfully created nice working
> gears with the library, and how this is done.

Here's my replacement shredder gear, scad included:
http://www.thingiverse.com/thing:343602/

It uses the gear from MCAD/gears/involute_gears.scad from the dev branch, but
<MCAD/involute_gears.scad> from the latest MCAD release should work just as
well.

The most confusing thing about the involute_gears.scad module is that gear()'s
circular pitch is defined in terms of actual circular pitch / PI * 180, so you
need to flip that around. For convenience's sake, and to preserve the meaning of
circular_pitch so that older designs may continue working, I have created a
function called convertcp() that handles this for you.

Here's a sample spur gear:

use <MCAD/gears/involute_gears.scad>

gear (
    number_of_teeth = 20,
    circular_pitch = convertcp (5),
    gear_thickness = 5,
    rim_width = 2,
    hub_diameter = 10,
    bore_dimaeter = 8,
    circles = 7
);


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Kind regards,
Loong Jin

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