This led to the replacement of the traditional wooden shaft by metal alloy shafts. Dynamic examples include rotating pump shafts and hydraulic cylinder pistons. She had two shafts and two propellers. These supply to the ship's two propeller shafts. Roots blower were coupled to create a bank for each of the two propeller shafts. Neutral was provided for disengagement of both propeller shafts. The ship was only capable of a speed of from her two operating propeller shafts. They also have different input shafts and torque converters. This is identical to the upper deviation for shafts and the lower deviation for holes. The material used for ordinary shafts is mild steel. Ferrofluids are used to form liquid seals around the spinning drive shafts in hard disks. Broaching is a machining operation used to cut keyways into shafts. Vibration is reduced with twin balance shafts. The cave veranda has pillars with octagonal shafts and square bases. This is used for slightly imperfect alignment of the two shafts.