Welcome to the Onshape forum! Ask questions and join in the discussions about everything Onshape.

First time visiting? Here are some places to start:
  1. Looking for a certain topic? Check out the categories filter or use Search (upper right).
  2. Need support? Ask a question to our Community Support category.
  3. Please submit support tickets for bugs but you can request improvements in the Product Feedback category.
  4. Be respectful, on topic and if you see a problem, Flag it.

If you would like to contact our Community Manager personally, feel free to send a private message or an email.

Planetary Gear Two Inputs Conundrum (Solved)

aaron_bergman616aaron_bergman616 Member Posts: 3
edited July 2020 in General
I've been designing a fun toy, a planetary gear with two inputs and one output.  I want two inputs to show how this can affect speed on the output.  I thought my design was on track, but I cannot get the animation to work. 

I don't need the teeth to be perfect, but I know the position of the gears are off since OnShape is preventing two gear ratios from formulating at the planet carrier, which causes "Unable to compute any steps for this animation. Unable to apply transform. Instance(s) may be constrained."

I tried using different mates on the same planet carrier only to receive the same error message.

I've tried combining the gear ratios into one ratio for one mate, but I'm not sure of the actual math.  Like dominoes, one misstep, and it all falls apart.

Anyone know how to handle two inputs?  

Thank you.



  • aaron_bergman616aaron_bergman616 Member Posts: 3
    edited July 2020
    I realized that I was missing an idler gear.  I updated the model.  I still haven't figured out why I can not get the ring, sun, and carrier speeds to sync up.  Setting the "Pulley to Pulley" gear ratio to 4.75 should sync the speeds.  When I'm not tinkering with the model online, I leave the setting at 4.75, changing it to a gear ratio of 1 gives a proper animation of the satellites moving around the ring.  Since I haven't figured out how to handle two inputs, the animation isn't perfect either way.
  • aaron_bergman616aaron_bergman616 Member Posts: 3
    I should have known my love of gears and my hatred for math would someday haunt me.  I finally broke down and solved the math after watching some youtube clips that knocked the rust of my brain cells.  The answer is pretty simple.  

    The "Ring/Carrier" formula with two inputs is: (24/114) +.2

    The 24/114 is for the rotation ring made by the belt added to the .2 for the actual ratio of the Ring/Carrier.

    If you changed the top pulley to something larger, causing a 2:1 pulley ratio, then simply change the 24 in the formula to 48 to indicate two rotations of the pulley gear.  
  • mahirmahir Member, Developers Posts: 1,277 ✭✭✭✭✭
    Glad you figured it out. Here's my example in case we did it differently.

Sign In or Register to comment.