Wheel-rod axis is one type of simple machine. It is originally different form of lever. Here, wheel acts as the force-arm and rod-axis act as the load-arm. An axle is a non rotating member that carries no torque and is used to support rotating wheels, pulleys, and the like. An axle has wheels at both ends of it. If it rotates with the wheels, it is also an shaft. If the axle remains static, it is not a shaft.
The load is fastened by one end of a rope and the rope is rolled-up by rotating the rod-axis. Its mechanical advantage depends on the ratio of the radius of the wheel to the radius of the rod axis. That means, if the radius of the wheel is 6 times greater than the radius of the rod-axis, 6 kilogram-weight load can be lifted by applying 1 kilogram-weight force. So, one thing is clear that to increase the mechanical efficiency of wheel rod-axis, the radius of its wheels need to be much greater. The wheel of motor car, screw driver, etc. work like wheel rod-axis.
