Take a look at the "Ikona" non-involute gear form. The contact forces form a curve instead of a line, with zero backlash, and multiple tooth contacts before/af

Take a look at the "Ikona" non-involute gear form. The contact forces form a curve instead of a line, with zero backlash, and multiple tooth contacts before/after top dead center. Amazing: http://www.ikona.ca/technologies_tooth.shtml http://www.ikona.ca/technologies_tooth.shtml And the patents are about to expire... EDIT: An application of the Ikona gear tooth form, implementing a CVT with no clutch plate or other frictional components: http://www.powertransmission.com/issues/1008/ikona.pdf http://www.powertransmission.com/issues/1008/ikona.pdf