Spiral Cam?

[RhoTu]

What I'm trying to do is create a nob/gear that when turned one full revolution will, from point zero to 359, have increased by .25 in.

Any math wiz know how to do this?  Can it be done in GT?

TIA

RT

[ArtF]

Hi:

  Try a logarithmic gear , and then strip its teeth after putting it in the project.

Art

[JohnHaine]

I have a simple spreadsheet too that generates "equi-angular spirals" and the necessary G-Code.  Used to make the spiral cam that lowers/lifts the gravity arm in my new clock, driven by a stepper motor.

Happy to share, no support though!

[BMeyers]

JohnHaine:
too much to ask for a photo of both the "spiral cam" and the "gravity arm".  thanks in advance.

[JohnHaine]

You can see the gravity arm in the clock here:
https://groups.io/g/synchronome1/photo/86249/13?p=Created,,,20,2,0,0

I don't have a photo of the final cam but here's a picture of the profile from Excel.

It spirals both ways - but easy to modify the code to only do one way (which was how my original was done but that can jam when driven the "wrong" way.  This is the toolpath - in practice you cut the blank using a cutter with the same diameter as the follower roller, a 6mm ballrace in my case.

[ArtF]

Hi:

Next release of Vexx will allow an "Archimedes" selection for the spiral generation.
When selected, the spiral ratio will become the number of equal rotations of
radius drawn by user. The formula then is r = c * ang, where the r is the dragged
radius end radius, and c is  r / (ratio*360).

Art

[BMeyers]

Thank you John for your informative response.

And thank you Art in advance for the "Archimedes" (quotes in the original) enhancement.