Toroidal CVTs?

[chrome700]

I'm playing with the demo a little bit, and was hoping I could create something like this:



where the mating surfaces are geared. Is that possible?

(apologize for the Spanish, but it was the best image I could find on Google on short notice)

Though, what I'd really like to see is the love child of Gearotic Motion and Linkages.

[ArtF]

Hi:

  Thanks for the link on Linkages.. great little program. Ill play with it, it does do much as I imagined
a new 4 bar linkage module to do. Ill give it much thought.

  In your example, it is impossibel to do it with geared surfaces I think. Imagine either the number of teeth or the module of the teeth must change as you go from max radius to min radius of the torus.. but you cant change the wheels mod or tooth count, this means theyu woudlnt gear in that way...I like the example of the CVT though,
very well done..

Art

[chrome700]

I see what you're saying; if the number of teeth on the torus is a constant, they'd get smaller as you moved towards the smaller diameter of the torus, and the teeth of the "gear" in the middle would stay the same size. Makes sense.

If I were to be able to CNC a CVT like that out of wood, I wonder how much torque that design could take before slippage? Currently I'm just playing with some ideas in the virtual space before imagining how to build them. Total theoretical hobbyist at this point.

With regard to linkages, it's a very neat little program with some quirks that one has to work around, but I like playing with it. Oddly enough, the author of the program is blogging about the difficulties of adding gears to his program. I suspect you may know a thing or two about that. 

[ArtF]

>>If I were to be able to CNC a CVT like that out of wood, I wonder how much torque that design could take before slippage?

  I suspect youd need rubber wheels or something... Cant imagine itd be easy to make that run tightly...

Art

[BobL]

Hi;

I agree with the rubber wheel, just like a snow blower's friction plate...

Cheers

[Mooselake]

If you were just making it as a display or demo, and didn't need to handle any real power, you could try spraying it with plasti-dip.  No guarantees but they claim to be a non-slip coating.

Instead of wood you could try 3D printing one, or maybe get one of the 3D printer guys here to give it a try.

Sounds like a fun project.  Post pictures if you make one; maybe Art'll add it to that endless list.  Thanks for the link to linkages, too.

Kirk

[chrome700]

What's the best rubber like material to CNC?

Again, may ultimately have to build a model and experiment.

[ArtF]

Actually, youd want to make the top and bottom from metal and use rubber wheels as the  side pinions.
If you look closely, youll see the top and bottom are not smooth, they have 45 degree slopes machined into them
to create ridges that will engage the rubber wheels to roll them.
The rubber wheel on the sides are then exposed to ( what is to the wheel 90 degree ridges) on the top and bottom
cones, this 90 degree ridge then rolls the wheel just iike a gear tooth that doesnt have to mesh.


Art

[ArtF]

Or at least thats my theory..
Art

[JustinO]

Frozen rubber is the most rubber like material to CNC.


Friction transmissions like this need to be high speed/low torque. I saw a Sears and Roebuck car that had a disk/wheel variable speed transmission, and my Dad's HiFi turntable had a disk/wheel speed control...