This oil pump is a type of internal gear pump called a gerotor. The pump is made up of two interlocking gears, one around the outside (the rotor) of the other (the idler).
What to do
Turn the knob to move the oil from one side to the other.
HOW MANY GEAR TEETH ARE THERE ON THE OUTER GEAR COMPARED TO THE INNER GEAR?
Answer:
There are 5 teeth on the outer gear and 4 teeth on the inner gear.
HOW DOES THE OIL GET INTO THE GEARS?
Answer:
There are two reservoirs that partially cover the gears on each side that allow the oil to get between the gears. You can see it by turning the exhibit to the side or the back.
What is going on?
Since the idler has one less tooth than the rotor, the idler is constantly changing which tooth is interlocked with the teeth of the rotor. As the gears turn, a gap opens between the interlocked teeth creating a suction that pulls oil between the gears on that side. As they continue to rotate, the oil gets trapped in pockets between the idler and rotor. When they are turned to the other side, the gear teeth begin to interlock again, creating pressure which then forces the fluid out the other side.