Fixed ratio traction roller transmission

A traction roller transmission comprising a traction ring structure having an inner traction surface, a sun roller disposed centrally within said traction ring structure and having a circumferential traction surface, said sun roller having a diameter substantially smaller than the inner diameter of said traction ring structure such that an annular space is formed between the traction surfaces of said sun roller and said traction ring structure and a number of planetary traction rollers rotatably supported in said annular space between, and in engagement with, the traction surfaces of said sun roller and said traction ring structure, said traction ring structure consisting of two concentric sleeves having complementary conical surfaces opposite, and spaced from, one another such that an annular gap is formed therebetween, a plurality of bearing balls disposed in said annular gap so as to facilitate relative axial and rotational motion of said two concentric sleeves, and axial cam means arranged adjacent the radially wider end of said inner sleeve for axially forcing said inner sleeve into said outer sleeve when a torque is transmitted through said transmission thereby to compress said inner sleeve and force the traction rollers into firm engagement with the traction surfaces of said sun roller and said traction ring structure.