Cycloid Mechanism Understanding

[tmday7]

Hello all,
Been looking at some various cycloid mechanisms for the first time and am trying to get my head around this one in-particular.

http://www.youtube.com/watch?v=SH46bpe1cNA

He has a web page about it.
http://www.zincland.com/hypocycloid/

One thing i don't understand is, what is the first stage for? With both cams being made one piece what is the purpose of the first stage? Is it just for direction of output shaft?

:) Dont know which is harder, figuring out how these work or asking a question as how they work.

Thanks,
Troy

[ArtF]

Troy:

  Its actually 4 gears. The first stage has 2, with 10:1 reduction.  The first gear is the case itself. Then he places 2 more inside, then the output gear is the casing itself on the end. That has another 10:1 on it, so a total of 100:1 using 4 gears.  Its hard to wrap your head aroudn it till you make one. Gearotic will put out the shapes, its basically a couple of cage gears. They use an offset shaft to make it so it doesnt wobble, but look to an internal cage and lantern and youll see the similarity... If you look up gearless clocks youll see they too use this method. ( The term gearless is really not correct in my view, they ARE gears, just not what people are used to seeing as gears..)


Art

[tmday7]

:) Its something, i understand what you are saying but both cams being attached to one another keeps be from grasping just how it works  ;D
Like you said ill need to make one to get it.

Troy

[bosr]

Are you planning to add a wizard for these to GT?

[ArtF]

Hi:


>>Are you planning to add a wizard for these to GT

Hi:

    I DO intend on making them much better and perhaps having a cycloidal module on its own.
Each module Im adding to GT gets a full redesign as I do it, so you'll get GT before I get to
such a decision. You guys will decide what module you get and when, once GT is released
anyway. Its looking like sometime in September for an alpha release, it will lack several things
GM can currently do, but its output will be more accurate, and easier to understand. It will much
more tightly follow industry standards. Im spending huge gobs of time ensuring this. While spurs
were always good, helicals and bevels were not quite to spec, they now are. While specs on standards
DO vary, Im trying to ensure we stick with the most commonly used spec. For example the new Bevels
will be all Gleason spec equations. Cycloidals, having only 1 real spec, shouldnt be too bad, but even there
some differences DO exist. For them there is a new formulation based on the mathmatically provable case
for maximum efficiency..which I suspect Ill end up using.

  But I digress...
 
Yes, a module for cycloidals will be done in the end, BUT after the new CNC module. This is
because while toolpaths are easy for 2.5D structures like gears, cycloidal planetaries require a more
complex machining strategy, so we'll need better toolpathing for them. The module I know that will
take the most time and work will be the new toolpath generator, so Ill likely release just prior to
writing one, this means GT will not be able to do Gcode on initial release, only 3d models, and printouts.
Cycloidals will really need a proper toolpathing module to handle their complex 3d model structures.
While I know this will cause trouble for some, my thought is that at least those with the capability to
3d print, or to machien 3d models from other software will at least be able to function with the new program
while I complete a new toolpathing generator. Such generators require alot of work and I need to do it in tandem with
a new toolpath visualiser , they will both act together as a way of visually verifying what you will
cut before you cut it. This is all pretty ambitious for a program like GM, so it will take awhile and require a
lot of feedback. We'll see how that all goes as we get there. :)

Art
     
     

[bosr]

The task you are undertaking on this is huge but also very valuable to the community.

I'm looking forward to the new tools.

Thanks.

Randy

[danmauch]

Now I am confused.. In GM when I click on Spur  Gears and then click on epi/cyc  and set it up for internal I get a tooth pattern that doesn't look anything like an hypocycloidal gear combination . But when I go to lantern Gears I can create what I think is a hypocycloidal gear but would need to modify the pins from a full pin to maybe2/3 of the pin for engagement.
Am I wrong that epi/cyc is not for epicyclodial gears? If not wrong what am I doing wrong?
Dan Mauch.

[danmauch]

Any comments on my previous post?

Dan

[BobL]

Hi Dan;

Sorry for the delay, but lately we've been having small issues with the forum's automatic notification system, so I'm assuming Art didn't see this post at all, and I would  prefer he answers you on this, so I'll make sure he is notified of it, hope he gets back to you soon.. 


Thanks
Bob
???

[ArtF]

Hi Dan:

  Ahh, I understand the confusion. ( Sorry for the delay, I didnt get notification as Bob suggested.)
 
