cycloidal gear animation

david_fisher031

How do I get this cycloidal gear to animate in the same way as in this video https://youtu.be/guvatctnjww?t=194   where the inner cam(yellow) turns ten times for every one of the grey gear. It would seem I would need a tangent relation with a relation ratio ?

konstantin_shiriazdanov

don't know what kind of kimatics generates the outer profile but I have an example of cyclo gear when cylindrical teeth are stationary in the housing. anyway there are no fundamental difference between evolvental and cycloidal gearing since its all about rolling of cylindrical surfaces, so you need to use gear mate with corresponding ratio
https://cad.onshape.com/documents/a0adddcc041efb15f8c3ad2a/w/4e997c4fe738a2030fa71786/e/6ad4a0108794308c4b7796aa

konstantin_shiriazdanov

don't know what kind of kimatics generates the outer profile but I have an example of cyclo gear when cylindrical teeth are stationary in the housing. anyway there are no fundamental difference between evolvental and cycloidal gearing since its all about rolling of cylindrical surfaces, so you need to use gear mate with corresponding ratio
https://cad.onshape.com/documents/a0adddcc041efb15f8c3ad2a/w/4e997c4fe738a2030fa71786/e/6ad4a0108794308c4b7796aa

philip_thomas

I can think of a couple of mating strategies that will work - If you post a link to the geometry, you will no doubt spark a competition to see who can do it in the fewest mates!

david_fisher031

> don't know what kind of kimatics generates the outer profile 
I used some code from here https://cad.onshape.com/documents/ba83d698b55b206c3363b305/w/3173b192860505117c164791/e/616651006a651403af9316a9

My project is here https://cad.onshape.com/documents/16343aeebf98d3d0b59407ee/w/9a522b966b1a0b38eb22e8ff/e/3c21c28d3ed3292a84c5762d

I am ultimately trying to model the Abacus Drive from SRI International https://www.youtube.com/watch?v=zoaHeamUqBE . I only need to have a sweep go round a circular inside and outside race following the cycloid path with a profile matching the abacus bead to get the variable width path I need. 

robert_morris

What I have done before for cycloid gears is to add a Revolute mate between the cam and the inner gear, and then another Revolute mate between the cam and central input shaft. After that, you should be able to create a Gear mate using those Revolute mates, and then enter in the specific gear ratio that this will have.
The gear ratio can be determined by the formula: Ratio = (Pins - Lobes) / Lobes.

david_fisher031

I manged to get this working after looking at konstantin_shiriazdanov  example. The gear ratio isn't Ratio = (Pins - Lobes) / Lobes  , but Ratio = Lobes/Pins.

robert_morris

Awesome, glad you got it working.
You are right about the gear ratio. My mistake. The ratio that I posted is actually the ratio of the final output (the red pins in konstantin's example).