Page 80 - The Jet Engine

Accessory drives

Fig. 7-4 An external gearbox and accessory units.

25. Spiral bevel gears are used for the connection
of shafts whose axes are at an angle to one another Gearbox sealing
but in the same plane. The majority of gears within a 26. Sealing of the accessory drive system is
gear train are of the straight spur gear type, those primarily concerned with preventing oil loss. The
with the widest face carry the greatest loads. For internal gearbox has labyrinth seals where the static
smoother running, helical gears are used but the casing mates with the rotating compressor shaft. For
resultant end thrust caused by this gear tooth pattern some o! the accessories mounted on the external
must be catered for within the mounting of the gear. gearbox, an air blown pressurized labyrinth seal is

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