Gearify

[Mooselake]

Gearify is aimed at non-circular gears, and especially non-circular planetary gears that I've been casually watching for the last year or so.  It was written by a grad student, no updates on YouTube or his site for 5 or 6 months, so I'm trying to get him to respond and see what it's current status is.  Judging from the tutorial video views it hasn't gotten a lot of attention.

It's got something similar to Gearotic's functional gears (including turning a picture into a gear, like make an Art gearhead), plus a tool to automatically create non-circular planetaries.  Certainly not in Gearotic's class,  but looks like it could create some fun looking toys.  Something else to make with my new K40 laser engraver/cutter...

Anybody here have any experience with it, seen it before, or have any comments on it?

Kirk

[ArtF]

Hi Kirk:

  Looks like great software for decorative gears. Its gears do not roll though, near as I can tell they rub.
So dont use them for loads at all,they are subtractions of a shape during a rotation, so they dont really follow a pitchline, as a result, they would have a speed wobble equal to the number of teeth per rev. and a wear pattern due to the mesh rub. Or at least thats what I saw last I looked. But as I say, for decorative gears, definitely a nice package.

Art

[Nate]

  Looks like great software for decorative gears. Its gears do not roll though, near as I can tell they rub. ...

Do you mean that they act by surface friction rather than normal forces on the faces?  (I think we all know that gears have to slip against each other a little bit to work properly.)  It does look like these gears 'roll' more than they mesh, but I'm not sophisticated enough to tell by looking.

[ArtF]

Nate:

The theory of gearing relies on the pitchpoint being the tangent to the pitch circle at all times. Youll notice in an involute set the teeth always
contact only on the tangent to the pitchcurve, this means the ratio of the two gears remains a constant at the radius of one vs the radius of the
other. To have this true, you need involute teeth.

  Watch those gears as they "mesh" and youll see the contact point moves from the outside of a tooth to the root of the tooth
during the rotation. Since the motion ratio at any point in time is the instantaneous ratio of the two radii , that radii
is changing by the distance of the top of tooth to the bottom. This causes a harmonic motion equal in frequency to the #teeth times the
speed of the gear. Thats what causes noisy gears. If youve heard silent transmissions when their new, iits because the pitchline contact
tangents are perfect, as they wear they can get noisier as the contact point starts to wobble about the perfect pitch radius.  The greater the distance
delta from pitch circle the greater the harmonic vibration, and the greater the wear. A worn out gear wears out much faster than one
that isnt worn..Its an accelerating effect.
    Those round teeth on a gearify gear have a harmonic equal to the full tooth depth from my look at them. They "seem" to mesh well,
but unless you have an involute profile of one sort or another, you cannot or should not bear a load.. 

  My non-circulars are based on similar mechanics, I too use subtraction for them, but you have to subtract a virtual hobb, you cant just
subtract from the mating gear. And if you do that then the arc length of the pitchline comes into effect and things get a lot more
complex.  Though as I said they are pretty and at the low price of the software, probably a bargain for that type of design.  :) )

Art


  Just my reading of the theory though..

[ArtF]

Nate:

>>I think we all know that gears have to slip against each other a little bit to work properly.

  Actually,  this statement is the key, gears should roll, not slip, slip is friction, frictions kills and is noisy.. could saved myself
a paragraph and some mental math.. lol

Art

[Nate]

>>I think we all know that gears have to slip against each other a little bit to work properly.

  Actually,  this statement is the key, gears should roll, not slip, slip is friction, frictions kills and is noisy.. could saved myself
a paragraph and some mental math.. lol

Involute gears have to flex or slip a little at the contact point.  Consider for example a simple case of 1:1 circular gears in some frame.  The only place where the gears are locally moving with the same velocity is where the pitch circles meet.  At any other point on the pressure line, the idealized contact surfaces of the gears will be moving at different velocities.  (If gears really worked better when they rolled against each other without slipping, then we wouldn't lubcricate them, right?)

The rollers that gearify produces, on the other hand, may well be able to roll against other without slipping, and the reason that they may be unsuitable for transferring torque is that their mechanism relies on friction, rather than on pressure between the contact surfaces.

[Mooselake]

I finally heard from the developer, who says he's got some updates in the works. 

The 60,000+ pound pile of 8 foot logs in my yard is going to be eating up some free time as it's being prepared for the 4 letter white stuff season, but trying the gearify trial is still high on my list.

