Abstract: A variable ratio transmission unit includes at least one first transmission element mounted for rotation about a first axis, and at least one second transmission element in contact with the first element and mounted for rotation about a second axis. The first and second axes define a predetermined angle with each other. The first transmission element is generally disc shaped, with a profiled contact face on one major surface thereof, and the second transmission element is generally cylindrical, with a complementary profiled contact face on its periphery. The second element is slidable axially along the second axis to vary the distance between the point of contact of the elements and the first axis, to vary the effective transmission ratio.