The azimuthing mechanism of original Z-peller consists of the worm wheel and worm shaft, In case of new Z-peller, large size swiveling bearing with a internal spur ring gear is applied to the azimuthing mechanism instead of the worm wheel system. Therefore it' s construction is become more simplicity and more compactness. (Refer to Fig. -1 and -2)
The lower gearcase is made by cast steel, and the kort nozzle and installation bed are fabricated by steel plate welding. So far the strength caluculation for them has not been carried out sufficiently, due to the complicated structure of them.
However, recentry the rational design has been possible by using FEM analysis and stress measurment by load testing device for large size strucure. Then it has been possible to design new Z-peller more compact and more lightness. Even though, ZP-21 is designed to be same max. horse power as ZP-3A, we have succeeded to reduce it's weight to 14 tons from 21.5 tons for a unit.
(2) Improvement of Shaft Arrangement
As we used the large size swivelling bearing to the azimuth mechanisum for new Z-peller, the height of the input shaft center become lower than original Z-peller ZF-3A. By this, the universal joints and the intermediate shaft could be arranged to be in small inclination angle, therefore life time of bearings on the inter mediate shaft is improved more longer.
(3) Low noise Level
As we applied high accuracy (DIN Q-class 6) HPG bevel gear units to new Z-pelle noise and vibration were improved upon more better than original Z-peller. Also new Z-peller equipped with skewed propeller instead of Kaplan type propeller to solve hull vibration problem caused by the propeller vibromotive force.
(4) Improvement of Lub. Oil Circulation
Considering the pumping function by tapered roller bearing itself, we designed the bearing housing to make better lub. oil circulation inside Z-peller. Therefore the bearing life time could be extended more long period.
(5) Improvement of shape of lower gearcase
Considering the fluid dynamics, the shape of lower gearcase was designed to make the stream to propeller to be smoothly. Section of lower gearcase was designed using streamline and efficiency of fluid resistance is lower than original Z-peller lower gearcase.