Kirk

[JustinO]

Hi Art,

My understanding is that for gears that obey the fundamental law of gearing, the pitch point is the only point where there is pure rolling; it is the only place where the two gears are going the same direction at the same velocity. Litvin's explanation of centrodes helped make this clear to me.

Gearify looks like an interesting little narrow utility. If I were interested in gears with "round, square, or triangle teeth" I might buy it.

Thanks Art,
--Justin

[Mooselake]

Don't forget about Mike's eccentric planetary gear calculator, "Astronomer", which is my main interest.

Been enjoying this discussion; nearly mentioned in the OP that they obviously weren't involute teeth and not suitable for any kind of load, but y'all have that one covered.  All I want to do is make cool looking gadgets that don't really do anything useful - kind of like me these days.

I should contact Mike again and see if he wants to chip in here.

Kirk

[ArtF]

Nate"

Well said. I agree. And in the case of the gears we're discussing Im suspicious of the line of action, I dont believe there is one. More of a constant
rotation. But as I said, Id like to hear of the experience in building a set..

Art

[Nate]

Well said. I agree. And in the case of the gears we're discussing Im suspicious of the line of action, I dont believe there is one. More of a constant
rotation. But as I said, I'd like to hear of the experience in building a set..

I'd be curious to see how well it produces circular 'gears' too.

[ArtF]

Nate:

  You know, I like to sleep on it in things like this, because although things have a habit of looking simple,
Ive found underlying complexities in most algorithms of this sort. Your math is much better than mine, I think its
obvious from your responses to questions such as this. I appreciate that expertise being around. 

    Justin was right of course in his statement that they must slide, mine is a confusion with sliding that
causes a angular change and sliding that doesnt. I had discounted sliding that doesnt.  As you pointed
out well, sliding in the tangental direction has no effect on the rotational velocity where sliding in other
vectors necessitates it.
  Personally, I have trouble thinking of it as sliding at that point as it implies more than than
its reality. Since the contact point is touched only instantaneously and the next contact point is moving
in its own rotation coordinate system to meet the next contact point at its admittedly different speed, the result
is a roll along an involuted trajectory curve where each point meets perfectly at its own relative speed with the next
contact being the proper distance and offset away. It isnt something I think of as a slide, but it IS sliding.

  I find when I start to compete multiple coordinate frames of referance I get confused easily as to context
in those frames. Consider any single point and they meet perfectly in time and space throughout the
curve, and for this I picture no sliding. A result of knowing that temporally each point meets perfectly
with the next one in space when designing the contact curve. The curves are though, of different lengths.
Enough to hurt my head. :)

  So I had to look into some other assumptions to ensure I have it right. The involute is the best shape to my
mind as it keeps the line of action as pure as possible, but what about circular teeth? From a freshen-up look
this morning at my references, it appears round teeth are fine, but with the proviso the contact point is kept to the
pitch circle point or as close as possible, something which can be done by using the proper generating curve.

  In essense, the method gearify uses, is a valid one, since it is rolling a gear around another its doing a virtual hob,
Im unsure if the generation profile changes to match the contact point, but its a valid a way as any other in terms of
the generation, and if the contact point is relatively stable, then Id say a load is fine. I do think though for a round
tooth gear to work, the generating profile would change from gear pair to pair in order to match that requirement.

  In any event, thx for the explanation, I like to have my confusions in math or terminology fixed as I go. :)


Art


 



Thx for the update of my internal model
on how that works.



     

 
   

[Nate]

If I understand the videos correctly, then gearify may produce gears for transferring load, but it will do so by accident more than design.

A better example for non-involute gears is the imaginary gear feature in gearotic, or cycloidal gears tha were historically used in clocks.  The 'virtual hob' in gearify seems considerably less sophisticated than what would be necessary to produce one of those.

[ArtF]

Nate:

Perhaps, I find noncircluars a bitch to subtract, but its possible it works as well as any other I suppose.
  I know when I began subtraction as a build method it really had a habbit of showing flaws in my thinking,
but round teeth may be better at it. I have sent the author an invite to join us, I was pleased he contacted me,
he may be able to tell us more about the way it works. They look nice in any event. :)

>>A better example for non-involute gears is the imaginary gear feature in gearotic

  Actually, those were an attempt to produce a floating pressure angle involute.. Im amazed how popular they were,
I guess I may have to add them back in.. maybe Ill put them in the new wizards program.. let people script some
changes to them.

Art


Art

[John T]

Hi Art
I am not qualified to weigh in mathematically,  all I know is that my involutes don't slide if I get the center distance right. This is based on observations of my clocks running for years, If the center distance is off all bets are off.

John