Paul,

I found a good paper on traction drives (34MB) complete with
illustration. It is interesting to note the researchers references to
the bearing like attributes of the device and the need for similar
alloys, hardness and tolerances.

http://www.grc.nasa.gov/WWW/StructuresMaterials/TribMech/research/A_gear_high_speed.html

Regards

Doug in Japan

I could not get this to load.
If somebody can get it to load please screen capture
the interesting parts and send them as jpg.

Paul Lamar