April 2, 2011
By Brian McMillin

Readme file for Moi3d Scripts for Epicycloid reducer profile generator, and
also for Hypocycloid reducer profile generator.

Based on the paper "On the lobe profile design in a cycloid reducer using
instant velocity center," by Joong-Ho Shin, Soon-Man Kwon.

Created by (slightly) modifying the MOI3d "Circular Helix Array" script program of Michael Gibson.
(A competent programmer could combine the cycloids into one script with check boxes....)
Note: These two scripts have not been extensively tested, but seem to work very well, and simply, with MoI.

Notepad++ makes a convenient editor for the two Script programs, and the two html programs.

Previously created cycloids, using an excel spreadsheet, with points imported to Alibre.

These two script programs, and two html programs are installed similarly to other Moi3d scripts.
Copy the 4 programs to the commands folder, under Moi2.0 folder, under Program Files(x86) (or equivalent folder).
Start MoI. Under Options, Shortcut keys, Add two unused shortcut keys. For example Key "E", and Command "Epicycloid".
For example Key "Y", and Command "Hypocycloid". Return to MoI. Done.
Hit the shortcut key to create the cycloid, and modify parameters.

Profiles can be further modified in MoI3d, offset, extruded, etc.
Export and import to Alibre can be done also.

Interesting shapes can be created.

Cycloid reducer could be designed, with rollers, or even Cycloid Ball Reducer.
A few References:
"The Development of gearless reducers with rolling balls" by Hidetsugu Terada.
"Geometric Design of Cycloidal Drives with Ceramic Ball Meshing Elements" by J.J. Zhou, J.X. Hu and M. Huang.

"Gear geometry of cycloid drives" by CHEN BingKui, Fang Ting Ting, LI ChaoYang & WANG Shu Yan. (For an alternative
universal formula.)

Edit 12/3/2011 see post 10 for updated versions.

Thanks bemfarmer,

Certainly usefull and i will use it for my mechanical projects.

Compliments,

Hi Brian, this is cool, thanks for posting it!

That's great that you were able to adapt the other circular helix array script to make these new curve generators. Seems to work well!

- Michael

Works like a charm!
Useful for some of crazzy forms :)

Ultra funny indeed !

Could someone possibly re-zip those files for me??? My zip is a bit older and wont utilize the 7z file.. I didnt want to load more software or upgrade my zip utility yet...

Thanks.

Hi Burr,

Here you go...

regards Colin

Thank you Colin.

7zip is free and works great.
http://www.7-zip.org/

At any rate I see someone else re-zipped it.
Cheers,
Nick

Revisions.
Switched to "interpcurve" from"curve". (Commented out curve statement.)
Eccentricity is no longer just an integer, it can include decimals now.
Eccentricity change now updates. (Corrected glaring error.)

Hi,

I am trying to get a hypocycloid shaped likE the one in the attachment
but just dont get it ;-( I would be thankful for a tip !

Hi TOM,
The two gear reducer profile scripts are poorly named, because they are for generating the rotors for Gear Reducers based upon
either epicycloids or hypocycloids, with an eccentricity. They should be named something like epiGearReducerProfile, and hypoGearReducerProfile.
The mathematics are relatively complex, and come from the cited academic paper.

They do NOT generate epicycloids, nor hypocycloids, although the gear math uses epi's and hypo's as initial math formulas.

So to generate the geometry you show, you should use the hypotrochoid script.
You can look up hypotrochoids on Wikipedia. Hypotrochoids contain hypocycloids, as a subset, when b = d.
(note, the selection window at the upper right for Hypotrochoids may say Epitrochoids, due to my failure to change the options name,
while adapting Epitrochoidscript to Hypotrochoid script.)

The aRadius to bRadius should be 12:2, and the d radius about 5 or 6, and the numcycles = 1.

So I think that your geometry is a hypotrochoid, not a hypocycloid...


- Brian

Good that I asked - I could have tried out parameter combinations for years ;-)

Thank you for the explanation, I will give the othet other script a try !

Works perfectly !!