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I've been looking into something like this:
https://www.mathworks.com/matlabcentral/fileexchange/6002-counting-teeth?focused=6779089&tab=example
in order to sort through gears that may have 120, 130, 150, .... 200, 210 teeth
Seems like it could be interesting to develop some macros using evalpigment,
trace, etc.
Looks like I might have to make some headway on my Fourier transform project, or
at least use a 3rd party tool to get far enough along the workflow...
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On 6/6/2017 3:12 PM, Bald Eagle wrote:
> I've been looking into something like this:
>
>
https://www.mathworks.com/matlabcentral/fileexchange/6002-counting-teeth?focused=6779089&tab=example
>
> in order to sort through gears that may have 120, 130, 150, .... 200, 210 teeth
>
> Seems like it could be interesting to develop some macros using evalpigment,
> trace, etc.
> Looks like I might have to make some headway on my Fourier transform project, or
> at least use a 3rd party tool to get far enough along the workflow...
>
>
>
>
Interesting, I'm going to find a way to categorise all the good stuff
you are posting. :D
--
Regards
Stephen
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Le 06/06/2017 à 16:12, Bald Eagle a écrit :
> I've been looking into something like this:
>
>
https://www.mathworks.com/matlabcentral/fileexchange/6002-counting-teeth?focused=6779089&tab=example
>
> in order to sort through gears that may have 120, 130, 150, .... 200, 210 teeth
>
> Seems like it could be interesting to develop some macros using evalpigment,
> trace, etc.
> Looks like I might have to make some headway on my Fourier transform project, or
> at least use a 3rd party tool to get far enough along the workflow...
>
The basic of gear (modern) is to choose a module (a pair of gear works
together only if they have the same module) and from the dimension of
the module, you specify the perimeter of the gear as an integer number
(of module).
The ratio of perimeters gives you the reduction of the pair, and the
radius is a direct computation from the previous pieces of data.
For the really accurate gear, you have also to specify the angle of
pressure (and they must match too in a pair).
Both module and angle have standardized values (which can vary with the
standard!).
That's it for normal gear.
For gear on your bicycle, it's a bit different, the basic link of the
chain is the base for the drawing: two cylinders spaced apart.
Now, could you explain what you intended to do with povray and gear ?
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Le_Forgeron <jgr### [at] free fr> wrote:
> That's it for normal gear.
Indeed. I learned a LOT when I started looking into modeling involute spur
gears.
> Now, could you explain what you intended to do with povray and gear ?
Well, the basic idea was to see if, using a simple photograph or scan of an
existing gear, if the number of teeth could be determined automatically and
accurately. Just like in the link.
There seems to be a fair amount of image processing algorithms employed, all of
which use a 2D Fourier transform and its inverse to do things like hole-filling,
edge-detection, etc.
It would also be an interesting extension of the idea, if, once the basic
parameters of the gear were established, a 3D model could be generated.
Then you could automatically generate a parameter file, an include, or a mesh
from existing gears.
But the main idea was to be able to count the teeth.
Especially when there are a LOT of teeth, and the gears look very similar.
http://images.esellerpro.com/2131/I/680/19/RU5-0175.jpg
http://images.esellerpro.com/2131/I/680/17/RU5-0174%20003.jpg
I thought perhaps I could start with some basic image clean-up, then try to
figure out the center point, and then the radii of the addendum and base circle
so that I could determine the pitch circle and maybe the dedendum.
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Le 06/06/2017 à 19:01, Bald Eagle a écrit :
> Le_Forgeron <jgr### [at] freefr> wrote:
>
>> That's it for normal gear.
>
> Indeed. I learned a LOT when I started looking into modeling involute spur
> gears.
>
That's the only reasonable gear !
(but most people draw the involute too far inside. inside the base
circle, it cannot be involute, and yet it need some clearance down to
dedendum circle.
And some of them think the distance between the base circle and the
pitch circle is proportional to them: IT IS NOT. It is part of the
teeth, and that's is fully set by the addendum, which must be identical
on each element of a pair)
>
>> Now, could you explain what you intended to do with povray and gear ?
>
> Well, the basic idea was to see if, using a simple photograph or scan of an
> existing gear, if the number of teeth could be determined automatically and
> accurately. Just like in the link.
