GearHeads Corner
May 27, 2020, 05:10:13 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Search Login Register  
Pages: [1] 2 3 ... 5
  Print  
Author Topic: Gearify  (Read 22348 times)
0 Members and 1 Guest are viewing this topic.
Mooselake
Hero Member
*****
Posts: 633



View Profile
« on: September 16, 2015, 11:22:56 AM »

Gearify is aimed at non-circular gears, and especiall y 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 functiona l gears (including turning a picture into a gear, like make an Art gearhead), plus a tool to automatic ally create non-circular planetari es.  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 experienc e with it, seen it before, or have any comments on it?

Kirk
Logged
ArtF
Administrator
Hero Member
*****
Posts: 5634



View Profile
« Reply #1 on: September 17, 2015, 12:05:20 PM »

Hi Kirk:

  Looks like great software for decorativ e gears. Its gears do not roll though, near as I can tell they rub.
 So dont use them for loads at all,they are subtracti ons 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 decorativ e gears, definitel y a nice package.

Art
Logged
Nate
Full Member
***
Posts: 107


View Profile
« Reply #2 on: September 18, 2015, 07:58:22 AM »

  Looks like great software for decorativ e 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 sophistic ated enough to tell by looking.
Logged
ArtF
Administrator
Hero Member
*****
Posts: 5634



View Profile
« Reply #3 on: September 18, 2015, 11:02:43 AM »

Nate:

 The theory of gearing relies on the pitchpoin t 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 pitchcurv e, 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 instantan eous 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 transmiss ions 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 accelerat ing 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 subtracti on 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.  Smiley )

Art


   Just my reading of the theory though..
Logged
ArtF
Administrator
Hero Member
*****
Posts: 5634



View Profile
« Reply #4 on: September 18, 2015, 11:04:32 AM »

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
Logged
Nate
Full Member
***
Posts: 107


View Profile
« Reply #5 on: September 18, 2015, 02:22:02 PM »

>>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 velocitie s.  (If gears really worked better when they rolled against each other without slipping, then we wouldn't lubcricat e 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 unsuitabl e for transferr ing torque is that their mechanism relies on friction, rather than on pressure between the contact surfaces.
Logged
Mooselake
Hero Member
*****
Posts: 633



View Profile
« Reply #6 on: September 19, 2015, 06:53:47 AM »

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


Logged
ArtF
Administrator
Hero Member
*****
Posts: 5634



View Profile
« Reply #7 on: September 19, 2015, 07:54:57 AM »

Nate>

 >>Involute gears have to flex or slip a little at the contact point.

 No. They dont. Let me put it this way, two round gears in a closed frame with perfect involutes and no wear, have no slip, no rub and
the only friction is rolling friction. Slipping is not part of the design. Since the contact point is always in tangent to the pitch circle, it rolls
on its mating surface at all points. Now DO they slip, you bet, we live in an imperfect world.

   Seriously though,I think its a mistake to think two involute gears slip by design..I dont believe they do.. at all or at any point in
the tooth. The whole point in most gear design is to eliminate most if not all slippage, rolling is the way they work. Gearify gears cannot
roll, if they did, their teeth would be involutes . One measure of slipage is the amount differenc e from involuted shape a tooth is. Thats a
quick measure, the more different from involute the shape, the more slipping there is. This is a generalit y, but math is math..   

>>the rollers that gearify produces, on the other hand, may well be able to roll against other without slipping

   Respectfu lly, I disagree. . Smiley , the math says no... ( While Im often wrong, the math never is...)


Art
Logged
ArtF
Administrator
Hero Member
*****
Posts: 5634



View Profile
« Reply #8 on: September 19, 2015, 08:59:28 AM »

Nate:

(Im not arguing the point here, but I do think a discussio n on this is valuable to people watching who may want to understan d more on this topic,
It is after all defined as "The fundament al law of Gearing" , and as it is the basis of all gearing, I think it bears a discussio n, and in such things
I do not pretend to expertise, Im simply explainin g what I have learned from experienc e in the math, so where Im wrong, please let me know..
(I hate carrying wrong informati on. Smiley )

 First, a quote from the involute gear wiki and repeated in another form by Faydor Litvin ( My god of noncircul ar gearing who is reponsibl e
for getting me intereste d in noncirclu ar gearing.. ...)

"Where the line of action crosses the line between the two centres it is called the Pitch Point of the gears, where there is no sliding contact".

  Any gear which does not maintain a line of action, is by definitio n a gear that slides. Involutio n though , as you are thinking intuitive ly, is
not the only shape a gear tooth can have, BUT, its the only shape that allows for each gear to share the shape. Youll notice in epicycloi dic
gears the pinion has a differing shape from the wheel. Same with cage gears and such. The shape of the mating gear to any gear is really
defined in the shape of the wheel's tooth by the cycloidic math of the motion of the originati ng shape. Involutio n gives each the same shape
and has the benefit of no slippage at any point in their contact. Any shape other than involute should never be run fast, it will wear quickly
as no other shape Im aware of has no slippage.

   Now, as to the instantan eous speed ratio, in involutes as you watch the contact point rise from bottom of tooth to top, youd be
forgiven for thinking this is causing an instaneou s shift in speed, .. but it doesnt. This is because the contact point is moving out from center
at the exact same curve as the pitch curve. At any point the ratio is identical . So long as the contact point on any tooth is tangent
to the point where the two pitch circles meet, the ratio is exactly the same ratio between the two circles. It never varies at all. In good gears,
this makes them silent and very smooth. In a polished gear you'd need no more lubricati on than a trains wheel, and it would be as quiet.
Measuring vibration s caused by speed variances is a good way to measure how worn a gear is.

