Make Geneva wheels of any size

This summer, in an effort to teach myself Autodesk Inventor 2012 I decided to construct a virtual Geneva wheel. I have made actual Geneva wheels in the past using a pre-existing templates but I had no idea how to lay out this mechanism from scratch.

After watching a few YouTube videos depicting Geneva wheels with a frustrating lack of useful information I finally dug up the necessary formulas in Ronald A. Walsh’s Handbook of Machining and Metalworking Calculations.  Some portions of this book are available for viewing on Google Books.

The video is pretty clear. What is really satisfying about this geometry is that everything is based off of two right triangles. Once I understood this, the math became a lot less mystifying.

(Note: These calculations are practical in that I have made accommodations for the tolerances required if the mechanism is expected to actually function. This is represented by value t and can be varied depending on the size of the overall Geneva and the materials it is to be constructed from.)

UPDATE: I noticed that this calculator and visualization tool was posted a few months ago in the YouTube comments section. Very nice! Thanks for posting user wjf213!

47 responses to “Make Geneva wheels of any size

  1. Muchas gracias!!

  2. Hello !!
    I am a final year undergraduate student studying Mechanical Engineering.My final year project is to do a Yogurt cup filling and sealing machine using the Geneva Mechanism.I do not know , how to design the mechanism or how to calculate the necessary details.Please help me

  3. Wow! This is exactly what I’ve been looking for! Sweet. Thanks for the post!

  4. nice work bro
    REGARDS….!

  5. Hi, do the calculations change if you wanted to change the number of slots? I want to make one with 4 slots so that it will turn a quarter each time. Any advice would be welcomed. Great video too! Thanks

    • Tony, I’m so glad you found your way to my blog. Can I assume you are the same Tony who asked about ratchets on the Automata / Automaton Facebook Group? I meant to post a link to my site after Dug suggested Geneva Wheels but I guess I didn’t get around to it.

      To answer your question: Yes, the calculations will work to as low as four slots. Below that and it may get a little weird. Good luck!

      • Hi, yes I am the very same Tony. Its a great blog full of good information. I struggle sometimes with mathematics but the video is really clear. I’ll be sure to put a picture up on the Facebook group. Many thanks!

      • I struggled with math all through school. I don’t know if I was just lazy or didn’t see the use of it. It started to all make sense for me when I took geometry. Glad this helps and I’m looking forward to seeing what you come up with.

    • Sir, thank you for sharing the video. It help me a lot…

      Regards

  6. Hi, I’m struggling with this and I hope you can help me out.

    I’m trying to work out the value of a or c. I know the value of b but it in order to work out a, I need to know c and vice versa. Is there a set tangent angle for the triangle or does it vary with each size geneva wheel (diameter and number of slots affecting the calculation?). Should I make a decision of my own about the distance of a which would therefore allow me to work out c? Is it better to design the geneva drive first?

    I’m probably just confusing myself here. The only thing I definitely know is that b is 105mm. Any advice would be appreciated.

    Thank you in advance!

    Tony

    • Thanks for your comment Tony. There is no reason at all for you to start with a instead of b. You just need to use the cosine instead of sine. I have added info above so that you can determine either. So for a 105mm, four slot Geneva wheel your center distance c = 105mm / (cos(180/4) = 148.5mm

      And here’s a handy image that helped me:

      Hope this helps.

  7. Also, I highly recommend this web based calculator: http://web2.0calc.com/

  8. Don’t worry, I figured it out. Thanks!

  9. can you maybe make a tutorial like this one, but for internal Geneva Mechanisms?

    Would be much appreciated

  10. So pleased to have found this. I will make a VERY slow moving turntable for time lapse photography. I looked at stepper motors but they are too fiddly to drive. This will have a micro switch activated by the drive shaft. The shutter signal from the intervalometer will close a latching relay to drive the motor. The micro switch will reset the relay after one revolution of the driver and stop the motor. The time delay is variable between 5 seconds and several days. The driven wheel will drive the turntable via a belt and pulley system. Turntable rotation angle (I guess) will be about 3 to 5 degrees (still to be calculated). Anticipated photo subjects are flowers, sprouts, ice melts etc. Thanks for a very clear instructable.

