! Updated: added profile shifting - just for fun!
the logarithmic spiral has wonderful features. As it is its own involute it seems to shout at you: gear me please!! There is more or less one dominant design in the internet which is also available here at Thingverse in multiple remixed versions.
As nobody seems to have ever given it a try to put proper involute gearing (instead of sloppy sine gearing) to this beauty I tried to use my "roll a toothed rack along it" method to provide a customizeable version.
See here: https://www.youtube.com/watch?v=NuWnDpQR3q0
Here my first print:
Yes, I'm pretty sure I will do a herringbone version in the next days (edit: here it is: http://www.thingiverse.com/thing:773764)
What you get:
- a customizable kinetic teaser. Click brackets in and glue them to any surface with gears aligned.
- any (reasonable) number of teeth
- any modulus
- any slope
- a structured code with a simple API for easy customizing
What you need:
- OpenScad 2015 (dynamic arrays)
- ShortCuts.scad library (sorry for that, but it simplifies programming so much). Description in: http://www.thingiverse.com/thing:644830
- on ratios larger than about 2.5 a file to draw file the outmost gear for a smoother run
- a 8 mm drillbit
- the code echos the inner/outer radii and intrinsic gear ratio of the design.
- Rising the slope value k of the spiral will enlarge it. The one I used to produce the file Nautilus_gears.stl are somehow at the limit from a mechanical point view.
- if gears hook up at the turnover point, it helps to drawfile the outermost gear a bit. (I did'nt want to pollute the generic software approach with this.)
- to mount to any surface clip the brackets in and use double faced tape after align