Variable speed secondary pulley

A variable speed secondary pulley includes a first pulley half and an abutment member connected together and mounted for rotation on and axial movement along a sleeve at axially spaced locations at the opposite sides of a second pulley half immovably fixed to the sleeve. The second pulley half includes a hub provided with axially inclined cam surfaces which are engaged with complementary surfaces provided on a hub of the abutment member. A compression spring is coxially mounted on the sleeve and is compressed between the second pulley half and the abutment member so as to urge the pulley halves toward each other while the cam surfaces serve as a torque responsive means which develops decreasing axial forces in response to decreasing driven shaft torque to effect increasing separation of the pulley halves. Means are provided for manually adjusting the preset torsional load in the spring without dismantling the pulley.