GearHeads Forum

Based on one attempt Gearify may not import DXFs from Gearotic.  I created a 4 sided gear in Gearotic, saved it as a DXF without toothing (which may be the problem...), then tried to import it into the Gearify demo.  No luck, while it didn't report an error nothing imported.

In the non-existent world of unlimited time, I was wondering if Gearotic could add a way to have optional plugins, and Mike could modify Gearify and offer it as a Gearotic plugin.  It'd probably take an Art clone or two before that'd happen, not to mention Mike deciding it'd help pay those school loans.

Nice to see that there's other interest in Gearify, and that Art and Mike are looking at each other's product.

I didn't see any equivalent to plating/boxing in Gearify, and haven't gotten far enough in the tutorial (giant log pile in the yard...) to learn anything about gear carriers (or whatever the correct term is) to make working devices.  How did you handle it, John?

Kirk

Kirk:

  The new scripting system  is coming along quite well, its starting to look impressive, and it will be my initial attempt to try to hook more things together.
Once its complete, Im hopeing it will offer a way to allow extra objects to be added to gearotics total, or to
massage various data that Gearotic or any other program puts out. As I've said before I hope to allow DXF imports ,but havent needed
them till now. ( Though spokes and indicators and such are all just dxf's so Gearotic has been able to load DXF's for some time..
  While Auggie will not be the final way to do this, its scripter will be involved I suspect as well as the ability I need to come up
with to attach hardware.Im hopeing to have a Visual Studio project thats open source to hook to Auggie and another to add objects
to Gearotic. AllObjects in Gearotic are encapsulated in a single class called a "3dObject Class", it hold all information needed to make
and simulate any object in Gearotic, so I really hope to get to the spot where I can allow others to define an object, so that it
imports to Gearotics database for machining , planning, or putting in a box.  We'll see how this year goes.. , I have several requests
and small bugs to get of the way from this past summer. Ill put more information on a post in the release topic , it time I posted a note to
new users as to what to expect this year.

Thx
Art


Art



Art

   

ArtF wrote:Ill put more information on a post in the release topic , it time I posted a note to
new users as to what to expect this year.

The unexpected things are always the best part of every Gearotic development season

Kirk

Hello All!

This is Michael Valle, and I am the creator of Gearify. I have been enjoying this discussion and I wanted to add some comments.

I want to begin by saying that I appreciate ArtF's perspective of Gearify and Gearotic being complimentary rather than rivals/competitors. I think his analysis of Gearify's current limitations are accurate.


My initial objective when creating Gearify for my father's project, was to help him produce an internal eliptical gear mechanism with teeth that would neither slip, nor grind to  a halt. I had a strong math and programming background, but at the time, no knowledge of the formal theory of gearing. I walked into a coffee shop with a pad of paper and played with a bunch of differential equations. I walked out with a solution on paper, not only for elliptical gears but for any reasonable shape. My solution, however, only described smooth, toothless gears. Producing the shape of the teeth puzzled me until I was on Winter break from college, and I devised the subtraction method and produced the very first version of Gearify.

I didn't realize at the time but what I had essentially done was created a piece software that:

1. Violates the fundamental law of gearing.
2. Gives you all the goodies you are entitled to if you are willing to violate that law.

Fewer constraints = More degrees of freedom. That's the philosophy behind Gearify.

An excerpt from Gearify's user manual:

"The creation of gears for industrial applications is
a highly developed engineering science. Gearify is only partially based on this science, and
instead relies on an original approach using Differential Equations, Numerical Methods, and
Computational Geometry in order to allow more freedom of design."


HOWEVER! It is my hope that I can eventually find or produce a suitable generalization of the involute tooth concept for arbitrary non-circular gears. So far I have the following possible strategies:


1. Find some credible literature with a clear and reasonable approach to generalize involute teeth to non-ciruclar gears (no luck so far)
2. Devise my own generalization that at LEAST removes vibration (I have some ideas)
3. approximate the non-circular shape as a series of circular segments and use appropriate involute teeth per segment (meh.. I don't even yet know if this makes sense)
4. Allow the user to upload a "virtual hob" (which Artf mentioned) so that the portion cut away from the subtracion process can be larger than the tooth itself. This is a big feature on my TODO list. May not solve the issue but may get me closer.

So that's where I'm at with involute teeth. Its definitely my most requested, and desired feature, but as ArtF mentioned, it is very very hard to involute tooth a non-circular gear.

Let me comment briefly on DXFs since this is a key issue for interoperability of Gearify and Gearotic. Gearify makes use of the popular NetDXF project https://netdxf.codeplex.com/ for all of its DXF importing and exporting functions, which is still being developed and maintained. They recently included support for Binary DXFs, and are still weeding out bugs in general (I actually contributed to the project by writing the Spline elevator). I have yet to update Gearify's NetDXF references to the newest version, so when I get a chance to do so, that may fix the compatibility issues! Otherwise, be aware that Gearify currently only imports and exports ASCII DXF files. In any case, this will continue to improve as that project is developed.

As for future updates, I have an arbitrary non-circular rack and pinion gear interface in the works, as well as an extended "Astronomer" interface. Non-circular planetary gears are of great interest to me, and I have found a solution that allows for more symmetrical and less eccentric designs. the current interface produces a class of gears that are so eccentric they are difficult to build.


Feel free to ask me any questions or offer ideas for how you would like to see Gearify improved, or possible solutions for how to make the gears more suitable for application.

Thank you all!