  In the spur screen, there is a choice for EPI gears, however, though such gears are called EPICycloidal
gears, they dont actually follow the math as youd expect, they instead represent the clockmakers EpiCycloidals
which are based solely on Epicycloidals generated by a specific radius ,( 1/2 of the mate's radius), this means
they always have a straight root. Good for the clockmakers, but not configurable to what youd expect as you wont get
anything other than a straight edged hypocycloidal inside. In future these types of Epi's will get further restricted
to the gears in the swiss clockmaking standard which are actually circular arc representations of epi's. In other
words the epi's on the spur page are clockmakers gears not really the math forms of epi/hypos as you need for such
speed reducers.

  Your right though, the cage gears ARE the same type of curves. You dont really have to modify the pin, they would
  work as the reducers do in any pin size. What you typically see in reducers are a third for of the epi/hypo gear sets
  where the pin size and outside curves are modified to match what a paper out there refers to as the most efficient form
  of hypocycloidics to reduce friction.
 
  Id use the pins as the outside ring. You actually then just cut a circle and put in half pins. The hypo's GM makes to
  match should then work fine to make speed reducers as the ones on this thread.
 
  So you can use the cage gears to get the forms now, but in future Ill be giving you better ways to make them as well
    as including the math of the third form as well.

Art

[danmauch]

Thank you, Thank you. I  I was going nuts trying to make the spur gear epi/cyc look like a hypocycloid gear. Your reply really confirms my conclusions about latern gears.
Thanks
Dan Mauch

[ArtF]

:) .. When I first started doing this, I figured.."Hey, how much can there be to know..its only gears.." lol

There is an unending supply of little tidbits to know about gears... and Im still learning everyday. 

Art

[danmauch]

Yesterday I laser cut a 10/1 ratio lantern and pin  gearset. The pinion has ten teeth and the cage 11 with a .68'D shaft ( the bearing was added just to see how things would rotate but will be removed on the next cut)and .5 pins. I modified the pins in my cad by 1/2. The picture shows the tooth profile but it doesn't look like the hypocloid shape that I have seen elsewhere.  It does rotate and seems to perform like a hypo  but would like your comments.
Dan Mauch

Hi Dan:

   Ahh, I understand the confusion. ( Sorry for the delay, I didnt get notification as Bob suggested.)
   
   In the spur screen, there is a choice for EPI gears, however, though such gears are called EPICycloidal
gears, they dont actually follow the math as youd expect, they instead represent the clockmakers EpiCycloidals
which are based solely on Epicycloidals generated by a specific radius ,( 1/2 of the mate's radius), this means
they always have a straight root. Good for the clockmakers, but not configurable to what youd expect as you wont get
anything other than a straight edged hypocycloidal inside. In future these types of Epi's will get further restricted
to the gears in the swiss clockmaking standard which are actually circular arc representations of epi's. In other
words the epi's on the spur page are clockmakers gears not really the math forms of epi/hypos as you need for such
speed reducers.

   Your right though, the cage gears ARE the same type of curves. You dont really have to modify the pin, they would
   work as the reducers do in any pin size. What you typically see in reducers are a third for of the epi/hypo gear sets
   where the pin size and outside curves are modified to match what a paper out there refers to as the most efficient form
   of hypocycloidics to reduce friction.
   
  Id use the pins as the outside ring. You actually then just cut a circle and put in half pins. The hypo's GM makes to
  match should then work fine to make speed reducers as the ones on this thread.
   
  So you can use the cage gears to get the forms now, but in future Ill be giving you better ways to make them as well
     as including the math of the third form as well.

Art

[ArtF]

Hi Dan:

  Probably work.. ( more than 1 way to skin a cat..), but hres the approach Id take.. It probably looks more normal to you.
I started with an internal lantern with 1 tooth difference.. ( you can use more for different ratios..). ( photo 1)
Then I cut the pins in half with a circle and removed their back side (photo 2), then joined each with semicircles that clear the gears lobes as in ( Photo3).

  As I say, there is a paper pubished ( Id have to find it) , that describes a modification of the equations for better
friction control which I hope to add in future..

Art

[danmauch]

Ahhh . I see you must have used a dp of 2, 3or 4 . I used a dp of 5 which explains why my gears did match what I thought they should.

Thanks


Dan

Hi Dan:

  Probably work.. ( more than 1 way to skin a cat..), but hres the approach Id take.. It probably looks more normal to you.
I started with an internal lantern with 1 tooth difference.. ( you can use more for different ratios..). ( photo 1)
Then I cut the pins in half with a circle and removed their back side (photo 2), then joined each with semicircles that clear the gears lobes as in ( Photo3).

  As I say, there is a paper pubished ( Id have to find it) , that describes a modification of the equations for better
friction control which I hope to add in future..

Art