   In any other case, the more off tangent you are, the more the ratio varies. So in round teeth, ( watch then carefully in slow
motion) the contact point basically moves around all the curves. So is starts at the root and the contact rises to the top and then back
to the bottom of the next tooth. Note the tangent at each point. they point wildly from straight out( at tip to bottom contact) and then
to straight up when the two teeth meet in the middle. This violates "The fundament al law of gearing" and the line of action varies from
0 to 90 degrees on each tooth. This causes the speed to vary by the ratio differenc es involved,the deeper the tooth , the more the vibration
in speed. This vibration has to happen, the math demands it, and as you rotate such a gear youd feel it vibrate, the deeper the tooth , the
higher the amplitude of vibration and frictiona l wear. Now as a disclaime r I can say I have never made such a gear, perhaps when youve made
 a set you can let us know if Im right or wrong, Im simply picturing the numbers not the reality.

  Ive been asked about this topic for over  a year now and haven't wanted to comment, I havent wanted someone think Im picking on
a competito r with some technical ity, Im really not. I like what the software does, I think its decorativ e and looks nice and at its price
point is a very good value. Its a clever subtracti on method and Ive not added it to Gearotic (for those that have asked) because its done,
the solution exists at a good fair price point, and Id rather spend my time researchi ng and programmi ng things that haven't been done
or aren't offered at a fair price.

   So, thats my take on it, correct me if you feel Im wrong, but let us all know how the gears work, might get a copy myself. Smiley

Art

 
Logged
JustinO
Full Member
***
Posts: 169


View Profile WWW
« Reply #9 on: September 19, 2015, 09:59:41 AM »

Hi Art,

My understan ding is that for gears that obey the fundament al 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 explanati on of centrodes helped make this clear to me.

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

Thanks Art,
--Justin
Logged
Mooselake
Hero Member
*****
Posts: 633



View Profile
« Reply #10 on: September 19, 2015, 11:01:36 AM »

Don't forget about Mike's eccentric planetary gear calculato r, "Astronome r", which is my main interest.

Been enjoying this discussio n; 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
Logged
ArtF
Administrator
Hero Member
*****
Posts: 5634



View Profile
« Reply #11 on: September 19, 2015, 03:29:14 PM »

>>My understan ding is that for gears that obey the fundament al law of gearing, the pitch point is the only point where there is pure rolling;

 "The angular velocity ratio between two gears of a gearset must remain constant throughou t the mesh".

  This is the fundament al law of gearing engraved in stone. Smiley

  Give this a moment of thought experimen t. If an involute tooth slipped on its contact point at any point in its travel , this law by logical inference
must be disobeyed . The speed at the time of slipage has just varied. It must at all times be a constant or the math simply falls apart. This is why
it is soo difficult to involute tooth a noncircul ar gear, you MUST maintain the pressure angle and tangent to the pitchpoin t, or you violate the law.
  As yet, I havent seen any men in black approachi ng so I suspect Im on the right side of the law.

Truths:

  1) Good Gears dont slip, they roll, on every point of contact.
  2) Taxes never really go down,
  3) You die.

-- you know, prove me wrong and Ill really feel the idiot. Smiley lol

Art
Logged
JustinO
Full Member
***
Posts: 169


View Profile WWW
« Reply #12 on: September 19, 2015, 04:13:12 PM »

Not my responsib ility.
Logged
Nate
Full Member
***
Posts: 107


View Profile
« Reply #13 on: September 19, 2015, 05:08:46 PM »

I think that we agree about what's going on but have different a different understan ding of what the words mean.

Lets suppose we have a pair of circular involute gears, asin(1/2) degree pressure angle (because it makes the math convenien t) both with a pitch radius of 10.  One gear centered at (0,10) rotating countercl ockwise at 60 rpm, and one centered at (0,-10) and rotating clockwise at 60 rpm.

The pressure line is at 30 degrees so let's say that two teeth are meshing, momentari ly, at the point  (2 , 1)

Now, the distance from the center of rotation of the top gear to the contact point is sqrt(4 + 91) and the distance from the center of rotation on the bottom gear is sqrt(4 + 121) so, at the point of contact the bottom gear is moving faster than point of contact on the top gear.  They're moving at different speeds at the point of contact so they can't be rolling against each other.

Discounti ng the effect of imperfect ions, gears behave like idealized rollers that do not slip so the angular velocity ratio of the gears as a whole will stay constant, but the action of the gears - in other words the meshing of the teeth - has to have some slippage to work, even with idealized gears.

As Justin correctly notes, the only point where ideal gears can actually roll against each other is the pitch point.

Quote
...If an involute tooth slipped on its contact point at any point in its travel , this law by logical inference
must be disobeyed ...

The idealized sliding is parallel (i.e. tangent) to the instantan eous contact surface, while mechanica l action of the gears is perpendic ular (i.e. normal) to that surface so the sliding doesn't influence the rate of rotation per se.
« Last Edit: September 19, 2015, 05:35:44 PM by Nate » Logged
ArtF
Administrator
Hero Member
*****
Posts: 5634



View Profile
« Reply #14 on: September 19, 2015, 07:43:59 PM »

Nate"

 Well said. I agree. And in the case of the gears we're discussin g Im suspiciou s 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 experienc e in building a set..

Art
 
Logged
Pages: [1] 2 3 ... 5
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!