-Michael Valle

Gearify wrote: ...
HOWEVER! It is my hope that I can eventually find or produce a suitable generalization of the involute tooth concept for arbitrary non-circular gears. So far I have the following possible strategies:


1. Find some credible literature with a clear and reasonable approach to generalize involute teeth to non-ciruclar gears (no luck so far)
2. Devise my own generalization that at LEAST removes vibration (I have some ideas)
3. approximate the non-circular shape as a series of circular segments and use appropriate involute teeth per segment (meh.. I don't even yet know if this makes sense)
4. Allow the user to upload a "virtual hob" (which Artf mentioned) so that the portion cut away from the subtracion process can be larger than the tooth itself. This is a big feature on my TODO list. May not solve the issue but may get me closer.

So that's where I'm at with involute teeth. Its definitely my most requested, and desired feature, but as ArtF mentioned, it is very very hard to involute tooth a non-circular gear.

....

Feel free to ask me any questions or offer ideas for how you would like to see Gearify improved, or possible solutions for how to make the gears more suitable for application.

My impression is that gearify produces 'roller' profiles which (in the idealized case) have a continuous point of contact between the two rollers, rather than one that "jumps around" like the red dots in this youtube video:

https://www.youtube.com/watch?v=14yMFdgWM-A

Is that impression correct?

IMO Generalizing involutes to no non-circular profiles really isn't that hard. It's basically just like generating involute tooth flanks point-by-point.

I worked through the basics earlier this year: http://gearotic.com/ESW/FavIcons/index.php?topic=1313.0

For more advanced topics like how to use profile shifting I can't help you much.

I played with interpolating the roll line as a series of circular arcs and putting involute teeth on those, but that can have mechanically undesirable properties. For example, it won't work properly for non-circular gears with a fixed pivot.

Nate:

  , you guys hurt my head, your math background is far advanced to mine. I struggle to do such things
as tooth a noncircular, and generalising it is something Ive spent many attempts at, including generation
point by point. While Ive gotten close, the virtual hob seems to be the only solution I can come up with
so far.
      Its a good discussion, and I agree with its direction, Ive always felt there is a formulaic generalization
of involution for any surface. Ive tried and tried to derive it, but its just over my head. When this happens
I just try to keep studying the subject till I understand. So your comments are helpful for what I can glean.
     
 
Art

Hi, Michael!  Welcome to the Gearotic forum.

Guess it's time to cough up a few bucks and get rid of the wiggling in the Gearotic display   They're forecasting rain in Mooseville, so the outside project I got talked into (running antenna wiring in an old firehall) might get cancelled, which will free up the day for dinking around with the laser and Gearify/Gearotic.

I didn't see any provision for shafts, either sizes or locations, in Gearify gears, did I miss them?  Also, does the postmaster address on your site still work?

Kirk

ArtF wrote: Nate:

 :), you guys hurt my head, your math background is far advanced to mine. I struggle to do such things
as tooth a noncircular, and generalising it is something Ive spent many attempts at, including generation
point by point. While Ive gotten close, the virtual hob seems to be the only solution I can come up with
so far.
...

Since Micheal was asking about it, I've been thinking about the best way to explain it.  So here's an attempt:

I'm going to assume that you can work out how to generate circular involute tooth profiles point-by point starting with the theory of involute gears.  So you know, for example, that there are two contact points on tooth flanks that correspond to every point on the pitch circle.   If that doesn't make sense then starting with a foundation of involute gear theory might be more productive.

The non-circular analogue of the pitch circle is called a roll line.  (I tend to call it a pitch line, or pitch profile, and there may be other terms, but I'll call it a roll line here.)  Similarly, let's call the analogue of the pitch point the roll point.

So let's say we want to make a set of involute non-circular gears, and let's suppose that we've produced two "nice" roll lines so that they'll roll against each other with fixed centers of rotation and with the point of contact - i.e. the roll point - always on the line between centers.

Then it's relatively straightforward to model the rolling action of one roll line against the other.  (For example, that's something that gearify already does.)

Now, to build involute tooth profiles from this action we need to pick some way to determine tooth phase, and a pressure line.  There are natural ways to do both of those:

The pressure line can be effectively the same as it would be for circular involutes:  It's the line that intersects the line between centers at the roll point, and is off perpendicular by the pressure angle.  (There are two of these pressure lines, one for the rising flank, and one for the falling flank that correspond to the two directions of the perpendicular.)

Similarly, the tooth phase is a linear sawtooth function of the arc length of the roll line.

So for every point on the roll line, we have a pressure line and a tooth phase, so we can work out the corresponding contact points, and this lets us generate the tooth flanks point-by-point.

Nate:

Very well explained, the problem Ive found is in the convexities.. that does work for me till the point where convexity causes a problem, been so long I cant say exactly what the problem was.. .. but you know, the one point you mentioned I hadnt tried was using a sawtooth phase on the arc length for flank position,...thats brilliant.. I may have to revisit
that code..

Art

Nate,

"Now, to build involute tooth profiles from this action we need to pick some way to determine tooth phase, and a pressure line."

Wow. This is essentially what I had in mind, only I was of the opinion that "picking" my own pressure line and tooth phase would not constitute something I could advertise as legitimate involute teeth, but rather my own personal bastardization of a precisely defined concept.  I have not had time to extensively review and understand in-volute tooth theory to know how much is good enough (I am involved in too many projects... )

This discussion is very motivating to me! If we can come up with a feasible definition I can definitely implement it in Gearify!

Here is my question for you though, Nate. By whatever definition you're working with, what is the pressure angle measured from on a non-circular gear? In circular gears, the line tangent to the roll lines at the point of contact is always perpendicular to the line through the centers of rotation (which gives us some nice properties). On non-circular gears (especially the more eccentric ones) the tangent line can be quite far from perpendicular to the line through the center. See the diagram below:



If measured from (p1-p2) I feel that there would be severe disortions where t1-t2 differs significantly. But if from t1-t2, the gears may not "push" on eachother properly and the entire benefit of involute teeth is compromised.

Thoughts?