This led to the replacement of the traditional wooden shaft by metal alloy shafts. It is held by a stainless steel shaft with roller bearings. There exists a high cylindrical ventilation shaft of diameter. The steam drove four geared turbines, one for each propeller shaft. Robin tells him the hull near the propeller shaft is only thick. There were bevel gears on the shaft. Propellants are fed via a single shaft, dual impeller turbo-pump. An auxiliary balance shaft reduces engine vibrations. These are typically disc-shaped assemblies mounted on the driven shaft. Propellants are fed via a single shaft, dual impeller turbopump. Other Powerglides came with an incompatible 16 spline output shaft. There is no distinct base at the bottom of the shaft. It consists of a flexible joint fixed to each shaft. The raised rim at the border of the shaft and glans is called the corona. Fisher debuts in the episode "The Crank in the Shaft".