Roto Flex Pumps Roto Flex pumps are a much simpler system to understand, as well as operate. There are four main components. http://www.alrdc.com/PicturesAndAnimations/Photographs/main.htm 1. Rods:  Connect down hole pump to surface pumping unit 2. Belt: The belt is what connects to rod to the counterweights 3. Pulley: Changes the direction of motion of the belt 4. Counterweights: Stacks of steel plates that are the same mass as the rod mass and fluid mass combined. Since the direction of motion of the rods is changed by an electric motor, the goal is to have the mass of the counterweight s equal to the mass of the fluid and the mass of the rods. This equation is shown as follows: Mcounter*g=(Mrods+Mfluids)*g A roto flex system is similar to the atwood machine below, where M1 and M2 are equal. http://www1.appstate.edu/dept/physics/labs/QuickGuides/atwood.htm Since the mass of the rods and weight of the fluid is a fixed number, we can make the equation true by adjusting the mass of the counterweight, putting the system in equilibrium. This makes it very easy for the electric motor on the surface unit to move the rod up and down with minimal effort. To see a roto flex pump in action click here.