A rotary machine such as a rotary engine, pump or compressor, comprising: a stator forming a chamber for a rotor, said stator having two sidewalls defining opposite sides of said chamber and a substantially continuous, circumferentially extending inner wall, said stator having at least one inlet and at least one outlet; a rotor mounted in said chamber for rotation about a central axis of rotation and defining with said stator two cavities at opposite ends of said chamber, said rotor having at least two radially extending slots evenly spaced about said central axis; at least two radially movable vanes each of which is mounted in a respective one of said slots and each of which has first and second primary rollers and first and second secondary rollers mounted on a radially inward section of the vane, the first primary and secondary rollers being mounted at a first side edge of their respective vane and the second primary and secondary rollers being mounted at an opposite second side edge of their respective vane; two roller cam devices (106, 108) each provided on a respective one of said stator sidewalls and positioned centrally adjacent opposite sides of said rotor, wherein during operation of the rotary machine, outer tips of said vanes slidingly engage said circumferentially extending inner wall of said stator, said primary rollers limit outward movement of the vanes due to centrifugal forces acting on the vanes and thereby limit substantially transfer of said forces to said inner wall, and said secondary rollers limit and control inwards movement of the vanes wherein said roller cam devices (106,108) each form primary and secondary camming surfaces for engaging and controlling radial movement of said primary and secondary rollers respectively, the camming surfaces being formed inside the roller cam devices and the primary and secondary camming surfaces of each roller cam device being offset from each other in an axial direction and in a radial direction relative to said axis of rotation, wherein during operation of the rotary machine, said primary rollers on each vane rotate in an opposite direction compared to the direction of rotation of said secondary rollers. characterized in that each roller cam device (106,108) is detachably connected by threaded fasteners to its respective stator sidewall. a stator forming a chamber for a rotor, said stator having two sidewalls defining opposite sides of said chamber and a substantially continuous, circumferentially extending inner wall, said stator having at least one inlet and at least one outlet; a rotor mounted in said chamber for rotation about a central axis of rotation and defining with said stator two cavities at opposite ends of said chamber, said rotor having at least two radially extending slots evenly spaced about said central axis; at least two radially movable vanes each of which is mounted in a respective one of said slots and each of which has first and second primary rollers and first and second secondary rollers mounted on a radially inward section of the vane, the first primary and secondary rollers being mounted at a first side edge of their respective vane and the second primary and secondary rollers being mounted at an opposite second side edge of their respective vane; two roller cam devices (106, 108) each provided on a respective one of said stator sidewalls and positioned centrally adjacent opposite sides of said rotor, wherein during operation of the rotary machine, outer tips of said vanes slidingly engage said circumferentially extending inner wall of said stator, said primary rollers limit outward movement of the vanes due to centrifugal forces acting on the vanes and thereby limit substantially transfer of said forces to said inner wall, and said secondary rollers limit and control inwards movement of the vanes wherein said roller cam devices (106,108) each form primary and secondary camming surfaces for engaging and controlling radial movement of said primary and secondary rollers respectively, the camming surfaces being formed inside the roller cam devices and the primary and secondary camming surfaces of each roller cam device being offset from each other in an axial direction and in a radial direction relative to said axis of rotation, wherein during operation of the rotary machine, said primary rollers on each vane rotate in an opposite direction compared to the direction of rotation of said secondary rollers. characterized in that each roller cam device (106,108) is detachably connected by threaded fasteners to its respective stator sidewall.