>
> There seems to be a fair amount of image processing algorithms employed, all of
> which use a 2D Fourier transform and its inverse to do things like hole-filling,
> edge-detection, etc.
>
> It would also be an interesting extension of the idea, if, once the basic
> parameters of the gear were established, a 3D model could be generated.
>
> Then you could automatically generate a parameter file, an include, or a mesh
> from existing gears.
The real (interesting) problem for povray is the computation of the
involute, as a native shape... then maybe some native gear shape, to
handle more natively than a complex union/intersection, per tooth ?
(nah, I would reuse my interunion object for that, probably...)
(or may be a "duplicate teeth" object, where all intersections get
rotated to a single teeth)
mmmhhh, interesting...
>
> But the main idea was to be able to count the teeth.
> Especially when there are a LOT of teeth, and the gears look very similar.
> http://images.esellerpro.com/2131/I/680/19/RU5-0175.jpg
> http://images.esellerpro.com/2131/I/680/17/RU5-0174%20003.jpg
>
helical gear... yet another beast... yummy (and more silent than the
basic gears at a small cost of maximal power)
The real hungry would go for hypoid gears, they are really painful.
>
> I thought perhaps I could start with some basic image clean-up, then try to
> figure out the center point, and then the radii of the addendum and base circle
> so that I could determine the pitch circle and maybe the dedendum.
>
If you have physical access to the gear, the fastest is to use a tailor
rule (the soft thing the tailor uses to measure) around the full circle,
and measure a small number of teeth. You might be off by a few unit, but
it's fast. (but does not work for gear with teeth on the inside,
including epicyclic gears)
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> The real (interesting) problem for povray is the computation of the
> involute, as a native shape... then maybe some native gear shape, to
> handle more natively than a complex union/intersection, per tooth ?
> (nah, I would reuse my interunion object for that, probably...)
> (or may be a "duplicate teeth" object, where all intersections get
> rotated to a single teeth)
>
> mmmhhh, interesting...
I've calculated the involute curve, so I would imagine just taking the
coordinates for a full tooth, and rotating those with a transform to make all
the teeth, and then make a prism.
> helical gear... yet another beast... yummy (and more silent than the
> basic gears at a small cost of maximal power)
> The real hungry would go for hypoid gears, they are really painful.
IIRC, someone designed a new type of gear that's an even wilder curve.
Trying to look that up, I found:
http://www.popularmechanics.com/science/animals/a9449/the-first-gear-discovered-in-nature-15916433/
:O
> If you have physical access to the gear, the fastest is to use a tailor
> rule (the soft thing the tailor uses to measure) around the full circle,
> and measure a small number of teeth. You might be off by a few unit, but
> it's fast. (but does not work for gear with teeth on the inside,
> including epicyclic gears)
I have hundreds of them.
I looked up reverse engineering of gear geometry, and a simple way is get it wet
with ink and roll it on a paper. I suppose if I removed one of the teeth or
part of one, that would be a marker for tooth #1....
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"Bald Eagle" <cre### [at] netscapenet> wrote:
> IIRC, someone designed a new type of gear that's an even wilder curve.
Aha. The "Eccentrically Cycloidal Drive".
I believe it was Stephen who brought this to my attention, based on the site:
http://www.otvinta.com/tutorial07.html
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On 6/7/2017 12:51 PM, Bald Eagle wrote:
> "Bald Eagle" <cre### [at] netscapenet> wrote:
>
>> IIRC, someone designed a new type of gear that's an even wilder curve.
>
> Aha. The "Eccentrically Cycloidal Drive".
> I believe it was Stephen who brought this to my attention, based on the site:
>
> http://www.otvinta.com/tutorial07.html
>
>
It hurts my eyes watching it. :)
I wonder how I can use it.
Thanks
--
Regards
Stephen
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So, I have a pretty good first approximation.
I'll post some results in the binary images section.
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There is also "the abacus":
http://spectrum.ieee.org/automaton/robotics/robotics-hardware/sri-demonstrates-abacus-rotary-transmission
a modern potential improvement over the harmonic wave drive:
https://en.wikipedia.org/wiki/Harmonic_drive
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