    • Awesome use of a Geneva wheel. I’d love to see how this work turns out!

      • I am sorry to report that I never did get around to using a Geneva wheel for my timelapse photography project. Construction would have been too complicated for my limited workshop equipment. I did however get a turntable working from salvaged computer parts and some electronics. The rotation angle turned out to be just short of half a degree per exposure. I will (sometime) post a brief description of the project on http://forum.allaboutcircuits.com/ under a heading something like “Timelapse Turntable Controller”.

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  12. Thank you this will help me a lot. I am designing a clock that runs on a sychronous motor at 1rpm all made of wooden gears and dials. This will help me with my final design.

  13. Great video. I am drawing a geneva drive with 5 slots. I did the drawing according to the geometry given. But the problem is I have to do each frame for the rotation in autocad and animate using jif animator. I dont knw how to rotate the drive and wheel properly. When I do it is out of the proper orientation. Can u help with that?

  14. great … just we are working in this mechanism … I want to share with you the physic model when this be finished …

  15. Hi Johson, Im trying to do this project and i found your blog, i have one doubt about the triangle….
    for to evaluate ‘c’ i use 125/sen(180/4) that is 176.77 and for find ‘b’ i use sqrt(c^2-a^2) that is sqrt(176.77^2-125^2) that is 124.99, where is wrong, because if i design ,make an isoceles triangle. thanks

  16. This is so adequate for me as I am learning inventor.

  17. hello,
    does the ‘p 1.5’ item in the calculation of the y value (third to last lines for both approaches) mean ‘1.5p’?
    i can’t seem to get a correct (positive) value in my case.

    thanks a lot in advance.

  18. thank you very much, nice video!

  19. Thanks – I used your info to make a parametric model in Autodesk Fusion 360… https://www.youtube.com/watch?v=tju7pLETqDg

  20. Just what I needed! Values were a bit hard to work with because I have three slots but it still works very smoothly, thank you. I highly recommend the use of the Desmos graphing calculator found on desmos.com because you can save variables and easily adjust everything to your liking.

  21. I had a good geneva mechanism, but I had to change the centerdistance. I am going to use these formulas tomorrow to find a good drive wheel radius, but I am not sure it is going to work because I have very limited space in the housing for a bigger geneva mechanism.

  22. I am not a SW expert, but hobby programming is my passion.I wanted to make a ‘Scratch’ project on Geneva Mechanism, and was in search of math for it. That landed me to your wonderful site. On Scratch there are limitations – so I may not be able to code it. So I made from a gif file a demo project…

    https://scratch.mit.edu/projects/102241850/

    And also posted on my hobby blog your web site and github project-

    http://evidyalay.net/hobbylobby/?p=5834

    Though it is is my language ( Gujarati – western part of India ) you may click on header picture of your web site there and come back here !

    Thank you very… very… very… much. Excellent math.

  23. How length of slot influence the length of the moving sheet

  24. what is the angles of triangle you drawn first is there any calculation for that

  25. hello
    Iam the final year student of mechanical engineering …Iam doing PAPER cutting machine useing GENEVA mechanism as a major project ,I dnt have any idea about GENEVA wheel design please help me out

  26. Thank you very much for such a good data. Using these formulae, I have made an excel file in which one just needs to enter defined parameters and it will give you the derived parameters. I am using this for my project.

  27. Pingback: geneva gears – Dormiveglia

  28. i have got a geneva wheel with a radius b=40mm, s= 30 mm, when i start with b & s i go a value of a=7.5cm now i used a =7.5 to calculate c and got c = 10.66cm whe i put back these values the donn’t satisfies what should i do do design the mechanism properly

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  30. Thanks for the great job!

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